Lauren O'Connell

All Publications

• Comparative analysis of amphibian genomes: An emerging resource for basic and applied research. Molecular ecology resources Kosch, T. A., Crawford, A. J., Lockridge Mueller, R., Wollenberg Valero, K. C., Power, M. L., Rodriguez, A., O'Connell, L. A., Young, N. D., Skerratt, L. F. 2024: e14025

  Abstract

  Amphibians are the most threatened group of vertebrates and are in dire need of conservation intervention to ensure their continued survival. They exhibit unique features including a high diversity of reproductive strategies, permeable and specialized skin capable of producing toxins and antimicrobial compounds, multiple genetic mechanisms of sex determination and in some lineages, the ability to regenerate limbs and organs. Although genomic approaches would shed light on these unique traits and aid conservation, sequencing and assembly of amphibian genomes has lagged behind other taxa due to their comparatively large genome sizes. Fortunately, the development of long-read sequencing technologies and initiatives has led to a recent burst of new amphibian genome assemblies. Although growing, the field of amphibian genomics suffers from the lack of annotation resources, tools for working with challenging genomes and lack of high-quality assemblies in multiple clades of amphibians. Here, we analyse 51 publicly available amphibian genomes to evaluate their usefulness for functional genomics research. We report considerable variation in genome assembly quality and completeness and report some of the highest transposable element and repeat contents of any vertebrate. Additionally, we detected an association between transposable element content and climatic variables. Our analysis provides evidence of conserved genome synteny despite the long divergence times of this group, but we also highlight inconsistencies in chromosome naming and orientation across genome assemblies. We discuss sequencing gaps in the phylogeny and suggest key targets for future sequencing endeavours. Finally, we propose increased investment in amphibian genomics research to promote their conservation.

  View details for DOI 10.1111/1755-0998.14025

  View details for PubMedID 39364691

• Effects of parental care on skin microbial community composition in poison frogs. bioRxiv : the preprint server for biology Fischer, M. T., Xue, K. S., Costello, E. K., Dvorak, M., Raboisson, G., Robaczewska, A., Caty, S. N., Relman, D. A., O'Connell, L. A. 2024

  Abstract

  Parent-offspring interactions constitute the first contact of many newborns with their environment, priming community assembly of microbes through priority effects. Early exposure to microbes can have lasting influences on the assembly and functionality of the host's microbiota, leaving a life-long imprint on host health and disease. Studies of the role played by parental care in microbial acquisition have primarily focused on humans and hosts with agricultural relevance. Anuran vertebrates offer the opportunity to examine microbial community composition across life stages as a function of parental investment. In this study, we investigate vertical transmission of microbiota during parental care in a poison frog (Family Dendrobatidae), where fathers transport their offspring piggyback-style from terrestrial clutches to aquatic nurseries. We found that substantial bacterial colonization of the embryo begins after hatching from the vitelline envelope, emphasizing its potential role as microbial barrier during early development. Using a laboratory cross-foster experiment, we demonstrated that poison frogs performing tadpole transport serve as a source of skin microbes for tadpoles on their back. To study how transport impacts the microbial skin communities of tadpoles in an ecologically relevant setting, we sampled frogs and tadpoles of sympatric species that do or do not exhibit tadpole transport in their natural habitat. We found more diverse microbial communities associated with tadpoles of transporting species compared to a non-transporting frog. However, we detected no difference in the degree of similarity between adult and tadpole skin microbiotas, based on whether the frog species exhibits transporting behavior or not. Using a field experiment, we confirmed that tadpole transport can result in the persistent colonization of tadpoles by isolated microbial taxa associated with the caregiver's skin, albeit often at low abundance. This is the first study to describe vertical transmission of skin microbes in anuran amphibians, showing that offspring transport may serve as a mechanism for transmission of parental skin microbes. Overall, these findings provide a foundation for further research on how vertical transmission in this order impacts host-associated microbiota and physiology.

  View details for DOI 10.1101/2024.09.11.612488

  View details for PubMedID 39314287

  View details for PubMedCentralID PMC11419107

• Activity of forkhead box P2-positive neurons is associated with tadpole begging behaviour. Biology letters Ludington, S. C., McKinney, J. E., Butler, J. M., Goolsby, B. C., Callan, A. A., Gaines-Richardson, M., O'Connell, L. A. 2024; 20 (9): 20240395

  Abstract

  Motor function is a critical aspect of social behaviour in a wide range of taxa. The transcription factor forkhead box P2 (FoxP2) is well studied in the context of vocal communication in humans, mice and songbirds, but its role in regulating social behaviour in other vertebrate taxa is unclear. We examined the distribution and activity of FoxP2-positive neurons in tadpoles of the mimic poison frog (Ranitomeya imitator). In this species, tadpoles are reared in isolated plant nurseries and are aggressive to other tadpoles. Mothers provide unfertilized egg meals to tadpoles that perform a begging display by vigorously vibrating back and forth. We found that FoxP2 is widely distributed in the tadpole brain and parallels the brain distribution in mammals, birds and fishes. We then tested the hypothesis that FoxP2-positive neurons would have differential activity levels in begging or aggression contexts compared to non-social controls. We found that FoxP2-positive neurons showed increased activation in the striatum and cerebellum during begging and in the nucleus accumbens during aggression. Overall, these findings lay a foundation for testing the hypothesis that FoxP2 has a generalizable role in social behaviour beyond vocal communication across terrestrial vertebrates.

  View details for DOI 10.1098/rsbl.2024.0395

  View details for PubMedID 39317327

• Physiological state matching in a pair bonded poison frog ROYAL SOCIETY OPEN SCIENCE Nowicki, J. P., Rodriguez, C., Lee, J. C., Goolsby, B. C., Yang, C., Cleland, T. A., O'Connell, L. A. 2024; 11 (7)

  View details for DOI 10.1098/rsos.240744

  View details for Web of Science ID 001260054800003

• Physiological state matching in a pair bonded poison frog. Royal Society open science Nowicki, J. P., Rodríguez, C., Lee, J. C., Goolsby, B. C., Yang, C., Cleland, T. A., O'Connell, L. A. 2024; 11 (7): 240744

  Abstract

  More than a century ago, Charles Darwin hypothesized that the empathy-like phenotype is a phylogenetically widespread phenomenon. This idea remains contentious, due to the challenges of empirically examining emotions, and few investigations among non-mammalian vertebrates. We provide support for Darwin's hypothesis by discovering partial evidence for the most ancestral form of empathy, emotional contagion (i.e. matching another individual's emotional state), in the pair bonding mimetic poison frog, Ranitomeya imitator. We found that male corticosterone, a physiological biomarker of stress, positively correlates with female partners in experimental and semi-natural conditions. This does not appear to coincide with behavioural state-matching. However, it is specific to female partners relative to familiar female non-partners, and is independent of effects that commonly confound studies on emotional contagion. Furthermore, this physiological state-matching is irrespective of partnership longevity or lifetime reproductive output. These results physiologically indicate socially selective emotional contagion in a monogamous amphibian, and paradigms that elicit coinciding neural and behavioural indicators and morphogenic co-variation are needed for further corroboration. Further studies on ancestral forms of empathy in non-mammalian vertebrates are warranted.

  View details for DOI 10.1098/rsos.240744

  View details for PubMedID 39076367

  View details for PubMedCentralID PMC11285483

• Neural and sensory basis of homing behavior in the invasive cane toad, Rhinella marina. bioRxiv : the preprint server for biology Shaykevich, D. A., Pareja-Mejía, D., Golde, C., Pašukonis, A., O'Connell, L. A. 2024

  Abstract

  The behavioral, sensory, and neural bases of vertebrate navigation are primarily described in mammals and birds. However, we know much less about navigational abilities and mechanisms of vertebrates that move on smaller scales, such as amphibians. To address this knowledge gap, we conducted an extensive field study on navigation in the cane toad, Rhinella marina. First, we performed a translocation experiment to describe how invasive toads in Hawai'i navigate home following displacements of up to one kilometer. Next, we tested the effect of olfactory and magnetosensory manipulations on homing, as these senses are most commonly associated with amphibian navigation. We found that neither ablation alone prevents homing, suggesting that toad navigation is multimodal. Finally, we tested the hypothesis that the medial pallium, the amphibian homolog to the hippocampus, is involved in homing. By comparing neural activity across homing and non-homing toads, we found evidence supporting the involvement of the medial pallium, lateral pallium, and septum in navigation, suggesting a conservation of neural structures supporting navigation across vertebrates. Our study lays the foundation to understand the behavioral, sensory, and neural bases of navigation in amphibians and to further characterize the evolution of behavior and neural structures in vertebrates.

  View details for DOI 10.1101/2024.06.25.600658

  View details for PubMedID 38979178

  View details for PubMedCentralID PMC11230440

• Tadpoles rely on mechanosensory stimuli for communication when visual capabilities are poor. Developmental biology Butler, J. M., McKinney, J. E., Ludington, S. C., Mabogunje, M., Baker, P., Singh, D., Edwards, S. V., O'Connell, L. A. 2024

  Abstract

  The ways in which animals sense the world changes throughout development. For example, young of many species have limited visual capabilities, but still make social decisions, likely based on information gathered through other sensory modalities. Poison frog tadpoles display complex social behaviors that have been suggested to rely on vision despite a century of research indicating tadpoles have poorly-developed visual systems relative to adults. Alternatively, other sensory modalities, such as the lateral line system, are functional at hatching in frogs and may guide social decisions while other sensory systems mature. Here, we examined development of the mechanosensory lateral line and visual systems in tadpoles of the mimic poison frog (Ranitomeya imitator) that use vibrational begging displays to stimulate egg feeding from their mothers. We found that tadpoles hatch with a fully developed lateral line system. While begging behavior increases with development, ablating the lateral line system inhibited begging in pre-metamorphic tadpoles, but not in metamorphic tadpoles. We also found that the increase in begging and decrease in reliance on the lateral line co-occurs with increased retinal neural activity and gene expression associated with eye development. Using the neural tracer neurobiotin, we found that axonal innervations from the eye to the brain proliferate during metamorphosis, with little retinotectal connections in recently-hatched tadpoles. We then tested visual function in a phototaxis assay and found tadpoles prefer darker environments. The strength of this preference increased with developmental stage, but eyes were not required for this behavior, possibly indicating a role for the pineal gland. Together, these data suggest that tadpoles rely on different sensory modalities for social interactions across development and that the development of sensory systems in socially complex poison frog tadpoles is similar to that of other frog species.

  View details for DOI 10.1016/j.ydbio.2024.05.006

  View details for PubMedID 38851558

• Water availability and temperature as modifiers of evaporative water loss in tropical frogs. Integrative and comparative biology Juarez, B. H., Quintanilla-Salinas, I., Lacey, M. P., O'Connell, L. A. 2024

  Abstract

  Water plays a notable role in the ecology of most terrestrial organisms due to the risks associated with water loss. Specifically, water loss in terrestrial animals happens through evaporation across respiratory tissues or epidermis. Amphibians are ideal systems for studying how abiotic factors impact water loss since their bodies often respond quickly to environmental changes. While the effect of temperature on water loss is well known across many taxa, we are still learning how temperature in combination with humidity or water availability affects water loss. Here, we tested how standing water sources (availability) and temperature (26 and 36°C) together affect water loss in anuran amphibians using a Bayesian framework. We also present a conceptual model for considering how water availability and temperature may interact, resulting in body mass changes. After accounting for phylogenetic and time autocorrelation, we determined how different variables (water loss and uptake rates, temperature, and body size) affect body mass in three species of tropical frogs (Rhinella marina, Phyllobates terribilis, and Xenopus tropicalis). We found that all variables impacted body mass changes with greater similarities between P. terribilis and X. tropicalis, but only temperature showed a notable effect in P. terribilis. Furthermore, we describe how the behavior of P. terribilis might affect its water budget. This study shows how organisms might manage water budgets across different environments and is important for developing our models of evaporative water loss and species distributions.

  View details for DOI 10.1093/icb/icae057

  View details for PubMedID 38839599

• Genome assembly of the dyeing poison frog provides insights into the dynamics of transposable element and genome-size evolution. Genome biology and evolution Dittrich, C., Hoelzl, F., Smith, S., Fouilloux, C. A., Parker, D. J., O'Connell, L. A., Knowles, L. S., Hughes, M., Fewings, A., Morgan, R., Rojas, B., Comeault, A. A. 2024

  Abstract

  Genome size varies greatly across the tree of life and transposable elements are an important contributor to this variation. Among vertebrates, amphibians display the greatest variation in genome size, making them ideal models to explore the causes and consequences of genome size variation. However, high-quality genome assemblies for amphibians have, until recently, been rare. Here, we generate a high-quality genome assembly for the dyeing poison frog, Dendrobates tinctorius. We compare this assembly to publicly available frog genomes and find evidence for both large-scale conserved synteny and widespread rearrangements between frog lineages. Comparing conserved orthologs annotated in these genomes revealed a strong correlation between genome size and gene size. To explore the cause of gene-size variation, we quantified the location of transposable elements relative to gene features and find that the accumulation of transposable elements in introns has played an important role in the evolution of gene size in D. tinctorius, while estimates of insertion times suggest that many insertion events are recent and species-specific. Finally, we carry out population-scale mobile-element sequencing and show that the diversity and abundance of transposable elements in poison frog genomes can complicate genotyping from repetitive element sequence anchors. Our results show that transposable elements have clearly played an important role in the evolution of large genome size in D. tinctorius. Future studies are needed to fully understand the dynamics of transposable element evolution and to optimise primer or bait design for cost-effective population-level genotyping in species with large, repetitive genomes.

  View details for DOI 10.1093/gbe/evae109

  View details for PubMedID 38753031

• Pavement ant extract is a chemotaxis repellent for C. elegans. microPublication biology Lopez, J. S., Ali, S., Asher, M., Benjamin, C. A., Brennan, R. T., Burke, M. L., Civantos, J. M., DeJesus, E. A., Geller, A., Guo, M. Y., Haase Cox, S. K., Johannsen, J. M., Kang, J. S., Konsker, H. B., Liu, B. C., Oakes, K. G., Park, H. I., Perez, D. R., Sajjadian, A. M., Torio Salem, M., Sato, J., Zeng, A. I., Juarez, B. H., Gonzalez, M., Morales, G., Bradon, N., Fiocca, K., Pamplona Barbosa, M. M., O'Connell, L. A. 2024; 2024

  Abstract

  Ant behavior relies on a collection of natural products, from following trail pheromones during foraging to warding off potential predators. How nervous systems sense these compounds to initiate a behavioral response remains unclear. Here, we used Caenorhabditis elegans chemotaxis assays to investigate how ant compounds are detected by heterospecific nervous systems. We found that C. elegans avoid extracts of the pavement ant ( Tetramorium immigrans ) and either osm-9 or tax-4 ion channels are required for this response. These experiments were conducted in an undergraduate laboratory course, demonstrating that new insights into interspecies interactions can be generated through genuine research experiences in a classroom setting.

  View details for DOI 10.17912/micropub.biology.001146

  View details for PubMedID 38596360

  View details for PubMedCentralID PMC11002644

• A toxic environment selects for specialist microbiome in poison frogs. bioRxiv : the preprint server for biology Caty, S. N., Alvarez-Buylla, A., Vasek, C., Tapia, E. E., Martin, N. A., McLaughlin, T., Weber, P. K., Mayali, X., Coloma, L. A., Morris, M. M., O'Connell, L. A. 2024

  Abstract

  Shifts in microbiome community composition can have large effects on host health. It is therefore important to understand how perturbations, like those caused by the introduction of exogenous chemicals, modulate microbiome community composition. In poison frogs within the family Dendrobatidae, the skin microbiome is exposed to the alkaloids that the frogs sequester from their diet and use for defense. Given the demonstrated antimicrobial effects of these poison frog alkaloids, these compounds may be structuring the skin microbial community. To test this, we first characterized microbial communities from chemically defended and closely related non-defended frogs from Ecuador. Then we conducted a laboratory experiment to monitor the effect of the alkaloid decahydroquinoline (DHQ) on the microbiome of a single frog species. In both the field and lab experiments, we found that alkaloid-exposed microbiomes are more species rich and phylogenetically diverse, with an increase in rare taxa. To better understand the strain-specific behavior in response to alkaloids, we cultured microbial strains from poison frog skin and found the majority of strains exhibited either enhanced growth or were not impacted by the addition of DHQ. Additionally, stable isotope tracing coupled to nanoSIMS suggests that some of these strains are able to metabolize DHQ. Taken together, these data suggest that poison frog chemical defenses open new niches for skin-associated microbes with specific adaptations, including the likely metabolism of alkaloids, that enable their survival in this toxic environment. This work helps expand our understanding of how exposure to exogenous compounds like alkaloids can impact host microbiomes.

  View details for DOI 10.1101/2024.01.10.574901

  View details for PubMedID 38260330

• Binding and sequestration of poison frog alkaloids by a plasma globulin. eLife Alvarez-Buylla, A., Fischer, M. T., Moya Garzon, M. D., Rangel, A. E., Tapia, E. E., Tanzo, J. T., Soh, H. T., Coloma, L. A., Long, J. Z., O'Connell, L. A. 2023; 12

  Abstract

  Alkaloids are important bioactive molecules throughout the natural world, and in many animals they serve as a source of chemical defense against predation. Dendrobatid poison frogs bioaccumulate alkaloids from their diet to make themselves toxic or unpalatable to predators. Despite the proposed roles of plasma proteins as mediators of alkaloid trafficking and bioavailability, the responsible proteins have not been identified. We use chemical approaches to show that a ~50 kDa plasma protein is the principal alkaloid-binding molecule in blood of poison frogs. Proteomic and biochemical studies establish this plasma protein to be a liver-derived alkaloid-binding globulin (ABG) that is a member of the serine-protease inhibitor (serpin) family. In addition to alkaloid-binding activity, ABG sequesters and regulates the bioavailability of 'free' plasma alkaloids in vitro. Unexpectedly, ABG is not related to saxiphilin, albumin, or other known vitamin carriers, but instead exhibits sequence and structural homology to mammalian hormone carriers and amphibian biliverdin-binding proteins. ABG represents a new small molecule binding functionality in serpin proteins, a novel mechanism of plasma alkaloid transport in poison frogs, and more broadly points toward serpins acting as tunable scaffolds for small molecule binding and transport across different organisms.

  View details for DOI 10.7554/eLife.85096

  View details for PubMedID 38206862

• Selection on Visual Opsin Genes in Diurnal Neotropical Frogs and Loss of the SWS2 Opsin in Poison Frogs. Molecular biology and evolution Wan, Y. C., Navarrete Méndez, M. J., O'Connell, L. A., Uricchio, L. H., Roland, A. B., Maan, M. E., Ron, S. R., Betancourth-Cundar, M., Pie, M. R., Howell, K. A., Richards-Zawacki, C. L., Cummings, M. E., Cannatella, D. C., Santos, J. C., Tarvin, R. D. 2023; 40 (10)

  Abstract

  Amphibians are ideal for studying visual system evolution because their biphasic (aquatic and terrestrial) life history and ecological diversity expose them to a broad range of visual conditions. Here, we evaluate signatures of selection on visual opsin genes across Neotropical anurans and focus on three diurnal clades that are well-known for the concurrence of conspicuous colors and chemical defense (i.e., aposematism): poison frogs (Dendrobatidae), Harlequin toads (Bufonidae: Atelopus), and pumpkin toadlets (Brachycephalidae: Brachycephalus). We found evidence of positive selection on 44 amino acid sites in LWS, SWS1, SWS2, and RH1 opsin genes, of which one in LWS and two in RH1 have been previously identified as spectral tuning sites in other vertebrates. Given that anurans have mostly nocturnal habits, the patterns of selection revealed new sites that might be important in spectral tuning for frogs, potentially for adaptation to diurnal habits and for color-based intraspecific communication. Furthermore, we provide evidence that SWS2, normally expressed in rod cells in frogs and some salamanders, has likely been lost in the ancestor of Dendrobatidae, suggesting that under low-light levels, dendrobatids have inferior wavelength discrimination compared to other frogs. This loss might follow the origin of diurnal activity in dendrobatids and could have implications for their behavior. Our analyses show that assessments of opsin diversification in across taxa could expand our understanding of the role of sensory system evolution in ecological adaptation.

  View details for DOI 10.1093/molbev/msad206

  View details for PubMedID 37791477

  View details for PubMedCentralID PMC10548314

• Tissue-specific in vivo transformation of plasmid DNA in Neotropical tadpoles using electroporation. PloS one Delia, J., Gaines-Richardson, M., Ludington, S. C., Akbari, N., Vasek, C., Shaykevich, D., O'Connell, L. A. 2023; 18 (8): e0289361

  Abstract

  Electroporation is an increasingly common technique used for exogenous gene expression in live animals, but protocols are largely limited to traditional laboratory organisms. The goal of this protocol is to test in vivo electroporation techniques in a diverse array of tadpole species. We explore electroporation efficiency in tissue-specific cells of five species from across three families of tropical frogs: poison frogs (Dendrobatidae), cryptic forest/poison frogs (Aromobatidae), and glassfrogs (Centrolenidae). These species are well known for their diverse social behaviors and intriguing physiologies that coordinate chemical defenses, aposematism, and/or tissue transparency. Specifically, we examine the effects of electrical pulse and injection parameters on species- and tissue-specific transfection of plasmid DNA in tadpoles. After electroporation of a plasmid encoding green fluorescent protein (GFP), we found strong GFP fluorescence within brain and muscle cells that increased with the amount of DNA injected and electrical pulse number. We discuss species-related challenges, troubleshooting, and outline ideas for improvement. Extending in vivo electroporation to non-model amphibian species could provide new opportunities for exploring topics in genetics, behavior, and organismal biology.

  View details for DOI 10.1371/journal.pone.0289361

  View details for PubMedID 37590232

• Activity of FoxP2-positive neurons correlates with begging behavior in a social tadpole. bioRxiv : the preprint server for biology Ludington, S. C., McKinney, J. E., Butler, J. M., O'Connell, L. A. 2023

  Abstract

  Motor function is a critical aspect of communication in a wide range of taxa. The transcription factor FoxP2 plays an important role in coordinating the development of motor areas related to vocal communication in humans, mice, and songbirds. However, the role of FoxP2 in regulating motor coordination of non-vocal communication behaviors in other vertebrate taxa is unclear. Here, we test the hypothesis that FoxP2 is associated with begging behavior in tadpoles of the Mimetic poison frog ( Ranitomeya imitator ). In this species, mothers provide unfertilized egg meals to tadpoles that perform a begging display to communicate hunger by vigorously dancing back and forth. We mapped the neural distribution of FoxP2-positive neurons in the tadpole brain, where its wide distribution paralleled that of mammals, birds, and fishes. We next evaluated the activity of FoxP2-positive neurons during tadpole begging and found that FoxP2-positive neurons showed increased activation in the striatum, preoptic area and cerebellum. Overall, this work suggests a generalizable function of FoxP2 in social communication across terrestrial vertebrates.

  View details for DOI 10.1101/2023.05.26.542531

  View details for PubMedID 37292748

• Home security cameras as a tool for behavior observations and science equity. bioRxiv : the preprint server for biology Goolsby, B. C., Fischer, M., Pareja-Mejia, D., Lewis, A. R., Raboisson, G., Oa Connell, L. A. 2023

  Abstract

  Reliably capturing transient animal behavior in the field and laboratory remains a logistical and financial challenge, especially for small ectotherms. Here, we present a camera system that is affordable, accessible, and suitable to monitor small, cold-blooded animals historically overlooked by commercial camera traps, such as small amphibians. The system is weather-resistant, can operate offline or online, and allows collection of time-sensitive behavioral data in laboratory and field conditions with continuous data storage for up to four weeks. The lightweight camera can also utilize phone notifications over Wi-Fi so that observers can be alerted when animals enter a space of interest, enabling sample collection at proper time periods. We present our findings, both technological and scientific, in an effort to elevate tools that enable researchers to maximize use of their research budgets. We discuss the relative affordability of our system for researchers in South America, which is home to the largest population of ectotherm diversity.

  View details for DOI 10.1101/2023.04.17.537238

  View details for PubMedID 37131676

• Definition of a saxitoxin (STX) binding code enables discovery and characterization of the anuran saxiphilin family. Biophysical journal Zakrzewska, S., Chen, Z., Hajare, H. S., Alvarez-Buylla, A., Abderemane-Ali, F., Bogan, M., Ramirez, D., O'Connell, L. A., Du Bois, J., Minor, D. L. 2023; 122 (3S1): 164a

  View details for DOI 10.1016/j.bpj.2022.11.1038

  View details for PubMedID 36782769

• Definition of a saxitoxin (STX) binding code enables discovery and characterization of the anuran saxiphilin family Zakrzewska, S., Chen, Z., Hajare, H. S., Alvarez-Buylla, A., Abderemane-Ali, F., Bogan, M., Ramirez, D., O'Connell, L. A., Du Bois, J., Minor, D. L. CELL PRESS. 2023: 164A

  View details for Web of Science ID 000989629700801

• Albino Xenopus laevis tadpoles prefer dark environments compared to wild type. microPublication biology Adebogun, G. T., Bachmann, A. E., Callan, A. A., Khan, U., Lewis, A. R., Pollock, A. C., Alfonso, S. A., Arango Sumano, D., Bhatt, D. A., Cullen, A. B., Hajian, C. M., Huang, W., Jaeger, E. L., Li, E., Maske, A. K., Offenberg, E. G., Ta, V., Whiting, W. W., McKinney, J. E., Butler, J., O'Connell, L. A. 2023; 2023

  Abstract

  Tadpoles display preferences for different environments but the sensory modalities that govern these choices are not well understood. Here, we examined light preferences and associated sensory mechanisms of albino and wild-type Xenopus laevis tadpoles. We found that albino tadpoles spent more time in darker environments compared to the wild type, although they showed no differences in overall activity. This preference persisted when the tadpoles had their optic nerve severed or pineal glands removed, suggesting these sensory systems alone are not necessary for phototaxis. These experiments were conducted by an undergraduate laboratory course, highlighting how X. laevis tadpole behavior assays in a classroom setting can reveal new insights into animal behavior.

  View details for DOI 10.17912/micropub.biology.000750

  View details for PubMedID 36824381

  View details for PubMedCentralID PMC9941856

• Argentine ant extract induces an osm-9 dependent chemotaxis response in C. elegans. microPublication biology Alfonso, S. A., Arango Sumano, D., Bhatt, D. A., Cullen, A. B., Hajian, C. M., Huang, W., Jaeger, E. L., Li, E., Maske, A. K., Offenberg, E. G., Ta, V., Whiting, W. W., Adebogun, G. T., Bachmann, A. E., Callan, A. A., Khan, U., Lewis, A. R., Pollock, A. C., Ramirez, D., Bradon, N., Fiocca, K., Cote, L. E., Sallee, M. D., McKinney, J., O'Connell, L. A. 2023; 2023

  Abstract

  Many ant species are equipped with chemical defenses, although how these compounds impact nervous system function is unclear. Here, we examined the utility of Caenorhabditis elegans chemotaxis assays for investigating how ant chemical defense compounds are detected by heterospecific nervous systems. We found that C. elegans respond to extracts from the invasive Argentine Ant ( Linepithema humile ) and the osm-9 ion channel is required for this response. Divergent strains varied in their response to L. humile extracts, suggesting genetic variation underlying chemotactic responses. These experiments were conducted by an undergraduate laboratory course, highlighting how C. elegans chemotaxis assays in a classroom setting can provide genuine research experiences and reveal new insights into interspecies interactions.

  View details for DOI 10.17912/micropub.biology.000745

  View details for PubMedID 37008729

• Glassfrogs conceal blood in their liver to maintain transparency. Science (New York, N.Y.) Taboada, C., Delia, J., Chen, M., Ma, C., Peng, X., Zhu, X., Jiang, L., Vu, T., Zhou, Q., Yao, J., O'Connell, L., Johnsen, S. 2022; 378 (6626): 1315-1320

  Abstract

  Transparency in animals is a complex form of camouflage involving mechanisms that reduce light scattering and absorption throughout the organism. In vertebrates, attaining transparency is difficult because their circulatory system is full of red blood cells (RBCs) that strongly attenuate light. Here, we document how glassfrogs overcome this challenge by concealing these cells from view. Using photoacoustic imaging to track RBCs in vivo, we show that resting glassfrogs increase transparency two- to threefold by removing ~89% of their RBCs from circulation and packing them within their liver. Vertebrate transparency thus requires both see-through tissues and active mechanisms that "clear" respiratory pigments from these tissues. Furthermore, glassfrogs' ability to regulate the location, density, and packing of RBCs without clotting offers insight in metabolic, hemodynamic, and blood-clot research.

  View details for DOI 10.1126/science.abl6620

  View details for PubMedID 36548427

• Poison frog dietary preference depends on prey type and alkaloid load. PloS one Moskowitz, N. A., D'Agui, R., Alvarez-Buylla, A., Fiocca, K., O'Connell, L. A. 2022; 17 (12): e0276331

  Abstract

  The ability to acquire chemical defenses through the diet has evolved across several major taxa. Chemically defended organisms may need to balance chemical defense acquisition and nutritional quality of prey items. However, these dietary preferences and potential trade-offs are rarely considered in the framework of diet-derived defenses. Poison frogs (Family Dendrobatidae) acquire defensive alkaloids from their arthropod diet of ants and mites, although their dietary preferences have never been investigated. We conducted prey preference assays with the Dyeing Poison frog (Dendrobates tinctorius) to test the hypothesis that alkaloid load and prey traits influence frog dietary preferences. We tested size preferences (big versus small) within each of four prey groups (ants, beetles, flies, and fly larvae) and found that frogs preferred interacting with smaller prey items of the fly and beetle groups. Frog taxonomic prey preferences were also tested as we experimentally increased their chemical defense load by feeding frogs decahydroquinoline, an alkaloid compound similar to those naturally found in their diet. Contrary to our expectations, overall preferences did not change during alkaloid consumption, as frogs across groups preferred fly larvae over other prey. Finally, we assessed the protein and lipid content of prey items and found that small ants have the highest lipid content while large fly larvae have the highest protein content. Our results suggest that consideration of toxicity and prey nutritional value are important factors in understanding the evolution of acquired chemical defenses and niche partitioning.

  View details for DOI 10.1371/journal.pone.0276331

  View details for PubMedID 36454945

• Contrasting parental roles shape sex differences in poison frog space use but not navigational performance. eLife Pasukonis, A., Serrano-Rojas, S. J., Fischer, M., Loretto, M., Shaykevich, D. A., Rojas, B., Ringler, M., Roland, A. B., Marcillo-Lara, A., Ringler, E., Rodriguez, C., Coloma, L. A., O'Connell, L. A. 2022; 11

  Abstract

  Sex differences in vertebrate spatial abilities are typically interpreted under the adaptive specialization hypothesis, which posits that male reproductive success is linked to larger home ranges and better navigational skills. The androgen spillover hypothesis counters that enhanced male spatial performance may be a byproduct of higher androgen levels. Animal groups that include species where females are expected to outperform males based on life-history traits are key for disentangling these hypotheses. We investigated the association between sex differences in reproductive strategies, spatial behavior, and androgen levels in three species of poison frogs. We tracked individuals in natural environments to show that contrasting parental sex roles shape sex differences in space use, where the sex performing parental duties shows wider-ranging movements. We then translocated frogs from their home areas to test their navigational performance and found that the caring sex outperformed the non-caring sex only in one out of three species. In addition, males across species displayed more explorative behavior than females and androgen levels correlated with explorative behavior and homing accuracy. Overall, we reveal that poison frog reproductive strategies shape movement patterns but not necessarily navigational performance. Together this work suggests that prevailing adaptive hypotheses provide an incomplete explanation of sex differences in spatial abilities.

  View details for DOI 10.7554/eLife.80483

  View details for PubMedID 36377473

• Definition of a saxitoxin (STX) binding code enables discovery and characterization of the anuran saxiphilin family. Proceedings of the National Academy of Sciences of the United States of America Chen, Z., Zakrzewska, S., Hajare, H. S., Alvarez-Buylla, A., Abderemane-Ali, F., Bogan, M., Ramirez, D., O'Connell, L. A., Du Bois, J., Minor, D. L. 2022; 119 (44): e2210114119

  Abstract

  American bullfrog (Rana castesbeiana) saxiphilin (RcSxph) is a high-affinity "toxin sponge" protein thought to prevent intoxication by saxitoxin (STX), a lethal bis-guanidinium neurotoxin that causes paralytic shellfish poisoning (PSP) by blocking voltage-gated sodium channels (NaVs). How specific RcSxph interactions contribute to STX binding has not been defined and whether other organisms have similar proteins is unclear. Here, we use mutagenesis, ligand binding, and structural studies to define the energetic basis of Sxph:STX recognition. The resultant STX "recognition code" enabled engineering of RcSxph to improve its ability to rescue NaVs from STX and facilitated discovery of 10 new frog and toad Sxphs. Definition of the STX binding code and Sxph family expansion among diverse anurans separated by ∼140 My of evolution provides a molecular basis for understanding the roles of toxin sponge proteins in toxin resistance and for developing novel proteins to sense or neutralize STX and related PSP toxins.

  View details for DOI 10.1073/pnas.2210114119

  View details for PubMedID 36279441

• Noninvasive Detection of Chemical Defenses in Poison Frogs Using the MasSpec Pen. ACS measurement science Au Krieger, A. C., Povilaitis, S. C., Gowda, P., O'Connell, L. A., Eberlin, L. S. 2022; 2 (5): 475-484

  Abstract

  Poison frogs are well-known for their fascinating ability to store alkaloids in their skin as chemical defense against predators. Chemical methods used to study these alkaloids are limited by requirements for euthanasia or stress during sampling. Here, we demonstrate sensitive and biocompatible alkaloid detection and monitoring in vivo using the MasSpec Pen, a handheld, noninvasive chemical detection device coupled to a mass spectrometer. The MasSpec Pen allowed rapid (<15 s), gentle, and consecutive molecular analysis without harm or undue stress to the animals. Through a month-long alkaloid-feeding study with the dyeing poison frog, we observed temporal dynamics of chemical sequestration in vivo by comparing frogs fed the alkaloid decahydroquinoline (DHQ) to vehicle-fed frogs. We also demonstrate the feasibility of the MasSpec Pen for the untargeted detection of rich alkaloid profiles from skin extracts of the Diablito poison frog, collected from two distinct geographical populations in Ecuador. The results obtained in this study demonstrate the utility of the MasSpec Pen for direct, rapid, and biocompatible analysis of poison frog alkaloids.

  View details for DOI 10.1021/acsmeasuresciau.2c00035

  View details for PubMedID 36281295

• Evidence that toxin resistance in poison birds and frogs is not rooted in sodium channel mutations and may rely on "toxin sponge'' proteins Abderemane-Ali, F., Rossen, N. D., Kobiela, M. E., Craig, R. Z., Garrison, C. E., Chen, Z., Colleran, C. M., O'Connell, L. A., Du Bois, J., Dumbacher, J. P., Minor, D. L. CELL PRESS. 2022: 25

  View details for Web of Science ID 000759523000117

• Aggressive but not reproductive boldness in male green anole lizards correlates with baseline vasopressin activity. Hormones and behavior Kabelik, D., Julien, A. R., Waddell, B. R., Batschelett, M. A., O'Connell, L. A. 1800; 140: 105109

  Abstract

  Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile3-vasopressin (VP, a.k.a., Arg8-vasotocin) signaling predispose boldness during social encounters. Boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. Vasopressin-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with boldness of aggressive behaviors, but not of reproductive behaviors. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of displayed aggression toward conspecifics by inhibiting behavioral output in these contexts.

  View details for DOI 10.1016/j.yhbeh.2022.105109

  View details for PubMedID 35066329

• Molecular physiology of pumiliotoxin sequestration in a poison frog. PloS one Alvarez-Buylla, A., Payne, C. Y., Vidoudez, C., Trauger, S. A., O'Connell, L. A. 2022; 17 (3): e0264540

  Abstract

  Poison frogs bioaccumulate alkaloids for chemical defense from their arthropod diet. Although many alkaloids are accumulated without modification, some poison frog species can metabolize pumiliotoxin (PTX 251D) into the more potent allopumiliotoxin (aPTX 267A). Despite extensive research characterizing the chemical arsenal of poison frogs, the physiological mechanisms involved in the sequestration and metabolism of individual alkaloids remain unclear. We first performed a feeding experiment with the Dyeing poison frog (Dendrobates tinctorius) to ask if this species can metabolize PTX 251D into aPTX 267A and what gene expression changes are associated with PTX 251D exposure in the intestines, liver, and skin. We found that D. tinctorius can metabolize PTX 251D into aPTX 267A, and that PTX 251D exposure changed the expression level of genes involved in immune system function and small molecule metabolism and transport. To better understand the functional significance of these changes in gene expression, we then conducted a series of high-throughput screens to determine the molecular targets of PTX 251D and identify potential proteins responsible for metabolism of PTX 251D into aPTX 267A. Although screens of PTX 251D binding human voltage-gated ion channels and G-protein coupled receptors were inconclusive, we identified human CYP2D6 as a rapid metabolizer of PTX 251D in a cytochrome P450 screen. Furthermore, a CYP2D6-like gene had increased expression in the intestines of animals fed PTX, suggesting this protein may be involved in PTX metabolism. These results show that individual alkaloids can modify gene expression across tissues, including genes involved in alkaloid metabolism. More broadly, this work suggests that specific alkaloid classes in wild diets may induce physiological changes for targeted accumulation and metabolism.

  View details for DOI 10.1371/journal.pone.0264540

  View details for PubMedID 35275922

• Long distance homing in the cane toad (Rhinella marina) in its native range. The Journal of experimental biology Shaykevich, D. A., Pasukonis, A., O'Connell, L. A. 1800

  Abstract

  Many animals exhibit complex navigation over different scales and environments. Navigation studies in amphibians have largely focused on species with life histories that require accurate spatial movements, such as territorial poison frogs and migratory pond-breeding amphibians that show fidelity to mating sites. However, other amphibian species have remained relatively understudied, leaving open the possibility that well-developed navigational abilities are widespread. Here, we measured short-term space use in non-territorial, non-migratory cane toads (Rhinella marina) in their native range in French Guiana. After establishing site fidelity, we tested their ability to return home following translocations of 500 and 1000 meters. Toads were able to travel in straight trajectories back to home areas, suggesting navigational abilities similar to those observed in amphibians with more complex spatial behavior. These observations break with the current paradigm of amphibian navigation and suggest that navigational abilities may be widely shared among amphibians.

  View details for DOI 10.1242/jeb.243048

  View details for PubMedID 34940881

• Evidence that toxin resistance in poison birds and frogs is not rooted in sodium channel mutations and may rely on "toxin sponge" proteins. The Journal of general physiology Abderemane-Ali, F., Rossen, N. D., Kobiela, M. E., Craig, R. A., Garrison, C. E., Chen, Z., Colleran, C. M., O'Connell, L. A., Du Bois, J., Dumbacher, J. P., Minor, D. L. 2021; 153 (9)

  Abstract

  Many poisonous organisms carry small-molecule toxins that alter voltage-gated sodium channel (NaV) function. Among these, batrachotoxin (BTX) from Pitohui poison birds and Phyllobates poison frogs stands out because of its lethality and unusual effects on NaV function. How these toxin-bearing organisms avoid autointoxication remains poorly understood. In poison frogs, a NaV DIVS6 pore-forming helix N-to-T mutation has been proposed as the BTX resistance mechanism. Here, we show that this variant is absent from Pitohui and poison frog NaVs, incurs a strong cost compromising channel function, and fails to produce BTX-resistant channels in poison frog NaVs. We also show that captivity-raised poison frogs are resistant to two NaV-directed toxins, BTX and saxitoxin (STX), even though they bear NaVs sensitive to both. Moreover, we demonstrate that the amphibian STX "toxin sponge" protein saxiphilin is able to protect and rescue NaVs from block by STX. Taken together, our data contradict the hypothesis that BTX autoresistance is rooted in the DIVS6 NT mutation, challenge the idea that ion channel mutations are a primary driver of toxin resistance, and suggest the possibility that toxin sequestration mechanisms may be key for protecting poisonous species from the action of small-molecule toxins.

  View details for DOI 10.1085/jgp.202112872

  View details for PubMedID 34351379

• Evolutionary insights into sexual behavior from whiptail lizards. Journal of experimental zoology. Part A, Ecological and integrative physiology O'Connell, L. A., Crews, D. 2021

  Abstract

  Is the brain bipotential or is sex-typical behavior determined during development? Thirty years of research in whiptail lizards transformed the field of behavioral neuroscience to show the brain is indeed bipotential, producing behaviors along a spectrum of male-typical and female-typical behavior via a parliamentary system of neural networks and not a predetermined program of constrained behavioral output. The unusual clade of whiptail lizards gave these insights as there are several parthenogenetic all-female species that display both male-typical and female-typical sexual behavior. These descendant species exist alongside their ancestors, allowing a unique perspective into how brain-behavior relationships evolve. In this review, we celebrate the over 40-year career of David Crews, beginning with the story of how he established whiptails as a model system through serendipitous behavioral observations and ending with advice to young scientists formulating their own questions. In between these personal notes, we discuss the discoveries that integrated hormones, neural activity, and gene expression to provide transformative insights into how brains function and reshaped our understanding of sexuality.

  View details for DOI 10.1002/jez.2467

  View details for PubMedID 33929097

• Rapid toxin sequestration modifies poison frog physiology. The Journal of experimental biology O'Connell, L. A., LS50: Integrated Science Laboratory Course, O'Connell, J. D., Paulo, J. A., Trauger, S. A., Gygi, S. P., Murray, A. W. 2021

  Abstract

  Poison frogs sequester chemical defenses from their diet of leaf litter arthropods for defense against predation. Little is known about the physiological adaptations that confer this unusual bioaccumulation ability. We conducted an alkaloid-feeding experiment with the Diablito poison frog (Oophaga sylvatica) to determine how quickly alkaloids are accumulated and how toxins modify frog physiology using quantitative proteomics. Diablito frogs rapidly accumulated the alkaloid decahydroquinoline within four days, and dietary alkaloid exposure altered protein abundance in the intestines, liver, and skin. Many proteins that increased in abundance with decahydroquinoline accumulation are plasma glycoproteins, including the complement system and the toxin-binding protein saxiphilin. Other protein classes that change in abundance with decahydroquinoline accumulation are membrane proteins involved in small molecule transport and metabolism. Overall, this work shows poison frogs can rapidly accumulate alkaloids, which alter carrier protein abundance, initiate an immune response, and alter small molecule transport and metabolism dynamics across tissues.

  View details for DOI 10.1242/jeb.230342

  View details for PubMedID 33408255

• The Parental Dilemma: How Evolution of Diverse Strategies for Infant Care Informs Social Behavior Circuits. Frontiers in neural circuits Autry, A. E., O'Connell, L. A. 2021; 15: 734474

  View details for DOI 10.3389/fncir.2021.734474

  View details for PubMedID 34867211

• Social boldness correlates with brain gene expression in male green anoles. Hormones and behavior Kabelik, D., Julien, A. R., Ramirez, D., O'Connell, L. A. 2021; 133: 105007

  Abstract

  Within populations, some individuals tend to exhibit a bold or shy social behavior phenotype relative to the mean. The neural underpinnings of these differing phenotypes - also described as syndromes, personalities, and coping styles - is an area of ongoing investigation. Although a social decision-making network has been described across vertebrate taxa, most studies examining activity within this network do so in relation to exhibited differences in behavioral expression. Our study instead focuses on constitutive gene expression in bold and shy individuals by isolating baseline gene expression profiles that influence social boldness predisposition, rather than those reflecting the results of social interaction and behavioral execution. We performed this study on male green anole lizards (Anolis carolinensis), an established model organism for behavioral research, which provides a crucial comparison group to investigations of birds and mammals. After identifying subjects as bold or shy through repeated reproductive and agonistic behavior testing, we used RNA sequencing to compare gene expression profiles between these groups within various forebrain, midbrain, and hindbrain regions. The ventromedial hypothalamus had the largest group differences in gene expression, with bold males having increased expression of neuroendocrine and neurotransmitter receptor and calcium channel genes compared to shy males. Conversely, shy males express more integrin alpha-10 in the majority of examined regions. There were no significant group differences in physiology or hormone levels. Our results highlight the ventromedial hypothalamus as an important center of behavioral differences across individuals and provide novel candidates for investigations into the regulation of individual variation in social behavior phenotype.

  View details for DOI 10.1016/j.yhbeh.2021.105007

  View details for PubMedID 34102460

• The skin microbiome facilitates adaptive tetrodotoxin production in poisonous newts. eLife Vaelli, P. M., Theis, K. R., Williams, J. E., O'Connell, L. A., Foster, J. A., Eisthen, H. L. 2020; 9

  Abstract

  Rough-skinned newts (Taricha granulosa) use tetrodotoxin (TTX) to block voltage-gated sodium (Nav) channels as a chemical defense against predation. Interestingly, newts exhibit extreme population-level variation in toxicity attributed to a coevolutionary arms race with TTX-resistant predatory snakes, but the source of TTX in newts is unknown. Here, we investigated whether symbiotic bacteria isolated from toxic newts could produce TTX. We characterized the skin-associated microbiota from a toxic and non-toxic population of newts and established pure cultures of isolated bacterial symbionts from toxic newts. We then screened bacterial culture media for TTX using LC-MS/MS and identified TTX-producing bacterial strains from four genera, including Aeromonas, Pseudomonas, Shewanella, and Sphingopyxis. Additionally, we sequenced the Nav channel gene family in toxic newts and found that newts expressed Nav channels with modified TTX binding sites, conferring extreme physiological resistance to TTX. This study highlights the complex interactions among adaptive physiology, animal-bacterial symbiosis, and ecological context.

  View details for DOI 10.7554/eLife.53898

  View details for PubMedID 32254021

• The plant terpenoid carvone is a chemotaxis repellent for C. elegans. microPublication. Biology Ellington, C., Hayden, A., LaGrange, Z., Luccioni, M., Osman, M., Ramlan, L., Vogt, M., Guha, S., Goodman, M., O'Connell, L. 2020; 2020

  View details for DOI 10.17912/micropub.biology.000231

  View details for PubMedID 32550506

• Multi-glomerular projection of single olfactory receptor neurons is conserved among amphibians. The Journal of comparative neurology Weiss, L., Jungblut, L. D., Pozzi, A. G., Zielinski, B. S., O'Connell, L. A., Hassenklover, T., Manzini, I. 2020

  Abstract

  Individual receptor neurons in the peripheral olfactory organ extend long axons into the olfactory bulb forming synapses with projection neurons in spherical neuropil regions, called glomeruli. Generally, odor map formation and odor processing in all vertebrates is based on the assumption that receptor neuron axons exclusively connect to a single glomerulus without any axonal branching. We comparatively tested this hypothesis in multiple fish and amphibian species (both sexes) by applying sparse cell electroporation to trace single olfactory receptor neuron axons. Sea lamprey (jawless fish) and zebrafish (bony fish) support the unbranched axon concept, with 94% of axons terminating in single glomeruli. Contrastingly, axonal projections of the axolotl (salamander) branch extensively before entering up to six distinct glomeruli. Receptor neuron axons labeled in frog species (Pipidae, Bufonidae, Hylidae and Dendrobatidae) predominantly bifurcate before entering a glomerulus and 59% and 50% connect to multiple glomeruli in larval and post-metamorphotic animals, respectively. Independent of developmental stage, lifestyle and adaptations to specific habitats, it seems to be a common feature of amphibian olfactory receptor neuron axons to frequently bifurcate and connect to multiple glomeruli. Our study challenges the unbranched axon concept as a universal vertebrate feature and it is conceivable that also later diverging vertebrates deviate from it. We propose that this unusual wiring logic evolved around the divergence of the terrestrial tetrapod lineage from its aquatic ancestors and could be the basis of an alternative way of odor processing. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/cne.24887

  View details for PubMedID 32080843

• Multiglomerular projections of single olfactory receptor neurons are a conserved and distinct feature of the amphibian olfactory system Weiss, L., Jungblut, L. D., Pozzi, A. G., Zielinski, B. S., O'Connell, L. A., Hassenkloever, T., Manzini, I. OXFORD UNIV PRESS. 2020: 122

  View details for Web of Science ID 000538788900015

• Studying convergent evolution to relate genotype to behavioral phenotype. The Journal of experimental biology Gallant, J. R., O'Connell, L. A. 2020; 223 (Pt Suppl 1)

  Abstract

  Neuroscience has a long, rich history in embracing unusual animals for research. Over the past several decades, there has been a technology-driven bottleneck in the species used for neuroscience research. However, an oncoming wave of technologies applicable to many animals hold promise for enabling researchers to address challenging scientific questions that cannot be solved using traditional laboratory animals. Here, we discuss how leveraging the convergent evolution of physiological or behavioral phenotypes can empower research mapping genotype to phenotype interactions. We present two case studies using electric fish and poison frogs and discuss how comparative work can teach us about evolutionary constraint and flexibility at various levels of biological organization. We also offer advice on the potential and pitfalls of establishing novel model systems in neuroscience research. Finally, we end with a discussion on the use of charismatic animals in neuroscience research and their utility in public outreach. Overall, we argue that convergent evolution frameworks can help identify generalizable principles of neuroscience.

  View details for DOI 10.1242/jeb.213447

  View details for PubMedID 32034050

• Prospects for sociogenomics in avian cooperative breeding and parental care. Current zoology Termignoni-Garcia, F. n., Louder, M. I., Balakrishnan, C. N., O'Connell, L. n., Edwards, S. V. 2020; 66 (3): 293–306

  Abstract

  For the last 40 years, the study of cooperative breeding (CB) in birds has proceeded primarily in the context of discovering the ecological, geographical, and behavioral drivers of helping. The advent of molecular tools in the early 1990s assisted in clarifying the relatedness of helpers to those helped, in some cases, confirming predictions of kin selection theory. Methods for genome-wide analysis of sequence variation, gene expression, and epigenetics promise to add new dimensions to our understanding of avian CB, primarily in the area of molecular and developmental correlates of delayed breeding and dispersal, as well as the ontogeny of achieving parental status in nature. Here, we outline key ways in which modern -omics approaches, in particular genome sequencing, transcriptomics, and epigenetic profiling such as ATAC-seq, can be used to add a new level of analysis of avian CB. Building on recent and ongoing studies of avian social behavior and sociogenomics, we review how high-throughput sequencing of a focal species or clade can provide a robust foundation for downstream, context-dependent destructive and non-destructive sampling of specific tissues or physiological states in the field for analysis of gene expression and epigenetics. -Omics approaches have the potential to inform not only studies of the diversification of CB over evolutionary time, but real-time analyses of behavioral interactions in the field or lab. Sociogenomics of birds represents a new branch in the network of methods used to study CB, and can help clarify ways in which the different levels of analysis of CB ultimately interact in novel and unexpected ways.

  View details for DOI 10.1093/cz/zoz057

  View details for PubMedID 32440290

  View details for PubMedCentralID PMC7233861

• Neural correlates of winning and losing fights in poison frog tadpoles. Physiology & behavior Fischer, E. K., Alvarez, H. n., Lagerstrom, K. M., McKinney, J. E., Petrillo, R. n., Ellis, G. n., O'Connell, L. A. 2020: 112973

  Abstract

  Aggressive competition for resources among juveniles is documented in many species, but the neural mechanisms regulating this behavior in young animals are poorly understood. In poison frogs, increased parental care is associated with decreased water volume of tadpole pools, resource limitation, and aggression. Indeed, the tadpoles of many poison frog species will attack, kill, and cannibalize other tadpoles. We examined the neural basis of conspecific aggression in Dyeing poison frog (Dendrobates tinctorius) tadpoles by comparing individuals that won aggressive encounters, lost aggressive encounters, or did not engage in a fight. We first compared patterns of generalized neural activity using immunohistochemical detection of phosphorylated ribosomes (pS6) as a proxy for neural activation associated with behavior. We found increased neural activity in the medial pallium and preoptic area of loser tadpoles, suggesting the amphibian homologs of the mammalian hippocampus and preoptic area may facilitate loser-associated behaviors. Nonapeptides (arginine vasotocin and mesotocin) and dopamine have been linked to aggression in other vertebrates and are located in the preoptic area. We next examined neural activity specifically in nonapeptide- and tyrosine-hydroxylase-positive cells using double-label immunohistochemistry. We found increased neural activity specifically in the preoptic area nonapeptide neurons of winners, whereas we found no differences in activity of dopaminergic cells among behavioral groups. Our findings suggest the neural correlates of aggression in poison frog tadpoles are similar to neural mechanisms mediating aggression in adults and juveniles of other vertebrate taxa.

  View details for DOI 10.1016/j.physbeh.2020.112973

  View details for PubMedID 32446779

• Gene expression correlates of social evolution in coral reef butterflyfishes. Proceedings. Biological sciences Nowicki, J. P., Pratchett, M. S., Walker, S. P., Coker, D. J., O'Connell, L. A. 2020; 287 (1929): 20200239

  Abstract

  Animals display remarkable variation in social behaviour. However, outside of rodents, little is known about the neural mechanisms of social variation, and whether they are shared across species and sexes, limiting our understanding of how sociality evolves. Using coral reef butterflyfishes, we examined gene expression correlates of social variation (i.e. pair bonding versus solitary living) within and between species and sexes. In several brain regions, we quantified gene expression of receptors important for social variation in mammals: oxytocin (OTR), arginine vasopressin (V1aR), dopamine (D1R, D2R) and mu-opioid (MOR). We found that social variation across individuals of the oval butterflyfish, Chaetodon lunulatus, is linked to differences in OTR,V1aR, D1R, D2R and MOR gene expression within several forebrain regions in a sexually dimorphic manner. However, this contrasted with social variation among six species representing a single evolutionary transition from pair-bonded to solitary living. Here, OTR expression within the supracommissural part of the ventral telencephalon was higher in pair-bonded than solitary species, specifically in males. These results contribute to the emerging idea that nonapeptide, dopamine and opioid signalling is a central theme to the evolution of sociality across individuals, although the precise mechanism may be flexible across sexes and species.

  View details for DOI 10.1098/rspb.2020.0239

  View details for PubMedID 32576103

• Conservation of Glomerular Organization in the Main Olfactory Bulb of Anuran Larvae. Frontiers in neuroanatomy Weiss, L., Jungblut, L. D., Pozzi, A. G., O'Connell, L. A., Hassenklover, T., Manzini, I. 2020; 14: 44

  Abstract

  The glomerular array in the olfactory bulb of many vertebrates is segregated into molecularly and anatomically distinct clusters linked to different olfactory functions. In anurans, glomerular clustering is so far only described in Xenopus laevis. We traced olfactory projections to the bulb in tadpoles belonging to six distantly related anuran species in four families (Pipidae, Hylidae, Bufonidae, Dendrobatidae) and found that glomerular clustering is remarkably conserved. The general bauplan consists of four unequally sized glomerular clusters with minor inter-species variation. During metamorphosis, the olfactory system undergoes extensive remodeling. Tracings in metamorphotic and juvenile Dendrobates tinctorius and Xenopus tropicalis suggest a higher degree of variation in the glomerular organization after metamorphosis is complete. Our study highlights, that the anatomical organization of glomeruli in the main olfactory bulb (MOB) is highly conserved, despite an extensive ecomorphological diversification among anuran tadpoles, which suggests underlying developmental constraints.

  View details for DOI 10.3389/fnana.2020.00044

  View details for PubMedID 32792916

• Frank Beach Award Winner: Lessons from poison frogs on ecological drivers of behavioral diversification. Hormones and behavior O'Connell, L. A. 2020: 104869

  Abstract

  Variation in natural behavior is tightly linked to the ecological resources with which they co-evolved. This review discusses poison frog behavior and neuroendocrinology to illustrate how ecological factors drive diversification of behavior and its underlying neural mechanisms. Poison frogs show tremendous diversity in reproductive strategies that are tightly linked to water resources in their environment. Different species utilize particular pool sizes to rear their offspring, which has selected for sex differences in parental behavior among poison frog species. Tadpole behavior reflects the behavioral diversity of adults, where tadpoles can display social group living or violent aggression and begging behavior, which are all associated with pool size and occupancy. Using this behavioral diversity among poison frog species, we have identified core brain regions, like the hippocampus and preoptic area, as being involved in regulating different aspects of amphibian parental behavior. In contrast to core brain regions, the neuromodulators governing these behaviors seem to be more labile across species. This work exemplifies how comparative studies are a prime experimental system to study how evolution tunes neural circuits that give rise to the diversity of behaviors we observe in the natural world. Finally, this review ends on a more important form of diversity - that of our scientific community - and how community outreach, decolonization of field based science, and inclusion of groups historically excluded from conducting research are needed for the scientific enterprise to transform into something truly beneficial for all members of our society.

  View details for DOI 10.1016/j.yhbeh.2020.104869

  View details for PubMedID 33039350

• Land use impacts poison frog chemical defenses through changes in leaf litter ant communities NEOTROPICAL BIODIVERSITY Moskowitz, N. A., Dorritie, B., Fay, T., Nieves, O. C., Vidoudez, C., Fischer, E. K., Trauger, S. A., Coloma, L. A., Donoso, D. A., O'Connell, L. A., Cambridge Rindge Latin 2017 Biol, Masconomet 2017 Biotechnology Clas 2020; 6 (1)

  View details for DOI 10.1080/23766808.2020.1744957

  View details for Web of Science ID 000528563300001

• Hormonal and neural correlates of care in active versus observing poison frog parents. Hormones and behavior Fischer, E. K., O'Connell, L. A. 2020: 104696

  Abstract

  The occasional reversal of sex-typical behavior suggests that many of the neural circuits underlying behavior are conserved between males and females and can be activated in response to the appropriate social condition or stimulus. Most poison frog species (Family Dendrobatidae) exhibit male uniparental care, but flexible compensation has been observed in some species, where females will take over parental care duties when males disappear. We investigated hormonal and neural correlates of sex-typical and sex-reversed parental care in a typically male uniparental species, the Dyeing Poison Frog (Dendrobates tinctorius). We first characterized hormone levels and whole brain gene expression across parental care stages during sex-typical care. Surprisingly, hormonal changes and brain gene expression differences associated with active parental behavior in males were mirrored in their non-caregiving female partners. To further explore the disconnect between neuroendocrine patterns and behavior, we characterized hormone levels and neural activity patterns in females performing sex-reversed parental care. In contrast to hormone and gene expression patterns, we found that patterns of neural activity were linked to the active performance of parental behavior, with sex-reversed tadpole transporting females exhibiting neural activity patterns more similar to those of transporting males than non-caregiving females. We suggest that parallels in hormones and brain gene expression in active and observing parents are related to females' ability to flexibly take over parental care in the absence of their male partners.

  View details for DOI 10.1016/j.yhbeh.2020.104696

  View details for PubMedID 31987899

• Bringing immersive science to undergraduate laboratory courses using CRISPR gene knockouts in frogs and butterflies. The Journal of experimental biology Martin, A. n., Wolcott, N. S., O'Connell, L. A. 2020; 223 (Pt Suppl 1)

  Abstract

  The use of CRISPR/Cas9 for gene editing offers new opportunities for biology students to perform genuine research exploring the gene-to-phenotype relationship. It is important to introduce the next generation of scientists, health practitioners and other members of society to the technical and ethical aspects of gene editing. Here, we share our experience leading hands-on undergraduate laboratory classes, where students formulate hypotheses regarding the roles of candidate genes involved in development, perform loss-of-function experiments using programmable nucleases and analyze the phenotypic effects of mosaic mutant animals. This is enabled by the use of the amphibian Xenopus laevis and the butterfly Vanessa cardui, two organisms that reliably yield hundreds of large and freshly fertilized eggs in a scalable manner. Frogs and butterflies also present opportunities to teach key biological concepts about gene regulation and development. To complement these practical aspects, we describe learning activities aimed at equipping students with a broad understanding of genome editing techniques, their application in fundamental and translational research, and the bioethical challenges they raise. Overall, our work supports the introduction of CRISPR technology into undergraduate classrooms and, when coupled with classroom undergraduate research experiences, enables hypothesis-driven research by undergraduates.

  View details for DOI 10.1242/jeb.208793

  View details for PubMedID 32034043

• Mechanisms of Convergent Egg Provisioning in Poison Frogs. Current biology : CB Fischer, E. K., Roland, A. B., Moskowitz, N. A., Vidoudez, C., Ranaivorazo, N., Tapia, E. E., Trauger, S. A., Vences, M., Coloma, L. A., O'Connell, L. A. 2019

  Abstract

  Parental provisioning of offspring with physiological products (nursing) occurs in many animals, yet little is known about the neuroendocrine basis of nursing in non-mammalian species. Within amphibians, maternal provisioning has evolved multiple times, with mothers of some species feeding unfertilized eggs to their developing offspring until tadpoles complete metamorphosis [1-3]. We conducted field studies in Ecuador and Madagascar to ask whether convergence at the behavioral level provides similar benefits to offspring and relies on shared neural mechanisms in dendrobatid and mantellid poison frogs. At an ecological level, we found that nursing allows poison frogs to provide chemical defenses to their tadpoles in both species. At the neural level, nursing was associated with increased activity in the lateral septum and preoptic area, demonstrating recruitment of shared brain regions in the convergent evolution of nursing within frogs and across vertebrates [4]. In contrast, only mantellids showed increased oxytocin neuron activity akin to that in nursing mammals [5], suggesting evolutionary versatility in molecular mechanisms. Our findings demonstrate that maternal provisioning provides similar potential benefits to offspring and relies on similar brain regions in poison frog species with convergently evolved toxicity and maternal care. VIDEO ABSTRACT.

  View details for DOI 10.1016/j.cub.2019.10.032

  View details for PubMedID 31761700

• The neural basis of tadpole transport in poison frogs. Proceedings. Biological sciences Fischer, E. K., Roland, A. B., Moskowitz, N. A., Tapia, E. E., Summers, K., Coloma, L. A., O'Connell, L. A. 2019; 286 (1907): 20191084

  Abstract

  Parental care has evolved repeatedly and independently across animals. While the ecological and evolutionary significance of parental behaviour is well recognized, underlying mechanisms remain poorly understood. We took advantage of behavioural diversity across closely related species of South American poison frogs (Family Dendrobatidae) to identify neural correlates of parental behaviour shared across sexes and species. We characterized differences in neural induction, gene expression in active neurons and activity of specific neuronal types in three species with distinct care patterns: male uniparental, female uniparental and biparental. We identified the medial pallium and preoptic area as core brain regions associated with parental care, independent of sex and species. The identification of neurons active during parental care confirms a role for neuropeptides associated with care in other vertebrates as well as identifying novel candidates. Our work is the first to explore neural and molecular mechanisms of parental care in amphibians and highlights the potential for mechanistic studies in closely related but behaviourally variable species to help build a more complete understanding of how shared principles and species-specific diversity govern parental care and other social behaviour.

  View details for DOI 10.1098/rspb.2019.1084

  View details for PubMedID 31311480

• Molecular physiology of chemical defenses in a poison frog. The Journal of experimental biology Caty, S. N., Alvarez-Buylla, A., Byrd, G. D., Vidoudez, C., Roland, A. B., Tapia, E. E., Budnik, B., Trauger, S. A., Coloma, L. A., O'Connell, L. A. 2019

  Abstract

  Poison frogs sequester small molecule lipophilic alkaloids from their diet of leaf litter arthropods for use as chemical defenses against predation. Although the dietary acquisition of chemical defenses in poison frogs is well-documented, the physiological mechanisms of alkaloid sequestration has not been investigated. Here, we used RNA sequencing and proteomics to determine how alkaloids impact mRNA or protein abundance in the Little Devil Frog (Oophaga sylvatica) and compared wild caught chemically defended frogs to laboratory frogs raised on an alkaloid-free diet. To understand how poison frogs move alkaloids from their diet to their skin granular glands, we focused on measuring gene expression in the intestines, skin, and liver. Across these tissues, we found many differentially expressed transcripts involved in small molecule transport and metabolism, as well as sodium channels and other ion pumps. We then used proteomic approaches to quantify plasma proteins, where we found several protein abundance differences between wild and laboratory frogs, including the amphibian neurotoxin binding protein saxiphilin. Finally, because many blood proteins are synthesized in the liver, we used thermal proteome profiling as an untargeted screen for soluble proteins that bind the alkaloid decahydroquinoline. Using this approach, we identified several candidate proteins that interact with this alkaloid, including saxiphilin. These transcript and protein abundance patterns suggest the presence of alkaloids influences frog physiology and that small molecule transport proteins may be involved in toxin bioaccumulation in dendrobatid poison frogs.

  View details for DOI 10.1242/jeb.204149

  View details for PubMedID 31138640

• Understanding the Loss of Maternal Care in Avian Brood Parasites Using Preoptic Area Transcriptome Comparisons in Brood Parasitic and Non-parasitic Blackbirds G3-GENES GENOMES GENETICS Lynch, K. S., O'Connell, L. A., Louder, M. M., Balakrishnan, C. N., Fischer, E. K. 2019; 9 (4): 1075–84

  View details for DOI 10.1534/g3.118.200992

  View details for Web of Science ID 000463929500011

• Understanding the Loss of Maternal Care in Avian Brood Parasites Using Preoptic Area Transcriptome Comparisons in Brood Parasitic and Non-parasitic Blackbirds. G3 (Bethesda, Md.) Lynch, K. S., O'Connell, L. A., Louder, M. I., Balakrishnan, C. N., Fischer, E. K. 2019

  Abstract

  Parental care is critical for offspring survival in many species. However, parental behaviors have been lost in roughly 1% of avian species known as the obligate brood parasites. To shed light on molecular and neurobiological mechanisms mediating brood parasitic behavior, we compared brain gene expression patterns between two brood parasitic species and one closely related non-parasitic Icterid (blackbird) species. Our analyses focused on gene expression changes specifically in the preoptic area (POA), a brain region known to play a critical role in parental behavior across vertebrates. Using comparative transcriptomic approaches, we identified gene expression patterns associated with brood parasitism. We evaluated three non-mutually exclusive alternatives for the evolution of brood parasitism: (1) retention of juvenile-like (neotenic) gene expression, (2) reduced expression of maternal care-related genes in the POA, and/or (3) increased expression of genes inhibiting maternal care. We find evidence for neotenic expression patterns in both species of parasitic cowbirds as compared to maternal, non-parasites. In addition, we observed differential expression in a number of genes with previously established roles in mediating maternal care. Together, these results provide the first insight into transcriptomic and genetics mechanisms underlying the loss of maternal behavior in avian brood parasites.

  View details for PubMedID 30760540

• Conserved transcriptomic profiles underpin monogamy across vertebrates PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Young, R. L., Ferkin, M. H., Ockendon-Powell, N. F., Orr, V. N., Phelps, S. M., Pogany, A., Richards-Zawacki, C. L., Summers, K., Szekely, T., Trainor, B. C., Urrutia, A. O., Zachar, G., O'Connell, L. A., Hofmann, H. A. 2019; 116 (4): 1331–36

  View details for DOI 10.1073/pnas.1813775116

  View details for Web of Science ID 000456336100039

• Conserved transcriptomic profiles underpin monogamy across vertebrates. Proceedings of the National Academy of Sciences of the United States of America Young, R. L., Ferkin, M. H., Ockendon-Powell, N. F., Orr, V. N., Phelps, S. M., Pogany, A., Richards-Zawacki, C. L., Summers, K., Szekely, T., Trainor, B. C., Urrutia, A. O., Zachar, G., O'Connell, L. A., Hofmann, H. A. 2019

  Abstract

  Social monogamy, typically characterized by the formation of a pair bond, increased territorial defense, and often biparental care, has independently evolved multiple times in animals. Despite the independent evolutionary origins of monogamous mating systems, several homologous brain regions and neuropeptides and their receptors have been shown to play a conserved role in regulating social affiliation and parental care, but little is known about the neuromolecular mechanisms underlying monogamy on a genomic scale. Here, we compare neural transcriptomes of reproductive males in monogamous and nonmonogamous species pairs of Peromyscus mice, Microtus voles, parid songbirds, dendrobatid frogs, and Xenotilapia species of cichlid fishes. We find that, while evolutionary divergence time between species or clades did not explain gene expression similarity, characteristics of the mating system correlated with neural gene expression patterns, and neural gene expression varied concordantly across vertebrates when species transition to monogamy. Our study provides evidence of a universal transcriptomic mechanism underlying the evolution of monogamy in vertebrates.

  View details for PubMedID 30617061

• Evolution of affiliation: patterns of convergence from genomes to behaviour. Philosophical transactions of the Royal Society of London. Series B, Biological sciences Fischer, E. K., Nowicki, J. P., O'Connell, L. A. 2019; 374 (1777): 20180242

  Abstract

  Affiliative behaviours have evolved many times across animals. Research on the mechanisms underlying affiliative behaviour demonstrates remarkable convergence across species spanning wide evolutionary distances. Shared mechanisms have been identified with genomic approaches analysing genetic variants and gene expression differences as well as neuroendocrine and molecular approaches exploring the role of hormones and signalling molecules. We review the genomic and neural basis of pair bonding and parental care across diverse taxa to shed light on mechanistic patterns that underpin the convergent evolution of affiliative behaviour. We emphasize that mechanisms underlying convergence in complex phenotypes like affiliation should be evaluated on a continuum, where signatures of convergence may vary across levels of biological organization. In particular, additional comparative studies within and across major vertebrate lineages will be essential in resolving when and why shared neural substrates are repeatedly targeted in the independent evolution of affiliation, and how similar mechanisms are evolutionarily tuned to give rise to species-specific variations in behaviour. This article is part of the theme issue 'Convergent evolution in the genomics era: new insights and directions'.

  View details for DOI 10.1098/rstb.2018.0242

  View details for PubMedID 31154971

• Diversity within diversity: Parasite species richness in poison frogs assessed by transcriptomics MOLECULAR PHYLOGENETICS AND EVOLUTION Santos, J. C., Tarvin, R. D., O'Connell, L. A., Blackburn, D. C., Coloma, L. A. 2018; 125: 40–50

  Abstract

  Symbionts (e.g., endoparasites and commensals) play an integral role in their host's ecology, yet in many cases their diversity is likely underestimated. Although endoparasites are traditionally characterized using morphology, sequences of conserved genes, and shotgun metagenomics, host transcriptomes constitute an underused resource to identify these organisms' diversity. By isolating non-host transcripts from host transcriptomes, individual host tissues can now simultaneously reveal their endoparasite species richness (i.e., number of different taxa) and provide insights into parasite gene expression. These approaches can be used in host taxa whose endoparasites are mostly unknown, such as those of tropical amphibians. Here, we focus on the poison frogs (Dendrobatidae) as hosts, which are a Neotropical clade known for their bright coloration and defensive alkaloids. These toxins are an effective protection against vertebrate predators (e.g., snakes and birds), bacteria, and skin-biting ectoparasites (e.g., mosquitoes); however, little is known about their deterrence against eukaryotic endoparasites. With de novo transcriptomes of dendrobatids, we developed a bioinformatics pipeline for endoparasite identification that uses host annotated RNA-seq data and set of a priori parasite taxonomic terms, which are used to mine for specific endoparasites. We found a large community of helminths and protozoans that were mostly restricted to the digestive tract and a few systemic parasites (e.g., Trypanosoma). Contrary to our expectations, all dendrobatid frogs regardless of the presence of alkaloid defenses have endoparasites, with their highest species richness located in the frog digestive tract. Some of these organisms (e.g., roundworms) might prove to be generalists, as they were not found to be co-diversifying with their frog hosts. We propose that endoparasites may escape poison frogs' chemical defenses by colonizing tissues with fewer alkaloids than the frog's skin, where most toxins are stored.

  View details for PubMedID 29551526

• Protection from UV light is an evolutionarily conserved feature of the haematopoietic niche NATURE Kapp, F. G., Perlin, J. R., Hagedorn, E. J., Gansner, J. M., Schwarz, D. E., O'Connell, L. A., Johnson, N. S., Amemiya, C., Fisher, D. E., Woelfle, U., Trompouki, E., Niemeyer, C. M., Driever, W., Zon, L. I. 2018; 558 (7710): 445-+

  Abstract

  Haematopoietic stem and progenitor cells (HSPCs) require a specific microenvironment, the haematopoietic niche, which regulates HSPC behaviour1,2. The location of this niche varies across species, but the evolutionary pressures that drive HSPCs to different microenvironments remain unknown. The niche is located in the bone marrow in adult mammals, whereas it is found in other locations in non-mammalian vertebrates, for example, in the kidney marrow in teleost fish. Here we show that a melanocyte umbrella above the kidney marrow protects HSPCs against ultraviolet light in zebrafish. Because mutants that lack melanocytes have normal steady-state haematopoiesis under standard laboratory conditions, we hypothesized that melanocytes above the stem cell niche protect HSPCs against ultraviolet-light-induced DNA damage. Indeed, after ultraviolet-light irradiation, unpigmented larvae show higher levels of DNA damage in HSPCs, as indicated by staining of cyclobutane pyrimidine dimers and have reduced numbers of HSPCs, as shown by cmyb (also known as myb) expression. The umbrella of melanocytes associated with the haematopoietic niche is highly evolutionarily conserved in aquatic animals, including the sea lamprey, a basal vertebrate. During the transition from an aquatic to a terrestrial environment, HSPCs relocated into the bone marrow, which is protected from ultraviolet light by the cortical bone around the marrow. Our studies reveal that melanocytes above the haematopoietic niche protect HSPCs from ultraviolet-light-induced DNA damage in aquatic vertebrates and suggest that during the transition to terrestrial life, ultraviolet light was an evolutionary pressure affecting the location of the haematopoietic niche.

  View details for PubMedID 29899448

• Circuit Architecture Underlying Distinct Components of Parental Care TRENDS IN NEUROSCIENCES Fischer, E. K., O'Connell, L. A. 2018; 41 (6): 334–36

  Abstract

  Parental care is a key evolutionary innovation that influences the fitness of parents and offspring. How the brain coordinates such a complex behavior remains poorly understood. Kohl and colleagues recently uncovered the organizational principles of hypothalamic galanin neurons and their connections in mice. Their findings revealed a striking picture in which discrete neuronal pools control distinct aspects of parental behavior.

  View details for PubMedID 29685403

• Variation in social systems within Chaetodon butterflyfishes, with special reference to pair bonding PLOS ONE Nowicki, J. P., O'Connell, L. A., Cowman, P. F., Walker, S. W., Coker, D. J., Pratchett, M. S. 2018; 13 (4): e0194465

  Abstract

  For many animals, affiliative relationships such as pair bonds form the foundation of society and are highly adaptive. Animal systems amenable for comparatively studying pair bonding are important for identifying underlying biological mechanisms, but mostly exist in mammals. Better establishing fish systems will enable comparison of pair bonding mechanisms across taxonomically distant lineages that may reveal general underlying mechanistic principles. We examined the utility of wild butterflyfishes (f: Chaetodontidae; g: Chaetodon) for comparatively studying pair bonding. Using stochastic character mapping, we provide the first analysis of the evolutionary history of butterflyfish sociality, revealing that pairing is ancestral, with at least seven independent transitions to gregarious grouping and solitary behavior since the late Miocene. We then formally verified social systems in six sympatric and wide-spread species representing a clade with one ancestrally reconstructed transition from paired to solitary grouping at Lizard Island, Australia. In situ observations of the size, selective affiliation and aggression, fidelity, and sex composition of social groups confirmed that Chaetodon baronessa, C. lunulatus, and C. vagabundus are predominantly pair bonding, whereas C. rainfordi, C. plebeius, and C. trifascialis are predominantly solitary. Even in the predominantly pair bonding species, C. lunulatus, a proportion of adults (15%) are solitary. Importantly, inter- and intra-specific differences in social systems do not co-vary with other previously established attributes, including parental care. Hence, the proposed butterflyfish populations are promising for inter- and intra-species comparative analyses of pair bonding and its mechanistic underpinnings. Avenues for further developing the system are proposed, including determining whether the aforementioned utility of these species applies across their geographic disruptions.

  View details for PubMedID 29641529

• Seasonal changes in diet and chemical defense in the Climbing Mantella frog (Mantella laevigata). PloS one Moskowitz, N. A., Roland, A. B., Fischer, E. K., Ranaivorazo, N., Vidoudez, C., Aguilar, M. T., Caldera, S. M., Chea, J., Cristus, M. G., Crowdis, J. P., DeMessie, B., desJardins-Park, C. R., Effenberger, A. H., Flores, F., Giles, M., He, E. Y., Izmaylov, N. S., Lee, C. C., Pagel, N. A., Phu, K. K., Rosen, L. U., Seda, D. A., Shen, Y., Vargas, S., Murray, A. W., Abebe, E., Trauger, S. A., Donoso, D. A., Vences, M., O'Connell, L. A. 2018; 13 (12): e0207940

  Abstract

  Poison frogs acquire chemical defenses from the environment for protection against potential predators. These defensive chemicals are lipophilic alkaloids that are sequestered by poison frogs from dietary arthropods and stored in skin glands. Despite decades of research focusing on identifying poison frog alkaloids, we know relatively little about how environmental variation and subsequent arthropod availability impacts alkaloid loads in poison frogs. We investigated how seasonal environmental variation influences poison frog chemical profiles through changes in the diet of the Climbing Mantella (Mantella laevigata). We collected M. laevigata females on the Nosy Mangabe island reserve in Madagascar during the wet and dry seasons and tested the hypothesis that seasonal differences in rainfall is associated with changes in diet composition and skin alkaloid profiles of M. laevigata. The arthropod diet of each frog was characterized into five groups (i.e. ants, termites, mites, insect larvae, or 'other') using visual identification and cytochrome oxidase 1 DNA barcoding. We found that frog diet differed between the wet and dry seasons, where frogs had a more diverse diet in the wet season and consumed a higher percentage of ants in the dry season. To determine if seasonality was associated with variation in frog defensive chemical composition, we used gas chromatography / mass spectrometry to quantify alkaloids from individual skin samples. Although the assortment of identified alkaloids was similar across seasons, we detected significant differences in the abundance of certain alkaloids, which we hypothesize reflects seasonal variation in the diet of M. laevigata. We suggest that these variations could originate from seasonal changes in either arthropod leaf litter composition or changes in frog behavioral patterns. Although additional studies are needed to understand the consequences of long-term environmental shifts, this work suggests that alkaloid profiles are relatively robust against short-term environmental perturbations.

  View details for PubMedID 30586404

• Y Radiation of the polymorphic Little Devil poison frog (Oophaga sylvatica) in Ecuador ECOLOGY AND EVOLUTION Roland, A. B., Santos, J. C., Carriker, B. C., Caty, S. N., Tapia, E. E., Coloma, L. A., O'Connell, L. A. 2017; 7 (22): 9750–62

  View details for DOI 10.1002/ece3.3503

  View details for Web of Science ID 000415900800046

• Interacting amino acid replacements allow poison frogs to evolve epibatidine resistance SCIENCE Tarvin, R. D., Borghese, C. M., Sachs, W., Santos, J. C., Lu, Y., O'Connell, L. A., Cannatell, D. C., Harris, R., Zakon, H. H. 2017; 357 (6357): 1261–65

  Abstract

  Animals that wield toxins face self-intoxication. Poison frogs have a diverse arsenal of defensive alkaloids that target the nervous system. Among them is epibatidine, a nicotinic acetylcholine receptor (nAChR) agonist that is lethal at microgram doses. Epibatidine shares a highly conserved binding site with acetylcholine, making it difficult to evolve resistance yet maintain nAChR function. Electrophysiological assays of human and frog nAChR revealed that one amino acid replacement, which evolved three times in poison frogs, decreased epibatidine sensitivity but at a cost of acetylcholine sensitivity. However, receptor functionality was rescued by additional amino acid replacements that differed among poison frog lineages. Our results demonstrate how resistance to agonist toxins can evolve and that such genetic changes propel organisms toward an adaptive peak of chemical defense.

  View details for PubMedID 28935799

  View details for PubMedCentralID PMC5834227

• Developmental morphology of granular skin glands in pre-metamorphic egg-eating poison frogs ZOOMORPHOLOGY Stynoski, J. L., O'Connell, L. A. 2017; 136 (2): 219–24

  View details for DOI 10.1007/s00435-017-0344-0

  View details for Web of Science ID 000401009200005

• Modification of feeding circuits in the evolution of social behavior JOURNAL OF EXPERIMENTAL BIOLOGY Fischer, E. K., O'Connell, L. A. 2017; 220 (1): 92–102

  Abstract

  Adaptive trade-offs between foraging and social behavior intuitively explain many aspects of individual decision-making. Given the intimate connection between social behavior and feeding/foraging at the behavioral level, we propose that social behaviors are linked to foraging on a mechanistic level, and that modifications of feeding circuits are crucial in the evolution of complex social behaviors. In this Review, we first highlight the overlap between mechanisms underlying foraging and parental care and then expand this argument to consider the manipulation of feeding-related pathways in the evolution of other complex social behaviors. We include examples from diverse taxa to highlight that the independent evolution of complex social behaviors is a variation on the theme of feeding circuit modification.

  View details for DOI 10.1242/jeb.143859

  View details for Web of Science ID 000392151400012

  View details for PubMedID 28057832

• Ant and Mite Diversity Drives Toxin Variation in the Little Devil Poison Frog JOURNAL OF CHEMICAL ECOLOGY McGugan, J. R., Byrd, G. D., Roland, A. B., Caty, S. N., Kabir, N., Tapia, E. E., Trauger, S. A., Coloma, L. A., O'Connell, L. A. 2016; 42 (6): 537–51

  Abstract

  Poison frogs sequester chemical defenses from arthropod prey, although the details of how arthropod diversity contributes to variation in poison frog toxins remains unclear. We characterized skin alkaloid profiles in the Little Devil poison frog, Oophaga sylvatica (Dendrobatidae), across three populations in northwestern Ecuador. Using gas chromatography/mass spectrometry, we identified histrionicotoxins, 3,5- and 5,8-disubstituted indolizidines, decahydroquinolines, and lehmizidines as the primary alkaloid toxins in these O. sylvatica populations. Frog skin alkaloid composition varied along a geographical gradient following population distribution in a principal component analysis. We also characterized diversity in arthropods isolated from frog stomach contents and confirmed that O. sylvatica specialize on ants and mites. To test the hypothesis that poison frog toxin variability reflects species and chemical diversity in arthropod prey, we (1) used sequencing of cytochrome oxidase 1 to identify individual prey specimens, and (2) used liquid chromatography/mass spectrometry to chemically profile consumed ants and mites. We identified 45 ants and 9 mites in frog stomachs, including several undescribed species. We also showed that chemical profiles of consumed ants and mites cluster by frog population, suggesting different frog populations have access to chemically distinct prey. Finally, by comparing chemical profiles of frog skin and isolated prey items, we traced the arthropod source of four poison frog alkaloids, including 3,5- and 5,8-disubstituted indolizidines and a lehmizidine alkaloid. Together, the data show that toxin variability in O. sylvatica reflects chemical diversity in arthropod prey.

  View details for PubMedID 27318689

• Convergent Substitutions in a Sodium Channel Suggest Multiple Origins of Toxin Resistance in Poison Frogs MOLECULAR BIOLOGY AND EVOLUTION Tarvin, R. D., Santos, J. C., O'Connell, L. A., Zakon, H. H., Cannatella, D. C. 2016; 33 (4): 1068–81

  Abstract

  Complex phenotypes typically have a correspondingly multifaceted genetic component. However, the genotype-phenotype association between chemical defense and resistance is often simple: genetic changes in the binding site of a toxin alter how it affects its target. Some toxic organisms, such as poison frogs (Anura: Dendrobatidae), have defensive alkaloids that disrupt the function of ion channels, proteins that are crucial for nerve and muscle activity. Using protein-docking models, we predict that three major classes of poison frog alkaloids (histrionicotoxins, pumiliotoxins, and batrachotoxins) bind to similar sites in the highly conserved inner pore of the muscle voltage-gated sodium channel, Nav1.4. We predict that poison frogs are somewhat resistant to these compounds because they have six types of amino acid replacements in the Nav1.4 inner pore that are absent in all other frogs except for a distantly related alkaloid-defended frog from Madagascar, Mantella aurantiaca. Protein-docking models and comparative phylogenetics support the role of these replacements in alkaloid resistance. Taking into account the four independent origins of chemical defense in Dendrobatidae, phylogenetic patterns of the amino acid replacements suggest that 1) alkaloid resistance in Nav1.4 evolved independently at least seven times in these frogs, 2) variation in resistance-conferring replacements is likely a result of differences in alkaloid exposure across species, and 3) functional constraint shapes the evolution of the Nav1.4 inner pore. Our study is the first to demonstrate the genetic basis of autoresistance in frogs with alkaloid defenses.

  View details for PubMedID 26782998

• Lenomyrmex hoelldobleri: a new ant species discovered in the stomach of the dendrobatid poison frog, Oophaga sylvatica (Funkhouser) ZOOKEYS Rabeling, C., Sosa-Calvo, J., O'Connell, L. A., Coloma, L. A., Fernandez, F. 2016: 79–95

  Abstract

  The ant genus Lenomyrmex was recently discovered and described from mid to high elevation rainforests in southern Central and northwestern South America. Lenomyrmex currently consists of six described species, which are only rarely collected. Here, we add a new species, Lenomyrmex hoelldoblerisp. n., which was discovered in a stomach content sample of the dendrobatid frog, Oophaga sylvatica, from northwestern Ecuador. Lenomyrmex hoelldobleri can be distinguished from other species in the genus by the presence of a well-developed petiolar node, whereas in all other species the node of the petiole is ill-defined. In addition to the shape of the petiolar node, Lenomyrmex hoelldobleri can be distinguished from the morphologically similar Lenomyrmex costatus by (i) the presence of the metanotal suture, (ii) the direction of the striae on dorsum of propodeum (concentrically transverse in Lenomyrmex hoelldobleri, longitudinal in Lenomyrmex costatus), (iii) the finely striate dorsum of postpetiole, (iv) its larger size, and (v) distinctly darker coloration. We also describe the gyne of Lenomyrmex foveolatus. This collection record from northwestern Ecuador extends the geographic distribution of Lenomyrmex foveolatus 400 km south from its previous record in Colombia. A revised taxonomic key to the workers and gynes of all described Lenomyrmex species is provided. We discuss the taxonomic relationship of Lenomyrmex hoelldobleri to other species in the genus and its biology based on the limited information that is currently available. Finally, we briefly discuss the feeding ecology of dendrobatid poison frogs in the context of providing a valuable source of rarely collected and cryptic new ant species.

  View details for DOI 10.3897/zookeys.618.9692

  View details for Web of Science ID 000383377300005

  View details for PubMedID 27853401

  View details for PubMedCentralID PMC5102051

• Poison frogs as a model system for studying the neurobiology of parental care CURRENT OPINION IN BEHAVIORAL SCIENCES Roland, A. B., O'Connell, L. A. 2015; 6: 76–81

  View details for DOI 10.1016/j.cobeha.2015.10.002

  View details for Web of Science ID 000218452000013

• Social odors conveying dominance and reproductive information induce rapid physiological and neuromolecular changes in a cichlid fish BMC GENOMICS Simoes, J. M., Barata, E. N., Harris, R. M., O'Connell, L. A., Hofmann, H. A., Oliveira, R. F. 2015; 16: 114

  Abstract

  Social plasticity is a pervasive feature of animal behavior. Animals adjust the expression of their social behavior to the daily changes in social life and to transitions between life-history stages, and this ability has an impact in their Darwinian fitness. This behavioral plasticity may be achieved either by rewiring or by biochemically switching nodes of the neural network underlying social behavior in response to perceived social information. Independent of the proximate mechanisms, at the neuromolecular level social plasticity relies on the regulation of gene expression, such that different neurogenomic states emerge in response to different social stimuli and the switches between states are orchestrated by signaling pathways that interface the social environment and the genotype. Here, we test this hypothesis by characterizing the changes in the brain profile of gene expression in response to social odors in the Mozambique Tilapia, Oreochromis mossambicus. This species has a rich repertoire of social behaviors during which both visual and chemical information are conveyed to conspecifics. Specifically, dominant males increase their urination frequency during agonist encounters and during courtship to convey chemical information reflecting their dominance status.We recorded electro-olfactograms to test the extent to which the olfactory epithelium can discriminate between olfactory information from dominant and subordinate males as well as from pre- and post-spawning females. We then performed a genome-scale gene expression analysis of the olfactory bulb and the olfactory cortex homolog in order to identify the neuromolecular systems involved in processing these social stimuli.Our results show that different olfactory stimuli from conspecifics' have a major impact in the brain transcriptome, with different chemical social cues eliciting specific patterns of gene expression in the brain. These results confirm the role of rapid changes in gene expression in the brain as a genomic mechanism underlying behavioral plasticity and reinforce the idea of an extensive transcriptional plasticity of cichlid genomes, especially in response to rapid changes in their social environment.

  View details for PubMedID 25766511

• Neural control of maternal and paternal behaviors SCIENCE Dulac, C., O'Connell, L. A., Wu, Z. 2014; 345 (6198): 765–70

  Abstract

  Parental care, including feeding and protection of young, is essential for the survival as well as mental and physical well-being of the offspring. A large variety of parental behaviors has been described across species and sexes, raising fascinating questions about how animals identify the young and how brain circuits drive and modulate parental displays in males and females. Recent studies have begun to uncover a striking antagonistic interplay between brain systems underlying parental care and infant-directed aggression in both males and females, as well as a large range of intrinsic and environmentally driven neural modulation and plasticity. Improved understanding of the neural control of parental interactions in animals should provide novel insights into the complex issue of human parental care in both health and disease.

  View details for DOI 10.1126/science.1253291

  View details for Web of Science ID 000340593100034

  View details for PubMedID 25124430

  View details for PubMedCentralID PMC4230532

• Evolutionary Development of Neural Systems in Vertebrates and Beyond JOURNAL OF NEUROGENETICS O'Connell, L. A. 2013; 27 (3): 69–85

  Abstract

  The emerging field of "neuro-evo-devo" is beginning to reveal how the molecular and neural substrates that underlie brain function are based on variations in evolutionarily ancient and conserved neurochemical and neural circuit themes. Comparative work across bilaterians is reviewed to highlight how early neural patterning specifies modularity of the embryonic brain, which lays a foundation on which manipulation of neurogenesis creates adjustments in brain size. Small variation within these developmental mechanisms contributes to the evolution of brain diversity. Comparing the specification and spatial distribution of neural phenotypes across bilaterians has also suggested some major brain evolution trends, although much more work on profiling neural connections with neurochemical specificity across a wide diversity of organisms is needed. These comparative approaches investigating the evolution of brain form and function hold great promise for facilitating a mechanistic understanding of how variation in brain morphology, neural phenotypes, and neural networks influences brain function and behavioral diversity across organisms.

  View details for DOI 10.3109/01677063.2013.789511

  View details for Web of Science ID 000324257300002

  View details for PubMedID 23745795

• Sex differences and similarities in the neuroendocrine regulation of social behavior in an African cichlid fish HORMONES AND BEHAVIOR O'Connell, L. A., Ding, J. H., Hofmann, H. A. 2013; 64 (3): 468–76

  Abstract

  An individual's position in a social hierarchy profoundly affects behavior and physiology through interactions with community members, yet little is known about how the brain contributes to status differences between and within the social states or sexes. We aimed to determine sex-specific attributes of social status by comparing circulating sex steroid hormones and neural gene expression of sex steroid receptors in dominant and subordinate male and female Astatotilapia burtoni, a highly social African cichlid fish. We found that testosterone and 17β-estradiol levels are higher in males regardless of status and dominant individuals regardless of sex. Progesterone was found to be higher in dominant individuals regardless of sex. Based on pharmacological manipulations in males and females, progesterone appears to be a common mechanism for promoting courtship in dominant individuals. We also examined expression of androgen receptors, estrogen receptor α, and the progesterone receptor in five brain regions that are important for social behavior. Most of the differences in brain sex steroid receptor expression were due to sex rather than status. Our results suggest that the parvocellular preoptic area is a core region for mediating sex differences through androgen and estrogen receptor expression, whereas the progesterone receptor may mediate sex and status behaviors in the putative homologs of the nucleus accumbens and ventromedial hypothalamus. Overall our results suggest sex differences and similarities in the regulation of social dominance by gonadal hormones and their receptors in the brain.

  View details for DOI 10.1016/j.yhbeh.2013.07.003

  View details for Web of Science ID 000325735800007

  View details for PubMedID 23899762

• Prostaglandin F2 alpha facilitates female mating behavior based on male performance BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY Kidd, M. R., Dijkstra, P. D., Alcott, C., Lavee, D., Ma, J., O'Connell, L. A., Hofmann, H. A. 2013; 67 (8): 1307–15

  View details for DOI 10.1007/s00265-013-1559-9

  View details for Web of Science ID 000321964800011

• Neuroendocrine Mechanisms Underlying Sensory Integration of Social Signals JOURNAL OF NEUROENDOCRINOLOGY O'Connell, L. A., Rigney, M. M., Dykstra, D. W., Hofmann, H. A. 2013; 25 (7): 644–54

  Abstract

  Individuals integrate information about their environment into adaptive behavioural responses, yet how different sensory modalities contribute to these decisions and where in the brain this integration occurs is not well understood. We presented male cichlid fish (Astatotilapia burtoni) with sensory information in three social contexts: intruder challenge, reproductive opportunity and a socially neutral situation. We then measured behavioural and hormonal responses along with induction of the immediate early gene c-Fos in candidate forebrain regions. In the intruder challenge context, males were exposed to either a visual stimulus of a dominant male, the putative male pheromone androstenedione, or both. We found that, compared to the neutral context, a visual stimulus was necessary and sufficient for an aggressive response, whereas both chemical and visual stimuli were needed for an androgen response. In the reproductive opportunity context, males were exposed to either a visual stimulus of a receptive female, a progesterone metabolite (female pheromone) only, or both. We further found that the visual stimulus is necessary and sufficient for an androgen response in the reproductive opportunity context. In the brain, we observed c-Fos induction in response to a visual challenge stimulus specifically in dopaminergic neurones of area Vc (the central region of the ventral telencephalon), a putative striatal homologue, whereas presentation of a chemical stimulus did not induce c-Fos induction in the intruder challenge context. Our results suggest that different sensory cues are processed in a social context-specific manner as part of adaptive decision-making processes.

  View details for DOI 10.1111/jne.12045

  View details for Web of Science ID 000320402900006

  View details for PubMedID 23631684

• Aromatase regulates aggression in the African cichlid fish Astatotilapia burtoni. Physiology & behavior Huffman, L. S., O'Connell, L. A., Hofmann, H. A. 2013; 112-113: 77-83

  Abstract

  The roles of estrogen and androgens in male social behavior are well studied, but little is known about how these hormones contribute to behavior in a social hierarchy. Here we test the role of aromatase, the enzyme that converts testosterone into estradiol, in mediating aggression and reproductive behavior in male Astatotilapia burtoni, an African cichlid fish that displays remarkable plasticity in social behavior. We first measured aromatase expression in subordinate and dominant males in brain regions that regulate social behavior and found that subordinate males have higher aromatase expression than dominant males in the magnocellular and gigantocellular regions of the preoptic area. Next, we functionally tested the role of aromatase in regulating behavior by intraperitoneally injecting dominant males with either saline or fadrozole (FAD), an aromatase inhibitor, and found that FAD treatment decreases aggressive, but not reproductive, behaviors compared to saline controls. To determine the underlying physiological and molecular consequences of FAD treatment, we measured estradiol and testosterone levels from plasma and brain aromatase expression in FAD and saline treated dominant males. We found that estradiol levels decreased and testosterone levels increased in response to FAD treatment. Moreover, FAD treated males had increased aromatase expression in the gigantocellular portion of the POA, possibly a compensatory response. Overall, our results suggest aromatase is a key enzyme that promotes aggression in A. burtoni males through actions in the preoptic area.

  View details for DOI 10.1016/j.physbeh.2013.02.004

  View details for PubMedID 23438371

• Female preference for males depends on reproductive physiology in the African cichlid fish Astatotilapia burtoni GENERAL AND COMPARATIVE ENDOCRINOLOGY Kidd, M. R., O'Connell, L. A., Kidd, C. E., Chen, C. W., Fontenot, M. R., Williams, S. J., Hofmann, H. A. 2013; 180: 56–63

  Abstract

  Mate choice is fundamental to sexual selection, yet little is known about underlying physiological mechanisms that influence female mating decisions. We investigated the endocrine underpinnings of female mate choice in the African cichlid Astatotilapia burtoni, a non-seasonal breeder. In addition to profiling behavioral and hormonal changes across the female reproductive cycle, we tested two hypotheses regarding possible factors influencing female mate choice. We first asked whether female mate choice is influenced by male visual and/or chemical cues. A. burtoni females were housed for one full reproductive cycle in the center of a dichotomous choice apparatus with a large (attractive) or small (unattractive) conspecific male on either side. Females associated mostly with small, less attractive males, but on the day of spawning reversed their preference to large, attractive males, with whom they mated almost exclusively, although this choice depended on the relative amount of androgens released into the water by small males. We next asked whether male behavior or androgen levels change in relation to the stimulus females' reproductive state. We found that stimulus male aggression decreased and reproductive displays increased as the day of spawning approached. Moreover male testosterone levels changed throughout the females' reproductive cycle, with larger males releasing more testosterone into the water than small males. Our data suggest that female association in a dichotomous choice assay is only indicative of the actual mate choice on the day of spawning. Furthermore, we show that male behavior and hormone levels are dependent on the reproductive state of conspecific females.

  View details for DOI 10.1016/j.ygcen.2012.10.014

  View details for Web of Science ID 000313535400008

  View details for PubMedID 23168085

• Neurochemical profiling of dopaminergic neurons in the forebrain of a cichlid fish, Astatotilapia burtoni JOURNAL OF CHEMICAL NEUROANATOMY O'Connell, L. A., Fontenot, M. R., Hofmann, H. A. 2013; 47: 106–15

  Abstract

  Across vertebrates, the mesolimbic reward system is a highly conserved neural network that serves to evaluate the salience of environmental stimuli, with dopamine as the neurotransmitter most relevant to its function. Although brain regions in the dopaminergic reward system have been well characterized in mammals, homologizing these brain areas with structures in teleosts has been controversial, especially for the mesencephalo-diencephalic dopaminergic cell populations. Here we examine the neurochemical profile of five dopaminergic cell groups (Vc, POA, PPr, TPp, pTn) in the model cichlid Astatotilapia burtoni to better understand putative homology relationships between teleosts and mammals. We characterized in the adult brain the expression patterns of three genes (etv5, nr4a2, and pitx3) that either specify dopaminergic cell fate or maintain dopaminergic cell populations. We then determined whether these genes are expressed in dopaminergic cells. We find many striking similarities in these gene expression profiles between dopaminergic cell populations in teleosts and their putative mammalian homologs. Our results suggest that many of these dopaminergic cell groups are indeed evolutionarily ancient and conserved across vertebrates.

  View details for DOI 10.1016/j.jchemneu.2012.12.007

  View details for Web of Science ID 000315549900012

  View details for PubMedID 23295359

• Androgens coordinate neurotransmitter-related gene expression in male whiptail lizards GENES BRAIN AND BEHAVIOR O'Connell, L. A., Mitchell, M. M., Hofmann, H. A., Crews, D. 2012; 11 (7): 813–18

  Abstract

  Sex steroid hormones coordinate neurotransmitter systems in the male brain to facilitate sexual behavior. Although neurotransmitter release in the male brain has been well documented, little is known about how androgens orchestrate changes in gene expression of neurotransmitter receptors. We used male whiptail lizards (Cnemidophorus inornatus) to investigate how androgens alter neurotransmitter-related gene expression in brain regions involved in social decision making. We focused on three neurotransmitter systems involved in male-typical sexual behavior, including the N-methyl-d-aspartate (NMDA) glutamate receptor, nitric oxide and dopamine receptors. Here, we show that in androgen-treated males, there are coordinated changes in neurotransmitter-related gene expression. In androgen-implanted castrates compared with blank-implanted castrates (control group), we found associated increases in neuronal nitric oxide synthase gene expression in the nucleus accumbens (NAcc), preoptic area and ventromedial hypothalamus, a decrease of NR1 gene expression (obligate subunit of NMDA receptors) in the medial amygdaloid area and NAcc and a decrease in D1 and D2 dopamine receptor gene expression in the NAcc. Our results support and expand the current model of androgen-mediated gene expression changes of neurotransmitter-related systems that facilitate sexual behavior in males. This also suggests that the proposed evolutionarily ancient reward system that reinforces sexual behavior in amniote vertebrates extends to reptiles.

  View details for DOI 10.1111/j.1601-183X.2012.00828.x

  View details for Web of Science ID 000309753600007

  View details for PubMedID 22862958

  View details for PubMedCentralID PMC3467320

• Distribution of nonapeptide systems in the forebrain of an African cichlid fish, Astatotilapia burtoni JOURNAL OF CHEMICAL NEUROANATOMY Huffman, L. S., O'Connell, L. A., Kenkel, C. D., Kline, R. J., Khan, I. A., Hofmann, H. A. 2012; 44 (2): 86-97

  Abstract

  Nonapeptides and their receptors have important functions in mediating social behavior across vertebrates. Where these nonapeptides are synthesized in the brain has been studied extensively in most vertebrate lineages, yet we know relatively little about the neural distribution of nonapeptide receptors outside of mammals. As nonapeptides play influential roles in behavioral regulation in all vertebrates, including teleost fish, we mapped the distributions of the receptors for arginine vasotocin (AVT; homolog of arginine vasopressin) and isotocin (IST; homolog of oxytocin/mesotocin) throughout the forebrain of Astatotilapia burtoni, an African cichlid fish with behavioral phenotypes that are plastic and reversible based on the immediate social environment. We characterized the distribution of the AVT V1a2 receptor (V1aR) and the IST receptor (ITR) using both immunohistochemistry for protein detection and in situ hybridization for mRNA detection, as well as AVT and IST using immunohistochemistry. Expression of the neuropeptide receptors was widely distributed throughout the fore- and midbrain, including the proposed teleost homologs of the mammalian amygdala complex, striatum, hypothalamus, and ventral tegmental area. We conclude that although the location of nonapeptide synthesis is restricted compared to tetrapod vertebrates, the distribution of nonapeptide receptors is highly conserved across taxa. Our results significantly extend our knowledge of where nonapeptides act in the brains of teleosts to mediate social transitions and behavior.

  View details for DOI 10.1016/j.jchemneu.2012.05.002

  View details for Web of Science ID 000307151800004

  View details for PubMedID 22668656

• Evolution of a Vertebrate Social Decision-Making Network SCIENCE O'Connell, L. A., Hofmann, H. A. 2012; 336 (6085): 1154–57

  Abstract

  Animals evaluate and respond to their social environment with adaptive decisions. Revealing the neural mechanisms of such decisions is a major goal in biology. We analyzed expression profiles for 10 neurochemical genes across 12 brain regions important for decision-making in 88 species representing five vertebrate lineages. We found that behaviorally relevant brain regions are remarkably conserved over 450 million years of evolution. We also find evidence that different brain regions have experienced different selection pressures, because spatial distribution of neuroendocrine ligands are more flexible than their receptors across vertebrates. Our analysis suggests that the diversity of social behavior in vertebrates can be explained, in part, by variations on a theme of conserved neural and gene expression networks.

  View details for DOI 10.1126/science.1218889

  View details for Web of Science ID 000304647900048

  View details for PubMedID 22654056

• Isotocin regulates paternal care in a monogamous cichlid fish HORMONES AND BEHAVIOR O'Connell, L. A., Matthews, B. J., Hofmann, H. A. 2012; 61 (5): 725–33

  Abstract

  While the survival value of paternal care is well understood, little is known about its physiological basis. Here we investigate the neuroendocrine contributions to paternal care in the monogamous cichlid, Amatitlania nigrofasciata. We first explored the dynamic range of paternal care in three experimental groups: biparental males (control fathers housed with their mate), single fathers (mate removed), or lone males (mate and offspring removed). We found that control males gradually increase paternal care over time, whereas single fathers increased care immediately after mate removal. Males with offspring present had lower levels of circulating 11-ketotestosterone (11-KT) yet still maintained aggressive displays toward brood predators. To determine what brain regions may contribute to paternal care, we quantified induction of the immediate early gene c-Fos, and found that single fathers have more c-Fos induction in the forebrain area Vv (putative lateral septum homologue), but not in the central pallium (area Dc). While overall preoptic area c-Fos induction was similar between groups, we found that parvocellular preoptic isotocin (IST) neurons in single fathers showed increased c-Fos induction, suggesting IST may facilitate the increase of paternal care after mate removal. To functionally test the role of IST in regulating paternal care, we treated biparental males with an IST receptor antagonist, which blocked paternal care. Our results indicate that isotocin plays a significant role in promoting paternal care, and more broadly suggest that the convergent evolution of paternal care across vertebrates may have recruited similar neuroendocrine mechanisms.

  View details for DOI 10.1016/j.yhbeh.2012.03.009

  View details for Web of Science ID 000304339800009

  View details for PubMedID 22498693

• Rising StARs: Behavioral, hormonal, and molecular responses to social challenge and opportunity HORMONES AND BEHAVIOR Huffman, L. S., Mitchell, M. M., O'Connell, L. A., Hofmann, H. A. 2012; 61 (4): 631-641

  Abstract

  Across taxa, individuals must respond to a dynamic social environment of challenges and opportunities on multiple biological levels, including behavior, hormone profiles, and gene expression. We investigated the response to a complex social environment including both territorial challenges and reproductive opportunities in the African cichlid fish Astatotilapia burtoni (Burton's mouthbrooder), a species well-known for its phenotypic plasticity. Male A. burtoni are either socially dominant or subordinate and can transition between the two phenotypes. We used this transition to simultaneously study changes in aggression, reproductive behavior, testosterone and estradiol levels, gonadal histology, and testes expression of three genes involved in testosterone synthesis. We have found that males immediately become aggressive and increase testosterone levels when they become dominant in this paradigm of challenge and opportunity. Reproductive behavior and estradiol increase slightly later but are also up-regulated within 24h. Increases in steroid hormone levels are accompanied by an increase in expression of steroidogenic acute regulatory protein (StAR), the rate-limiting enzyme during testosterone synthesis, as well as an increase in testis maturation as measured by histological organization. Reproductive behavior was found to correlate with female gravidity, suggesting that males were able to perceive reproductive opportunity. Our study demonstrates the rapid plasticity at multiple levels of biological organization that animals can display in response to changes in their complex social environment.

  View details for DOI 10.1016/j.yhbeh.2012.02.016

  View details for Web of Science ID 000302763700023

  View details for PubMedID 22373495

• Social Status Predicts How Sex Steroid Receptors Regulate Complex Behavior across Levels of Biological Organization ENDOCRINOLOGY O'Connell, L. A., Hofmann, H. A. 2012; 153 (3): 1341–51

  Abstract

  Social status strongly affects behavior and physiology, in part mediated by gonadal hormones, although how each sex steroid acts across levels of biological organization is not well understood. We examine the role of sex steroids in modulating social behavior in dominant (DOM) and subordinate (SUB) males of a highly social fish, Astatotilapia burtoni. We first used agonists and antagonists to each sex steroid receptor and found that androgens and progestins modulate courtship behavior only in DOM, whereas estrogens modulate aggressive behavior independent of social status. We then examined the hormonal and physiological responses to sex steroid receptor antagonist treatment and uncovered substantial changes in circulating steroid hormone levels and gonad size only in SUB, not in DOM. Consistent with status-based physiological sensitivities to drug manipulation, we found that neuropeptide and steroid receptor gene expression in the preoptic area was sensitive only in SUB. However, when we compared the transcriptomes of males that received either vehicle or an estrogen receptor antagonist, 8.25% of all genes examined changed expression in DOM in comparison with only 0.56% in SUB. Finally, we integrate behavior, physiology, and brain gene expression to infer functional modules that underlie steroid receptor regulation of behavior. Our work suggests that environmentally induced changes at one level of biological organization do not simply affect changes of similar magnitude at other levels, but that instead very few key pathways likely serve as conduits for executing plastic responses across multiple levels.

  View details for DOI 10.1210/en.2011-1663

  View details for Web of Science ID 000300645600038

  View details for PubMedID 22166981

• The Vertebrate mesolimbic reward system and social behavior network: A comparative synthesis JOURNAL OF COMPARATIVE NEUROLOGY O'Connell, L. A., Hofmann, H. A. 2011; 519 (18): 3599–3639

  Abstract

  All animals evaluate the salience of external stimuli and integrate them with internal physiological information into adaptive behavior. Natural and sexual selection impinge on these processes, yet our understanding of behavioral decision-making mechanisms and their evolution is still very limited. Insights from mammals indicate that two neural circuits are of crucial importance in this context: the social behavior network and the mesolimbic reward system. Here we review evidence from neurochemical, tract-tracing, developmental, and functional lesion/stimulation studies that delineates homology relationships for most of the nodes of these two circuits across the five major vertebrate lineages: mammals, birds, reptiles, amphibians, and teleost fish. We provide for the first time a comprehensive comparative analysis of the two neural circuits and conclude that they were already present in early vertebrates. We also propose that these circuits form a larger social decision-making (SDM) network that regulates adaptive behavior. Our synthesis thus provides an important foundation for understanding the evolution of the neural mechanisms underlying reward processing and behavioral regulation.

  View details for DOI 10.1002/cne.22735

  View details for Web of Science ID 000297010700001

  View details for PubMedID 21800319

• The distribution of an AVT V1a receptor in the brain of a sex changing fish, Epinephelus adscensionis JOURNAL OF CHEMICAL NEUROANATOMY Kline, R. J., O'Connell, L. A., Hofmann, H. A., Holt, G., Khan, I. A. 2011; 42 (1): 72–88

  Abstract

  The present study describes the distribution of an arginine vasotocin (AVT) V1a receptor (AVTr) throughout the brain of a sex-changing grouper, rock hind Epinephelus adscensionis. The objectives of this study were to describe the AVTr distribution in the brain of rock hind for potential linkages of the AVT hormone system with sex-specific behaviors observed in this species and to examine sex-specific differences that might exist. An antibody was designed for rock hind AVTr against the deduced amino acid sequence for the third intracellular loop. Protein expression, identified with immunohistochemistry showed high concordance with mRNA expression, identified with in situ hybridization. AVTr protein and mRNA expression was widely distributed throughout the brain, indicating that AVT may act as a neuromodulator via this V1a receptor subtype. AVTr protein and mRNA were present in regions associated with behavior, reproduction and spatial learning, as well as sensory functions such as vision, olfaction and lateral line sensory processing. We observed high AVTr expression in granular cell formations in the internal cellular layer of olfactory bulbs, torus longitudinalis, granular layer of the corpus cerebellum, valvula of the cerebellum, nuclei of the lateral and posterior recesses, and granular eminence. High protein and mRNA expression was also observed in the preoptic area, anterior hypothalamus, and habenular nucleus. No obvious sex differences were noted in any region of the rock hind brain.

  View details for DOI 10.1016/j.jchemneu.2011.06.005

  View details for Web of Science ID 000295149200008

  View details for PubMedID 21723386

• Genes, hormones, and circuits: An integrative approach to study the evolution of social behavior FRONTIERS IN NEUROENDOCRINOLOGY O'Connell, L. A., Hofmann, H. A. 2011; 32 (3): 320–35

  Abstract

  Tremendous progress has been made in our understanding of the ultimate and proximate mechanisms underlying social behavior, yet an integrative evolutionary analysis of its underpinnings has been difficult. In this review, we propose that modern genomic approaches can facilitate such studies by integrating four approaches to brain and behavior studies: (1) animals face many challenges and opportunities that are ecologically and socially equivalent across species; (2) they respond with species-specific, yet quantifiable and comparable approach and avoidance behaviors; (3) these behaviors in turn are regulated by gene modules and neurochemical codes; and (4) these behaviors are governed by brain circuits such as the mesolimbic reward system and the social behavior network. For each approach, we discuss genomic and other studies that have shed light on various aspects of social behavior and its underpinnings and suggest promising avenues for future research into the evolution of neuroethological systems.

  View details for DOI 10.1016/j.yfrne.2010.12.004

  View details for Web of Science ID 000293726400004

  View details for PubMedID 21163292

• Neural distribution of the nuclear progesterone receptor in the tungara frog, Physalaemus pustulosus JOURNAL OF CHEMICAL NEUROANATOMY O'Connell, L. A., Ding, J. H., Ryan, M. J., Hofmann, H. A. 2011; 41 (3): 137–47

  Abstract

  The gonadal steroid hormone progesterone plays an important role across all vertebrates in mediating female reproductive physiology and behavior. Many effects of progesterone are mediated by a nuclear progesterone receptor (PR), which is crucial for integration of external signals and internal physiological cues in the brain to produce an appropriate behavioral output. The túngara frog, Physalaemus pustulosus, is an excellent model system for the study of mechanisms by which sensory signals, such as auditory communication, are processed within neural circuits where mate choice decisions are made. To establish a framework for studying the neural basis of mate choice and social behavior in this species, we first describe the cytoarchitecture of the brain using Nissl-stained sections. Then, in order to better understand where progesterone acts to regulate social decisions, we determined the distribution of PR protein throughout the brain of P. pustulosus by immunohistochemistry. We found PR immunoreactivity in key brain regions known to modulate the processing of auditory cues and social behavior in other vertebrates. Due to its widespread distribution, PR likely also plays important roles in non-limbic brain regions that mediate non-social information processing. Further, we have colocalized PR with tyrosine hydroxylase, providing a functional context for the role of progesterone in mediating motivation and motor behavior. Our results significantly extend our understanding of hormonal modulation in the anuran brain and support the important role of the nuclear progesterone receptor in modulating female mate choice and receptivity in amphibians and across vertebrates.

  View details for DOI 10.1016/j.jchemneu.2011.01.002

  View details for Web of Science ID 000289700900002

  View details for PubMedID 21256209

• Neuronal Nitric Oxide Synthase as a Substrate for the Evolution of Pseudosexual Behaviour in a Parthenogenetic Whiptail Lizard JOURNAL OF NEUROENDOCRINOLOGY O'Connell, L. A., Matthews, B. J., Crews, D. 2011; 23 (3): 244–53

  Abstract

  The evolution of neuroendocrine mechanisms governing sex-typical behaviour is poorly understood. An outstanding animal model is the whiptail lizard (Cnemidophorus) because both the ancestral and descendent species still exist. The ancestral little striped whiptail, Cnemidophorus inornatus, consists of males and females, which exhibit sex-specific mating behaviours. The descendent desert grassland whiptail, Cnemidophorus uniparens, consists only of females that alternately exhibit both female-like and male-like pseudosexual behaviour. Castrated male C. inornatus will mount a conspecific in response to exogenous androgen, although some are also sensitive to progesterone. This polymorphism in progesterone sensitivity in the ancestral species may have been involved in evolution of progesterone-mediated male-typical behaviour in the descendant unisexual lizards. We tested whether progesterone activates a typically androgenic signalling pathway by investigating hormonal regulation of neuronal nitric oxide synthase (nNOS) using in situ hybridisation and NADPH diaphorase histochemistry, a stain for nNOS protein. NADPH diaphorase is widely distributed throughout the brain of both species, although only in the periventricular nucleus of the preoptic area (pvPOA) are there differences between mounting and non-mounting individuals. The number of cells expressing nNOS mRNA and NADPH diaphorase is higher in the pvPOA of individuals that mount in response to progesterone or androgen. Furthermore, the nNOS promoter has both androgen and progesterone response elements, and NADPH diaphorase colocalises with the progesterone receptor in the pvPOA. These data suggest that a polymorphism in progesterone sensitivity in the sexual ancestor reflects a differential regulation of nNOS and may account for the male-typical behaviour in unisexual whiptail lizards.

  View details for DOI 10.1111/j.1365-2826.2010.02099.x

  View details for Web of Science ID 000288105000006

  View details for PubMedID 21126273

  View details for PubMedCentralID PMC4509676

• Molecular characterization and brain distribution of the progesterone receptor in whiptail lizards GENERAL AND COMPARATIVE ENDOCRINOLOGY O'Connell, L. A., Matthews, B. J., Patel, S. B., O'Connell, J. D., Crews, D. 2011; 171 (1): 64–74

  Abstract

  Progesterone and its nuclear receptor are critical in modulating reproductive physiology and behavior in female and male vertebrates. Whiptail lizards (genus Cnemidophorus) are an excellent model system in which to study the evolution of sexual behavior, as both the ancestral and descendent species exist. Male-typical sexual behavior is mediated by progesterone in both the ancestral species and the descendant all-female species, although the molecular characterization and distribution of the progesterone receptor protein throughout the reptilian brain is not well understood. To better understand the gene targets and ligand binding properties of the progesterone receptor in whiptails, we cloned the promoter and coding sequence of the progesterone receptor and analyzed the predicted protein structure. We next determined the distribution of the progesterone receptor protein and mRNA throughout the brain of Cnemidophorus inornatus and Cnemidophorus uniparens by immunohistochemistry and in situ hybridization. We found the progesterone receptor to be present in many brain regions known to regulate social behavior and processing of stimulus salience across many vertebrates, including the ventral tegmental area, amygdala, nucleus accumbens and several hypothalamic nuclei. Additionally, we quantified immunoreactive cells in the preoptic area and ventromedial hypothalamus in females of both species and males of the ancestral species. We found differences between both species and across ovarian states. Our results significantly extend our understanding of progesterone modulation in the reptilian brain and support the important role of the nuclear progesterone receptor in modulating sexual behavior in reptiles and across vertebrates.

  View details for DOI 10.1016/j.ygcen.2010.12.010

  View details for Web of Science ID 000287769800008

  View details for PubMedID 21185292

  View details for PubMedCentralID PMC3041865

• Characterization of the Dopaminergic System in the Brain of an African Cichlid Fish, Astatotilapia burtoni JOURNAL OF COMPARATIVE NEUROLOGY O'Connell, L. A., Fontenot, M. R., Hofmann, H. A. 2011; 519 (1): 75–92

  Abstract

  Catecholamines, such as dopamine, are evolutionarily ancient neurotransmitters that play an essential role in mediating behavior. In vertebrates, dopamine is central to the nigrostriatal motor and mesolimbic reward systems. Despite its importance, the distribution of the dopaminergic system has not been well studied in the teleost brain. The African cichlid fish Astatotilapia burtoni has become an important model system in social neuroscience and lends itself to uncovering how social decisions are implemented in the brain. To understand better where dopamine acts to regulate social behavior in this species, we have determined the distribution of putative dopaminergic cells and fibers (by tyrosine hydroxylase immunohistochemistry) and dopamine receptors (by in situ hybridization for the D(1A) and D(2) dopamine receptor subtypes) throughout the forebrain and part of the mesencephalon of A. burtoni. Tyrosine hydroxylase immunoreactivity was evident in several regions of the fore- and midbrain, in support of putative homologies to tetrapods. Additionally, the D(1A) and D(2) receptors were identified in brain regions known to modulate social behavior in other vertebrates, including the proposed teleost homologues of the mammalian amygdalar complex, hippocampus, striatum, preoptic area, anterior hypothalamus, ventromedial hypothalamus, and ventral tegmental area/substantia nigra pars compacta. Tyrosine hydroxylase-immunoreactive fibers as well as D(1A) and D(2) receptor expression overlap almost completely in their distribution. These results significantly extend our understanding of the distribution of the dopaminergic system in the teleost brain and suggest a conserved role of dopamine in modulating behavior across vertebrates.

  View details for DOI 10.1002/cne.22506

  View details for Web of Science ID 000285310100007

  View details for PubMedID 21120929

• Characterization of the Dopamine System in the Brain of the Tungara Frog, Physalaemus pustulosus BRAIN BEHAVIOR AND EVOLUTION O'Connell, L. A., Matthews, B. J., Ryan, M. J., Hofmann, H. A. 2010; 76 (3-4): 211–25

  Abstract

  Dopamine is an evolutionarily ancient neurotransmitter that plays an essential role in mediating behavior. In vertebrates, dopamine is central to the mesolimbic reward system, a neural network concerned with the valuation of stimulus salience, and to the nigrostriatal motor system and hypothalamic nuclei involved in the regulation of locomotion and social behavior. In amphibians, dopaminergic neurons have been mapped out in several species, yet the distribution of dopaminoreceptive cells is unknown. The túngara frog, Physalaemus pustulosus, is an excellent model system for the study of neural mechanisms by which valuations of stimuli salience and social decisions are made, especially in the context of mate choice. In order to better understand where dopamine acts to regulate social decisions in this species, we have determined the distribution of putative dopaminergic cells (using tyrosine hydroxylase immunohistochemistry) and cells receptive to dopaminergic signaling (using DARPP-32 immunohistochemistry) throughout the brain of P. pustulosus. The distribution of dopaminergic cells was comparable to other anurans. DARPP-32 immunoreactivity was identified in key brain regions known to modulate social behavior in other vertebrates including the proposed anuran homologues of the mammalian amygdalar complex, nucleus accumbens, hippocampus, striatum, preoptic area, anterior hypothalamus, ventromedial hypothalamus, and ventral tegmental area/substantia nigra pars compacta. Due to its widespread distribution, DARPP-32 likely also plays many roles in non-limbic brain regions that mediate non-social information processing. These results significantly extend our understanding of the distribution of the dopaminergic system in the anuran brain and beyond.

  View details for DOI 10.1159/000321715

  View details for Web of Science ID 000286661000007

  View details for PubMedID 21099197