Session 48: Herpetology Morphology, Histology, & MicrobesRoom: Ballroom 111B2022-07-31 13:30 - 14:45 |
| Moderator: Alessandro Catenazzi |
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1. 13:30 Spatiotemporal and Ontogenetic Variation, Microbial Selection, and Predicted Antifungal Function in the Skin-Associated Microbiome of a Rocky Mountain Amphibian. Kenen Goodwin*, Utah State University; Jaren Hutchinson*, Utah State University; Zachariah Gompert, Utah State University urodelan@gmail.com
Host-associated microbiomes play important roles in host health and pathogen defense. In amphibians, the skin-associated microbiome serves as an innate immune defense with potential implications for disease management. Few studies have examined season-long temporal variation in the amphibian skin-associated microbiome, and the interactions between bacteria and fungi on amphibian skin remain poorly understood. We characterize season-long temporal variation in the skin-associated microbiome of the western tiger salamander (Ambystoma mavortium) for both bacteria and fungi between sites and across salamander life stages. 207 skin-associated microbiome samples were collected from salamanders at two Rocky Mountain lakes throughout the summer and fall of 2018, and 127 additional microbiome samples were collected from lake water and lake substrate. We used 16S and ITS next-generation sequencing data with Bayesian Dirichlet-multinomial regression to determine the relative abundances of bacterial and fungal taxa, test for differential abundance, examine microbial selection, and derive alpha and beta diversity. The antifungal function of bacterial communities was predicted using stochastic character mapping and a database of antifungal bacterial isolates. We examined microbial absolute abundances using Bayesian negative binomial LASSO coupled with synthetic gene spike-ins. For both bacteria and fungi, we observed variation in community composition through time, between sites, and with salamander age and life stage. We found salamander skin to be selective for microbes, with many taxa disproportionately represented relative to the environment, and we observed selection for predicted antifungal bacteria. Ultimately, this ecological knowledge may assist in the conservation of amphibian species threatened by chytridiomycosis and other emerging diseases. |
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2. 13:45 Epidermal Glands and Chemical Communication in Lizards: Novel Gland System and an Emerging Research Program. André L. G. Carvalho*, University of Washington; Adriana M. Jeckel, University of Bern; Carolina Nisa, Universidade de São Paulo; María Celeste Luna, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’; Carla Piantoni, Universidade de São Paulo; Matthew K. Fujita, University of Texas; Adam D. Leaché, University of Washington andreluizherpeto@gmail.com
Chemical signaling enabled by epidermal glands is an important component of communication systems of lizards. Our analysis of the South American lizard family Tropiduridae confirmed that a glandular tissue lays underneath ventral flash marks of at least 39 species with diverse ecological habits distributed in forested and open landscapes. To test the hypothesis that this structure represents a novel glandular organ, we analyzed the structural and ultra-structural organization and protein profile of skin samples of species from four genera. As hypothesized, the tropidurid gland represents a novel type of generation gland—named “?-gland”—that emerged in the ancestor of Uracentron, Plica, Strobilurus, Eurolophosaurus, and Tropidurus. We are currently investigating the convergent evolution of epidermal glands in the Lizard-Tree-of-Life, while jointly characterizing their diversity and exploring their function in chemical signaling across groups. Combining transcriptomics, comparative phylogenetics, ultrastructural imaging, and mass spectrometry of chemical compounds, we seek to elucidate the genetic and structural mechanisms behind chemical signaling. Surprisingly, the genetic machinery of epidermal glands remained completely unexplored until now. We are exploring the origins of multiple epidermal glands types and correlations between the evolution of chemo-signals and environmental and ecological parameters through the comparative analysis of South American, African, and North American lizard groups. Our investigation challenges the general view about epidermal gland homology, suggesting that the gland types (generation and follicular) analyzed thus far are much more related functionally and evolutionarily than previously thought. |
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3. 14:00 Automated 3D morphometrics of alligator lizards. Simon Scarpetta*, University of California Berkeley; Peter Kloess, University of California Berkeley scas100@berkeley.edu
Alligator lizards (Squamata: Gerrhonotinae) comprise a well-known clade that inhabits forest, grassland, and chaparral environments in the USA, Mexico, and Central America. Historically, researchers encountered difficulty detecting osteological differences between alligator lizard genera. More recently, researchers examined qualitative variation and established phylogenetically informative characters in the skulls of alligator lizards using x-ray computed tomography (XRCT), but cranial osteology has not yet been quantified across the skull using a morphometric approach. We leveraged automated 3D geometric morphometrics (Auto3Dgm) to quantitatively examine variation in the skulls of alligator lizards in the skull, cranium, and mandible, and across genera, species, and putative ecomorphs. In particular, we were interested in determining whether terrestrial and arboreal species of Abronia, which were previously recognized as separate genera, occupied similar or different regions of morphospace. We found that arboreal species of Abronia occupy a cranial and mandibular morphospace that does not overlap with other alligator lizards. Surprisingly, we also found that the terrestrial species of Abronia cluster close to the arboreal Abronia in the cranial and skull morphospace rather than with other, terrestrial alligator lizards. Among other alligator lizards, we found broad overlap between Elgaria, Barisia, Desertum, and Gerrhonotus. Species pairs within these genera often clustered together, however, and some individual analyses separated species of Barisia and Desertum from other alligator lizards. Our results support the utility of Auto3Dgm for disentangling variation in closely related and morphologically conservative groups and appear to indicate both ecological and phylogenetic controls on skull morphology in alligator lizards. |
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4. 14:15 Coevolution of male and female genitalia in Helicops pastazae using 3D morphometrics. Daniela Garcia Cobos*, Instituto Humboldt; Diego A. Gomez-Sanchez, Reserva Natural Rey Zamuro; Patricia LR Brennan, Mount Holyoke College pbrennan@mtholyoke.edu
Squamates are known for variation in male genital morphology. Variation in the vaginal pouch is known, but is less studied. Here we report on out observations of the shape of the genitalia in adult female and male Helicops pastazae, a semiaquatic snake native to the neotropics that is becoming well known in recent years. We collected 22 females and 20 males that were near of above reproductive SVL. We made models of the lumen of the female vaginal pouch, and inflated and removed both male hemipenes before preserving them. We generated 3D models of the pouch and are working towards completing the hemipene models. The vaginal pouch is divided in three chambers, the proctodeum is separated by a deep groove from two urodeal chambers that continue cranially into separate structures, while the oviducal connection is lateral to these chambers. In smaller females the connection between the procotodeum and urodeum is closed, whereas in larger females, the connection opens. When this occurs, often is a single side that opens first. Examination of the hemipenes shows that their apical portion has close correspondence with the shape of the urodeal chambers, while the rest of the hemipene would fit in the proctodeum. Even in small males the hemipenes are well developed, but the spines in the shaft are softer in smaller males. When this work is completed we will have quantified allometric shape changes in the vaginal pouch and hemipene, as well as measure covariation associated with copulatory function and hemipene asymmetry. |