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    P2: Herpetology: Physiology

    2021-07-27   16:00 - 18:00

    To view the posters go to You will be able to chat one-on-one during the Tuesday poster session, the e-poster platform.

    1.  16:00  Day vs. Night: LPS Effects on Immunity, Splenic Cytokines mRNA, and Hormone Mediators in Toads. Stefanny Titon, University of São Paulo; Braz Titon Jr, University of São Paulo; Aymam Figueiredo, University of São Paulo; Felipe Floreste*, University of São Paulo; Alan Lima, University of São Paulo; Fernando Gomes, University of São Paulo; Vania Assis, University of São Paulo

    Recently, the lipopolysaccharide (LPS)-induced immune-endocrine interactions and their implications have been demonstrated in amphibians. However, how the daily variation impacts immune-endocrine alterations remains to be further explored. In this study, we stimulated Rhinella icterica toads with LPS during the day (10 am) or night (10 pm) and analyzed the immune response (plasma bacterial killing ability - BKA, phagocytosis of blood cells - PP, and neutrophil: lymphocyte ratio - NLR), splenic pro-inflammatory cytokines mRNA (IL-1β and IL-6), and endocrine mediators (corticosterone - CORT and melatonin - MEL plasma levels). Our results showed LPS-induced increases in CORT, NLR, PP, and IL-1β mRNA compared with saline-injected individuals. For NLR, the increase happened at both times (day and night) in the LPS-stimulated toads. Interestingly, for CORT levels, the response was more pronounced during the night, while for PP and IL-1β, the effect was more evident during the day. However, no changes were observed in BKA, plasma MEL levels, or IL-6. Altogether, our results demonstrate LPS injection promoting an inflammatory response in toads (higher PP, NLR, and IL-1β mRNA), followed by activation of the hypothalamic-pituitary-interrenal axis (higher CORT levels). Additionally, the time in which the toads received the immune challenge (day or night) affected the endocrine and immune mediators (higher PP and IL-1β mRNA by day, contrasting with higher CORT at night). Overall, we highlight the importance of considering daily variation to understand immunomodulation in amphibians better.

    2.  16:00  The thermal performance of innate immune function in three species of reptile. Matthew Mershon*, Stockton University; Nilanjana Das, Stockton University; Kathryn McLaughlin, Stockton University; Terence Farrell, Stetson University; Craig Lind, Stockton University

    With the increasing impact of climate change and the continued emergence and spread of wildlife diseases, understanding the immune system of diverse wildlife has become increasingly important. Most immune research has focused on birds and mammals, and this bias towards endotherms that tightly regulate their body temperature has resulted in a lack of information regarding how temperature affects immune performance. The goal of this experiment was to add to our understanding of reptile immune function by analyzing how temperature affects in vitro innate immune performance in three reptile species (Pseudemys rubriventris, Nerodia sipedon, Sistrurus miliarius). We hypothesized that these species would perform best near their preferred body temperatures and would not perform as well at extreme high and low temperatures. A bacterial killing assay was performed to assess the ability of blood plasma to kill a gram-negative bacterium, E. coli, at a range of temperatures (15-45°C). Non-linear regression was used to create a thermal performance curve (TPC) for each individual. TPC metrics (thermal optimum and 80% performance breadth) were extracted from each individual curve and used in species comparisons. Additionally, a RMANOVA was used to identify performance differences across temperatures. In all species immune performance was influenced by temperature. TPC metrics were similar across species and thermal optima were near the high end of observed field body temperatures. The observed temperature-dependence of immune function may underlie seasonal patterns of disease observed in ectothermic wildlife, and our findings may inform effective conservation and management of reptiles threatened with emerging pathogens.

    3.  16:00  The glycemic and glucocorticoid response to acute capture stress in the northern water snake, Nerodia sipedon. Nauera Abou Abdou*, Stockton University; Xin Rou Tan, Stockton University; Craig Lind, Stockton University

    The vertebrate fight or flight response involves the release of adrenal hormones that make energy available to cope with acute stressors. Adrenal glucocorticoids may increase circulating glucose by impacting the rate of glycogenolysis, gluconeogenesis, or uptake by peripheral tissues. The glucocorticoid response to acute stressors has been extensively studied in reptiles and may vary seasonally or in association with life history stage. However, the intrinsic (e.g. sex or reproductive status) and extrinsic (e.g. season or temperature) factors that impact the relationship between glucocorticoid release and the mobilization of glucose have received little attention. Here, we measured corticosterone (CORT) and glucose in response to acute (30 minute) capture stress in free-living male, reproductive female, and non-reproductive female northern water snakes, Nerodia sipedon. Both CORT and glucose were elevated in response to capture stress across all snake categories. Pre and post-stress glucose were significantly correlated with CORT. Pre-stress and post-stress CORT were also correlated. There was a significant negative relationship between cloacal body temperature and CORT. Our results indicate that CORT and glucose increase in response to capture stress in both males and females and that these physiological responses are correlated and may be influenced by body temperature.

    4.  16:00  Skin Lipids in Burmese Pythons: Comparison of Data analysis Approaches to Multidimensional Data. Julianna M. Lincoln*, James Madison University; Isabella M.G. Bukovich, James Madison University; Holly R. Rucker, James Madison University; Paige E. Baedke, James Madison University; Bryan M. Kluever, U.S. Department of Agriculture, National Wildlife Research Center - Florida Field Station; Ian A. Bartoszek, Conservancy of Southwest Florida; M. Rockwell Parker, James Madison University

    Chemical signals in vertebrates are often complex blends of molecules, many of which have independent and/or synergistic effects on receiver behavior. While isolation of these chemical mixtures is relatively straightforward, meaningful, targeted analysis of the blends can be challenging. Our lab studies the chemical composition of skin lipids that serve as communication signals in many reptile species. We treat these lipid blends as multidimensional datasets to which Bayesian statistical techniques can be applied. Here, we present an analytical framework for dealing with multidimensional chemical data from Burmese pythons (Python bivittatus). In collaboration with scientists at the Conservancy of Southwest Florida, we isolated a series of skin lipid fractions from reproductive pythons caught in mating aggregations during the breeding season across two years (n=17 males; n=19 females). These pythons are a major invasive predator of concern in Florida, and discovering the chemicals comprising their mating signals is a major target for biological control. In R, we used randomForest to predict the response variable “sex” based on gas chromatograph (GC) retention times to identify informative chemical peaks. In parallel, multiple response permutation procedure (mrpp) was used to conduct a global analysis of sex differences per fraction followed by nonmetric multidimensional scaling to visualize differences. Lipid profiles varied significantly between sexes in specific fractions, with randomForest accurately predicting sex in ~80% of the fractions. By using importance plots, we have identified key GC peaks for further behavioral testing. We are currently adapting our sampling approach as well.

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