Physiological effects of capture and short-term captivity in an invasive snake species, the Burmese python (Python bivittatus) in Florida

Effects of blood extraction and ecophysiological experiments on stress in adult males of Liolaemus attenboroughi

Stress during laboratory experiments can affect the outcomes of ecophysiological studies. The serum corticosterone concentration (CORT), the leukocyte profile, heterophil/lymphocyte ratio (H/L), and the presence of blood endoparasites were analyzed as a proxy of stress and immunological state in adult males of the lizard Liolaemus attenboroughi, endemic to Patagonia, Argentina. The results of the ecophysiological variables (preferred temperature, running speed, locomotor endurance, and body condition index, BCI) were analyzed in relation to stress indicators obtained from blood samples taken at three different times: at capture, and on the third and seventh days in the laboratory. Males at capture showed a high percentage of lymphocytes and heterophils and a low of basophils, monocytes, and eosinophils. Haemogregorina-type endoparasites have been recorded in the genus Liolaemus for the first time. The proportion of infected males remained stable during captivity; however, these males showed higher CORT levels, increased percentages of basophils, and decreased percentages of lymphocytes. There was a significant increment in CORT and H/L, and a decrease in BCI during laboratory experiments, compared with baseline values at capture. The performance was not related to the CORT or the repeated blood sampling. The BCI decreased, possibly due to energy reserve mobilization caused by acute stress. This study shows that blood extraction and ecophysiological experiments over 7 days have a minor effect on the stress indicators used.

Burmese pythons in Florida: A synthesis of biology, impacts, and management tools

Burmese pythons (Python molurus bivittatus) are native to southeastern Asia, however, there is an established invasive population inhabiting much of southern Florida throughout the Greater Everglades Ecosystem. Pythons have severely impacted native species and ecosystems in Florida and represent one of the most intractable invasive-species management issues across the globe. The difficulty stems from a unique combination of inaccessible habitat and the cryptic and resilient nature of pythons that thrive in the subtropical environment of southern Florida, rendering them extremely challenging to detect. Here we provide a comprehensive review and synthesis of the science relevant to managing invasive Burmese pythons. We describe existing control tools and review challenges to productive research, identifying key knowledge gaps that would improve future research and decision making for python control.

The Impacts of Transdermal Application of Corticosterone on Toad (Rhinella icterica) Immunity

Recent studies have shown that acute physiological increases in endogenous glucocorticoid levels have immunostimulatory effects. Although post-acute stress immunosuppressive effects have also been described, the difference between enhancing and suppressing the immune response seems mediated by the stressor's duration, intensity, and the immune component under analysis. To elicit physiologically relevant corticosterone levels that can be found in Rhinella icterica toads after stressful events (e.g., restraint or captivity) and understand how acute increased glucocorticoid levels of different intensities affect corticosterone and testosterone plasma levels and immune parameters (in vitro plasma bacterial killing ability, neutrophil-to-lymphocyte ratio, and in vivo phagocytosis of peritoneal leukocytes), we submitted toads to the transdermal application of two corticosterone doses (1 and 10 μg). Corticosterone transdermal application increased corticosterone plasma levels with different intensities: 3 times for 1 μg and fourteen times for 10 μg, compared to the vehicle, and the neutrophil-to-lymphocyte ratio increased regardless of the corticosterone dose. However, there was no effect on testosterone levels and bacterial killing ability. Interestingly, both corticosterone doses promoted immunosuppression, decreasing peritoneal leukocytes' phagocytosis activity by 60% for toads receiving the dose of 1µg and 40% for those receiving 10 μg. Our results show the complexity of the relationship between increased corticosterone levels and immunomodulation. The different corticosterone doses promoted increases of distinct magnitudes in corticosterone plasma levels, with the less intense increase in corticosterone levels generating greater cell-mediated immunosuppression. Future studies using different corticosterone doses to achieve and compare physiological vs. pharmacological hormone levels are imperative to understanding these interrelationships between corticosterone and immune response.

Divergent Serpentoviruses in Free-Ranging Invasive Pythons and Native Colubrids in Southern Florida, United States

Burmese python (Python bivittatus) is an invasive snake that has significantly affected ecosystems in southern Florida, United States. Aside from direct predation and competition, invasive species can also introduce nonnative pathogens that can adversely affect native species. The subfamily Serpentovirinae (order Nidovirales) is composed of positive-sense RNA viruses primarily found in reptiles. Some serpentoviruses, such as shingleback nidovirus, are associated with mortalities in wild populations, while others, including ball python nidovirus and green tree python nidovirus can be a major cause of disease and mortality in captive animals. To determine if serpentoviruses were present in invasive Burmese pythons in southern Florida, oral swabs were collected from both free-ranging and long-term captive snakes. Swabs were screened for the presence of serpentovirus by reverse transcription PCR and sequenced. A total serpentovirus prevalence of 27.8% was detected in 318 python samples. Of the initial swabs from 172 free-ranging pythons, 42 (24.4%) were positive for multiple divergent viral sequences comprising four clades across the sampling range. Both sex and snout-vent length were statistically significant factors in virus prevalence, with larger male snakes having the highest prevalence. Sampling location was statistically significant in circulating virus sequence. Mild clinical signs and lesions consistent with serpentovirus infection were observed in a subset of sampled pythons. Testing of native snakes (n = 219, 18 species) in part of the python range found no evidence of python virus spillover; however, five individual native snakes (2.3%) representing three species were PCR positive for unique, divergent serpentoviruses. Calculated pairwise uncorrected distance analysis indicated the newly discovered virus sequences likely represent three novel genera in the subfamily Serpentovirinae. This study is the first to characterize serpentovirus in wild free-ranging pythons or in any free-ranging North America reptile. Though the risk these viruses pose to the invasive and native species is unknown, the potential for spillover to native herpetofauna warrants further investigation.