Harvey B. Lillywhite’s research while affiliated with University of Florida and other places

The lung of marine snakes varies in structure and function related to diversity of phylogeny, behavior, and environment. All species are secondarily marine and retain dependence on aerial breathing, although some also exchange gases across the skin. Generally, there is an elongated functional right lung, and the left lung is vestigial or absent. Respiratory gases are exchanged in the 'vascular lung' segment, which may include the trachea, whereas the more distal 'saccular lung' has a poorly vascularized muscular wall, terminates blindly, and facilitates storage of oxygen. In terrestrial scansorial species of snakes, the vascularized segment of the lung is relatively short to prevent gravity-induced edema when the body is vertical or upright. In contrast, the vascular lung in marine snakes is relatively long. In the file snake Acrochordus granulatus, an exceptionally elongated vascular lung is shown to maximize oxygen storage when the snake is submerged at neutral buoyancy in shallow-water habitats. In deeper diving sea snakes, the entire lung is shorter, and the saccular segment functions to store oxygen. Movement of air within the lung is possible by means of body movements, but such behavior in naturally diving snakes is not well understood. Marine snakes avoid decompression sickness (the bends) by 'metering' the transfer of nitrogen from lung to seawater by varying pulmonary bypass of blood flow via intraventricular shunts and simultaneously varying blood flow to the skin. These complex cardiovascular actions are also influenced by the need of metabolizing tissues for oxygen uptake from lung stores or ambient water.

Lepidosaurian reptiles, particularly snakes, periodically shed the outer epidermal layers of their skin (ecdysis) to restore or enhance vital functions such as regulating water and gaseous exchange, growth, and protection against insult, infection or physical injury. Although many studies have focused on the nature and mechanisms of skin shedding, little attention has been paid to the timing of the first ecdysis in neonates following birth or hatching. A recent study investigated patterns of the time to first postnatal ecdysis in snakes based on a large dataset taken from the literature. The analysis demonstrated patterns in the time to first postnatal ecdysis related to phylogeny as well as several life history traits. While this assessment provides important advances in our knowledge of this topic, data on known biophysical drivers of ecdysis – temperature and humidity – were largely unavailable and were not evaluated. The first postnatal ecdysis of neonatal snakes can be viewed as an adaptive adjustment to the transition from the aqueous environment of the embryo to the aerial environment of the newborn. Hence, the timing of the first postnatal ecdysis is logically influenced by the aerial environment into which a newborn snake or hatchling finds itself. Therefore, in this Commentary, we first emphasize the putative plasticity of ecdysis with respect to epidermal lipids that structure the water permeability barrier and are established or renewed during ecdysis to reduce transepidermal evaporative water loss. We then discuss the likely importance of biophysical variables as influential covariates that need future investigation as potential co-determinants of the timing of first postnatal ecdysis.

Snakes have been successful colonizers of islands, where some have replaced mammals as top carnivores and are key elements in food webs. Snakes are present or dominant on islands because of speciation in situ, invasion from the sea, and various immigration events involving dispersal or human introductions. In this second volume of Islands and Snakes, the authors emphasize the diversity of insular snakes, discuss their biogeography and evolution, and point out the need for conservation of insular species. As in the first volume, aspects of insular ecology and evolution are important topics for understanding the successes and challenges of insular snakes. New emphases on diversity and conservation include some important topics that were not addressed in the earlier volume, such as reproductive biology, historical biogeography and taxonomy of insular species, snake diversity on large islands, threats and collapse of insular systems, and the impacts of invasive species on islands. This volume also includes descriptions of natural history and diversity of snakes on important islands not previously given much popular attention. In diverse ways, the various authors create an awareness of conservation issues and hopefully promote interest and mitigation actions to preserve insular snakes and the islands on which they live. As with all biodiversity, snakes are important in several well-known contexts including evolutionary history, scientific value, ecosystem services, and enhancing the richness of life’s experiences here on Earth. Conservation of insular snakes is important for aesthetic and cultural values as well as for the scientific reasons discussed in this and the previous volume.

Snakes have been successful colonizers of islands, where some have replaced mammals as top carnivores and are key elements in food webs. Snakes are present or dominant on islands because of speciation in situ, invasion from the sea, and various immigration events involving dispersal or human introductions. In this second volume of Islands and Snakes, the authors emphasize the diversity of insular snakes, discuss their biogeography and evolution, and point out the need for conservation of insular species. As in the first volume, aspects of insular ecology and evolution are important topics for understanding the successes and challenges of insular snakes. New emphases on diversity and conservation include some important topics that were not addressed in the earlier volume, such as reproductive biology, historical biogeography and taxonomy of insular species, snake diversity on large islands, threats and collapse of insular systems, and the impacts of invasive species on islands. This volume also includes descriptions of natural history and diversity of snakes on important islands not previously given much popular attention. In diverse ways, the various authors create an awareness of conservation issues and hopefully promote interest and mitigation actions to preserve insular snakes and the islands on which they live. As with all biodiversity, snakes are important in several well-known contexts including evolutionary history, scientific value, ecosystem services, and enhancing the richness of life’s experiences here on Earth. Conservation of insular snakes is important for aesthetic and cultural values as well as for the scientific reasons discussed in this and the previous volume.

Snakes have been successful colonizers of islands, where some have replaced mammals as top carnivores and are key elements in food webs. Snakes are present or dominant on islands because of speciation in situ, invasion from the sea, and various immigration events involving dispersal or human introductions. In this second volume of Islands and Snakes, the authors emphasize the diversity of insular snakes, discuss their biogeography and evolution, and point out the need for conservation of insular species. As in the first volume, aspects of insular ecology and evolution are important topics for understanding the successes and challenges of insular snakes. New emphases on diversity and conservation include some important topics that were not addressed in the earlier volume, such as reproductive biology, historical biogeography and taxonomy of insular species, snake diversity on large islands, threats and collapse of insular systems, and the impacts of invasive species on islands. This volume also includes descriptions of natural history and diversity of snakes on important islands not previously given much popular attention. In diverse ways, the various authors create an awareness of conservation issues and hopefully promote interest and mitigation actions to preserve insular snakes and the islands on which they live. As with all biodiversity, snakes are important in several well-known contexts including evolutionary history, scientific value, ecosystem services, and enhancing the richness of life’s experiences here on Earth. Conservation of insular snakes is important for aesthetic and cultural values as well as for the scientific reasons discussed in this and the previous volume.

Snakes have a successful and pervasive presence on islands, and in many cases populations of snakes on islands are robust. Like many other insular biota, snakes can be sensitive to disturbance and extinction. Insular snakes also exhibit, in general, endemic, interesting, and unusual species and are exemplars of evolutionary adaptation and plasticity of responses to new or changing environments, especially prey. Because of the isolation and size of islands, insular snakes can be models for studies of diversification and extinction. In this chapter, the authors assess the success of snake populations on islands and summarize the threats to extant insular species. The authors believe it is imperative that increasing attention be given to conservation of insular snakes and the islands on which they live. They propose that conservation of these species is important for aesthetic, cultural, and scientific values in addition to other reasons discussed in this chapter and volume.

Behaviour is shaped by the perception of the surrounding world, which is created by the senses. Reptilian sensory systems are shaped by the varied ecologies and complex evolutionary histories of reptiles. In this chapter, we outline the major senses of reptiles: photoreception (vision, parietal eyes, cutaneous), mechanoreception (hearing, balance, and touch), chemoreception (gustation, olfaction, vomeronasal), thermoreception (cutaneous, heat-pit), and magnetoreception. We give general descriptions of the sensory anatomy, including relevant examples of how senses relate to the behaviour and sensory evolution of these animals. We also focus on how major senses mediate intraspecific communication in reptiles, focusing on visual communication via colouration and other visual displays, acoustic communication through calls and songs, and chemical communication using specialised scent glands. Among the diverse sensory specialisations of reptiles, we also outline some of the rare senses for select taxa including magnetoreception navigation in archosaurs, and heat-pit foraging in snakes. Although these unusual senses can be directly related to important behaviours, reptiles do not rely solely on one sensory system for any behaviour, and almost all stimuli are integrated in the brain to inform immediate decision-making. Thus, all sensory capabilities should be considered when attempting to understand the relative importance of sensory systems to reptilian behaviour. We aim to impart an appreciation for how different stimuli may be perceived by reptiles in captivity. Further, signals salient to various reptiles may be invisible to humans (e.g. UV colouration, pheromones), and different reptiles may have heightened or impoverished sensory abilities. Thus, an understanding of reptilian sensory systems is vital for ensuring animal health and welfare in captivity.

Physiology and morphology are interactive determinants of behaviours that are especially sensitive to environmental influences and are important to the health and welfare of captive reptiles. Although many reptiles appear to be easily managed in captive circumstances, others have special requirements to remain in health and vigour. This chapter focuses on understanding the functional attributes of reptiles as they relate to behaviour and the health of captive individuals. Comparative studies of reptilian physiology and ecology illustrate how guidelines for optimal care will vary not only among higher order taxa but also between closely related species. Ambient temperature, light, and humidity strongly influence the health of reptiles. Important aspects of physiology include ectothermy, generally low energy requirements, diet, periodic inactivity, reproductive mode and cycling, health of skin, adequate hydration, cardiovascular and respiratory health, and infectious disease. Conditions of poor husbandry may include obesity, inappropriate temperature, humidity, and lighting conditions, lack of access to seclusion, and suppression of the immune system that can interact synergistically with other forms of stress related to captivity. Further research is needed to understand stressful states and how they can be ameliorated in captive animals. In view of the diversity and complex evolutionary histories of reptiles, variation among species must be appreciated in order for these animals to live, thrive, and reproduce in captive settings.

The advanced snakes (Alethinophidia) include the extant snakes with a highly evolved head morphology providing increased gape and jaw flexibility. Along with other physiological and morphological adaptations, this allows them to immobilize, ingest, and transport prey that may be disproportionately large or presents danger to the predator from bites, teeth, horns, or spines. Reported incidents of snakes failing to consume prey and being injured or killed during feeding mostly reflect information in the form of natural‐history notes. Here we provide the first extensive review of such incidents, including 101 publications describing at least 143 cases of mortality (including six of ‘multiple individuals’) caused by ingestion or attempted consumption of injurious prey. We also report on 15 previously unpublished injurious feeding incidents from the USA, Austria, and Bulgaria, including mortality of five juvenile piscivorous dice snakes (Natrix tessellata) from a single location. Occurrences are spread across taxa, with mortality documented for at least 73 species from eight families and 45 genera. Incidents were generally well represented within each of three major categories: oversized prey (40.6%), potentially harmful prey (40.6%), and predator's behavioural/mechanical errors (18.9%). Reptile (33%) and fish (26%) prey caused disproportionately high mortality compared to mammals (16%). Feeding can be dangerous throughout a snake's life, with the later stages of feeding likely being more perilous. The number of reports has increased over time, and the data seem biased towards localities with a higher number of field‐working herpetologists. We propose a standardized framework, comprising a set of basic information that should ideally be collected and published, and which could be useful as a template for future data collection, reporting, and analyses. We conclude that incidents of mortality during feeding are likely to be more common than previously assumed, and this hypothesis has implications for the ecology of persistence where populations are impacted by changing trophic environments.

Sublethal dehydration can cause negative physiological effects, but recent studies investigating the sub-lethal effects of dehydration on innate immune performance in reptiles have found a positive correlation between innate immune response and plasma osmolality. To investigate if this is an adaptive trait that evolved in response to dehydration in populations inhabiting water-scarce environments, we sampled free-ranging cottonmouths (n=26 adult cottonmouths) from two populations inhabiting contrasting environments in terms of water availability: Snake Key (n=12), an island with no permanent sources of fresh water and Paynes Prairie (n=14), a flooded freshwater prairie. In addition to field surveys, we manipulated the hydration state of 17 cottonmouths (Paynes Prairie n=9, Snake Key n=8) in a laboratory setting and measured the response of corticosterone and innate immune performance to dehydration with the aim of identifying any correlation or trade-offs between them. We measured corticosterone of cottonmouths at a baseline level and then again following a 60-min stress test when at three hydration states: hydrated, dehydrated, and rehydrated. We found that innate immune performance improved with dehydration and then returned to baseline levels within 48 hours of rehydration, which agrees with previous research in reptiles. Despite the frequent exposure of cottonmouths on Snake Key to dehydrating conditions, we did not find cottonmouths inhabiting the island to show a greater magnitude or more prolonged immune response compared to cottonmouths from Paynes Prairie. We also found a positive association between dehydration and corticosterone values.