Complexity in the timing of the first postnatal ecdysis in snakes.

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.

Perils of ingesting harmful prey by advanced snakes.

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.

Intraspecific investigation of dehydration-enhanced innate immune performance and endocrine stress response to sublethal dehydration in a semi-aquatic species of pit viper.

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 whether this is an adaptive trait that evolved in response to dehydration in populations inhabiting water-scarce environments, we sampled free-ranging cottonmouth snakes (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.

Osmoregulatory ability predicts geographical range size in marine amniotes.

Species that are distributed over wide geographical ranges are likely to encounter a greater diversity of environmental conditions than do narrowly distributed taxa, and thus we expect a correlation between size of geographical range and breadth of physiological tolerances to abiotic challenges. That correlation could arise either because higher physiological capacity enables range expansion, or because widely distributed taxa experience more intense (but spatially variable) selection on physiological tolerances. The invasion of oceanic habitats by amniotic vertebrates provides an ideal system with which to test the predicted correlation between range size and physiological tolerances, because all three lineages that have secondarily moved into marine habitats (mammals, birds, reptiles) exhibit morphological and physiological adaptations to excrete excess salt.

Thirst and drinking in North American watersnakes ( spp.).

We quantified drinking behavior in three species of North American watersnakes: , which is a marine or brackish water amphibious species, and and , both freshwater amphibious species. All three species have relatively small and similar thresholds of dehydration (TH, approximately -4% loss of body mass) that elicit thirst and drinking of fresh water. These species have higher thirst sensitivity than several species of hydrophiine and laticaudine sea snakes, which are characterized by much lower TH (greater dehydration, -9% to <-20%).

A tale of two islands: evidence for impaired stress response and altered immune functions in an insular pit viper following ecological disturbance.

The frequency and intensity of ecological perturbations affecting wild animal populations is expected to increase in the future with animals facing numerous global threats. Seahorse Key is a continental island off mainland Florida that has historically been a major rookery for several species of waterbirds. As a result of an unknown disturbance, the entire rookery abandoned Seahorse Key in April 2015 and shifted nesting activities to nearby Snake Key, resulting in an influx of food resources in the form of fish carrion to resident Florida cottonmouth snakes (), while snakes on Seahorse Key experienced a drastic reduction in food resources.

Variation of organ position in snakes.

The complex and successful evolutionary history of snakes produced variation in the position and structure of internal organs. Gravity strongly influences hemodynamics, and the impact on structure and function of the cardiovascular system, including pulmonary circulation, is well established. Therefore, we hypothesized that interspecific variation in the position of the heart and vascular (faveolar) lung should exceed that of other internal organs that are less sensitive to gravity.

Water relations of an insular pit viper.

Colonization of novel habitats often requires plasticity or adaptation to local conditions. There is a critical need to maintain hydration in terrestrial environments having limited water. Atypical populations of Florida cottonmouth snakes, , inhabit continental islands with no permanent sources of fresh water.

Structure and function of skin in the pelagic sea snake, Hydrophis platurus.

We describe and interpret the functional morphology of skin of the Yellow-bellied sea snake, Hydrophis platurus. This is the only pelagic sea snake, and its integument differs from what is known for other species of snakes. In gross appearance, the scales of H.

Drinking by sea snakes from oceanic freshwater lenses at first rainfall ending seasonal drought.

Acquisition of fresh water (FW) is problematic for FW-dependent animals living in marine environments that are distant from sources of FW associated with land. Knowledge of how marine vertebrates respond to oceanic rainfall, and indeed the drinking responses of vertebrates generally following drought, is extremely scant. The Yellow-bellied Sea Snake (Hydrophis platurus) is the only pelagic species of squamate reptile and ranges across the Indo-Pacific oceans, having one of the largest geographic distributions of any vertebrate species.

Physiological and behavioral responses to salinity in coastal Dice snakes.

Secondarily marine tetrapods have evolved adaptations to maintain their osmotic balance in a hyperosmotic environment. During the transition to a marine habitat, the evolution of a euryhaline physiology likely encompassed successive changes in behavior and physiology that released organisms from regular access to fresh water. Deciphering these key steps is a complicated task.

Feeding begets drinking: insights from intermittent feeding in snakes.

An important question related to the survival of dehydrating animals is whether feeding provides a net gain of water - contributing postprandial free water and metabolic water - or, alternatively, whether digestion and assimilation of ingested food incur a net loss of water because of requirements for digestion and the excretion of resulting metabolic wastes. Here, I address the question whether voluntary drinking increases or decreases following the ingestion of food. Increased postprandial drinking implies that food consumption increases rather than decreases the requirement for free water, whereas decreased postprandial drinking suggests there is a net profit of water from food.

Ontogenetic shifts of heart position in snakes.

Heart position relative to total body length (TL) varies among snakes, with anterior hearts in arboreal species and more centrally located hearts in aquatic or ground-dwelling species. Anterior hearts decrease the cardiac work associated with cranial blood flow and minimize drops in cranial pressure and flow during head-up climbing. Here, we investigate whether heart position shifts intraspecifically during ontogenetic increases in TL.

Oceanic circulation models help to predict global biogeography of pelagic yellow-bellied sea snake.

It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied sea snake (Hydrophis [Pelamis] platurus). State-of-the-art world ocean circulation models show how H.

Pelagic sea snakes dehydrate at sea.

Secondarily marine vertebrates are thought to live independently of fresh water. Here, we demonstrate a paradigm shift for the widely distributed pelagic sea snake, Hydrophis (Pelamis) platurus, which dehydrates at sea and spends a significant part of its life in a dehydrated state corresponding to seasonal drought. Snakes that are captured following prolonged periods without rainfall have lower body water content, lower body condition and increased tendencies to drink fresh water than do snakes that are captured following seasonal periods of high rainfall.

Dehydration and drinking behavior of the marine file snake Acrochordus granulatus.

Dehydration and drinking behaviors were investigated in the little file snake (Acrochordus granulatus) collected from marine populations in the Philippines and in Australia. File snakes dehydrate in seawater and do not drink seawater when dehydrated in air and offered seawater to drink. Dehydrated file snakes drink freshwater, and the threshold of dehydration for first drinking response is a deficit of -7.

Non-lethal sampling of liver tissue for toxicologic evaluation of Florida cottonmouths snakes, Agkistrodon piscivorus conanti.

Due to their longevity, strong site tenure, poikilothermic metabolism, and low-energy specializations, reptiles might serve as excellent environmental sentinels. Cottonmouth snakes are generalist predators and scavengers, and as such, may have higher exposure to persistent environmental contaminants as a result of bioaccumulation. Traditionally, assessment and monitoring of contaminant exposure in reptiles have involved lethal sampling techniques.

Sequestered defensive toxins in tetrapod vertebrates: principles, patterns, and prospects for future studies.

Chemical defenses are widespread among animals, and the compounds involved may be either synthesized from nontoxic precursors or sequestered from an environmental source. Defensive sequestration has been studied extensively among invertebrates, but relatively few examples have been documented among vertebrates. Nonetheless, the number of described cases of defensive sequestration in tetrapod vertebrates has increased recently and includes diverse lineages of amphibians and reptiles (including birds).

Habitat selection by sea kraits (Laticauda spp.) at coastal sites of Orchid Island, Taiwan.

Three species of amphibious sea kraits (Laticauda spp.) spend variable time at sea and require fresh water for water balance. Both the rate of cutaneous evaporative water loss and the extent of terrestriality are known to differ among them.

Preliminary insights into the phylogeography of the yellow-bellied sea snake, Pelamis platurus.

The yellow-bellied sea snake, Pelamis platurus (Elapidae, Hydrophiinae), has the largest distribution of any snake species, and patterns related to its distribution and regional color variation suggest there is population structuring in this species. Here, we use mitochondrial (ND4, Cyt-b) and nuclear (RAG-1) DNA to (1) test whether genetic variation is associated with local variation in color pattern, and (2) assess whether large-scale patterns of genetic variation are correlated with geographic distribution across the Pacific Ocean. We found low levels of genetic variation and shallow population structure that are correlated with local variation in color pattern and with geographic distribution.

Introduction to the symposium "New frontiers from marine snakes to marine ecosystems".

Interest in sea snakes and mythological "sea serpents" dates to ancient times and is represented in the writings of Aristotle, early voyagers, and explorers, and references in the Bible. Since then, awareness of the myriad species of snakes inhabiting the oceans has grown at a gradual pace. Scientific investigations into the biology of marine snakes-especially those in behavior, physiology, and other disciplines requiring living animals or tissues-have been comparatively challenging owing to difficulties in acquiring, transporting, handling, and husbanding these secondarily marine vertebrates.

Dehydration and drinking responses in a pelagic sea snake.

Recent investigations of water balance in sea snakes demonstrated that amphibious sea kraits (Laticauda spp.) dehydrate in seawater and require fresh water to restore deficits in body water. Here, we report similar findings for Pelamis platurus, a viviparous, pelagic, entirely marine species of hydrophiine ("true") sea snake.

Marine snake epibiosis: a review and first report of decapods associated with Pelamis platurus.

Under circumstances in which area for settlement is limited, the colonization of living substrata may become a highly valuable strategy for survival of marine invertebrates. This phenomenon, termed epibiosis, results in spatially close associations between two or more living organisms. Pelamis platurus, the yellow-bellied sea snake, is the only exclusively pelagic marine snake and its propensity for foraging along ocean slicks facilitates its colonization by pelagic epibionts.