The life aquatic: an association between habitat type and skin thickness in snakes

Abstract

An aquatic animal faces challenges not encountered by its terrestrial counterparts, promoting adaptive responses in multiple traits. For example, a thicker dermis might protect snakes when they are pushed against sharp objects by water currents, and might enable a snake to shed fouling organisms attached to its skin. We thus predicted that marine snakes should have thicker skin than terrestrial species, and that smaller sea snakes should have relatively thicker skin (because absolute, not relative, thickness determines vulnerability to fouling). Measurements of 192 snakes of 44 species supported those predictions. Many (but not all) sea snakes have skins 50% thicker than those of terrestrial and amphibious snake species, representing multiple independent evolutionary origins of thicker skin (in acrochordids, Laticauda sea kraits and both main clades of hydrophiine sea snakes). Marine snakes showed different allometries of skin thickness compared with their terrestrial counterparts; larger snakes had thicker skin within and among species of amphibious and terrestrial snakes, but larger aquatic snake species had thinner skin compared with smaller taxa. Interspecific variation in skin thickness was primarily due to increased collagen in the deep dermis, a physical barrier well suited to protecting against physical injury and to resisting penetration by epibionts.

Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease

“…The lower observed prevalence in certain species and genera may be due to inherent resistance shared among closely related species, the smaller size of the snake resulting in smaller surface area for sampling, or sharing life history traits/habitats that are less permissive to developing ophidiomycosis. One potential explanation for differences in disease prevalence involves differences in the structure of the skin, as skin is an important immune barrier to microbial invasion 23 and skin thickness has been found to vary among snakes with different life histories 24 . Future investigations are needed to characterize the mechanisms leading to disease prevalence differences between species and should continue to sample these species in the wild, evaluate environmental factors that influence snakes' exposure to the fungus, and conduct challenge studies to evaluate disease progression and host immune responses.…”

An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes

“…For example, modern cheloniids frequently visit reef environments 64 , and some species, e.g., the www.nature.com/scientificreports/ hawksbill sea turtle (Eretmochelys imbricata) and green sea turtle (Chelonia mydas), are known to subsist on food items (e.g., sponges and algae) that are common in such habitats 64 . Thus, in similarity with certain sea snakes (e.g., Aipysurus) 65,66 , the retention of prominent scales and scutes in these turtles could be a consequence of abrasive hazards imposed by corals and other sharp objects in their nearshore feeding grounds 64,66 . By contrast, the leatherback turtle is rarely observed in reef environments 67 , but instead typically inhabits pelagic settings 10 , occasionally even venturing into deep 68 and cool 69 waters in pursuit of prey.…”

Peaceful coexistence between people and deadly wildlife: Why are recreational users of the ocean so rarely bitten by sea snakes?

“…seaweed, coral fragments). Perhaps for this reason, sea snakes tend to have thicker skin (more resistant to abrasion) than do terrestrial snakes (Shine et al., 2019). As a result of frequent and unpredictable contact with hard objects, the snakes may not interpret firm contact (e.g.…”

“…Our long‐term studies on sea snakes in the Pacific archipelago of New Caledonia offer a good example of coexistence between snakes and people. New Caledonia contains at least 15 species of marine elapids: three species of amphibious Laticaudines (sea kraits) and 12 species of ‘true’ (viviparous) Hydrophiines (Ineich & Laboute, 2002; Shine et al., 2019). Several of those species are common around the capital city of Noumea, in sites used by thousands of tourists annually (Borsa, 2008).…”