Water exchange and permeability properties of the skin in three species of amphibious sea snakes (Laticauda spp.)

Abstract

SUMMARYEvolutionary transitions between different environmental media such as air and water pose special problems with respect to skin permeability because of the dramatic changes in the driving gradients and nature of water exchange processes. Also, during the transitional periods prior to complete adaptation to a new medium, the skin is exposed to two very different sets of environmental conditions. Here, we report new data for transepidermal evaporative water loss (TEWL) and cutaneous resistance to evaporative water loss (R s ) of sea snakes that are transitional in the sense of being amphibious and semi-terrestrial. We investigated three species of sea kraits (Elapidae: Laticaudinae) that are common to Orchid Island (Lanyu), Taiwan. Generally, R s of all three species is lower than that characteristic of terrestrial/xeric species of snakes measured in other taxa. Within Laticauda, R s is significantly greater (TEWL lower) in the more terrestrial species and lowest (TEWL highest) in the more aquatic species. Previously reported losses of water from snakes kept in seawater exhibit a reversed trend, with lower rates of loss in the more aquatic species. These data suggest selection for adaptive traits with respect to increasing exposure to the marine environment. Thus, a countergradient of traits is reflected in decreased TEWL in aerial environments and decreased net water efflux in marine environments, acting simultaneously in the three species. The pattern for TEWL correlates with ultrastructural evidence for increased lipogenesis in the stratum corneum of the more terrestrial species. The skin surfaces of all three species are hydrophobic. Species differences in this property possibly explain the pattern for water efflux when these snakes are in seawater, which remains to be investigated.

Renal responses to salinity change in snakes with and without salt glands

“…Mean rates of mass loss in L. semifasciata and N. fasciata were similar to those previously reported for these species (Dunson, 1978;Lillywhite et al, 2009), whereas estimates in N. c. clarkii were slightly higher than previously reported (Dunson, 1980;Pettus, 1963). Among-individual variation in mean daily mass loss was very high in both species of Nerodia, likely reflecting the large overall range in body mass in these two species, and mass loss did not differ among treatments in any of the species examined.…”

Physiological regulation of evaporative water loss in endotherms: is the little red kaluta (Dasykaluta rosamondae) an exception or the rule?

“…It is customary to calculate Dwvp as the difference between wvp at 100% RH and ambient T a and wvp at ambient RH and T a [7,14,20]. Skin temperature is more appropriate than T a to calculate Dwvp [16], but its measurement is more difficult, so ambient temperature is generally used as a proxy. The Dwvp will be similar, particularly at low ambient wvp, unless there is a very large difference between T a and T skin .…”

“…This raises the important question of whether these endotherms have physiological regulation of EWL at low and moderate T a , which could confer substantial advantages for balancing their water budget. However, complexities with these studies, such as use of RH, wvp or Dwvp, heterothermy [13], postural adjustments [14], measurement method and protocols [13,15], and use of skin or ambient temperature to calculate Dwvp [16] make it difficult to interpret these patterns.…”

Dry friction of microstructured polymer surfaces inspired by snake skin

“…The surface energy of snake skin has been mostly assumed according to the chemical analysis of the skin material [14–18]. Only Lillywhite et al [19] directly measured contact angles of the snake skin and showed its hydrophobic properties. The mechanical properties of the skin have been investigated in great detail by Klein and Gorb [20].…”