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First published online May 29, 2009
Journal of Experimental Biology 212, 1921-1929 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.028704

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

H. B. Lillywhite^1,*, J. G. Menon², G. K. Menon³, C. M. Sheehy, 3rd⁴ and M. C. Tu⁵

¹ Department of Zoology, University of Florida, Gainesville, FL 32611, USA
² Department of Biology, William Paterson University of New Jersey, Wayne, NJ 07470, USA
³ Department of Ornithology and Mammalogy, California Academy of Sciences, Golden Gate Park, San Francisco, CA 94118, USA
⁴ Department of Biology, Amphibian and Reptile Diversity Research Center, University of Texas at Arlington, Arlington, TX 76019, USA
⁵ Department of Biology, National Taiwan Normal University, Taipei, Taiwan 116, Republic of China

^* Author for correspondence (e-mail: hbl{at}zoo.ufl.edu)

Accepted 24 March 2009

Evolutionary 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.

Key words: snake, sea snake, skin, ecophysiology, evaporative water loss, skin resistance, lipid, epidermis, permeability barrier, mesos layer, alpha keratin, marine, seawater

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