Meeting Abstract
6.4 Jan. 4 Sea Snakes Dehydrate in Sea Water LILLYWHITE, H.B.*; BABONIS, L.S.; SHEEHY III, C.M.; TU, M.C.; Univ. of Florida, Gainesville; Univ. of Florida, Gainesville; Univ. of Florida, Gainesville; National Taiwan Normal University, Taipei, Taiwan hbl@zoo.ufl.edu
Sea snakes are generally thought to remain in water balance without consuming fresh water owing to salt excretion by extrarenal salt glands. We studied dehydration and drinking behavior in three species of laticaudine sea snakes inhabiting Lanyu (Orchid Island), Taiwan. These species differ with respect to degree of terrestrial tendency and permeability of skin to water: Laticauda colubrina is semi-terrestrial and its mean cutaneous evaporation rate (CEWL) is 0.118 ± 0.11 mg/cm2 h1; L. laticaudata is relatively more aquatic and CEWL = 0.37 ± 0.20 mg/cm2 h1; L. semifasciata is the most fully aquatic and CEWL = 0.54 ± 0.31 mg/cm2 h1 (P<0.0001, ANOVA for CEWL differences measured at 23-24 °C). We report direct evidence that sea snakes do not drink sea water and require fresh water to replenish water stores that are depleted by dehydration in air or water. Moreover, a conservative input/output analysis of water balance indicates that snakes in sea water will dehydrate with or without food. We further show that populations of these species are most abundant at coastal sites where sources of fresh water such as springs are present (P=0.004). Elsewhere these snakes presumably acquire fresh water from brackish surface lenses that form on the ocean during rainstorms. The threshold salinity for drinking is 25% SW < 50% SW. Globally, species diversity of sea snakes correlates positively with mean annual precipitation. The stochastic nature of rainfall patterns, both in time and space, appears likely to limit the distribution of marine snakes, which is characteristically patchy. This work was supported by the National Geographic Society and Delfin Technologies Ltd.
