Sea Snakes & Freshwater

Sea Snakes & Freshwater - 785 Sea Snakes (Laticauda...

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785 Sea Snakes ( Laticauda spp.) Require Fresh Drinking Water: Implication for the Distribution and Persistence of Populations * Corresponding author; e-mail: Present address: Department oF Biology, Amphibian and Reptile Diversity Re- search Center, University oF Texas, Arlington, Texas 76019. Physiological and Biochemical Zoology 81(6):785–796. 2008. q 2008 by The University of Chicago. All rights reserved. 1522-2152/2008/8106-7208$15.00 DOI: 10.1086/588306 Harvey B. Lillywhite 1, * Leslie S. Babonis 1 Coleman M. Sheehy III 1,† Ming-Chung Tu 2 1 Department oF Zoology, University oF ±lorida, Gainesville, ±lorida 32611-8525; 2 Department oF LiFe Science, National Taiwan Normal University, Taipei, Taiwan Accepted 3/17/2008; Electronically Published 9/26/2008 ABSTRACT Dehydration and procurement oF water are key problems For vertebrates that have secondarily invaded marine environments. Sea snakes and other marine reptiles are thought to remain in water balance without consuming Freshwater, owing to the abil- ity oF extrarenal salt glands to excrete excess salts obtained either From prey or From drinking seawater directly. Contrary to this long-standing dogma, we report that three species oF sea snake actually dehydrate in marine environments. We investigated dehydration and drinking behaviors in three species oF am- phibious sea kraits ( Laticauda spp.) representing a range oF habits From semiterrestrial to very highly marine. Snakes that we dehydrated either in air or in seawater reFused to drink seawater but drank Freshwater or very dilute brackish water (10%–30% seawater) to remain in water balance. We Further show that Laticauda spp. can dehydrate severely in the wild and are Far more abundant at sites where there are sources oF Freshwater. A more global examination oF all sea snakes dem- onstrates that species richness correlates positively with mean annual precipitation within the Indo–West Paci²c tropical re- gion. The dependence oF Laticauda spp. on Freshwater might explain the characteristically patchy distributions oF these rep- tiles and is relevant to understanding patterns oF extinctions and possible Future responses to changes in precipitation related to global warming. In particular, metapopulation dynamics oF the Laticauda group oF sea snakes are expected to change in relation to projected reductions oF tropical dry-season precipitation. Introduction The evolutionary transition oF animals between land and water alters selection Forces and leads to dramatic changes in body Form, prey type, physiology, reproduction, and other characters (Zimmer 1998; Mazin and BuFFrenil 2001). The marine tran- sition appears to be especially diF²cult, with salinity posing a strong physiological barrier (Dunson 1979; Dunson and Maz- zotti 1989). In spite oF this, numerous reptilian lineages contact or utilize coastal waters, including various turtles, crocodilians, the marine iguana, and disparate lineages oF snakes. However, relatively Few species have become adapted to a Fully marine existence. ±ive evolutionary lineages oF snakes have invaded the marine environment. The
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Sea Snakes & Freshwater - 785 Sea Snakes (Laticauda...

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