S5-1.3 Thursday, Jan. 5 Dehydration and Freshwater Drinking Requirements of Marine Snakes LILLYWHITE, HB*; BRISCHOUX, F; SHEEHY III, CM; PFALLER, JB; Univ. of Florida, Gainesville; Univ. of Florida, Gainesville; Univ. of Texas at Arlington; Univ. of Florida, Gainesville email@example.com
Osmoregulation is a key problem for vertebrates that have secondarily invaded marine environments. Here we report new data for dehydration and drinking behaviors of Yellow-bellied sea snakes, Pelamis platurus. This species is pelagic, ranges throughout the Indo-Pacific, and is arguably the most marine-adapted of sea snake species. Dehydrated snakes refused to drink seawater (SW), but drank freshwater (FW) to restore water balance. The mean dehydration threshold before drinking was 18.8 ± 1.0 % loss of body mass, roughly twice that of previously studied Laticauda spp. of sea snakes, which are partly terrestrial. A fraction of dehydrated Pelamis drank brackish water ≤ 50% SW, whereas dehydrated Laticauda drink only water ≤ 30% SW. Compared with Laticauda spp., Pelamis dehydrate more quickly when exposed to air but maintain low rates of water loss in SW. From 0 to 40% of snakes collected from the Guanacaste coast of Costa Rica drank FW when provided with the opportunity immediately following capture during both dry (Dec–May) and wet (June–Nov) season sampling. The percentage of snakes drinking FW correlated with time since heavy rainfall and inversely with body condition index. Hematocrit values varied from 30-56% (mean = 38 ± 0.9 %), further suggesting that snakes are dehydrated at sea. Thus, Pelamis dehydrate in their pelagic environment where they must depend on brackish or FW lenses formed by precipitation. This marine species appears to tolerate chronic dehydration and exhibits evolutionary reduction of FW drinking response. Rainfall and salinity may influence the distribution of marine snakes that are variably adapted to life in the salty sea. Supported by NSF IOS–0926802 to HBL.