S5-1.6 Thursday, Jan. 5 Ectothermy in the marine environment: new perspectives from the ecology and geography of sea snakes HEATWOLE, Harold*; GRECH, Alana; MONAHAN, John; KING, Sue; MARSH, Helene; NC State Univ., Raleigh; James Cook Univ., Townsville; NC State Univ., Raleigh; Eastern Kentucky Univ., Richmond; James Cook Univ., Townsville email@example.com
“True” sea snakes (marine Oxyuraninae) are small, linear in shape with a high surface area to mass ratio, and have no morphological attributes that conserve body heat; their body temperatures track those of their surrounding medium. Their thermoregulatory repertory is entirely behavioral, and includes diving to cooler depths, or basking at the surface. The latter is relatively ineffective because of the high surface area to volume ratio of snakes and the high conductivity of water. Most species are bottom-feeders and spend little time at the surface. Sea kraits (Laticaudinae) that feed in the sea but come out on land to rest, digest, and reproduce, thermoregulate by selecting appropriate terrestrial shelter, but are influenced by sea temperatures. The banded sea krait (Laticauda colubrina) has a distribution that straddles the equator and is subjected sea temperatures symmetrically distributed around the equator. Its poleward limits of distribution are restricted by low sea temperatures as boundaries relate to specific isotherms, even on a local scale, such as where currents carry cool water into areas otherwise inhabited by kraits. Morphological features under thermal control during development, or with differential fitness under different thermal regimes would be expected to show convergences between northern and southern populations relative to central ones. For sea kraits multivariate analyses, incorporating latitude and sea temperatures as environmental variables, revealed a strong latitudinal component that varied from west to east but that was not linked strongly to specific thermal conditions. Future research should investigate intraspecific geographic variation in physiological attributes and tolerance limits in relation to temperature.