Meeting Abstract

62.7  Wednesday, Jan. 6  Larvae of sand dollar behaviorally compensate for temperature constraints on swimming CHAN, K.Y.K.*; GRÜNBAUM, D. ; Univ. of Washington, Seattle; Univ. of Washington, Seattle kychan@u.washington.edu

Many marine invertebrate larvae actively swim to regulate water column position. Because environmental characteristics such as food availability and temperature often vary strongly with depth, vertical position has important consequences for larval growth, survival and dispersal. Little is known about effects of these environmental characteristics on larval swimming, but previous work suggests that larvae displaced downwards into colder water swim more slowly and consequently may have difficulty returning to warmer surface layers. We used non-invasive video tracking techniques to quantify swimming in larvae of the sand dollar, Dendraster excentricus, raised on four algal diets differing in fatty acid profile and exposed to an ecologically relevant temperature reduction from 20°C to 12°C. While larval swimming speeds decreased across all diet treatments, larvae’s net vertical velocities did not decrease. Changes in swimming trajectories suggest larvae behaviorally compensated for reduced swimming speeds by reducing horizontal movement. Differences in diet quality led to significant morphological differences by the 8-arm larval stage, accompanied by significant diet/temperature interaction effects on swimming patterns. The observed behavioral compensation effectively circumvents swimming constraints due to lowered temperatures. More generally, video tracking of free-swimming larvae can yield quantitative data to inform coupled biophysical models to better predict consequences of larval dispersal for adult population dynamics under current and future environmental conditions.