Meeting Abstract

87.2  Sunday, Jan. 6  Egg size and exogenous food level interact to affect larval growth in tropical Echinometra spp. sea urchins MCALISTER, J/S*; MORAN, A/L; College of the Holy Cross; Clemson University jmcalist@holycross.edu

Planktotrophic larvae of marine invertebrates develop and grow by utilizing energy and materials from a combination of maternally-supplied endogenous egg reserves and exogenous food. Egg size varies considerably among planktotrophic species, and egg size is thought to evolve in the context of food availability; large eggs will be favored if food for larvae is scarce, and small eggs will be favored if food is abundant. Evolutionary changes in egg size can also affect maternal fitness by altering the balance between per-offspring maternal investment and fecundity. To test the hypothesis that egg size alters the effect of food availability on larval growth and development, we reared larvae of three closely related species of Echinometra that differ in egg size and egg energetic content at three different food levels. We found that overall, at a given food level, larvae of species with larger eggs developed more rapidly than larvae of species with smaller eggs; larvae reared at higher food levels also grew more rapidly than those fed less. We also found a significant interaction between egg size and food level for larval size and developmental rate: food level had a greater effect on species with smaller eggs than those with larger eggs. These data support the prediction that larger eggs act as a nutritional and energetic buffer against the unpredictability of food in the plankton, and that smaller eggs may enhance maternal fitness in high-food environments.