Meeting Abstract

101.11  Wednesday, Jan. 7  Unscrambling the relationship between egg size and egg composition using geminate species pairs MCALISTER, J/S*; MORAN, A/L; Clemson University; Clemson University jmcalis@clemson.edu

Egg size is one of the most important life-history parameters in marine organisms. Among species with a planktonic larval stage, egg size is strongly associated with developmental mode (planktotrophy or lecithotrophy) and is linked to numerous fundamental traits, i.e. larval form, the length of larval development and fertilization success. Among planktotrophic species however, egg size can be a poor predictor of energetic content. To examine the evolutionary association between egg size and egg energetic composition, we are analyzing the protein, carbohydrate, and lipid content of eggs of echinoid geminate species pairs from tropical America, which have known differences in egg size between geminates. Geminates are closely related species that formed when the Panamanian Isthmus raised 2-4 mya and split previously continuous populations of marine organisms. Geminates inhabit two different larval food-level environments: high in the eastern Pacific (EP) vs. low in the western Atlantic (WA). These environments are associated with the differences in egg size, which have been attributed to changes in maternal investment per egg: an increase in the WA and/or a decrease in the EP. Our results indicate that per-egg protein content is similar between members of each geminate pair. When corrected for volume, however, the EP species have significantly and substantially higher protein densities than their WA geminates. Analyses of carbohydrate and lipid content are ongoing. The results from this study, the first to be conducted in a rigorous, phylogenetically-controlled, comparative context, will increase our understanding of the evolutionary association between egg size and egg composition.