Robert D. Podolsky and Jonathan D. Allen University of North Carolina at Chapel Hill
One important trade-off in life-history evolution is between the size and number of offspring that a female produces. For free-spawning marine invertebrates, many models of life-history evolution assume that the fecundity gains of a reduction in egg size are offset by an increase in time to metamorphosis or a reduction in juvenile quality. Experimental manipulations of egg size are a powerful method for testing this assumption and confirming that changes in egg size alone can account for the variation in life-history strategies among marine invertebrates. The goal of this project is to test the effects of an experimental reduction in egg size in four species of echinoid echinoderms, which span a range of natural egg sizes. Blastomere separations will be used to mimic the effects of a reduction in egg size for the following species: Arbacia punctulata, Stongylocentrotus purpuratus, Dendraster excentricus and Clypeaster rosaceus. At different egg sizes, reductions in parental investment are predicted to have different effects on life-history parameters. The results of these experiments will test important assumptions about the relationships between egg size, development time and juvenile quality in echinoderms. In addition, these experiments will help to clarify the role of changes in egg size in life history transitions, such as the shift from obligate to facultative feeding.
