P1.83 Thursday, Jan. 3 How do changes in parental investment influence larval development in Gulf of Maine echinoids? ALCORN, N*; ALLEN, JD; Bowdoin College; Bowdoin College firstname.lastname@example.org
The relationship between egg size, development time and juvenile size is a central component of most models of life history evolution in marine invertebrates. However, few laboratory experiments have provided empirical data to support assumptions of the nature of this relationship. In order to address this deficiency, we manipulated egg size and food level during the development of two common Gulf of Maine echinoid echinoderms, Strongylocentrotus droebachiensis and Echinarachnius parma, that develop via planktotrophic larvae. Based on previous manipulations of egg size and comparative datasets, we hypothesized that decreasing food availability and egg size would increase development time and reduce juvenile size. To test this hypothesis, blastomere separations were performed to reduce egg volume by 50% for both S. droebachiensis and E. parma and the resultant whole-size and half-size larvae were reared to metamorphosis under high or low food levels. Upon settlement we recorded time to settlement, juvenile size, spine number and spine length. Both egg size and food availability had significant effects on disk area and time to metamorphosis, but food availability had a stronger effect on the development of both species. These results suggest that while egg size is an important factor in the larval development of these two echinoids, food availability is a better predictor of juvenile quality and time to metamorphosis. Along with previous egg size manipulations in other echinoids, this study confirms that the relationship between egg size, development time and juvenile size is strongly dependent upon the initial size of the egg.