Meeting Abstract

81.5  Monday, Jan. 6 11:15  Are Planktotrophic Calyptraeids “Pre-adapted” for Adelphophagic Development? THOMSEN, O.; COLLIN, R.*; CARRILLO-BALTODANO, A.; Univ. Oldenburg; Smithsonian Tropical Res. Inst.; Clark Univ. collinr@si.edu

Adelphophagy, development where embryos grow large by consuming morphologically distinct nutritive embryos or their own normal siblings is common in some families of marine gastropods and worms and rare or unknown in others. In calyptraeid gastropods phylogenetic analysis indicates that adelphophagy has arisen at least 9 times, generally from species with planktotrophic larval development. This suggests that the evolution of adelphophagy is relatively simple in this group, and that the embryos of planktotrophic species might already express features that enable them to take advantage of dead or damaged siblings. Here we used three species of planktotrophic calyptraeids, one from each of three major genera in the family, to answer the following 3 questions: (1) Can planktotrophic developers benefit from the ingestion of yolk and tissue from siblings? (2) Does ingestion of yolk and tissue from siblings increase the variation in offspring size? and (3) Does ingestion of yolk and tissue from siblings alter the allometry between the velum and the shell, increasing morphological similarity to embryos of adelphophagic species? We found an overall increase in shell length and velum diameter when embryos could feed on smashed siblings within their capsules, but we did not detect any increase in variation or changes in allometry. The overall effect of our treatment was small compared to the growth observed in naturally adelphophagic development, but each embryo probably consumed only one sibling on average, whereas adelphophages usually consume at least 10-30 siblings.