9633193 Strathmann Animals in numerous phyla release eggs into the plankton where they develop without parental protection. Their development to first swimming is briefer than in related species with more protected embryos. Selection appears to favor their short time to swimming, but the time varies. In this research, four questions will be answered by comparisons within and between groups of marine animals. (1) Is duration of embryonic development to first swimming correlated with the number of cells in locomotory structures? (2) Is this duration influenced more strongly by functional differences that occur within phyla, such as presence/absence of a feeding larval stage or egg size? (3) Do more protected embryos develop more slowly (in addition to developing for a longer time) before first swimming? (4) Is duration of development to first feeding correlated with numbers of cells in structures used for ciliary feeding? This study may demonstrate extraordinarily persistent limits on convergence in embryonic durations and functional reasons for those limits. Alternatively, this study could show that diverse forms of animals have converged on similar embryonic durations in diverse ways. Either outcome will indicate clade-specific constraints on how marine animals pass through the one-cell bottleneck in their life history.
