Meeting Abstract

P3.106  Friday, Jan. 6  The Development of Particle Capture and Ingestion Abilities in Calyptraeid Gastropods with Different Modes of Development SHISHIDO, C.M.*; COLLIN, R.; LESOWAY, M.P.; Smithsonian Tropical Research Institute; Smithsonian Tropical Research Institute; McGill University

In marine invertebrate larvae, it is generally understood that evolutionary changes between modes of development (planktoptrophy, lecithotrophy, direct development w/large eggs, or direct development w/nurse eggs) occur predominantly from feeding planktotrophic larvae to non-feeding direct developers. It is thought that once complex structures such as the velum, the gastropod larval feeding and swimming organ, are lost they are almost impossible to regain. Molecular phylogenies of calyptraeid gastropods indicate that changes in the mode of development occur rapidly and frequently and also support instances of the re-evolution of planktotrophic larvae from lineages of direct developers. Observations suggest that the velum is retained in several species with complete intracapsular development. We examined 13 species of calyptraeids to determine if the form and function of the velum is retained in species without feeding larvae. We measured the size of the velum and length of the cilia, and compared the ability of each species to capture and ingest particles from suspension. Several developmental stages of each species were exposed to solutions of plastic microspheres ranging from 2 – 90 µm to determine the range of sizes that can be captured by each species and to understand how this relates to velum morphology. Veligers from six planktotrophs, three direct developers with large eggs, and three direct developers with nurse eggs all ingested beads from 2um to 90um. Crepidula ustulatulina, the sole species with lecithotrophic larvae only consumed beads up to 25um in diameter. While velum size increased in the early development of all species, the velum of the direct developers and lecithotrophs were absorbed as they neared hatching.