Meeting Abstract
P3.76 Wednesday, Jan. 6 Particle capture and ingestion abilities in larvae of calyptraeid gastropods with different modes of development LESOWAY, M.P.*; COLLIN, R.; McGill University, Montreal, Canada; Smithsonian Tropical Research Institute, Panama maryna.lesoway@mail.mcgill.ca
For marine invertebrate larvae, it is thought that larval feeding structures, once lost, are difficult or impossible to regain (Strathmann 1974, 1978; Hart 1996), owing to lack of stabilising selection once these complex structures have been lost. Recent work with calyptraeid gastropods indicates that mode of development (planktotrophy, lecithotrophy, direct development or direct development with nurse eggs) changes quickly and frequently, and suggests the re-evolution of larval planktotrophy from direct developing lineages in three instances (Collin 2004, Collin et al. 2007). The possible re-evolution of larval feeding in this group represents a unique opportunity to investigate the evolutionary consequences of the loss of complex structures, such as the velum; the gastropod larval organ used for swimming and feeding. We investigated the particle capture and ingestion abilities of several species exhibiting different modes of development. Larval size, velum size, prototrochal ciliar length, food groove length, and mouth width were compared across two planktotrophs, a lecithotroph and two direct developers. Larvae were exposed to a suspension of microspheres (ranging from 2 – 90µm) to observe size selectivity and the rate of particle ingestion. The mechanisms of particle capture were also observed. In all species velum size increased after the initiation of the velar ridge in early development. In the direct developers the velum decreased in size and was absorbed prior to hatching. In the other species the velum continued to grow until hatching. In all species embryos and larvae ingested beads. Details of the differences in the size and number of particles ingested will be discussed in terms of transitions between different modes of development.
