Int. J. Dev. Biol. In Press
doi: 10.1387/ijdb.200154rc
© UPV/EHU Press

Ancestral form and function of larval feeding structures are retained during development of non-planktotrophic gastropods

Rachel Collin*,1, Caitlin M. Shishido2, Anabell J. Cornejo1, Maryna P. Lesoway3

1Smithsonian Tropical Research Institute, Balboa Ancon, Panama, 2Department of Biology, University of Hawaii at Manoa, Honolulu, HI, USA and 3Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA

ABSTRACT Mode of development (MOD) is a key feature that influences the rate and direction of evolution of marine invertebrates. Although many groups include species with different MODs, the evolutionary loss of feeding larvae is thought to be irreversible as the complex structures used for larval feeding and swimming are lost, reduced, or modified in many species lacking feeding larvae. This view is largely based on observations of echinoderms. Phylogenetic analysis suggests that feeding larvae have been re-gained in at least one species of calyptraeid gastropod. Further, its sister species has retained the velum, the structure used for larval feeding and swimming. Here, we document velar morphology and function in calyptraeids with 4 different MODs. Embryos of Crepidula navicella, Crepidula atrasolea, Bostrycapulus aculeatus, Bostrycapulus odites, Bostrycapulus urraca, Crepipatella dilatata, Crepipatella occulta, Crucibulum quiriquinae and Crepidula coquimbensis all hatch as crawling juveniles, yet only Crepidula coquimbensis does not make a well-formed velum during intracapsular development. The velar dimensions of 6 species with non-planktotrophic development were similar to those of planktotrophic species, while the body sizes were significantly larger. All of the species studied were able to capture and ingest particles from suspension, but several non-planktotrophic species may ingest captured particles only occasionally. Video footage suggests that some species with adelphophagic direct development capture but frequently fail to ingest particles compared to species with the other MODs. Together these lines of evidence show that, among calyptraeids at least, species that lack planktotrophic larvae often retain the structures and functions necessary to successfully capture and ingest particles, reducing the barriers to the re-evolution of planktotrophy.

Keywords:

adelphophagy, veliger, particle capture, Crepidula

*Corresponding author e-mail: collinr@si.edu