Diversity and evolution of parasitic gastropods

Abstract

At least ten families of the molluscan class Gastropoda contain parasitic species. Parasitic gastropods exhibit an extraordinarily large number of species and wide varieties of morphologies and host-exploitation strategies. Here, I introduce our evolutionary studies based on molecular phylogenetic analysis for two lineages of parasitic gastropods: Caledoniella (Caledoniellidae) and Eulimidae. Species of Caledoniella parasitize stomatopods (mantis shrimps) and have close phylogenetic kinship to burrow commensals of marine benthic invertebrates. Interestingly, Sigaretornus sp. from mantis shrimp burrows was found to be sister to Caledoniella, suggesting the following evolutionary scenario from free-living organisms to parasites: (1) colonization into benthic invertebrates’ burrows, (2) specialization to mantis shrimps, and (3) habitat-shift to the host body surface with the acquisition of the parasitic nature. Members of the other group Eulimidae show the widest range of parasitic strategies (i.e., temporary, ecto- and endoparasitism) on their echinoderm hosts. Molecular phylogenies of the family have revealed the polyphyly of endoparasitic taxa and repeated evolutionary changes from slender to globose shells. Recurrent specializations to the parasitic mode of life probably have an important role in the diversification of eulimid gastropods.