No evidence of host specialization in a parasitic pea-crab exploiting two echinoid hosts

摘要

ABSTRACT: The pinnotherid crab Dissodactylus primitivus lives parasitically on 2 burrowing echinoid species, Meoma ventricosa and Plagiobrissus grandis. The fecundity of female crabs varies between hosts, and is higher when parasitizing P. grandis than M. ventricosa. Moreover, the hosts present great variations in morphology (size and density of spines). These characteristics suggest the potential to differentiate crabs according to host species. We investigated the genetic (microsatellites) and morphometric (outline analysis) differentiation of this parasitic crab between 2 host species at 1 Jamaican site (Western Lagoon, Discovery Bay), and compared it with geographic differentiation among 4 sites along the north coast of Jamaica. Greater genetic differences between parasites of the 2 sympatric hosts than between parasites of a single host at different geographic locations would indicate host differentiation. Genetic analyses (microsatellites) did not detect spatial differentiation (probably due to local hydrography) or differentiation according to host species. This lack of host differentiation could be explained by mobility of adult crabs between hosts. However, there was weak but significant morphological differentiation between female crabs from the 2 hosts. This morphological difference may reflect constraints due to host morphology.