How specialized are the diets of Northeastern Pacific sponge-eating dorid nudibranchs?

摘要

Cryptobranch dorids are typically thought to have specialized diets limited by prey skeletal architecture and chemistry, but recorded diets for some species are broader than expected. Few studies have directly compared prey use with prey availability over multiple sites to test the dietary range of separate populations. Diets of dorids at sites in British Columbia, Canada were not simply related to the richness and diversity of the local sponge assemblage, partly because all dorids avoided the most common sponges and instead consumed rare, inconspicuous species. At each site, three dorid species (Cadlina luteomarginata, Diaulula sandiegensis and Peltodoris nobilis) consumed multiple species, while two others (Doris montereyensis and D. odhneri) each consumed one species almost exclusively, so total dietary ranges may sometimes reflect true oligophages and sometimes mosaics of stenophage populations. Diets in all cases shifted greatly among sites and geographic regions and included sponges with different skeletal types, indicating that all species are nonstereotyped specialists. The diets of these dorids may be determined primarily by haphazard encounters among scarce or patchy palatable prey, with other prey attributes playing a lesser role.