Parasites of California Spionid Polychaetes

Intertidal, sand dwelling, spionid polychaetes from the San Gabriel River estuary and Alamitos Bay (southern California) were examined for parasites over a period of 16 months. The worms surveyed were Boccardia hamata, B. proboscidea, Polydora ligni, P. nuchalis, P. socialis, Pseudopolydora paucibranchiata, Pygospio elegans, Scolelepis (Nerinides) maculata, and Streblospio benedicti. A total of 26 parasite species was observed of which only a few infected more than a single host. The average number of parasite species per host was 3.9. Endoparasites were found in all species except P. paucibranchiata, an introduced species. The endoparasites seen included 13 species of gregarines, 3 coccidia, 4 microsporidia, 1 astome ciliate, 1 mesozoan and 2 species of bacteria. The discovery of bacterial parasites may be the first for the Class Polychaeta. An ectoparasitic ancistrocomid ciliate was found on all of the polydorid species except B. proboscidea. In addition, P. ligni served as host for an urceolariid ciliate. The three nonpolydorids were free of ectoparasites.