The turbellarian urastoma cyprinae from edible mussels mytilus galloprovincialis and mytilus californianus in baja california, NW Mexico.

The turbellarian Urastoma cyprinae (Graff, 1913) was found in the mantle cavity of Mytilus galloprovincialis Lamarck and Mytilus californianus Conrad, on the Pacific coast of Baja California NW Mexico. This is the first record of this turbellarian for bivalves from the Pacific coast of North America. In M. galloprovincialis from an exposed rocky shore, prevalence ranged from 10 to 87% and mean number of turbellarians per infested mussel was 1.9; in a culture area prevalence ranged from 57 to 100% and the mean number of turbellarians per infested mussel was 7.4. In the protected and polluted areas U. cyprinae was scarce or absent, prevalence ranging from 0 to 15% and the mean number of turbellarian per infested mussel being 0.07. The prevalence and the mean number of turbellarians per M. californianus in the exposed rocky shore ranged from 20 to 100% and 5.1, respectively. There were more worms in the larger mussels. Demibranches of M. galloprovincialis and M. californianus may be injured by the presence of turbellarians. An infiltration of hemocyte cells around the turbellarians was observed in both species and the blood sinuses in the infected area were engorged. Recorded damage was not related to a negative effect on the condition index of mussels. Copyright 1998 Academic Press.