Urastoma cyprinae in natural and cultured mussel (Mytilus galloprovincialis LmK) populations in México

The turbellarian Urastoma cyprinae (Urastomidae) was found parasitizing Mytilus galloprovincialis in natural beds and culture long-lines at Ensenada, Baja California, north-west Mexico. The parasite caused some damage to the gills of the host. Prevalence was monitored between January 1995 and January 1996 and ranged from 0 to 100% according to sampling locality. Mussels from polluted water at the Ensenada pier showed a low prevalence rate (0-13%) and intensity of infection (0-5 parasites/host). Cultured mussels showed the highest prevalence (50-100%) and intensity of infection (0-84), while mussels from the upper intertidal zone of an exposed rocky shore showed intermediate prevalence (10-87%) and intensity of infection (0-20). This is the first report of U. cyprinae in mussels from the Pacific coast of North America.