Attraction of Urastoma cyprinae (Turbellaria: Urastomidae) to the eastern oyster Crassostrea virginica

Abstract

Urastoma cyprinae Graff, 1882 has been reported on the gills of various bivalve species, including the eastern oyster Crassostrea virginica. While earlier workers refer to U. cyprinae as a commensal, recent findings reveal that the 'gill-worm' can be pathogenic to its molluscan host and may, therefore, also be considered to be parasitic. To determine whether there exists a definite attraction of U. cyprinae to oysters, a series of experiments were conducted using specially designed glass chambers. Results indicate that U. cyprinae is negatively phototactic and that it is more attracted to oysters when compared to other molluscan species such as mussels and clams. U. cyprinae was found to be highly attracted to isolated oyster mucus, and, to a lesser extent, to mucus-coated gill tissue. Findings confirm that the presence of U. cyprinae in oysters is not coincidental and that mucus plays an important role in attracting the worms to its host.