Virginia Institute of Marine Science
Pinnotheres ostreum SAY, 1817, commonly parasitic in the oyster Crassostrea virginica (GMELIN, 1791), also may infest the jingle shell Anomia simplex 0RBIGNY, 1845, and the edible mussel Mytilus edulis LINNAEUS, 1758 (McDERMOTT, 1961, 1962). A fourth host, the ribbed mussel M odiolus demissus (DILLWYN, 1817) should now be added to the list of bivalves parasitized by this crab.
Mussels were collected from intertidal mussel beds at Sandy Point in the lower York River, Virginia (37°16'N, 76°33'W), from November, 1968, through June, 1969. Of 747 Modiolus demissus collected, 136 ( 18.2o/o) contained Pinnotheres ostreum. All of the crabs were small (0.71 to 3.15 mm carapace width) pre-hard and hard-stage (Stage I) crabs. No developmental stages later than the hard stage were seen. Gill erosions similar to those caused by young P. ostreum in Crassostrea virginica (CHRISTENSEN & McDERMOTT, 1958) were of ten associated with the presence of the crabs in M. demissus.
Sandifer, Paul A. and van Engel, Willard A., Modiolus demissus: A New Host for the Oyster Crab Pinnotheres ostreum in Virginia (1970). The Veliger, 13(2), 145-146.