Pea Crabs in Scallops


Category 1 (Not Reported in Canada)

Common, generally accepted names of the organism or disease agent

Oyster crab, Pea crab.

Scientific name or taxonomic affiliation

Tumidotheres (=Pinnotheres) maculatus, Pinnotheres ostreum, Pinnotheres pholadis (Decapoda: Pinnotheridae)

Geographic distribution

Eastern U.S., Japan.

Host species

Placopecten magellanicus, Argopecten irradians, Argopecten gibbus, Chlamys nipponensis. Other bivalves, including oysters, mussels, clams and cockles, may also harbour pea crabs.

Impact on the host

The mantle cavity may contain several crabs thereby reducing market value (numbers limited by mantle space). No evidence of direct pathology although some scientists believe reduced growth in A. irradians was due to T. maculatus competing for food items collected by the scallop or disrupting normal feeding behaviour.

Diagnostic techniques

Gross Observations: Pea crabs are visible to the naked eye within the mantle cavity of their hosts.

Methods of control

Precautions should be taken to prevent their introduction. Note: they can invade other commercially important bivalves such as Crassostrea virginica, Mya arenaria, Mytilus edulis.


Cheng, T.C. 1967. Marine molluscs as hosts for symbioses with a review of known parasites of commercially important species. In: F.S. Russell (ed.). Advances in Marine Biology. Volume 5. Academic Press Inc., London, p. 315-335.

Getchell, R.G. 1991. Diseases and parasites of scallops. In: S.E. Shumway (ed.). Scallops: Biology, Ecology and Aquaculture. Developments in Aquaculture and Fisheries Science No. 21. Elsevier Press, p. 471-494.

Karlsson, J.D. 1991. Parasites of the bay scallop, Argopecten irradians (Lamarck, 1819). In: S.E. Shumway and P.A. Sandifer (eds.). An International Compendium of Scallop Biology and Culture. The World Aquaculture Society. Baton Rouge, p. 180-190.

Kruczynski, W.L. 1972. The effect of the pea crab Pinnotheres maculatus on growth of the bay scallop, Argopecten irradians. Chesapeake Science 13: 218-220.

Citation Information

Bower, S.M., McGladdery, S.E., Price, I.M. (1994): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Pea Crabs in Scallops.

Date last revised: Fall 1994
Comments to Susan Bower

Date modified: