Pea Crabs in Oysters


Category 2 (In Canada and of Regional Concern)

Common, generally accepted names of the organism or disease agent

Oyster Crab, Pea Crab.

Scientific name or taxonomic affiliation

  1. Pinnotheres pisum.
  2. Pinnotheres ostreum and possibly Tumidotheres (=Pinnotheres) maculatus.
  3. Pinnixa littoralis.
  4. Pinnnotheres pholadis.

Geographic distribution

  1. Europe.
  2. Eastern USA.
  3. Western USA, British Columbia.
  4. Japan.

Host species

  1. Ostrea edulis as well as other species of bivalves including mussels, clams, cockles and scallops.
  2. Crassostrea virginica as well as other species of bivalves.
  3. Ostrea conchaphila (=Ostrea lurida) as well as other species of bivalves.
  4. Crassostrea gigas as well as other species of bivalves.

Impact on the host

The mantle cavity may contain several crabs, thereby reducing market value. The number of crabs per oyster is limited by mantle space. No evidence of direct pathology has been reported. The crabs feed on food items collected by their hosts.

Diagnostic techniques

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

Methods of control

Precautions should be taken to prevent their introduction. Note: they can invade other commercially important bivalves such as Mytilus edulis, Mya arenaria, Modiolus modiolus, Placopecten magellanicus and Argopecten irradians.


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.

Hart, J.F.L. 1982. Crabs and their relatives of British Columbia. British Columbia Provincial Museum, Victoria. p. 236-237.

McDermott, J.J. 1962. The incidence and host-parasite relations of pinnotherid crabs in bivalve molluscs of New Jersey. Bulletin of the Ecological Society of America 42: 82.

Moller Christensen, A. and J. J. McDermott. 1958. Life-history and biology of the oyster crab. Pinnotheres ostreum Say. Biological Bulletin Marine Biology Laboratory Woods Hole 114: 146-179.

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 Oysters.

Date last revised: September 1994
Comments to Susan Bower

Date modified: