Sphenophrya-like Ciliates of Clams and Cockles


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Sphenophrya-like ciliates, Sphenophyriid infections.

Scientific name or taxonomic affiliation

Sphenophrya dosiniae, Sphenophrya cardii and other unidentified species in the order Rhynchodida.

Geographic distribution


Host species

Dosinia exoleta, Timoclea ovata, Corbula gibba, Spisula solidissima, Mya truncata, Mya arenaria, Cardium lamarcki, Cerastoderma (=Cardium) edule, Sphaerium corneum, Dreissena polymorpha, Tapes philippinarum, and similar ciliates are found on a wide variety of other bivalves including oysters and mussels.

Impact on the host

Large numbers occur with no obvious host-response. All pathology to date describes the effect of suctorial tubule attachment to the host-cell (which in some species involves insertion of fibres into the host-cell). No mortalities have been associated with sphenophyriid infections.

Diagnostic techniques

Histology: Pear-shaped ciliates (often lacking cilia during life stage that is attached to host) with large, densely basophilic nuclei. Attached to the gill and palp surfaces during parasitic stage of the life cycle.

Methods of control

Prevention and control impractical.


Bower, S.M., J. Blackbourn and G.R. Meyer. 1992. Parasite and symbiont fauna of Japanese littlenecks, Tapes philippinarum (Adams and Reeve, 1850), in British Columbia. Journal of Shellfish Research 11: 13­19.

Fenchel, T. 1965. Ciliates from Scandinavian Molluscs. Ophelia 2(1): 71-174.

Otto, S. V., Harshbarger, J. C. and Chang, S. C. 1979. Status of selected unicellular eucaryote pathogens and prevalence and histopathology of inclusions containing obligate prokaryote parasites in commercial bivalve mollusks from Maryland estuaries. Haliotis 8 (1977): 285-295.

Sprague, V. 1970. Some protozoan parasites and hyperparasites in marine bivalve molluscs. American Fisheries Society Special Publication 5: 511-526.

Citation Information

Bower, S.M., McGladdery, S.E., Price, I.M. (1994): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Sphenophrya-like Ciliates of Clams and Cockles.

Date last revised: Fall 1994
Comments to Susan Bower

Date modified: