Sphenophrya-like Ciliates of Mussels


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Sphenophrya-like ciliates.

Scientific name or taxonomic affiliation

Gargarius gargarius, and other unidentified Sphenophrya-like ciliates.

Geographic distribution

On mussels from eastern and western U.S., Canada, Europe and Scandinavia. These ciliates appear to be ubiquitous in distribution, although different genera and species may occur in different areas.

Host species

Mytilus spp. and other bivalves including oysters, clams and cockles.

Impact on the host

Large numbers can be observed with no obvious host-response. Most pathology involves the effect of suctorial tubule attachment to the host-cell (which in some species comprises the insertion of fibres into the host-cell). Most sphenophryids attach superficially, however, parasite induced xenomas have been reported from the gills of Mytilus edulis from the Gulf of St. Lawrence. The only other xenoma lesions reported for sphenophyrids are from Crassostrea virginica from the eastern United States. No mortalities have yet been associated with sphenophryiid infections and prevalence of infection is usually low (2% or less).

Diagnostic techniques

Histology: Examine transverse sections for spindle shaped ciliates, with large, densely basophilic nuclei, attached to the gill and palp surfaces.

Methods of control

No known methods of prevention or control.


Bower, S.M. and A.J. Figueras. 1989. Infectious diseases of mussels, especially pertaining to mussel transplantation. World Aquaculture Review 20(4): 89-93.

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

McGladdery, S.E., R.E. Drinnan and M.F. Stephenson. 1993. A Manual of the parasites, pests and diseases of Canadian Atlantic bivalves. Canadian Technical Report of Fisheries and Aquatic Sciences No. 1931, p. 70-71.

Moret, K., C. Couturier, G.J. Parsons and K. Williams. 1999a. Monitoring shellfish health in Newfoundland: a preventative approach. Journal of Shellfish Research 18: 297-298. (Abstract).

Moret, K., K. Williams, C. Couturier and J. Parsons. 1999b. Newfoundland cultured mussel (Mytilus edulis) industry 1997 health survey. Bulletin of the Aquaculture Association of Canada 99-3: 35-37.

Otto, S.V., Harshbarger, J.C. and S.C. Chang. 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. (2001): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Sphenophrya-like Ciliates of Mussels.

Date last revised: July 2001
Comments to Susan Bower

Date modified: