Parasitic Copepods on Mussel Gills


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Parasitic copepods attached to gills.

Scientific name or taxonomic affiliation

Modiolicola gracilis and Pseudomyicola spinosus.

Geographic distribution

Reported from Baja California, NW Mexico.

Host species

Mytilus galloprovincialis and Mytilus californianus. Species of parasitic copepods in these two genera have also been reported from oysters.

Impact on the host

Modiolicola gracilis occurred in 27% of M. galloprovincialis (up to 5 specimens per mussel) and in 70% of M. californianus (up to 15 specimens per mussel) in Baja California with a slight increase in prevalence during the autumn and winter. From the same geographic locations, P. spinosus was scarce or absent from these two species of mussels except for M. galloprovincialis from a polluted environment where the prevalence reached 100% (up to 59 specimens per mussel). With both species of parasitic copepods, damage to the host tissue was negligible. However, most parasitised mussels showed a lower condition index.

Diagnostic techniques

Squash Preparations: Parasitic copepods can be observed attached to dissected gills and/or mantle pressed between two plexiglass plates and examined under a dissecting microscope (50x).

Histology: Cross sections of copepods attached to the gills.

Methods of control

No known methods of prevention or control.


Caceres-Martinez, J., R. Vasquez-Yeomans and E.S. Morales. 1996. Two parasitic copepods, Pseudomyicola spinosus and Modiolicola gracilis, associated with edible mussels, Mytilus galloprovincialis and Mytilus californianus, from Baja California, NW Mexico. Journal of Shellfish Research 15: 667-672.

Lauckner, G. 1983. Diseases of Mollusca: Bivalvia. In: O. Kinne (ed.) Diseases of Marine Animals. Volume II: Introduction, Bivalvia to Scaphopoda. Biologische Anstalt Helgoland, Hamburg, p. 817-833.

Marteil, L. 1976. La conchyliculture française, 2 partie: biologie de l'huitre et de la moule. Chapitre VI: maladies et mortalites. Revue des Travaux de l'Institut des Pêches Maritimes. 40: 285-313. (In French)

Citation Information

Bower, S.M. (2001): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Parasitic Copepods on Mussel Gills.

Date last revised: June 2001
Comments to Susan Bower

Date modified: