Brood-pouch Copepod of Scallop Gills


Category 1 (Not Reported in Canada)

Common, generally accepted names of the organism or disease agent

Brood-pouch copepod on gills.

Scientific name or taxonomic affiliation

Pectenophilus ornatus - a highly modified parasitic copepod with a brood pouch. This parasite has been misidentified as a Rhizocephala (Class of parasitic barnacles).

Geographic distribution


Host species

Patinopecten yessoensis, Chlamys farreri nipponensis, Chlamys farreri farreri.

Impact on the host

The sac-like female (up to 8 mm in width), brilliant yellowish orange in colour is orally attached to the gill arch and is covered by the scallop's ciliated gill epithelium. The attachment site consists of hypertrophied host tissue that is perfused with host blood upon which the copepod feeds. It is a serious pest that has a negative effect on the scallop's condition (fatness) and reduces market acceptability. It may infect up to 100% of cultured Japanese scallop populations and is present throughout the year with maximum recruitment occurring from spring to summer.

Diagnostic techniques

Gross Observations: Presence of parasites attached to gills as described above. This copepod can be differentiated from other parasitic copepods by its superficial resemblance to the Rhizocephala.

Histology: The presence of a digestive tract within the parasite differentiates it from all Rhizocephala.

Methods of control

No known methods of prevention or control. Scallops from bottom culture were more frequently and heavily infected than those from hanging culture.


Elston, R.A., M.T. Wilkinson and R. Burge. 1985. A rhizocephalan­like parasite of a bivalve mollusc, Patinopecten yessoensis. Aquaculture 49: 359­361.

Nagasawa, K., J. Bresciani and J. Lützen. 1988. Morphology of Pectenophilus ornatus, new genus, new species, a copepod parasite of the Japanese scallop Patinopecten yessoensis. Journal of Crustacean Biology 8: 31­42.

Nagasawa, K. and M. Nagata. 1992. Effects of Pectenophilus ornatus (Copepoda) on the biomass of cultured Japanese scallop Patinopecten yessoensis. Journal of Parasitology 78: 552-554.

Nagasawa, K., K. Takahashi, S. Tanaka and M. Nagata. 1991. Ecology of Pectenophilus ornatus, a copepod parasite of the Japanese scallop Patinopecten yessoensis. Bulletin of the Plankton Society of Japan 1991: 495-502.

Citation Information

Bower, S.M., McGladdery, S.E., Price, I.M. (1994): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Brood-pouch Copepod of Scallop Gills

Date last revised: Fall 1994
Comments to Susan Bower

Date modified: