Scallop Haplosporidian


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Haplosporidian infection of bay scallops.

Scientific name or taxonomic affiliation

Unknown genus and species of the phylum Haplosporidia.

Geographic distribution

Cultured stocks from Bohai Sea region of the Yellow Sea in China.

Host species

Argopecten irradians introduced into China for aquaculture purposes.

Impact on the host

Found in more than 83% of the A. irradians examined from two of seven cultured stocks experiencing mortalities which were highest in the spring after the period of spawning and in juvenile scallops. However, the majority of the infections were categorized as light and only plasmodial stages were observed (Chu et al. 1996). Thus, Chu et al. (1995) suggested that the parasite was not causing significant mortalities in the period in which the samples were collected (March and April 1993).

Diagnostic techniques

Histology: Spherical to oval multinucleate plasmodia (4.0 to 17.0 µm in diameter and contained 2 to 18 nuclei) typical of the phylum Haplosporidia scattered throughout the connective tissue. No spores were observed.

DNA Probes: No positive in situ hybridization occurred with a DNA probe known to be specific for Haplosporidium nelsoni.

Methods of control

No known method of prevention or control.


Chu, F.L.E., E. Burreson, F. Zhang, K. Chew and S. Blake (1995)

An unidentified parasite in bay scallops (Argopecten irradians) cultured in the Shandong and Liaoning provinces, China. In: Book of Abstracts, 10th International Pectinid Workshop, Cork, Ireland, April 27 - May 2, 1995.

Chu, F.L.E., E.M. Burreson, F. Zhang and K.K. Chew. 1996. An unidentified haplosporidian parasite of bay scallop Argopecten irradians cultured in the Shandong and Liaoning provinces of China. Diseases of Aquatic Organisms 25: 155-158.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Scallop Haplosporidian.

Date last revised: September 1996
Comments to Susan Bower

Date modified: