Marteilioides branchialis of Oysters


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Marteilioides of the gills.

Scientific name or taxonomic affiliation

Marteilioides branchialis.

Geographic distribution

New South Wales, Australia.

Host species

Saccostrea commercialis.

Impact on the host

Causes focal lesions on the gill lamellae. In conjunction with Marteilia sydneyi, this parasite causes significant economic losses among Sydney rock oysters being cultured in trays during the autumn.

Diagnostic techniques

Gross Observations: Focal patch (1-2 mm in diameter) of discolouration and swelling on the gill lamellae.

Histology: Epithelial hyperplasia and granulocyte infiltration at the site of the lesion. Uninucleate primary cells containing two to six and rarely up to 12 secondary cells in the the cytoplasm of epithelial cells, connective tissue cells, and occasionally in inflammatory cells within the lesion.

Electron Microscopy: This species can be differentiated from other Marteilioides spp. in that the spore contains two concentric cells rather than three. Marteilioides branchialis has from two to six and rarely 12 sporonts per stem cell in comparison to only two or sometimes three for Marteilioides chungmuensis in Crassostrea gigas. Also, multivesicular bodies similar to those of Marteilia spp. occur in primary cells of M. branchialis but not those of M. chungmuensis.

Methods of control

No known methods of prevention or control. Infected oysters should not be transported into areas known to be free of the disease.


Anderson, T.J. and R.J.G. Lester. 1992. Sporulation of Marteilioides branchialis n.sp. (Paramyxea) in the Sydney rock oyster, Saccostrea commercialis: an electron microscope study. Journal of Protozoology 39: 502-508.

Citation Information

Bower, S.M., McGladdery, S.E., Price, I.M. (1994): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Marteilioides branchialis of Oysters.

Date last revised: Fall 1994
Comments to Susan Bower

Date modified: