Spotted Gonad Disease of Sea Urchins


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Spotted gonad disease.

Scientific name or taxonomic affiliation

Unknown. Proctoeces maculatus (trematode in the family Fellodistomidae) was observed in most spotted gonads but was not detected in some sea urchins with gonads that contained numerous spots.

Geographic distribution

Along the coast of Hokkaido, Japan.

Host species

Strongylocentrotus intermedius.

Impact on the host

Spotted disease cause partial degradation of germinal tissue, probably damages the reproductive capacity of the gonadal tissues, and causes a reduced market value for affected gonads due to their anomalous colour.

Diagnostic techniques

Gross Observations: Spots on the gonad vary from a few blackish-red spots on a few of the gonad lobules to extensive blackish-brown or blackish-purple spots on most of the lobules. In extreme cases, most of the gonad has turned the colour of the spots and appeared seriously ulcerated or atrophied.

Smears: Squashed and smeared spotted gonad stained with alizarin red S using Dal's method for calcium detection contained numerous, intensely red staining, C-shaped spicules. The brown granules also stained red but were weaker than the spicules.

Histology: Accumulation of eleocytes (coelomocytes containing brown granules) and extracellular brown granules in the germinal epithelium and germinal layer. Enlarged granule masses may eventually occupy lumen spaces. Adjacent to the spots, germ cells are scarce or nearly nonexistant and accessory cells are atrophied. However, even in severely affected gonads, normal lobules filled with mature germ cells are present among the spotted lobules. Some spots surround coiled P. maculatus.

Methods of control

No known methods of prevention or control. Water temperature of 20 to 26 °C may induce the onset of spotted disease.


Shimazu, T. 1979. A metacercaria of a digenic trematode of the genus Proctoeces (Fellodistomidae) parasitic to the sea urchin, Strongylocentrotus intermedius. Zool. Mag. Tokyo 88: 318-320.

Shimizu, M. 1994. Histopathological investigation of the spotted gonad disease in the sea urchin, Strongylocentrotus intermedius. Journal of Invertebrate Pathology 63: 182-187.

Shimizu, M. and K. Nagakura. 1993. Acid phosphatase activity in the body wall of the sea urchin, Strongylocentrotus intermedius, cultured at varying water temperatures. Comparative Biochemistry and Physiology 106B: 303-307.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Spotted Gonad Disease of Sea Urchins.

Date last revised: September 1996
Comments to Susan Bower

Date modified: