GROSS AND HISTOPATHOLOGICAL SIGNS OF THE SPOTTING DISEASE IN THE SEA-URCHIN STRONGYLOCENTROTUS-INTERMEDIUS

Histopathological and scanning electron microscopic observations were performed in the lesional tissues of the test and appendages of the se a urchin Strongylocentrotus intermedius affected by ''spotting disease .'' Spotting lesions with blackish red color on the test surface, sepa ration of spines and attachment failure of tube feet are typical exter nal signs. The epidermal lesions of the test and appendages is disorga nized and infiltrated by migrating coelomic red spherule cells (eleocy tes) and brown granules. Muscle fibers in the spine base, tube feet an d ampullae are fragmented. These pathological signs are very similar t o those of the bald-sea-urchin disease in S. purpuratus and S. droebac hiensis. Invasions of the ameba Paramoeba invadens that was identified as a pathogen of the bald-sea-urchin disease, were not found in the d iseased S. intermedius. However, seriously damaged epidermis, dermis a nd connective tissue were invaded by bacteria, one of which was a fili form bacillus. The results suggest that the spotting disease of S. int ermedius would associate with a bacterial infection.