Abstract
A workshop entitled “Emerging diseases of cultured marine molluscs in Japan” was held by the Japanese Society of Fish Pathology in Sendai on 25th September 1999. This was aimed to have an overview of the researches on the mass mortality of cultured pearl oyster (Pinctada fucata martensii) occurring in Japan. Prior to the main subject, two diseases, amyotrophia of Japanese black abalone (Nordotis discus discus) and abnormal coloration of adductor muscle in Japanese scallop (Patinopecten yessoensis), were presented, both being suspected to be infectious diseases caused by filterable agents. Since 1994 mass mortalities of pearl oyster have occurred in western Japan, giving much economic losses to the pearl culture industry. Various factors such as blooms of toxic dinoflagellate Heterocapsa circularisquama, perkinsosis, virus or filterable agent infection, and environmental factors were suspected as causes of the mortality. In the workshop, invited speakers gave talks on the history of pearl oyster culture, results of epizootiological observations, histopathological examinations, microbiological examinations, and infection experiments, and their own views of the etiology of the disease. At present, although the causative virus has not been determined, the viral etiology seems to be most probable, and some environmental parameters such as high water temperature might affect the mass mortality.
