Potential disease-causing organisms associated with mantle cavity of Pacific oyster Crassostrea gigas in northern New Zealand

Abstract

Bimonthly samples of oysters Crassostrea gigas examined from June 1979 to June 1981, as part of a disease monitoring survey, showed the presence of several organisms within their mantle cavity, such as copepods, nematodes, ciliates and mudworms. A rnyicolid copepod and an alloeocoel turbellarian appear to be persistent and facultative invaders. A peculiar association is that of a chironornid insect larva whlch probably completes its developmental stages withn the oyster. fis- topathological examination reveals occasional swelling and disorganisation of the connective tissue and leucocyte infiltration around the oyster gut and the digestive diverticula, but these are considered to be histological anomahes, probably seasonal in character. The possible role of associated organisms in disease transmission and in contributing to stress is discussed.