Abnormal Enlargement of the Ovary of Oyster, Crassostrea gigas (Thunberg) by an Unidentified Parasite

Abstract

Etiological study was carried out on abnormally enlarged ovary of Japanese oyster, Carssostrea gigas (Thunberg). Light and electron microscopic examination revealed that follicle cells and ova of abnormal ovary contained one or more inclusion bodies in addition to their own nuclei. These inclusion bodies were observed to grow with the development of the ova. The body is covered with electron dense wall and contained mitochondria, endoplasmic reticulum, granuels of various size and various electron density and nuclear body with a nucleolus like body. The above mentioned structure clearly indicates that the inclusion body is a parasite possibly belonging to Subclass Coccidiida. © 1981, The Japanese Society of Fish Pathology. All rights reserved.