Occurrence and characteristics of the haemocyte parasite Bonamia sp. in the New Zealand dredge oyster Tiostrea lutaria

Abstract

Bonamiasis, first detected in the New Zealand dredge oyster Tjostrea lutaria (Hutton) during the southern autumn of 1986 was investigated through 2 surveys of oyster beds carried out over spring (Sep 1986) and summer (Jan 1987). In spring, a 'lighter' form of the parasite occurred most frequently, confined largely to the sub-epithelia1 tissue. In summer, a 'dense' form, nearly identical to the 'classic' European and American Bonamia ostreae, was the dominant type; it occurred in subsurface tissue around the digest~ved iverticula and gut, and ~nvadedg onadal follicles and gill filaments Other forms, such as a second type of the 'dense form' and what appeared to be intermediate stages between the 'lighter' and 'dense' types were also detected. The significance of these different types in the life cycle of the parasite is discussed. The New Zealand species shows distinct size and morphological differences from B. ostreae.