IN-VITRO CULTIVATION AND DEVELOPMENTAL CYCLE IN CULTURE OF A PARASITIC DINOFLAGELLATE (HEMATODINIUM SP.) ASSOCIATED WITH MORTALITY OF THE NORWAY LOBSTER (NEPHROPS-NORVEGICUS) IN BRITISH WATERS

Dinoflagellates are common and often important parasites of aquatic or ganisms, but their developmental cycles are poorly known and have not been established in in vitro culture. The parasitic dinoflagellate (He matodinium sp.) associated with mortality of the Norway lobster (Nephr ops norvegicus) in British waters has been cultivated in vitro in 10% foetal calf serum in a balanced Nephrops saline. In culture the parasi te undergoes a characteristic cycle of development. Circulating sporob lasts from the host's haemolymph in vitro generate 2 kinds of flagella ted uninucleate dinospore, macrospores and microspores, either of whic h will, after 5 weeks in fresh medium, germinate to produce multinucle ate unattached filamentous trophonts. These trophonts multiply by frag mentation and growth and may be serially subcultured in this form, at 2 week intervals, indefinitely. If not subcultured, the filamentous tr ophonts give rise to colonies of radiating filaments ('gorgonlocks') w hich Subsequently attach to the substratum to form flattened web-like 'arachnoid' multinucleate trophonts. Arachnoid trophonts become arachn oid sporonts when they synthesize trichocysts and flagellar hairs and may give rise to secondary arachnoid sporonts or to dinospores which i nitiate a new cycle.