Appleton, Paul Lawrence
Investigations on the cytology and life-cycle of the parasitic dinoflagellate Hematodinium sp associated with mortality of Nephrops norvegicus.
PhD thesis, University of Glasgow.
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Dinoflagellate parasites of the genus Hematodinium are associated with heavy mortality of the Norway lobster (Nephrops norvegicus) off the west coast of Scotland. The Syndinean dinoflagellate has been isolated from N. norvegicus and has been successfully cultured axenically in vitro. Twelve isolates have been serially cultivated in a medium of 10% fetal calf serum in a balanced Nephrops saline with added antibiotics at 8-10°C. In this medium the parasite undergoes developmental changes that are believed to represent stages in the life cycle of the parasite in vivo. This is the first complete life cycle in vitro to be described for a Syndinean dinoflagellate.
Flagellate dinospores arise in vitro from circulating sporogenic parasite forms - sporoblasts removed in the haemolymph from infected lobsters. Sporogenic parasites are recognised by the presence in the cytoplasm of structures not found in the trophont. These are (1) trichocysts and (2) flagellar hairs within swollen endoplasmic reticulum cisternae. Dinospores are of two types - a larger macrospore and a smaller, more active microspore. Individual isolates produce one or the other, not both. Condensation of chromosomes in the nucleus is more pronounced in the microspore than in the macrospore. Both spore types germinate after 18-62 days in the culture medium to produce the main multiplicative stage of the parasite in vitro - the multinucleate filamentous trophont. No fusion of flagellates has been observed and each type of spore can germinate independently of the presence of the other, indicating that the spores are not gametes. The filamentous trophonts correspond to the only form of the type species of the genus, Hematodinium perezi, found circulating in the blood of infected crabs by Chatton and Poisson (1931). (DXN004,487)
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