Dominique Hervio

Interactions between Bonamia ostreae (Protozoa: Ascetospora) and hemocytes of Ostrea edulis and Crassostrea gigas (Mollusca: Bivalvia): Entry mechanisms

Entry mechanisms of the intrahemocytic parasite Bonamia ostreae (Ascetospora) into hemocytes of the sensitive (Ostrea edulis) and a resistant (Crassostrea gigas) oyster species have been analyzed. The study was based upon the development of a B. ostreae-hemocyte in vitro system. Ultrastructural features and Cytochalasin B sensitivity of the phenomenon demonstrate that B. ostreae enters into the two oyster species hemocytes by host-specified phagocytosis, although parasite contribution to entry into O. edulis hemocytes cannot be discarded. Possible receptors and the postphagocytic fate of the parasite are discussed.

Establishment of an experimental infection protocol for the flat oyster, Ostrea edulis, with the intrahaemocytic protozoan parasite, Bonamia ostreae: application in the selection of parasite-resistant oysters

Abstract The availability of purified Bonamia ostreae suspensions and the development of an inoculation protocol enabled experimental infections with the European flat oyster, Ostrea edulis , to be carried out. Different infectious doses were tested and the kinetics of bonamiasis studied. The 50% infectious dose (ID), determined from inoculations with 10 to 10 6 B. ostreae per individual, was estimated to be 80 000 parasites for 3-year-old oysters. This 50% ID was used to screen for parasite-resistant oysters. Preliminary results suggested that the F 1 progeny of oysters that survived previous outbreaks of bonamiasis were more resitant to B. ostreae .

Interactions between Bonamia ostreae (Protozoa: Ascetospora) and hemocytes of Ostrea edulis and Crassostrea gigas (Mollusca: Bivalvia): in vitro system establishment

Abstract Based on parasite purification and hemocyte primary culture, an in vitro system was established for studying early interactions between Bonamia ostreae and the hemocytes of sensitive Ostrea edulis and resistant Crassostrea gigas. Infections were observed whichever the hemocytic types and the oyster species. The advantages and disadvantages of the system are discussed with regard to the study of recognition, entry, and survival mechanisms of the parasite.

Evidence of neutralizing activity against T3 coliphage in oyster Crassostrea gigas hemolymph

To investigate defense reactions of bivalve molluscs against viruses, experimental in vitro assays have been developed using T3 coliphage as a test virus. A native neutralizing factor in oyster Crassostrea gigas serum showed high individual variability and was enhanced significantly by repeated sampling of hemolymph from the same oysters. The responsible factor is apparently thermolabile and sensitive to EDTA treatment. Because of an inhibitory effect by the enzymatic inhibitor, phenylmethylsulphonyl fluoride (PMSF), the T3-neutralizing factor may be related to serine protease.

Development of new methodologies for diagnosis of infectious diseases in mollusc and shrimp aquaculture

Abstract The development of new methodologies for diagnosis of infectious diseases of molluscs and shrimps is related to progress in biotechnology and molecular biology. The different kinds of immunoreagents and nucleic-acid probes and the respective advantages and disadvantages of immunological and nucleic-acid hybridization-based methods are described and analysed in terms of developments and applications in marine invertebrates aquaculture.