Premiers resultats d'une etude histologique sur la maladie des branchies

It was only in September 1967 that we observed in Ostrea edulis the symptoms of a disease that had already been infecting Crassostrea angulata for some time. The disease manifests itself in gills that become indented rather deeply and appear, in extreme cases, completely eroded. Since we focused our observations on Portuguese as well as flat oysters, we were able to compare the disease's manifestation in both species. The extreme stages only very rarely exist in O. edulis, since the most infected oysters are in this stage at stage II of the classification. The indentations are usually distinct and the perforations that manifest themselves cannot be seen in C. angulata even when in the early stages. We have not observed the presence of indentations or perforations on the flat oyster's palpi, while indentations or perforations are frequent in Portuguese oysters. This study focused on many batches of oysters from diverse sources and of various ages: Ostrea edulis: France, Italy, Denmark, Norway Crassostrea gigas: Japan, Canada, Korea Crassostrea angulata: France (Charentes-Maritimes, Arcachon, Brittany). After a macroscopic examination of the oysters from these various batches, we started observing in vivo fragments of the various organs (palpi, gills, visceral mass...) and their histological study after setting and dyeing; we created cultures in many media to try to isolate the agent or agents responsible for these lesions that, in the case of the most developed ones, appear to be followed by the death of the mollusc.