L'emission des gametes chez l'huitre portugaise (Crassostrea Angulata LMK)

LE DANTEC (1968), in his research on the ecology and reproduction of the Portuguese oyster in the Arcachon basin, recounts a few experiments involving heat stimulation of genital product emissions. He conducted them in order to confirm his observation in situ, since temperature variations are presumably the most common factor of external stimulation in nature. However, the act of emitting male or female gametes in Crassostrea angulata was not, to our knowledge, the subject of any special study. In a general way, the authors seem to admit that it is possible to extend to the entire Crassostrea SACCO species the results obtained about C. virginica, C. gigas and C. commercialis, mainly by American and Japanese researchers. We wanted to verify it for the Portuguese oyster. On the one hand, studies on sex ratio and sex change in alternating-hermaphrodite lamellibranchia must contain individual observations on gametes and their emission rhythm (LUBET, 1959). Yet taking sex-product specimens by biopsy, when there are lesions of the upper valve of the shell and coat, has the effect of causing perturbations in the later development of the sexes in subjects returned to their natural habitat (GALTSOFF, 1964); identification of the male state or female state must therefore rely preferably on observing sex products emitted by the oysters. As for emission rhythm, it can be known with accuracy by observing tracings obtained while recording valve activity. In fact, egg laying of short duration is easily seen on the myograms obtained, while they can escape notice if the quantity of eggs emitted is very low. In light of the experimental results obtained by GALTSOFF with C. virginica, we tried to induce emission of sex products in C. angulata in order to observe the phenomena of egg-laying and ejaculation and to record valve activity of oysters during the sex act.