Histological study of the sex ratio and reproductive cycle of the mangrove oyster Crassostrea tulipa (Lamarck, 1819) in the Saloum Delta (Senegal)

Abstract

The mangrove oyster Crassostrea tulipa has considerable socio-economic value in Senegal, as in many other West African countries. To better understand its biology, the objective of this study was to determine the sex ratio and the evolution of gonadal development stages of oyster populations in the Saloum Delta. To this end, a monthly sampling of 30 oysters between 34.19 mm and 96.68 mm height was carried out between January 2021 and January 2022. The part of the flesh that encloses the gonads was removed and fixed using Davidson's solution. After dehydration, paraffining and inclusion of the materials, 7 μm thick sections were made using a microtome. These sections were stained with Haris’s hematoxylin and eosin and the slides were observed under an optical microscope (Olympus BX41 microscope).The results showed a predominance of females over males, with a sex ratio of 1 in 2.85. The results also revealed that reproduction was continuous over the year and that spawning was asynchronous: Individuals at the spawning stage were more frequent in the warm season. These results will contribute to a better management of natural stocks and to improve oyster farming.