Oocyte atresia in the Mangrove oyster, <i>Crassostrea gasar</i> (Dautzenberg 1891), (Bivalvia, Ostreidae) in tropical environment

Abstract

The mangrove oyster, Crassostrea gasar, is exploited in a natural state in the Casamance estuary in Senegal by rural women Diola. The decrease of its size on natural deposits and the remoteness of the harvesting areas, are at the origin of the Oyster culture project in Lower Casamance. It is in this context that the reproduction of the oyster, C. gasar in the Casamance estuary was studied between 1992 and 1994 to optimize its capture of its spats. Each month, a sample of about 30 adult oysters was collected at the same location in the Karabane region, 6 km from the mouth of Casamance. Of the thirty oysters monthly collected, 3-5 females were selected for study among larger individuals. A fragment of gonadal tissue was collected from each oyster and prepared for histological study: alcohol fixation, alcohol washing, dehydration, impregnation and paraffin embedding, cutting, staining, blade-slat assembly, and blade observation using a computer. A program has been installed to automatically calculate the occupation rate of the different oocytes observed. A large percentage of atretic oocytes are observed in follicles of the oyster gonad, within 04 months, before the main oyster reproduction period in the Karabane area. This situation would be caused when the reserves accumulated by the oysters during the gametogenesis of the oyster are insufficient in the quantity and quality of reserves accumulated by the oysters during the gametogenesis of the oyster.

Spawning season and size at first sexual maturity of freshwater mussel Lamellidens marginalis (Lamarck, 1819) in the Brahmaputra River, Bangladesh

“…However, the present findings contradict with Siddique et al (2020) and Diadhiou et al (2019) who reported spawning peak of this species during rainy season based on the histological observation of gonads. The potential reasons for this phenomenon could be attributed to the increased accessibility of food resources, favourable hydrological conditions, and enhanced opportunities for mating in the studied riverine water (Morriconi et al, 2002;Saeedi et al, 2009;Silva-Cavalcanti et al, 2018).…”

The effects of experimental temperature increase on gametogenesis and heat stress parameters in oysters: Comparison of a temperate-introduced species (Crassostrea gigas) and a native tropical species (Crassostrea corteziensis)

“…Oocytes degenerate as a strategy to recycle the energy reserves used to mature oocytes and channel them to other tissues to cope with periods of stress and energy depletion (Beninger et al, 2017). In the tropical oyster C. gasar, gametes are not expelled and are recycled in the digestive system (Diadhiou et al, 2019). Here, we found that degenerated oocytes significantly increased at higher temperatures in both species (Fig.…”

Survival and growth of mangrove oyster Crassostrea gasar (Dautzenberg, 1891) reared at different depths in ponds in Benin (West Africa)

“…Mangroves (Rhizophora racemosa and Avicennia germinans) are characteristic of mangrove ecosystems and constitute the natural habitat of the mangrove oyster [9] . In Benin, the mangrove oyster is subject to artisanal exploitation at the coastal water levels especially in Lake Nokoué and the coastal lagoon [8,10] .Several scientific studies have been conducted on the reproduction, feeding and growth of the mangrove oyster [6,10,11,12] , but there is a lack of scientific data on rearing in controlled systems of the species. Oyster research is absent so that currently at the coastal lagoon, oyster farming remains traditional without any improvement.…”