Gonad development in the freshwater oyster Etheria elliptica (Bivalvia: Etheriidae) in northern Ghana

Abstract

Gonad development in the freshwater oyster Etheria elliptica from the White Volta River at Nawuni and the Oti River at Sabari (northern Ghana) was studied by histological examination from March to July 1999. Five developmental stages—developing, ripening, ripened, spawning and spent—were encountered in both populations. The dominant stages were ripening and spawning, whereas spent gonads were rare. Males and females were nearly equally represented in the White Volta River stock, but the Oti River stock had more females than males. Hermaphrodites were encountered occasionally in both populations. By the end of the dry season (March-April), gonad development in both populations had progressed to the ripening stage, suggesting that they began active differentiation much earlier. From May through June, when the rains began and intensified, spawning had begun and was progressing. It was not possible to establish the limits of the breeding season because sampling was limited to only part of the year.