Sexual strategy in the freshwater bivalve Galatea paradoxa (Donacidae) from the Volta River estuary, Ghana

摘要

The reproductive biology, sexual strategy and sex ratio of the freshwater donacid Galatea paradoxa in the Volta River estuary, Ghana, was studied from March 2008 to February 2010. Histological observations of the gonads showed that G. paradoxa is gonochoristic with dominance by females (80%) and a high incidence of hermaphrodites (9.4%) for individuals ranged between 20 and 82 mm in shell length. There was a single spawning event between July and October. Gametogenesis started in December, progressing steadily to a peak in June-July when spawning began, until November when individuals were spent. The dominance of females coupled with the high incidence of hermaphroditism may be a reflection of populations subjected to increasing fishing pressure and over-exploitation.