Caracterização do ciclo reprodutivo do gastrópode Nassarius vibex (SAY, 1822) (MOLLUSCA: GASTROPODA: NASSARIIDAE) em um estuário contaminado pelo TBT no Estado do Ceará

Abstract

Nassarius vibex is a species of caenogastropod mollusc that can be found on the American atlantic coast. Their reproductive cycle is relatively little studied, being the studies more focused on the occurrence of the imposex, making the species can be used as a tributyltin (TBT) pollution bio indicator. In order to study the reproductive cycle of Nassarius vibex on the estuary of the Ceará River, environment affected by pollution, samples were collected during seventeen months between the years of 2007 and 2008. Forty animals were collected in each month, and environmental variables such as temperature, salinity and rainfall were measured. Histological studies were performed to determine the reproductive stage of males and females collected. Five reproductive stages were found in both sexes: Immature, Early Maturation, Advanced Maturation, Elimination and Regeneration, besides individuals considered Undifferentiated, that is, animals that could not have their gender identified. It was observed that Immature animals are found in greater quantity in the periods with higher precipitation and that the stages of Early and Advanced Maturation are more found in the dry periods. Reproduction has been continuous and the reproductive stages of both sexes showed synchrony, in addition to each stage being related to a different gonad color. Histological changes absence in the females’ gonad indicates that the imposex does not affect the reproductive cycle of this population. However, the predominance of imposex in immature and in regeneration females also suggests that some effect on the gametogenic cycle should occur, delaying gonadal maturation in the population studied.