Rainfall seasonal variation effect on the reproductive cycle of the bivalve Phacoides pectinatus from semiarid coast of Brazil

Abstract

This study tested the hypothesis that the reproductive cycle of bivalve Phacoides pectinatus from Ceará river estuary, at semiarid coast of Brazil, is influenced by rainfall and dry seasonal variations. Thus, the seasonality of gonadal development stages of P. pectinatus was evaluated by histological analyzes of the gonads and correlated with temporal variations of temperature, salinity, and local rainfall. Specimens (> 8mm) were collected monthly from April 2008 to September 2009. Four stages of gonadal development were identified. A total of 366 specimens were analyzed and measured between 8.93 mm and 68.5 mm of total shell length. The P. pectinatus population in the Ceará river estuary presented a 1:1 sexual ratio with continuous reproduction, strongly conditioned by precipitation and salinity variations. The gametogenesis was predominant in February to May (rainy season) and the ripe and spawning occurs in July to December (dry period). The increased rainfall with the consequent decrease in salinity act as natural disturbance in the estuary, on an annual rate, contributing to the renewal of the population.