Classes de comprimento e descrição histológica das gônadas de Diplodon ellipticus (Wagner, 1827) (Mollusca, Bivalvia, Hyriidae) em um lago artificial, Morretes, Paraná, Brasil

Abstract

This study aimed to analyze the frequency by length classes and the histological organization of gonads of Diplodon ellipticus at an artificial lake located in the town of Morretes, Paraná, Brazil. Six bimonthly sampling campaigns were conducted within the period from July 2009 to May 2010, with capture of 150 specimens. The total length of shells was measured for determining the frequencies of length classes and an analysis of the presence of marsupials in branchiae was performed. Sex determination was performed through histological analysis of cross sections of the visceral mass. We registered 8 length classes, with an interval of 9 mm, and the modal class varied between 50 and 59 mm. The population is predominantly dioecious, with occurrence of hermaphrodite specimens at low frequency. Marsupials were registered among females (86%) in all sampling campaigns and in 2 hermaphrodite specimens. Histological analyses showed that spermatogenesis and oogenesis occur over the year, indicating that D. ellipticus has a strategy that provides continuous reproduction, with peaks of glochidia release.