Sexual system of the freshwater shrimps of the genus Potimirim Holthuis (Decapoda : Caridea : Atyidae): is there a pattern in this genus?

Abstract

Among the genus Potimirim, the sexual system has been studied only in Potimirim mexicana, which was suggested as being a sequential protandric shrimp. The genus Potimirim comprises five described species that occur in drainages along the western Atlantic coast. We tested the hypothesis that there is a common shared sexual system pattern for the genus Potimirim, and that both species reported for Brazil (P. brasiliana and P. potimirim) are sequentially protandric. The animals were analysed with respect to sex, external morphology and nature of the gonads. We found similar results for both species: females were significantly larger than males; the appendix masculina increased significantly as the carapace enlarged; all adult males had cincinnuli and only well-developed testes; all females lacked cincinnuli and had only well-developed ovaries; and all males and females had a non-prehensile third pereopod. The absence of any characteristic that could be interpreted as evidence of sex change indicates that these species are gonochoric species. Therefore we concluded that there is no sexual system shared by all members of this genus. Additionally, we compared our results with a molecular phylogeny previously proposed for the genus Potimirim, as the baseline to discuss the sexual system in this genus.