Characterization of the sexual pattern of Parastacus varicosus Faxon, 1898 (Crustacea: Decapoda: Parastacidae) through macro and microscopic analysis of its reproductive system.

SILVA-CASTIGLIONI, D. LÓPEZ GRECOO LL OLIVEIRARA, G.T. AND BOND-BUCKUP, G.

INVERTEBRATE BIOLOGY

BLACKWELL SCIENCE

Año: 2008

1077-8306

Freshwater crayfishes of the genus Parastacus are intersex, i.e., show characteristics of both sexes in the same individual; also, intersexuality has been documented in hermaphroditic species. The aim of this study was to analyze the gonads of P. varicosus, characterizing its sexual pattern. The animals were collected at Cova do Touro, Gravataí, Rio Grande do Sul, Brazil. Three sexual forms were identified: intersex females, intersex males and transitionals specimens showing an ovotestes gonad that could be only identified by means of histological analysis. All specimens had two pairs of gonopores and gonoducts. The oviduct had a wider diameter in females, whereas in males the vasa deferentia were more developed. Gonads were composed of two parallel structures located in the cephalothorax. Female gonads were classified into three stages. The presence of transitional specimens may indicate that sex change occurs, with protandric hermaphroditism, as observed in other species of Parastacus. Since previous studies had demonstrated that P. varicosus is  a gonochoristic species in a population from Uruguay, the present study addressed the possibility that the sexual pattern depends on differences in environmental factors among populations. To improve understanding of evolution of hermaphroditism in these crustaceans, their reproductive dynamics should be studied, including identification of the factors stimulating male and female function.