Gonad morphology and type of sexuality in Parastacus defossus Faxon 1898, a burrowing, intersexed crayfish from southern Brazil (Decapoda: Parastacidae)

The aim of this study was to characterize the morphology of the reproductive system and the type of sexuality of Parastacus defossus, an intersexed, freshwater crayfish that occurs in the southeast of Brazil and Uruguay. The specimens were examined for the appearance of the genital pores, and the gonads were macroscopically analysed by size and colour. The histology of some gonads was examined. Males and females have two pairs of genital ducts: one anterior (oviduct) and one posterior (vas deferens). The gonads are located in the thorax and consist of one pair of lobules. Through macroscopic and histological analyses of the female gonads, six stages of ovarian development could be distinguished. The histological description of the testis was made only from adult males. Through analyses of the genital pores and gonads, three sexual forms were distinguished in P. defossus: intersexed females (246), intersexed males (259), and individuals with an ootestis (7). Individuals with an ootestis had a gonad that produced male and female reproductive cells simultaneously. Parastacus defossus can be classified as a partially protandric hermaphrodite species.