Sexual differentiation in the freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae).

VAZQUEZ, F.J. AND L. S. LÓPEZ G.

REVISTA DE BIOLOGíA TROPICAL

UNIVERSIDAD DE COSTA RICA

Lugar: SAN JOSE DE COSTA RICA; Año: 2007 vol. 55 p. 33 - 38

0034-7744

Abstract: The aim of this work was to determine the earliest stage of the postembryonic development at which primary and secondary sexual differentiation occur in the freshwater (“red claw”) crayfish Cherax quadricarinatus (von Martens, 1868). For this purpose, 797 males, 506 females and 456 intersex within a weight range of 0.02 to 89.96 g were observed under stereoscopic microscope to determine the presence of the genital openings at the basis of the third (females) or fifth (males) pair of pereiopods. Animals presenting both pairs of genital openings were considered as intersex. The differentiation of the appendix masculinae and red patch were also recorded. A subsample of 106 males, 69 females and 59 intersex were dissected for the macroscopic characterization of the gonad morphology. The development of the genital openings began at 0.10 g simultaneously with the differentiation of the reproductive system in females, males and intersex. Although the differentiation of the reproductive system starts very early in the postembryonic development, the definitive form and colour of ovaries, oviducts, testes and vasa deferentia was later acquired. Concerning the differentiation of the appendix masculina, this process began its differentiation at 0.12 g and acquired the elongated shape of the adult at 1 g.  The soft red patch characteristic of adult males was seen as beginning at 2.3 g of body weight in both chelipeds. Key words: Cherax quadricarinatus, sexual differentiation, primary sexual characters, secondary sexual characters, gonad, appendix masculinae, red patch