Expression of Müllerian-inhibiting Substance (MIS) during temperature sexual determination in the pejerrey fish, Odontesthes bonariensis.

JUAN IGNACIO FERNANDINO; CARLOS AUGUSTO STRÜSSMANN; GUSTAVO MANUEL SOMOZA

Buenos Aires

Jornada; VII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología.; 2005

IBYME

The process of sex determination/differentiation in bony fish species can by controlled either by genetic, environmental or combination of both factors. In the pejerrey fish, a fish with marked temperature-dependent sex determination (TSD), the proportion of males changes gradually from 0% at 19°C to 100% at 29°C, whereas at 23–25°C there is almost a 1:1 sex ratio. The anti-Müllerian hormone or Müllerian-inhibiting substance (AMH or MIS) is a glycoprotein belonging to the transforming growth factor b (TGF-b) superfamily. In mammals, MIS is responsible for the regression of the Müllerian ducts in the male fetus. For example, in mice, MIS starts to be expressed in Sertoli cells at the onset of testicular differentiation and its expression persists even after regression of the Müllerian ducts. However, the role of MIS on gonadal sex differentiation in teleost fishes, which do not form the Müllerian ducts, has not been cleared out yet. The first demonstration of sexually dimorphic expression of MIS mRNA during sex differentiation in a teleost fish species was demonstrated in the Japanese flounder and was then observed in zebrafish. In the present work were pejerrey larvae were incubated at 17°C, 25°C and 29°C and the expression of MIS was followed from hatching to 9 weeks old by relative quantitation real time PCR. MIS showed a statistically significant expression in male promoting temperatures starting at 5 weeks. The current results suggest that the up-regulation of MIS in pejerrey may play a role in male sex differentiation.