The Sex Determination mechanism in pejerrey fish as a potential model to study endocrine disruption.

MANUEL SOMOZA, GUSTAVO; CARRIQUIRIBORDE, P; JUAN IGNACIO FERNANDINO; STÜSSMANN, C.A.

Montevideo

Congreso; VIII Congreso SETAC LA; 2007

Fish are particularly useful as sentinel species for monitoring of aquatic pollution since they are the only vertebrates spending the whole life cycle in the water media. The pejerrey (Odontesthes bonariensis) is a gonochoristic species characterized by presenting a marked temperature sex determination (TSD). For instance, similar proportions of females and males can be obtained if the fish are reared during the temperature sensitive window (weeks 1 to 5) at intermediate temperatures (24-25 °C), however all males or females can be produced if they are reared at high (29 °C) or low (17 °C) temperatures, respectively. On the other hand, exogenous sex steroids administered at the time of sex determination/differentiation can strongly influence the course of sex differentiation in pejerrey, overriding the thermal control and suggesting that they play a critical role in assignment of gonad determination as well as subsequent differentiation. Total or partial feminization of the fish can be induced by estradiol at 25 or 29 ºC respectively. The lability of sex-determination systems in pejerrey makes this species susceptible to environmental pollutants capable of mimicking or disrupting sex hormone actions. In addition, current advances in the knowledge of the response of morphological gonadal differentiation and some molecular sex markers to temperature and natural estrogens, allowed us to propose the pejerrey as a potential model to study environmental problems induced by endocrine disruptors and their synergy with temperature changes. Such observations will also provide insights into potential impacts from endocrine disruptors, and may represent useful monitoring tools for assessing impacts on aquatic environments.