The presence of the sex-determining gene amhy in South American silversides and its role on gonadal fate.

RICARDO S. HATTORI; CARLOS A. STRÜSSMANN; GUSTAVO M. SOMOZA; LURDES ALMEIDA-TOLEDO

Foz do Iguaçu

Congreso; 58 Congresso Brasileiro de Genética; 2012

Sociedade Brasileira de Genética

In many vertebrates, gonadal sex determination follows a sequence of genetically programmed events (genotypic sex determination), which are triggered by a master sex determining gene during early stages of development. However, this process can be modulated by environmental factors, a mechanism known as environmental sex determination. In teleost fish, water temperature is known to affect sex ratios and in some species all-female or all-male populations can be produced at low and high rearing temperatures, respectively. This process has been largely investigated in silverside species (Atherinopsidae family), particularly in the pejerrey Odontesthes bonariensis. But interestingly, a recent study identified the master sex determining gene amhy (Anti-müllerian hormone on the Y chromosome) in the congeneric species O. hatcheri (Patagonian pejerrey), a species with XX-XY sex determining system. Thus, the availability of a sex-determining gene and the occurrence of temperature-dependent sex determination make of atherinopsids, interesting models to clarify the mechanisms of sex determination in fish. In this study, a fieldsurvey was conducted in 11 species of Odontesthes genus from marine, estuarine and freshwater habitats in order to assess the presence of the sex-determining gene amhy and to assess the occurrence of sex-reversed animals in natural populations. Amhy could be amplified in all species collected and was used for determining the genotypic sex. The concomitant analysis of phenotypic sex allowed the identification of sex-reversed animals and interestingly they could be found only in species inhabiting inland waters like rivers and lakes. On the other hand, no sex reversal was found in species inhabiting marine or estuarine environments. Those results could be related to the highersusceptibility and vulnerability of inland waters to environmental changes like the thermal ones, which in turn could lead to the appearance of sex-reversed animals. The present study has great implications on the clarification of molecular mechanisms of sex determination, both environmental and genotypic, in this group of fish and can provide substantial information for the monitoring and management of Neotropical silversides natural resources. Financial Support: FAPESP and JSPS.