Sex determination in fish depends on the genotype and environmental factors, among them is the temperature that determines sex during embryogenesis, days or weeks after fertilization. Sex is determined only until after the eggs hatch, during the larval and postlarval stages. The increase in temperature in these early stages increases the number of males, due to the inhibition of the expression of aromatase isoforms (Cyp19a and Cyp19b genes). In this study, the effect of temperature in eggs and larvae on the sex determination of red Tilapia (Oreochromis sp.) Was analyzed, through expression analysis of the aforementioned genes. The decrease in the expression of Cyp19a was observed in eggs at 33ºC, and in larvae at 33ºC and 35ºC. The expression of the Cyp19b gene did not decrease in any of the treatments. The variability in the expression patterns of aromatases poses a challenge to use the temperature in tilapia cultures as an inducer of male production. The analysis of intrinsic and extrinsic gene expression regulation phenomena is required to approximate a more stable monosex production model.

Funding: Fondo Nacional de Regalías del departamento del Huila 2010.