Résumé
Sex of Nile tilapia is under a complex control. It is determined by sex chromosomes following an XX/XY system, but it is also influenced by parental factors and by temperature. Elevated temperatures >32°C applied during early sex-differentiation can induce a female to male sex reversal producing functional testis and a male reproductive behaviour. The male proportion induced by temperature (the thermosensitivity) is an inherited trait, and varies between families, strains and populations. We now know that one of the mechanisms by which temperature exerts its masculinization effects is through the methylation of the DNA. Here we analyzed the effects of high temperature induced-masculinization in adult gonads between two families showing respectively a high and a low thermosensitivity. After fry exposure to 36°C, Family K14 had 90% male proportion whereas, Family K13 only showed 59.8% males. We compared the methylation marks persistent in testis and ovaries of the 27°C and 36°C exposed groups from both families and found differences in DNA methylation. Likewise, differences in RNA expressions were also seen. Correlation between DNA methylated levels and gene expressions will be discussed.