Sex reversal of Nile tilapia using honey and analysis of aromatase gene expression

Abstract

The use of synthetic steroid hormones to produce monosex populations of tilapia for intensive productive systems may lead to environmental and public health concerns. Such a situation is derived from the fact that female tilapine species have a high fecundity, generally reproducing at a small size and exhibiting stunted somatic growth at higher densities, while male tilapias exhibit faster growth rates and are often the preferred gender for monosex aquaculture.The study was conducted to determine the effect of immersion Nile tilapia larvae in water containing different honey source on male fish percentage and aromatase gene expression. In the first experiment, in a total of 30 tilapia larvae at 12 days posthatch were immersed in the water containing honey derived from the forest, cultured and mangrove bees, with a dose of 10 mL/L water for 10 hours. Fish were then maintained in the same condition for 2 months. The results showed that percentage of male fish immersed by different honey was similar (p>0.05), and all treatment was significantly different with the control (p<0.05). In the second experiment tilapia larvae were immersed in two bioactive compounds of honey, namely chrysin and potassium solution in a dose of 20 mg/L and 0.026 g/L, respectively, to verify the materials of honey that affects sex differentiation in Nile tilapia. The results showed that both compounds increased male fish percentage compared to that of control (p<0.1). This indicated that chrysin and potassium were involved in Nile tilapia sex reversal. Growth, survival and biomass of honey bee treated fish were similar with the control (p>0.05), while chrysin and potassium treated fish have lower survival rate than that of control (p<0.1). The lower survival rate maybe caused slightly higher specific growth in the chrysin and potassium treated fish compared to control (p<0.1). Furthermore, RT-PCR analysis showed that honey bee, chrysin and potassium down-regulated gonadal-type aromatase gene expression at 12 hours post immersion. Thus, honey can be use to sex reverse of Nile tilapia, and evolved the gonadal-type aromatase expression.