Abstract
Sex control is an essential technology to produce mono-sex populations with high growth rates and product quality in aquaculture. To produce an all-female population in fish with the XX/XY sex determination system, the generation of XX neomales is the critical step and they have been successfully created by different approaches, such as androgens, aromatase inhibitors and high temperature treatment. However, there is no comprehensive comparison of testis structure, quality of sperm and offspring in XX neomales produced by different approaches. Yellow catfish are an excellent model to study sex determination and sex reversal since robust sex-specific molecular markers and genetic sex determination have been identified. Previously, we observed that 17α-methyltestosterone (MT) treatment could not induce functional testes in XX yellow catfish. In this study, we found that high-temperature treatment caused a delay in ovarian development instead of sex reversal in yellow catfish. However, high temperature combined with aromatase inhibitor (Letrozole, LZ) treatment could dramatically improve the efficiency of sex reversal compared with using LZ alone (the neomale was designated XXm-LZ), while they showed the same testis phenotype. Interestingly, the offspring of XXm-LZ transitioned from genetic to temperature-dependent sex determination, which could be easily sex reversed after treatment with high temperature (the neomale was designated XXm-HT-1). Then, we evaluated the reproductive performances and sperm parameters in XY male, XXm-LZ and XXm-HT-1 neomales. Strikingly, the fertilization rate, hatching rate and survival rate of XXm-HT-1 catfish were as good as those of XYm yellow catfish and better than those of XXm-LZ yellow catfish, while the malformation rate of fries produced by XXm-HT-1 catfish was significantly lower than that of XXm-LZ catfish. In addition, the expression of miR-141/−200a/−429b and dmrt1/pfpdz1 was negatively and positively correlated with sperm quality, respectively. However, the transition from genetic to temperature-dependent sex determination was transient and cannot be completely inherited by the next generation in yellow catfish. We concluded that precise application of the transition from genetic to temperature-dependent sex determination could produce the highest quality neomales for sex control in aquaculture after comparing different approaches.
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