Cortisol Antagonists Rescue High Temperature-Induced Masculinization Of XX Genotypic Female In Yellow Catfish (Tachysurus Fulvidraco)

To solve the shortage problem of female broodstock in yellow catfish,we established a large-scale production system of XX all-female for the first time.However,under high water temperature conditions in the pond,at 60 DPH and 120 DPH,2.8%and 12.0% of XX genotype females were masculinized and developed into phenotypic males,which will be detrimental to the production of the all-female population,subsequent selection and large-scale breeding of new varieties.Therefore,we aimed to clarify the mechanism of high temperature-induced masculinization in yellow catfish,and thus to inhibit or rescue high temperature-induced masculinization.This is an urgent problem to be solved to improve the all-female population production system.In this study,we treated different populations of yellow catfish larvae with similar high temperature regimes,and investigate the population differences of masculinization;we treated larvae using two cortisol antagonist metyrapone and curcumin under high temperature rearing condtion,and analyze the effect of cortisol synthesis inhibition on sex differentiation.The main research findings were as follows:(1)Under the same high temperature treatment conditions,the proportions of XX pseudo-male induced by high temperature in different populations were 22.7%,39.1%,and 20.0%,respectively.The results indicate that high temperature-induced masculinization may be influenced by genetic factors.(2)At the end of sex differentiation(52DPH),the sex reversal rates of XX genotype in the high temperature group and high temperature plus metyrapone group were 41.7% and 14.3% respectively.In the high temperature plus curcumin group,XX pseudo-male was not observed.Only 10.0% of XX females were found to have significantly delayed germ cell development compared with the normal XX female in the same group and the control group.These results indicate that high temperatureinduced masculinization can be rescued by inhibiting the synthesis of cortisol.(3)High temperature treatment resulted in decreased survival of XY male yellow catfish.By feeding cortisol antagonists(metyrapone and curcumin),the high mortality of XY males under high temperature can be relieved.The result indicates that for natural populations,there are sex differences in tolerance to environmental stress;in previous studies involving sex differentiation,the statistics of phenotypic sex of yellow catfish may have overlooked the existence of XX pseudo males.The present work demonstrated that high temperature-induced masculinization can be rescued by inhibiting cortisol synthesis.As a natural plant extract,curcumin can be used as the preferred medicine to rescue the masculinization induced by environmental stress such as high temperature.The results not only provide an important reference for improving the large-scale breeding system of all-female population in yellow catfish,but also provide an important way for inducing and rescuing the masculinization induced by environmental stress.