Effects Of High Temperature And Cortisol On Sex Differentiation Of Yellow Catfish (Tachysurus Fulvidraco)

Sex differentiation in fish is extremely susceptible to environmental stresses?such as high temperature,high density,etc?,and generally causes masculinization.Environmental stresses during the critical period of sex differentiation invariably lead to elevated serum cortisol in the process of masculinization.Cortisol treatments caused female-to-male sex reversal,while antagonist of cortisol synthetase rescued the high temperature-induced masculinization.Estrogen 17?-estradiol?E₂?rescued cortisol-and high temperature-induced masculinization.Evidence from these four aspects strongly suggest that cortisol is the vital mediator in stress-induced masculinization.Currently,there are few studies about physiological mechanisms involved in stress-induced masculinization.Therefore,in the present work,taking yellow catfish?Tachysurus fulvidraco,with confirmed sex chromosome XX-XY and sex-linked marker?as the research object,we studied the effects of high temperature and cortisol administration on the histological process in the masculinization of XX genotype.Combining genotypic sex identification via applying sex-linked markers and phenotypic sex identification through histology,we found that 24 days?12-35 days post-hatching?treatments of high temperature or cortisol induced partial masculinization of XX individuals.In this process,germ cells development of XX gonad was repressed,and therefore developed to testis-like structure.In addition,we observed seminiferous lobules and typical male genitalia in XX pseudo-male,strongly suggesting these pseudo-males may have reproductive capacity.We also found that testis size and body weight of XX pseudo-male were significantly higher than XY males and XX females.These results provide important information for understanding the mechanisms of environmental stress factors-induced masculinization.We also found that some XX individuals were not sensitive to high temperature?or cortisol?treatments,meanwhile high temperature accelerated ovarian development.The genetic difference between the two kinds of XX individuals with different sensitivities to temperature deserved further investigation.Further research in stress-induced masculinization will be helpful in the establishment of mass production of mono-sex population.