Hormone And High Temperature Induced XX Pseudo-males And Successful Reproduction And Cultivation Of All-female Population In Yellow Catfish

The shortage of female has impeded the development of aquaculture industry of yellow catfish(Pelteobagrus fulvidraco)in China in recent years.Therefore,large-scale production system of all-female is urgently needed.In the first part of this study,17α-methyltestosterone(MT)and letrozole(LZ)were used to treat the diet of yellow catfish from 32 days post-hatching(dph)to 72 dph.Histological sections of the experimental fish at92 dph and 186 dph showed that LZ and MT treatments resulted in the dedifferentiation of sexually differentiated yellow catfish and the conversion of differentiated ovaries to spermatophores,but the mean sex reversal rates in the MT(5 mg/kg),LZ(300 mg/kg)and ML groups(MT 5 mg/kg + LZ 300 mg/kg)were only 9.3%,9.1% and 23.2%.9.1%,and23.2%.The second part of this study,12-65 days post-hatching larvae were treated with the combination of three male-promoting factors,17 α-Methyltestosterone(MT,5mg/kg),Letrozole(LZ,300 mg/kg),and high temperature(33.5℃).XX pseudo-males were mated with normal XX females and large-scale production of all-female population was conducted.Results showed that the combination of MT,LZ,and high temperature-induced masculinization of XX individuals,the completely sex-reversed XX males displayed a similar percentage of motile sperm with XY males.Histological observation found that there are a large number of spermatids in the testis of XX males,indicating normal reproductive ability.Subsequently,this study mate XX males and XX females,produced 570000 genotypic XX larvae,and successfully reared them to large fingerlings in a pond.The results indicated that 2.8% and 12.0% XX individuals reversed to XX males which is probably due to the high temperature during the critical time of sex differentiation in the rearing pond.The ovary developed very well for the rest of XX females and can be used as female parents in the coming spawning season.In the current work,we successfully conducted large-scale production of the all-female population in yellow catfish,and the results will provide an important foundation for the large-scale production system of the all-female population,technique supports for the shortage of female parents,and important safeguard for female selection in genetic breeding of new varieties.