Effects Of Exogenously Compensated High Temperature Down-regulated Estradiol Levels On Nile Tilapia Sex Ratio And Cyp19a1a Expression

The sex of fish is very plastic,and it is easy to affect the female and androgen in the receptor.Studies have shown that estrogen plays an important role in the sex differentiation of fish.Whether the fish is transferred from female to male or from male to female,the estrogen level is down-regulated or up-regulated.In the critical period of fish sex differentiation,the synthesis of estrogen in fish is earlier than the synthesis of androgen,so the expression of estrogen-synthesizing enzyme(aromatase)in the gonad is earlier than that of catalytic androgen synthase.expression.For example,the sex determination of Nile tilapia is controlled by both genetics and temperature,and is called a hybrid of genetic sex determination and temperature sex determination.Although it has been reported that during the critical period of sex differentiation of Nile tilapia,the female fish is reversible into male fish by high temperature(36?),accompanied by a decrease in estrogen concentration and estrogen synthase gene Cyp19a1 a in this process.The downregulation of expression.However,it is unclear whether it is possible to change the hormone levels in the body and the expression level of Cyp19a1 a and the effect on the sex ratio by adding exogenous estrogen and high temperature to treat female fish.This experiment intends to simultaneously treat Nile tilapia female fish by concentration gradient of exogenous estrogen and high temperature during the gonad differentiation of Nile tilapia,and compare the analysis of sex steroid hormone level and group female rate between treatment groups.Optimal exogenous estrogen compensatory concentration.The effects of exogenous estrogen at the optimal compensatory concentration and high temperature on the expression of estrogen synthesis related gene(Cyp19a1a)in the early gonads of Nile tilapia were analyzed.In this study,wild females and pseudo-male fish were naturally fertilized and fertilized,and three Nile tilapia all-female families were obtained.The female fish control group,themale fish control group,the high temperature(36 ?)treatment group and the different concentrations of estradiol(E2)compensation group(high temperature and E2 co-treatment)were separately set,and the treatment groups were compared in the early sex gonads of gender differentiation.E2 and 11-KT levels.The results showed that at 13 dpf,the E2 level in the gonads of Nile tilapia was significantly higher in the XX+HT+E:(16,64)group than in the control group,and there was no significant difference in the other treatment groups.At 21 dpf,the E2 level in the gonads of male fish was significantly lower than that in females,and the E2 level in the gonads was also significantly lower in the high temperature treatment group,which was reduced to half of the E2 level in the gonads of the control females,but at XX+HT+E:4.The E2 level of the group was close to that of the control female.E2 compensation group also increased E2 level in gonads with the increase of exogenous E2 concentration.The level of 11-KT was low in the gonads of the early sex differentiation of Nile tilapia(13dpf and 21dpf)and did not change.By comparing and analyzing the male rate of each treatment group after gonad maturation,it was found that in the XX+HT+E:4 group,4?g/L E2 treatment increased the 39.7% female rate in the high temperature treatment group,and the female rate was Compared with the female control group,the E2 level and female rate in each treatment group showed that the optimal E2 compensation concentration in the estrogen compensation group was 4 ?g/L,and the estrogen level in the early gonads of Nile tilapia It plays a key role in gender differentiation.What is the effect of optimal E2 compensation and high temperature treatment on estrogen synthesis related genes in the early gonads of Nile tilapia?During the sex differentiation of Nile tilapia,the gonad aromatase Cyp19a1 a is a key rate-limiting enzyme that catalyzes the synthesis of estrogen in the body.In this experiment,qRT-PCR and in situ hybridization(ISH)were used to detect and analyze the expression level of gonadal aromatase Cyp19a1 a in the early sex differentiation of Nile tilapia.The results showed that compared with the female control group,the high temperature treatment group significantly down-regulated the expression level of the gonad aromatase Cyp19a1 a in Nile tilapia.The expression level of Cyp19a1 a in the optimal E2 compensation group returned to the level similar to that of the female control group,that is,the optimal E2 treatment and the high temperature induction had the same effect on the expression of the gonadal aromataseCyp19a1 a,but the opposite result.In summary,this study preliminarily demonstrated that the high temperature-induced reversal of Nile tilapia female fish is associated with a decrease in estrogen concentration in fish during the critical period of sex differentiation of Nile tilapia.