Molecular Mechanisms Of Tebuconazole Affecting The Social Behavior And Reproduction Of Zebrafish

In recent years,triazole fungicides have been widely used due to their high activity.Currently,triazole fungicides are one of the categories with the largest market share,with Tebuconazole(TEB)consistently ranking first in triazole usage for many years and second among all fungicide varieties.TEB is widely used in agricultural production due to its high efficacy and wide bactericidal spectrum.Because of its long the degradation half-life,TEB can be left in large amounts in media such as water and soil,posing a serious threat to the health of human.According to literature reports,TEB has adverse effects on the reproduction of various aquatic organisms.However,the molecular mechanism of TEB-induced reproductive toxicity in aquatic organisms is still unclear,so this study used zebrafish as experimental animals to explore the potential molecular mechanism of TEB-induced reproductive toxicity in zebrafish.To investigate the effects of TEB on reproduction,zebrafish aged 4 months was used in this study and exposed to TEB at concentrations of 0,0.01% dimethyl sulfoxide(DMSO)(solvent control group),0.4 mg/L,0.8 mg/L,and 1.6 mg/L for 21 days.In this study,we firstly counted the cumulative egg production and fertilization rate of offspring(F1 generation)of zebrafish adults and evaluated the changes in gonadal development and sperm motility.Then the content of estradiol(E2)and testosterone(T)in the serum and the changes of behavior in zebrafish(social behavior and swimming behavior)were further detected.Finally,the expression levels of genes related to the HPG axis and social behavior were detected at the molecular level to explain the molecular mechanism of TEB-induced reproductive toxicity in zebrafish.The main research results as follows:1.Compared with the control group,the 21 days of cumulative egg production of zebrafish was significantly decreased,while the fertilization rate of F1 embryos was significantly decreased in the 1.6 mg/L exposed to 1.6 mg/L TEB group.This indicated that TEB reduced the reproductive ability of zebrafish and could induce reproductive toxicity of zebrafish.2.After TEB exposure,the proportion of primary oocyte in the ovaries were significantly increased in the 0.8 mg/L and 1.6 mg/L TEB group,but the proportion of cortical alveolar oocyle in all exposure groups(0.4 mg/L,0.8 mg/L,and 1.6 mg/L TEB)and mature oocyte were significantly decreased in the 1.6 mg/L TEB group.In testis,the proportion of spermatogonia were significantly decreased,but the proportion of spermatocyte was significantly increased in all exposed groups(0.4mg/L,0.8 mg/L and 1.6 mg/L TEB),the proportion of spermatid in 0.8 mg/L and 1.6mg/L TEB group were significantly decreased.These indicated that TEB inhibited the formation and development of reproductive cells in zebrafish.3.Compared with the control group,the sperm motility of male zebrafish exposed to 1.6 mg/L TEB was significantly decreased,indicating that TEB had an inhibitory effect on sperm motility and affected the process of fertilization to lead to a significant decrease in the fertilization rate of F1 embryos.4.TEB significantly inhibited the social behavior(numbers of contact,contact time)and swimming behavior(the average speed of swimming,the cumulative swimming distance)of female and male zebrafish after exposure.After testing the expression levels of genes related to social behavior,it was found that scg2 b,avp,and oxt were significantly down-regulated in both female and male fish,which were consistent with behavioral changes.5.Compared with the control group,the levels of E2 and T in the serum of female zebrafish were significantly decreased in the 1.6 mg/L TEB group,while the levels of T in the serum of male zebrafish was significantly decreased in the 0.8 mg/L and 1.6 mg/L TEB group.These indicated that TEB interfered with the secretion of sexual hormones in zebrafish.6.The expression levels of genes related to the HPG axis in female and male zebrafish had been changed after exposure,thereby interfering with the secretion of sexual hormones in zebrafish.Taken together,it could be concluded that TEB affected gonadal development,sex hormone secretion,and social behavior,which were eventually attributed to the disruption of the expressions of genes associated with HPG axis and social behavior.This study provides a new perspective to understand the mechanism of TEB-induced reproductive toxicity.