水温和光照调节对五条鰤性成熟及脑垂体促性腺激素fshβ和lhβ基因表达的影响

Effects of water temperature and photoperiod on sex maturation and pituitary gonadotropin fshβand lhβgenes expression in yellowtail Seriola quinqueradiata

为了解环境因子对五条鰤Seriola quinqueradiata内分泌系统的影响,分析综合运用水温和光照调节对其性腺发育成熟度及与繁殖相关的促卵泡激素基因(fshβ)和黄体生成素基因(lhβ)表达的影响,试验设置对照组和处理组(每组水槽放置20尾鱼),对照组为自然水温和光照饲养,处理组在水温恒定20℃和光照10L∶14D条件下饲养,试验时间为2018年1月20日—3月20日,每月采样一次,比较各阶段试验鱼的性腺指数(GSI)、性腺发育成熟度、脑垂体中fshβ和lhβ基因含量,以及血清中类固醇激素雌二醇(E_(2))和睾酮(T)含量的差异。结果表明:对照组鱼在各采样阶段其GSI均无显著性差异(P>0.05),且性腺发育为未成熟阶段,处理组鱼在试验进行1个月和2个月后,其GSI均显著高于对照组(P<0.05),且性腺发育为成熟阶段;试验进行1个月和2个月后,对照组鱼脑垂体中fshβ和lhβ基因含量均无显著性变化(P>0.05),但处理组鱼脑垂体中fshβ基因含量均显著高于对照组(P<0.05),试验进行2个月后,处理组鱼脑垂体中lhβ基因含量显著高于对照组(P<0.05);试验进行1个月和2个月后,对照组鱼血清中E_(2)和T含量均无显著性变化(P>0.05),但处理组鱼血清中E_(2)和T含量均显著高于对照组(P<0.05)。研究表明,综合运用水温和光照调节有利于促进五条鰤脑垂体中fshβ和lhβ含量的增加,从而促进其血清中E_(2)和T浓度的上升,最终诱导其性腺发育成熟。

To understand the effects of environmental factors on the endocrine system of yellowtail Seriola quinqueradiata,the maturation and gene expression of reproduction-related hormones including gonadosomatic index(GSI),gonadal maturity,expression of fshβand lhβgenes and levels of serum estradiol(E_(2))and testosterone(T)were investigated and compared in female yellowtail with body mass of 2.0-3.0 kg reared in 2 octagonal tanks with a volume of 90000 L at water temperature from 9.2℃to 12.4℃and photoperiod of 12L∶12D(control group)and at constant water temperature of 20℃and photoperiod of 10L∶14D(treatment group)from January 20,2018 to March 20,2018.The results showed that the immature gonad was observed in the yellowtail in the control group,without significant difference in the GSI between the two groups(P>0.05)during the experimental period.The one month or two months old yellowtail in the treatment group had mature gonad,with significantly higher GSI than that in control group(P<0.05).There was no significant difference in the fshβand lhβcontent in pituitary gland of one month or two months old yellowtail in the control group(P>0.05).However,there was significantly higher fshβcontent in the yellowtail in the treatment group than that in control group after one month or two months(P<0.05),and the lhβcontent was significantly higher in two months than that in control group(P<0.05).However,the serum E_(2) and T levels were shown to be significantly higher in the treatment group than those in control group(P<0.05),without significant difference in the serum E_(2) and T levels in one month or two months in the control group(P>0.05).The findings indicated that the comprehensive regulation of water temperature and photoperiod promoted the increase in fshβand lhβcontent,and thus elevated the level of serum E_(2) and T to induce maturation.