不同光照时间对大口黑鲈性腺发育的影响

Effects of different photoperiods on gonadal development of Micropterus salmoides

  • 摘要: 探究光照时间对大口黑鲈 (Micropterus salmoides) 性腺发育的影响,以解决反季节繁殖中因光照不足导致的亲鱼产卵量少、出苗率低等问题。选取450尾体质量为 (420.8±30.5) g、性腺发育至III期的大口黑鲈,随机分为3组 (6L18D、12L12D和18L6D组),每天分别在6、12和18 h的光照时间下养殖,其他时间为黑暗,每组设3个平行,包括雌雄个体共50尾,实验周期为60 d。通过测定和分析大口黑鲈体质量、肝体比 (Hepatosomatic index, HSI)、脏体比 (Viscerasomatic index, VSI)、性腺指数 (Gonadsomatic index, GSI)、性类固醇激素水平,以及性腺组织学切片观察和性腺发育相关基因的表达分析,评估光周期对其性腺发育和生长性能的影响。结果显示,18L6D组大口黑鲈体质量虽高于12L12D和6L18D组,但差异不显著 (p>0.05),其HSI、VSI和GSI显著高于12L12D和6L18D组 (p<0.05)。性腺组织学切片显示,18L6D和12L12D组的精巢与卵巢大多发育至V期,6L18D组多处于IV期,少数发育至V期。18L6D与12L12D组雄鱼睾酮 (Testosterone, T) 浓度差异较小 (p>0.05),但均显著高于6L18D组 (p<0.05)。18L6D组雌鱼雌二醇 (Estradiol, E2) 浓度显著高于其他2组 (p<0.05)。18L6D组雄鱼精巢中dmrt1gsdf基因与雌鱼卵巢中foxl2cyp19a1基因的表达量均显著高于其他2组 (p<0.05)。综上,适宜范围内增加光照时间有助于促进大口黑鲈性腺发育。

     

    Abstract: To investigate the effects of photoperiod on gonadal development in largemouth bass (Micropterus salmoides), aiming to address issues such as reduced spawning and low hatching rates in broodstock caused by insufficient light during off-season reproduction. We randomly divided 450 individuals Body mass of (420.8±30.5) g and gonadal development at Stage IIIinto three groups (Group 6L18D, 12L12D, 18L6D), and cultured them under photoperiods of 6, 12 and 18 h per day respectively; for the rest of the time the fish were was in darkness. Each group had three replicates with a total of 50 individualsincluding both males and females, and the experiment lasted 60 d. We evaluated the effects of photoperiod on their gonadaldevelopment and growth performance by measuring the body mass (Wt), hepatosomatic index (HSI), viscerasomatic index (VSI), gonadsomatic index (GSI), levels of sex steroid hormones, as well as observing the histological sections of gonads and analyzing the expression of genes related to gonadal development. The results show that although the Wt value in 18L6D group was higher than that in 12L12D and 6L18D groups without significant difference (p>0.05), its HSI, VSI and GSI values were significantly higher (p<0.05). The histological sections of gonads show that most of the testes and ovaries in 18L6D and 12L12D groups developed to Stage V, while those in 6L18D group were mostly at Stage IV, and a few developed to Stage V. The difference in the testosterone (T) concentration of male between 18L6D and 12L12D group was insignificant (p>0.05), but both were significantly higher than that in 6L18D group. The estradiol (E2) concentration of female in 18L6D group was significantly higher than that in the other two groups. The expression levels of dmrt1 and gsdf genes in the testes of male and foxl2 and cyp19a1 genes in the ovaries of female in 18L6D group were significantly higher than those in the other two groups (p<0.05). In conclusion,increasing photoperiod within a suitable range helps promote the gonadal development of M. salmoides.

     

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