人工繁育绿鳍马面鲀幼鱼的生长、性腺分化及性激素含量的变化

    Growth, sex differentiation and changes in sex hormone content of juvenile Thamnaconus modestus under artificial breeding conditions

    • 摘要:
      目的 了解人工繁育后绿鳍马面鲀(Thamnaconus modestus)幼鱼生长、性腺分化过程及调节机制。
      方法 自孵化后10 d开始,每5 d取样1次,每次30 尾,测定绿鳍马面鲀幼鱼(以下简称“幼鱼”)体质量、全长、体长、肛前长、头长、体高、吻长和眼径生长指标;采用石蜡包埋切片和苏木精−伊红染色对幼鱼性腺发育进行观察。同时,将样本进行匀浆,测定幼鱼体内雌激素(雌二醇)和雄激素(睾酮)浓度的变化。
      结果 幼鱼体质量、全长和体长在10日龄~20日龄未见显著差异(P>0.05),从25日龄开始显著增加(P<0.05);肛前长在10日龄~15日龄未见显著差异(P>0.05),从20日龄开始显著增加(P<0.05);头长、体高、吻长和眼径在10日龄~20日龄未见显著差异(P>0.05),从30日龄开始显著增加(P<0.05)。此外,在25日龄和35日龄幼鱼中,观察到未分化的性腺成对出现于肠道附近,与肠系膜相连;在35日龄幼鱼中,观察到未分化性腺的血管;在部分60日龄幼鱼中,观察到卵原细胞或精原细胞。在性别转变为雌性的过程中,当性腺未分化时, 幼鱼的雌二醇浓度较低;在60日龄性腺分化完成后,幼鱼的雌二醇浓度显著增加(P<0.05)。在性别转变为雄性的过程中,当性腺未分化时,幼鱼的睾酮浓度较低;在性腺分化完成后,幼鱼的睾酮浓度较以前增加。
      结论 幼鱼的生长转折点可能出现在20~30日龄,性分化年龄可能出现在35日龄~60日龄之间;雌激素、雄激素可能是诱导幼鱼的性别分别转变为雌性、雄性的关键因素。本文阐明了绿鳍马面鲀幼鱼生长和性分化的过程,以及在性腺分化过程中的雌、雄激素浓度的变化规律,为其性别调控和人工繁殖提供理论依据。

       

      Abstract:
      Objective This study aims to understand the growth, gonadal differentiation process and regulatory mechanism of juvenile Thamnaconus modestus under artificial breeding conditions.
      Methods  After 10 days post-hatching, 30 fish were sampled every 5 days. The growth indices such as body mass, total length (TL), body length (BL), preanal length (PL), head length (HL), body height (BH), snout length (SL), and eye diameter (ED) were measured. Paraffin-embedded sections and hematoxylin-eosin staining were used to observe the development of gonads. At the same time, the samples were homogenized, and the changes in the content of 17β-estradiol (E2) and testosterone (T) were determined.
      Results There were no significant differences in the growth indices such as body mass, TL, and BL of juvenile T. modestus among 10−20 days (P>0.05), while they increased significantly from 25 days (P<0.05). There was no significant difference in PL between 10 and 15 days (P>0.05), while it increased significantly from 20 days (P<0.05). There were no significant differences in HL, BH, SL and ED between 10 days and 20 days (P>0.05), but they began to increase significantly at 30 days (P<0.05). In addition, at 25−35 days, the undifferentiated gonads were observed to appear in pairs near the intestine and connect with the mesentery, and the blood vessels were observed in the gonads. At 60 days, oogonia or spermatogonia were observed in some juvenile T. modestus, indicating that the gonads had differentiated into females and males. In the process of sex transition to female, the E2 content was low, when the gonads were undifferentiated. However, the E2 content significantly increased after the finish of sex differentiation at 60 days (P<0.05). In the process of sex transition to male, the T content was lower when the gonads were undifferentiated and increased after the finish of sex differentiation at 60 days.
      Conclusion These results suggested that the growth turning point of juvenile T. modestus may occur at 20−30 days, and the age of sex differentiation may be 35−60 days. Estrogen and testosterone may be the key factors that induced juvenile T. modestus to change their gender to female and male, respectively. This study clarifies the process of sex differentiation and the changes in hormone content during the differentiation process, which may provide the theoretical basis for the sex regulation and artificial reproduction in T. modestus.

       

    /

    返回文章
    返回