Department of Zoology, Sidho-Kanho-Birsha University, Purulia, 723104, India.
Department of Zoology, Sidho-Kanho-Birsha University, Purulia, 723104, India.
Theriogenology. 2023 Sep 15;208:15-27. doi: 10.1016/j.theriogenology.2023.06.001. Epub 2023 Jun 2.
Melatonin, the pineal hormone, is synthesized and secreted rhythmically in accordance with various environmental cues especially photo-thermal conditions. The reproductive physiology of seasonal breeders is synchronized with the surroundings by melatonin as a neuroendocrine mediator to acts as an important factor in fish reproduction. However, the data on the participation of melatonin in male reproduction and the putative interaction with the process of spermatogenesis in fish is scarce till date. So, major objectives of the current study are to determine for the first time, the relationship, if any, between seasonal levels of melatonin and testicular development and maturation of the germ cells, and also the involvements of specific meteorological parameters in spermatogenesis under natural photo-thermal conditions. We measured the concentration of circulatory and testicular melatonin; value of gonadosomatic index (GSI), relative percentages of different developing spermatogenic cells, area and perimeter (size and shape) of seminiferous lobules along with the level/duration of rainfall, water temperature and day length in six reproductive phases throughout an annual cycle in adult male catfish (Clarias batrachus). Intra-testicular and serum melatonin concentration showed a similar seasonal pattern with a peak during "functional maturity" phase and trough during "slow spermatogenesis" phase. Correlation as well as regression analyses also supported this positive relationship. Interestingly, intra-testicular melatonin also showed a significant positive correlation with GSI and relative percentage as well as lobular size of mature stages (spermatid and spermatozoa) of germ cells in an annual cycle. Furthermore, meteorological factors exhibited as critical cues to regulate the dynamics (in %) of spermatogenic cells and the level of testicular melatonin throughout the annual gonadal cycle. Our results corroborated by principal component (PC) analysis and showed very clearly that active "functional maturity" state is characterized by GSI, testicular melatonin, relative abundance and lobular size of mature spermatogenic stages as key internal oscillators; and studied environmental variables as the external clues for the regulation of spawning process. Collectively, the present data revealed that there is a relationship between melatonin levels and testicular growth and development of germ cells in Clarias batrachus under natural photo-thermal conditions.
褪黑素是松果腺激素，根据各种环境线索（尤其是光热条件）有节奏地合成和分泌。季节性繁殖者的生殖生理学通过褪黑素作为神经内分泌介质与周围环境同步，作为鱼类生殖的重要因素。然而，迄今为止，关于褪黑素在鱼类雄性生殖中的作用以及与精子发生过程的相互作用的相关数据还很少。因此，本研究的主要目的是首次确定褪黑素的季节性水平与睾丸发育和精母细胞成熟之间的关系，如果有的话，以及在自然光热条件下特定气象参数在精子发生中的作用。我们测量了循环和睾丸褪黑素的浓度；性腺体指数（GSI）的值、不同发育阶段的精母细胞的相对百分比、曲细精管小叶的面积和周长（大小和形状），以及在整个成年鲶鱼（Clarias batrachus）的年度周期中的六个生殖阶段的降雨水平/持续时间、水温和日长。睾丸内和血清褪黑素浓度表现出相似的季节性模式，在“功能成熟”阶段达到峰值，在“缓慢精子发生”阶段达到低谷。相关分析和回归分析也支持了这种正相关关系。有趣的是，睾丸内褪黑素也与 GSI 以及相对百分比以及成熟阶段（精母细胞和精子）的小叶大小呈显著正相关。此外，气象因素显示为调节整个年度性腺周期中精子发生细胞的动态（%）和睾丸褪黑素水平的关键线索。我们的结果通过主成分（PC）分析得到证实，非常清楚地表明，活跃的“功能成熟”状态的特征是 GSI、睾丸褪黑素、成熟精子发生阶段的相对丰度和小叶大小作为关键的内部振荡器；以及研究的环境变量作为调节产卵过程的外部线索。总的来说，本研究数据表明，在自然光热条件下，鲶鱼的褪黑素水平与睾丸生长和精母细胞发育之间存在关系。
