Abstract

Although photoperiod plays a critical role in seasonally breeding fish, effect of altered photoperiod on reproduction of continuously breeding fish is not well understood. The objective of this investigation is to determine the effect of continuous light exposure on testicular activity in Oreochromis mossambicus. The fish were exposed to simulated photoperiod and continuous light for 21 days. Although the mean numbers of spermatogonia and primary spermatocytes did not show significant difference, the mean numbers of secondary spermatocytes, early spermatids and late spermatids were significantly lower in fish exposed to continuous light compared to those of initial controls (fish euthanized on the day of commencement of experiment), controls (fish kept in natural photoperiod) and fish exposed to simulated photoperiod. Furthermore, diminished immunoreactivity of androgen receptors was observed in the Sertoli cells concomitant with significantly lower serum levels of testosterone in fish exposed to continuous light compared to other experimental groups. In addition, the mean serum cortisol levels were significantly higher in continuous light fish group compared to other experimental groups. Overall, these results indicate that exposure to continuous light inhibits advanced stages of spermatogenesis, possibly through the suppression of testicular steroidogenesis and that this effect might be mediated through the stress-axis in O. mossambicus.

中文翻译：

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持续暴露于光线下会抑制莫桑比克罗非鱼Oreochromis mossambicus（丽鱼科鱼）的睾丸活性。

摘要

尽管光周期在季节性繁殖鱼中起着关键作用，但是光周期改变对连续繁殖鱼繁殖的影响尚不清楚。这项研究的目的是确定连续光照对莫桑比克罗非鱼的睾丸活性的影响。将鱼暴露于模拟的光周期和连续光下21天。尽管暴露于连续光照的鱼中精原细胞和原代精母细胞的平均数量没有显着差异，但与初始对照组相比，暴露于连续光照的鱼中次生精细胞，早期精子和晚期精子的平均数量要低得多（在开始使用当日安乐死的鱼）实验），对照（保持在自然光周期的鱼）和暴露于模拟光周期的鱼。此外，与其他实验组相比，在持续照射的鱼的睾丸支持细胞中观察到雄激素受体的免疫反应性降低，同时血清睾丸激素水平明显降低。此外，连续轻鱼组的平均血清皮质醇水平显着高于其他实验组。总体而言，这些结果表明，暴露于连续光下可能会抑制睾丸类固醇生成，从而抑制精子发生的晚期阶段，并且这种作用可能是通过应激轴介导的。O. mossambicus。