Photoperiod is important in initiation or suppression of reproductive timing and gonadal maturation which varies with species. The aim of the present study was to investigate the effect of two photoperiodic manipulating regimes, i.e., long (18L:6D) and short (10L:14D) photoperiods for a period of 60 days on somatic growth and gonadal maturation of a live-bearer ornamental fish, Mickey Mouse platy (Xiphophorus maculatus). The control fish were further kept under the laboratory environmental condition. The results showed a significant increase in weight gain, specific growth rate, and gonadosomatic index in fish under long photoperiod than those exposed to short photoperiod and control condition (P < 0.05). A condition factor showed significant variations between long photoperiod and control groups. Furthermore, a long photoperiod also induced a significant increase in the number of fish with mature embryo and middle-eyed embryo in the ovary. Similarly, histological analysis of testes of males showed an increase in the number of mature spermatid and spermatozoa under long photoperiod when compared to those of control and short photoperiod ones. Thus, it can be concluded that long-day photoperiodic manipulation may be applied for healthy growth and early gonadal maturation of live-bearer ornamental fishes.

中文翻译：

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光周期对体细胞生长和性腺成熟的影响在米老鼠鸭嘴兽，Xiphophorus maculatus（Gunther，1866）中。

光周期对于开始或抑制生殖时机和性腺成熟（随物种而异）很重要。本研究的目的是研究两种光周期操纵方式，即长（18L：6D）和短（10L：14D）光周期持续60天对活体动物的体细胞生长和性腺成熟的影响观赏鱼，米老鼠板鸭（Xiphophorus maculatus）。将对照鱼进一步饲养在实验室环境条件下。结果表明，与在短光周期和对照条件下暴露的鱼相比，在长光周期下鱼的体重增加，比生长速率和性腺体激素指数显着增加（P <0.05）。条件因素显示长光周期和对照组之间存在显着差异。此外，长时间的光周期也导致卵巢中具有成熟胚和中眼胚的鱼的数量显着增加。同样，男性睾丸的组织学分析显示，与对照和短光周期相比，长光周期下成熟精子和精子的数量增加。因此，可以得出结论，长时间的光周期操作可用于活体观赏鱼的健康生长和性腺的早期成熟。