Photoperiodic effects on somatic growth and gonadal maturation in Mickey Mouse platy, Xiphophorus maculatus (Gunther, 1866).

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.