Effects of temperature and photoperiod on ovarian cycle in the mosquitofish, Gambusia affinis.

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Mosquitofish, <I>Gambusia affinis</I>, repeat parturition at constant intervals under constant temperature and photoperiod. Although the intervals change with rearing condition, it is unclear whether or not environmental factors affect the process from vitellogenesis to parturition. To clarify the effects of temperature and photoperiod on the ovarian cycle (between ssuccessive parturition events), the parturition intervals and oocyte and embryonic development were investigated under various temperatures (20-31°C) and photoperiod (14-16 hr light-phase). The parturition intervals became shorter at higher temperatures under constant photoperiod. It is suggested that temperature primarily influences the rate of embryonic development; the effects being large at less than 25°C, and smaller at more than 25°C. The parturition intervals became shorter under long daylength periods at a constant temperature. It is suggested that photoperiod primarily affects the progress of vitellogenesis (timing of fertilization after parturition) and has little effect on embryonic development.
日本魚類学会の論文