The effects of powdered carp pituitary on ovarian development, ovarian ascorbic acid and ovulation in Carassius carassius L. exposed to various photoperiod and temperature regimes

The effects of temperature, photoperiod and powdered carp pituitary on ovarian development (measured by change in diameter of intraovarian eggs and gonadosomatic index), ovulation and ovarian ascorbic acid have been studied in crucian carp in winter. Short photoperiods stimulated ovarian development but long photoperiods were inhibitory. Photoperiod seemed to exert this effect by altering the release of pituitary gonadotropin. Temperature affected ovarian development independently of photoperiod. High temperatures were stimulatory and overcame the negative effect of a long photoperiod. The results suggested that temperature acts at the level of the gonad rather than the pituitary. On the basis of these findings a hypothesis is suggested to explain gonadal cycles in cyprinids and similarities to previous findings in other fish groups are discussed. Levels of ovarian ascorbic acid varied according to treatments. Ovulation was associated with a decreased level. The results suggested that this vitamin aids biosynthesis of sex steroids in a similar fashion to that observed in higher animals. The results also demonstrated that measurement of gonadal ascorbic acid can provide a useful indication of physiological events at the level of the gonad.