Photoperiodic effect on reproductive physiology of fresh water teleost, Channa punctatus

Abstract

Photoperiod is considered  as one of the important environmental cues to affect the seasonal rhythm and reproductive physiology. It is well accepted that photoperiod particularly long days affects  reproduction in fish in one way or another and it is considered as one of the most important environmental cue for breeding seasonality and maturation. Photoperiodic manipulation plays an important role in   gonadal physiology, Short photoperiods (SD) and Continuous darkness (DD) instead shows negative effect on development of gonads by showing non inhibitory effect on hypothalamus releasing GnRH that acts on ovarian hormones like LH and FSH causing positive development of gonads. Channa is found in tropical and subtropical countries and is a fresh water fish inhabiting lotic and lentic aquatic systems and it plays an important role in meeting nutritional requirements because of its high protein content and also has an ornamental value as well.Exposing fish to long photoperiod(16L:8D) shows significant difference at 95% confidence interval for GSI that is possibly due to increase in number of oocytes but no significant difference on exposing fish to short photoperiod (8L:16D) was recorded. Histological study of gonads showed oocytes in primary growth phase having maximum oocytes in chromatin nucleolar stage on exposing fish to long photoperiod but maximum oocytes in oogonium stage on exposing fish to short photoperiod. Therefore, reproductive physiology is an important parameter that should be considered to improve quality as well as farming trends. For the same a proposed experimental model was designed to see the effect of different photoperiod for 45 days of exposure. Exposing fish to long photoperiod(16L:8D) shows significant difference at 95% confidence interval for GSI that is possibly due to increase in number of oocytes but no significant difference on exposing fish to short photoperiod (8L:16D) was recorded. Histological study of gonads showed oocytes in primary growth phase having maximum oocytes in chromatin nucleolar stage on exposing fish to long photoperiod but maximum oocytes in oogonium stage on exposing fish to short photoperiod.