Seasonal Effects of Pinealectomy on the Ovary of the Catfish Heteropneustes fossilis (Bloch) Under Normal Photothermal Conditions

Abstract

Pinealectomy of Heteropneustes fossilis held under normal photoperiod and ambient temperature produced season-dependent effects on ovarian activity. When the fish were pinealectomized in the preparatory phase (early light-responsive period) and maintained until the early prespawning phase, there was an accelerated growth of the ovary, as adjudged from increased gonado-somatic index (GSI), ovarian histology, elevated ovarian total protein and ascorbic acid levels, and an increased level of serum alkali-labile protein phosphorus (vitellogenin). Pinealectomy was ineffective in the prespawning and spawning (late light-responsive phase) and postspawning (light refractory) phases. The results suggest that the pineal exerts an inhibitory effect on the hypothalamo-hypophysial-ovarian axis and synchronizes temporally ovarian activity in response to increasing photothermal conditions such that spawning takes place at a time most suitable for the survival of the young.