Significance of retinal and the pineal photoreceptors in the photoperiodic regulation of reproduction in the bony fish Channa punctatus (Bloch)

K Renuka; B N Joshi

Volume : IV, Issue : IV, April - 2014

Significance of retinal and the pineal photoreceptors in the photoperiodic regulation of reproduction in the bony fish Channa punctatus (Bloch)

K Renuka, B N Joshi

Abstract :

Most poikilotherms perceive photic signal through retinal and non-retinal photoreceptors. The photoreceptors present in the pineal organ are important in mediating the non-retinal photoreception in fish. The purpose of this study was to assess the significance of retinal and pineal photoreception in the regulation of reproduction in Channa punctatus. While the retinal pathway was disrupted by surgical enucleation (EN), the pineal pathway was cut off by pinealectomy (PX). Both, EN and PX led to a stimulation of ovarian function in fish held in light-dark (LD) 12:12 cycle. Highest stimulation was noticed in fish that underwent both EN and PX. However, when the EN and PX fish were challenged with short photoperiod (LD 06:18) their ovaries were inhibited. The results indicate that both retinal and the pineal photoreceptors are important in the photoperiodic regulation of reproduction. In addition, the findings also provide a clue for the involvement of some non-retinal and non-pineal photoreceptors in the photic signal transduction in this fish. Pineal gland is known to convert the physical photic signal into a chemical hormonal signal in the form of melatonin produced rhythmically. Since both, the lateral eyes and the pineal organ are known to produce melatonin the observed changes in ovarian function could be due changes in melatonin turnover under the experimental conditions