Saumen Kumar Maitra
Visva-Vharati University, India
Posters & Accepted Abstracts: J Aquac Res Development
Reproduction in most fish species is seasonal and under ambient conditions, the reproductive events in an annual cycle are essentially under the control of a species-specific endogenous timing system, that largely relies upon a well-equipped physiological response mechanism to changing environmental cues, especially the duration of solar light or photoperiod. In seasonally breeding vertebrates, including fish, the pineal gland is the major photoneuroendocrine component of the brain that rhythmically synthesizes and releases melatonin (N-acetyl-5-methoxytryptamine) into the circulation to perform its actions in the regulation of reproduction in synchronization with the environmental light-dark cycle. Researches in recent years have witnessed an enormous progress in understanding the mechanisms by which melatonin regulates seasonal reproduction in fish. Most studies emphasized G-protein (guanine nucleotide binding protein) coupled receptor mediated hormonal actions of melatonin on the hypothalamus-pituitary-gonad (HPG) axis of fish. However, the discovery that melatonin due to its lipophilic nature can cross the plasma membrane of all cells and thereby acts as a potent scavenger of free radicals and stimulant of different antioxidants has opened up a possibility that antioxidant actions of melatonin may be associated with the process of final maturation. Recent studies on carp demonstrated clearly that melatonin, apart from playing the role of a hormone, may act as an antioxidant to reduce oxidative stress and augment ovarian functions during spawning. This paper highlights potential actions of melatonin as a hormone in determining seasonality of spawning and as an antioxidant in regulating oocyte maturation at the downstream of HPG axis in fish.
Email: dgp_skmaitra@yahoo.co.in