IMPACT OF SEROTONIN ON MOULTING, OVARIAN MATURATION AND SPAWNING IN A MOLE CRAB, EMERITA EMERITUS.

The commercial brood production through eyestalk ablation is often associated with high mortality in the brood stock and inferior quality of offspring and it is necessary to find an alternative for worldwide expansion of fishculture. The present study was designed to find the possible role of serotonin (5-hydroxytryptamine, 5-HT) in moulting, reproduction and spawning in the mole crab Emerita emeritus. Serotonin in brain, hemolymph and ovary of the mole crab was correlated with moulting and reproduction to elucidate its modulatory effect. Immuno cytochemical observation indicated positivity to serotonin in neurosecretary cells and ovarian cells at various phases of development. Quantitative analysis of serotonin, using HPLC clearly exhibited a gradual increase in brain and thoracic ganglia during intermoult. Similarly ovary and hemolymph showed highest concentration, whereas the concentration of serotonin gradually declined from premoult stages indicating that the amine act as a neurotransmitter through the mediation of eyestalk neuropeptide hormone. To augument the impact of serotonin, exogenous 5 HT, at various concentration (1x10-6, 1x10-7 and1x10-8 mol/crab) were injected into the crab at immature stage of ovarian development. The effect was compared against a control group, which received the injection of the sterile vehicle solution. Serotonin induced ovarian maturation and increased the spawning rate at a dose of 1x10-6 mol/crab. Thus exogenous form of 5-HT influenced ovarian maturation and enhanced the spawn on 12th day while the control crabs spawned only on the 22nd day of the experiment. From the results we conclude that, serotonin regulated ovarian maturation and advanced spawning by overcoming the inhibition of gonad inhibitory hormone from the optic lobe of the mole crab or in the brain and thoracic ganglia to stimulate gonad stimulating hormone synthesis or indirect effect on the ovary.