THE INVESTIGATE OF PHOTOPERIOD AND LIGHT INTENSITY EFFECTS ON MELATONIN RHYTHMS IN MALE AND FEMALE WHITESPOTTED RABBITFISH (SIGANUS SUTOR) OF PERSIAN GULF

Annual variation of photoperiod is the most regular phenomenon that has strong predictive value in the temporal organization of seasonal activities in biological world, especially reproduction. The pineal organ, has the most important role in melatonin release under the different light condition. Melatonin is a much conserved feature in vertebrates that plays a central role in the entrainment of daily and annual physiological rhythms. The present study carried out in order to underestand different light intensity and photoperiod effects on melatonin release in whitespotted rabbitfish (siganus sutor) brood stock. For this purpose, 9 treatments, under artificial lighting conditions with 3 levels of photoperiod and light intensity include (16L/8D), (12L/12D), (6L/16D) and 1000, 2000, 3000 Lux, with a control treatment (natural light) on a period of 60 days studied. At the end of period analyzing the blood showed that the rate of melatonin in all of the male and female treatments in treatment of higher light intensity and photoperiod was lower than control treatment with a significant difference (P < 0.05). Key words: melatonin - photoperiod- light intensity- siganus sutor- Persian gulf.