The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


THE INFLUENCE OF THE PINEAL ORGAN AND MELATONIN
ON THE REPRODUCTIVE SYSTEM AND OF LIGHT INTENSITY
AND WAVELENGTH ON MELATONIN IN THE GILTHEAD SEA
BREAM (SPARUS AURATA)


Alon Naor¹, Nitzan Segev¹, Keren Bressler¹, Adi Peduel¹, Eran Hadas² and Benny Ron¹*

1 Israel Oceanographic and Limnological Research Ltd., National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel

2 Suf Fish Farm Ltd., North Shore, Eilat 88000, Israel


Abstract

Effects of full-spectrum white (at normal room intensities) and monochromatic light (at various wavelengths) on pineal (in vitro ) and plasma (in vivo ) melatonin were investigated in the gilthead sea bream (Sparus aurata) during the naturally dark hours of the day (18:00 to 06:00). The evaluated zenith wavelengths (lambda max) of the intensity treatments tested in the in vivo experiment were 434 nm (blue) with a light intensity of 5 lux, 548 nm (green) with a light intensity of 20 lux, 614 nm (red) with a light intensity of 50 lux and white light with an intensity of 550 lux. The treatments for the in vitro experiment were 434 nm (blue) with a light intensity of 60 lux, 548 nm (green) with a light intensity of 100 lux, 614 nm (red )with a light intensity of 80 lux and white light with a light intensity of 800 lux. The potency of the tested lights to suppress melatonin levels in the plasma were ranked in the following order:white >green >blue >red. On the other hand, light suppression of melatonin levels in the pineal organ ranked: white >blue >green >red. The results demonstrate that the suppression of melatonin by light depends on the wavelength of the light and the circadian phase.

We tested the consequences of applying monochromatic light in gilthead sea bream aqua-culture and found that the growth rate improved with white and blue light before and during the reproductive season. There were significant differences between the gonad weights of the treated groups and those of the control groups. Another experiment tested the effect of pinealectomy on gonad maturation. The results showed that male maturation in pinealectomized fish was delayed almost three weeks compared with that of sham-operated and control animals. In addition, we investigated the effects of melatonin given in the food on gonad maturation. Our findings showed that the melatonin treatment affected the gonadosomatic index and that the pineal organ has an important role in the alteration of the reproductive system in fish via pineal melatonin.

*email: ronbenny@agri.huji.ac.il

home