The Israeli Journal of Aquaculture Bamidgeh 56(4), 2004, 281-285

 
IN VITRO MELATONIN RHYTHM REVEALS A CLOCKED PINEAL 
IN THE EUROPEAN SEA BASS, DICENTRARCHUS LABRAX  


Benny Ron*

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


(Received 3.10.04, Accepted 8.11.04)


Key words: circadian oscillator; Dicentrarchus labrax; melatonin; pineal gland


Abstract


The melatonin-generating system of the European sea bass, Dicentrarchus labrax, was studied in vitro using a perfusion tissue culture methodology. The examined properties included photic entrainment in the pineal gland, and circadian rhythmicity in alternating dark and light, in continuous darkness, and in continuous light. Pineal glands were removed from adult fish and placed in a perfusion tissue culture at a constant temperature of 24C. Melatonin discharge into the culture medium was measured using radioimmunoassay. Melatonin concentrations during a photoperiod of 12h light:12h dark were low during the light periods and high during the dark. The melatonin discharge was inhibited by continuous light but strong and rhythmic in continuous dark with a circadian period (Tau) of about 24 h (n = 10). The results demonstrate that the European sea bass pineal gland is photosensitive, with ability to be entrained, and contains an internal circadian oscillator that regulates melatonin production.


* E-mail: ronbenny@agri.huji.ac.il

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