The Israeli Journal of Aquaculture Bamidgeh 57(1), 2005, 19-24

 
EFFECT OF PHOTOPERIOD ON PLASMA THYROXINE HORMONE 
LEVEL OF MIRROR CARP (CYPRINUS CARPIO) RAISED AT A 
LOW WATER TEMPERATURE IN A CONTROLLED ENVIRONMENT


Sukriye Aras Hisar1, Birsen Kirim1, Serdar Bektas1, Konca Altinkaynak2, Olcay Hisar1* and Telat Yanik1 
 

1Ataturk University, Agriculture Faculty, Department of Aquaculture, Erzurum, Turkey
 
2Ataturk University, Medical Faculty, Department of Biochemistry, Erzurum, Turkey

(Received 7.5.04, Accepted 18.10.04)


Key words: mirror carp, photoperiod, thyroxin hormone, weight gain


Abstract


The objective of this study was to examine the effects of various lighting regimes on the plasma thyroxin hormone (T4) level of mirror carp (Cyprinus carpio). The carp were kept at the low temperature of 9C to eliminate any influence of water temperature on feed intake, growth, and the hormone level. Treatments were 8 h light:16 h dark, 12 h light:12 h dark, and 16 h light:8 h dark. Plasma thyroxin levels were measured every four weeks for 12 weeks. The levels were significantly higher ( p<0.05) in the groups exposed to 8 or 12 h light than in the group exposed to 16 h. The T4 levels significantly dropped with time in all photoperiods.


* Corresponding author. Tel: +90-442-2313482; fax: +90-442-2360948; e-mail: ohisar@atauni.edu.tr

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