CONTRIBUTION OF FACTORS REGULATING MELATONIN RELEASE FROM PINEAL GLAND OF CARP (Cyprinus carpio L.) IN NORMAL AND IN POLLUTED ENVIRONMENTS

Włodzimierz Popek; Piotr Epler; Krzysztof Bieniarz; Mirosława Sokołowska-Mikołajczyk

Włodzimierz Popek
Piotr Epler
Krzysztof Bieniarz
Mirosława Sokołowska-Mikołajczyk

Keywords: PINEAL, MELATONIN, RHYTHMS, GONADOTROPIN, ZINC, CARP

Abstract

The study concerned the following issues: source and circadian melatonin concentration in blood of mature carp females during the spawning period, influence of a several days’ decrease in light intensity, influence of long term fish feeding with zinc added fodder on the system: pineal gland - hypothalamus - pituitary gland - gonads.

It was demonstrated that the pineal gland was the only organ responsible for the presence of melatonin in the blood and that the sense of sight was indispensable only for the circadian synchronisation of the changes in hormone concentration. The melatonin level oscillated regularly over 24 h showing low values during day and high over night.Adrop in light intensity evoked disturbances in the circadian rhythm of melatonin and of GtH2, resulting in a diminished efficiency of hormonal stimulation of spawning. Also a long term encumbrance of zinc salt perturbed the circadian rhythm of the two hormones, evoking changes in the central nervous system and, in the effect, retardation of gonadal activity during the spawning period.