Annual Cycles of Cortisol, Thyroid Hormones, Electrolytes, Feeding, and Growth of Sea Bass (Dicentrarchus labrax L.) Adapted to Different Salinities

Trabajo presentado en el 13th Conference of European Comparative Endocrinologists, celebrado en Belgrado (Yugoslavia), del 7 al 12 de septiembre de 1986The present study investigates the annual effect of constant temperature (19-20”) (except for summer months that follow natural variation) and different salinitiea (0.3%, _ 7%. 1.7%) on 36 adult male \ea bass (Dicrntrarc,hus luhrux) (average. 190 g weight, 27 cm length). evenly distributed in three groups. Periodic samples from each group were taken for assay of cortisol. T,. ‘T,. d’a , and Na and for determination of hematocrit (H~J, condition factor (CF). instantaneous growth rate (G). daily food intake (RJ, and gross conversion efficiency t K). G, R, and K decrease steadily during the reproductive period (December-April) and plasma electrolytes tend to be low at the end of this period. Cortisol, T,. and T? were high especially during January and/or March depending on the osmotic medium considered. Evolution of CF during this time reflects changes in gonad weight and shows different patterns comparing different salinities. Hematocrit levels present an inverse correlation with CF during this period. From May to June CF reaches the lowest values of the year, as do the corti\ol levels in plasma (400 ngiml). During this time (especially for animals adapted to sea water) an increase of’ T,. Ua + , and Na- was noticed, coinciding with a surge of plasma testosterone observed previously CF. Pmt. M. Carrillo, and A. Fostier, 1985 Eur. Sot. Comp. Physiol. Biochem., 7th Conf.. Al.16. University of Barcelona. Spain) for the same species and probably as result of the onset of gametogenesis. A sudden decrease of the forementioned parameters occurs at the end of this period. G, R. and K also increase during this time but continue further on until November. Coinciding with the growth period of the sea bass (S. Zanuy and M. Carrillo. 1985) Ayuac~ullure, 44, ll-25), a steady increase of CF was observed which reflects mesenteric fat accumulation instead of gonadal development. A progressive increase of T,. Ca’ &, and Na+ was observed, which was more evident in sea water-adapted animals. A mechanism of action of hormones and electrolytes are discussed according to the different osmotic medium considered and the time of the year.Peer reviewe