High density and food deprivation affect arginine vasotocin, isotocin and melatonin in gilthead sea bream (Sparus auratus)

6 páginas, 3 figuras, 1 tabla.Arginine vasotocin (AVT) and isotocin (IT) levels in plasma and pituitary, and melatonin (MEL) levels in plasma were determined in gilthead sea bream (Sparus auratus) subjected to two different types of stress: i) high density (HD) and ii) food deprivation (NF: non-fed). Fishes were randomly assigned to one of 4 treatments that lasted for 14 days: 1) fed fish under normal low density (ND, 4 kg m− 3); 2) non-fed (NF) fish under ND; 3) fed fish under high density (HD, 70 kg m− 3); and 4) non-fed fish under HD. Ten fish from each tank were anaesthetized, weighed and plasma and pituitary samples were taken. Plasma and pituitary AVT and IT content were determined by HPLC, while plasma MEL was assayed by RIA. Plasma AVT and IT values were enhanced in all fish kept at high density. The response of AVT was much stronger than that of IT. The highest pituitary AVT and IT levels were shown in NF fish kept at normal density. The significantly higher plasma MEL levels were measured in fed fish kept at HD. These results suggest a role of AVT, IT and MEL in response of sea bream to a common stress factor, high density. Although food deprivation does not influence AVT and IT plasma levels, it seems to affect hypothalamic synthesis of nonapeptides. Further studies are required to elucidate the complex role of AVT, IT and MEL in the sea bream's response to different stress stimuli.This study was partly supported by grant BFU2004-04439-C02-01B (Ministerio de Educación y Ciencia and FEDER, Spain) to J.M.M. The authors wish to thank Planta de Cultivos Marinos (CASEM, Universidad de Cádiz, Puerto Real, Cádiz, Spain) for providing experimental fish. Dr. G. Martinez-Rodriguez and Dr. E. Kulczykowska were supported by the Consejo Superior de Investigaciones Científicas Project 2004PL0019 and the Polish Academy of Sciences travel grants.Peer reviewe