Macrophage aggregates in gilthead sea bream fed copper, iron and zinc enriched diets

Gilthead sea bream Sparus aurata from consecutive year classes (0+ and 1+) and from the same parent stock were fed four diets, three of which were for tified with copper, iron and zinc. Concentrations of these elements were li ttle affected by the diet. Hepatic, renal and splenic tissues sections were examined to detect the influence of the diet on the number and morphology of macrophage aggregates (MAs); in particular their structure was examined in the spleen. Three different types of MAs were detected: (1) unstructured , (2) partially structured and scarcely defined and (3) fully structured an d well defined. Melanin was the most abundant pigment in the pigmented macr ophages which form MAs and the amount of this pigment was influenced by sea son. Ferritin, in contrast with previous data obtained in other fish specie s, was more abundant in renal than in splenic MAs. Significant differences in splenic MA numbers among fish fed different diets and among different pe riods of the year were detected. The results suggest that a polyfactorial r egulation could act on the splenic MA number in gilthead sea bream. (C) 200 0 The Fisheries Society of the British Isles.