Histochemical localization of zinc in the retina cells of gilthead sea bream (Sparus aurata) fed different presentations of zinc

Abstract

To describe the distribution of zinc in the retina of a representative marine fish species and to determine whether the intracellular deposition amount correlates with the presentation of the zinc included in the practical diets (organic, inorganic, encapsulated, fish meal, and Control diet), we examined the precise localization of endogenous zinc in the gilthead sea bream (Sparus aurata) retina by autometallography. As observed by light microscopy, reaction products were widely distributed throughout the retina, including the outer segments of photoreceptors, except in the nuclear layers. Differing from other species previously studied, zinc depositions were not different between the outer and inner retina, and the retinal ganglion cell layer showed reaction products with a characteristic disposition surrounding the neuronal soma. An additional finding in this species was the rich disposition around photoreceptors, so abundant that it outlines the shape of the rods and cones. With regards to the diet, the zinc organic formulation was able to produce a higher amount of precipitates, followed by fish meal and encapsulated zinc diets. The inorganic and the Control diet produced a basal zinc deposition in the same layers above mentioned although less evident and similar to that determined in other species fed with non-supplemented diets.