The Essential Nature of Vitamin A in the Diet of Goldfish (Carassius auratus)

In an attempt to determine whether or not fish require dietary sources of vitamin A, commercially reared goldfish (Carassius auratus) were procured and maintained in a darkened animal room in glass tanks with continuously circulating, filtered water which was constantly aerated. The fish, divided into two groups, were fed synthetic diets: one of which, the control diet, contained crystalline retinol acetate; the other, the experimental, was the same diet but without the vitamin A acetate. Periodically a fish from one group or the other was sacrificed and the vitamin A of both liver and eyes determined. The carcasses were fixed in Bouinˈs fluid and preserved for histological study. The amount of vitamin A in the livers of the deficient fish decreased while that in the livers of the controls increased. At approximately the same time the deficient fish developed pathological signs such as hemorrhage into the eyes and other sites, exophthalmos, loss of scales, and anorexia followed by death. There was still considerable vitamin A in the eyes of the deficient fish. None of these signs appeared in the fish on the complete diet, and the amount of vitamin A in the tissue remained high. Without exception every fish showing pathological changes also developed a severe, generalized infection. On the other hand only one control fish became infected and that was very slight. Similar results, but fewer in number, were obtained from preliminary experiments. These experiments demonstrate clearly that goldfish cannot synthesize vitamin A from ordinary dietary constituents. They also suggest that the vitamin deficiency increases the susceptibility of the fish to infectious agents.