ABSTRACT
Iron is a trace mineral of fundamental importance for most higher ani mals, including fish, because of its functions in oxidation-reduction activity and oxygen transport. In biological systems, iron can exist in the ferrous (Fe2+) or ferric (Fe2+) state, and this permits iron to donate or accept elec trons and thus participate in the oxidation-reduction reactions, including those involved in oxygen transport. It occurs in the animal body as a compo nent of the respiratory pigment (heme compounds), such as hemoglobin in red blood cells and myoglobin in muscle, as well as the heme enzymes such as peroxidase, catalase, and cytochromes. The remainder of the iron in the body is found in nonheme compounds such as transferrin (siderophilin), lactoferrin, ferritin, and hemosiderin (Harper 1973; Kaneko 1980). Trans ferrin, which is the principal protein carrier of iron in the blood, plays an im portant role in iron metabolism. Ferritin and hemosiderin are iron storage compounds found in the liver, spleen, and bone marrow.
