Distribution of Iron in Daphnia in Relation to Haemoglobin Synthesis and Breakdown

Daphnia synthesizes haemoglobin in poorly aerated water and loses it in well-aerated water. A histochemical study has been made of iron in the tissues of partheno-genetic female D. magnawhen gaining or losing haemoglobin, and with a steady content of the respiratory pigment. In animals gaining haemoglobin, loosely-bound iron was found especially in the gutwall, fat-cells, and ovaries. The iron in the gut-wall was probably being absorbed into the body, and that in fat-cells and ovary being incorporated into newly synthesized haemoglobin. In animals losing haemoglobin, loosely-bound iron was found especially in the walls of the gut caeca, in the fat-cells, and in the excretory shell-glands. Several lines of evidence indicate that iron was being excreted by the shell-glands. It was probably also being excreted through the gut caeca. In the fat-cells haemoglobin can accumulate during haemoglobin loss and it is probably broken down here with the deposition of iron. This iron is subsequently excreted.