Functions of haemoglobin inDaphnia

Abstract

In Daphnia a manifold increase in the hemoglobin (Hb) content of the blood results from O2 deficiency in the water; pale animals become red. The functions of this additional hemoglobin were studied. In poorly-aerated water Daphnia benefits from it in the following ways: (1) The additional Hb increases length of life; red individuals survive longer than pale ones. (2) The additional Hb enables more food to be gathered. Red Daphnia clears a suspension of graphite or of Chlorella more quickly than pale Daphnia, and normal red animals clear suspensions quicker than others whose Hb has been activated as an O2 carrier by CO. The rate of clearance is proportional to the concn. of blood pigment; even a small increase in Hb has a beneficial effect. (3) The addition Hb causes Daphnia to swim more energetically. (4) The additional Hb results in an increased egg production; parthogenetic females lay fewer eggs in the brood pouch if treated with CO. (5) Previous work had shown that the extra Hb passing from blood into eggs assists reproduction in another way; it accelerates embryonic development.