Molecular adaptation of Daphnia magna hemoglobin.

Daphnia magna responds to changing environmental conditions impeding aerobic metabolism by synthesizing hemoglobin of adequate quantity and quality to maintain oxygen supply of the tissues. Hemoglobin subunit composition and its oxygen affinity were analyzed as a function of temperature as well as depending on the oxygen partial pressure of the medium. Additionally, the time course of acclimation to hypoxia was studied. Correlating structural and functional changes, the role of individual subunits for the increase in oxygen affinity is discussed.