Influences of haemoglobin concentration and temperature on oxygen uptake of Daphnia magna under low oxygen concentration

1. 1. The haemoglobin concentration in the blood of a single Daphnia magna was determined with a microspectrophotometer. The haemoglobin concentration of an adult female (2.5 mm body length) was observed to range between 1.7 and 0.1 g haemoglobin per 100ml of blood. 2. 2. The ability of animals to imbibe oxygen in the water depended on the blood haemoglobin concentration. The functional significance of the haemoglobin was studied in association with the effect of temperature on this ability.