Physiological properties of hemoglobin in the branchiopod crustacean Triops.

HORNE, FRANCIS R., AND KLAUS W. BEYENBACH. Physiological properties of hemoglobin in the branchiopod crustacean Triops. Am. Je Physiol. 220(6) : 1875188 1. 197 1 .-Hemoglobin of the freshwater crustacean, Triops longicaudatus, was found to have oxygen equilibrium curves similar to those of the white rat when compared under identical experimental conditions (e.g. pH-7.1; temp = 22-23 C; Hb = 2 mg/lOO ml; P50 = 6.8 mm 02 (Triops) ; PsO = 6.1 mm 02 (rat)). Magnitudes of temperature and Bohr effects, however, were different. Triops hemoglobin was affected least by both parameters. Physiological concentrations of the chloride salts of calcium, magnesium, potassium, and sodium did not affect equilibria, whereas high concentrations of calcium (52 I& and magnesium (15 mM) increased oxygen affinity (PM reduced from 8.73 to 6.7 mm 0,). Oxygen-carrying capacity of the blood, hemoglobin concentration, and carbon monoxide affinity of hemoglobin were 3.22 vol %, 1.62 g/100 ml, and 282:l (CO:Oz). By comparing respiratory rates of normal and carbon monoxide-treated animals, Trio/q hemoglobin was found not to be essential for survival. Instead, hemoglobin seems only to assist in oxygen delivery to the tissues during periods of oxygen stress. Some individuals in all Triops populations have little, if any, hemoglobin.