Abstract
The effects of salinity changes on the oxygen binding properties of hemocyanin have been examined in the blue crab Callinectes sapidus. Oxygen affinity increases measurably with increases in Ca+2, Mg+2 or Na+ but, within the physiological range, not K+. Unlike its large and specific influence on other arthropod hemocyanins, Cl- has little or no effect. Ca+2, alone and in physiological concentrations, restores oxygen affinity to the level observed in a complete physiological saline. Ca+2 also restores the Bohr shift to the physiological level. Physiological variation in inorganic ions (or pH) does not affect the cooperativity of oxygen binding.Physiological variation in Ca+2 explains only a minor fraction of the actual change in oxygen affinity that accompanies acclimation to a new salinity. The aclimation, which occurs within 8 days, requires a non-dialyzable factor in the blood. The non-dialyzability of the factor and the previous reports of a large increase in blood protein levels at low salinity might ...
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