Osmoregulation in marine and estuarine animals: Its influence on respiratory gas exchange and transport

Abstract

Abstract Three examples of recent findings illustrating the intricacy of inter‐relationships between mechanisms responsible for gas exchange and transport and salt and water balance are described: 1) Divalent cations raise the oxygen affinity of crustacean hemocyanins (Hcs). At low salinity the respiratory consequences of a loss of Ca++ from the blood of an estuarine crab are offset by a concomitant and compensatory rise in blood pH and a shift in intrinsic oxygen binding properties, possibly brought about by a change in composition of the constituent subunits of the He molecule. The net result is a return to the original oxygen affinity during normoxia but not hypoxia, when anaerobic metabolism results in acidosis due to the accumulation of acidic end products. The acidosis requires compensation by allosteric actions of L‐lactate, the chief end product, and Ca++, a product of acid dissolution of the exoskeleton. The combined actions of these two effectors restores oxygen affinity to the original level. 2...