The effects of environmental oxygen levels on the respiratory function of hemocyanin in the crabs, Libinia emarginata and Ocypode quadrata

The respiratory function of the hemocyanin (Hcy)‐containing blood in the aquatic spider crab, Libinia emarginata, and the terrestrial ghost crab, Ocypode guadrata, was studied in animals exposed to normoxic and hypoxic conditions a t 25°C. In L. emarginata low concentrations of Hcy, although 90% O2, saturated at the gill, necessitate a high blood and water convection strategy. O. quadrata has blood with a higher concentration of hemocyanin which is 96% O2 saturated at the gill, obviating a very high rate of blood circulation. During progressive hypoxia convection initially increases on both sides of the gill in L. emarginata while in O. quadrata cardiac output decreases. Blood pH increases with decreasing ambient P , below 60 torr in L. emarginata, inducing a greater hemocyanin O2 affinity.