The physiological ecology of haemocyanin in some selected crabs. I. The characteristics of haemocyamn in a tropical population of the blue crab Callinectes sapidus Rathbun

The haemocyanin in Callinectes sapidus Rathbun, a fully aquatic crab has been investigated in a population inhabiting a salt pond in a tropical mangrove swamp. Compared with the results of an earlier study on the haemocyanin perhaps on a subtropical population (Redfield, Coolidge & Hurd, 1926), the P 50 found here at 0 mm Hg CO 2 is remarkably low. It is suggested that this is in adaptation to low environmental oxygen concentrations resulting from, 1) high mean water temperature and salinity, and 2) the tendency of the animals to burrow into the sediment. High sensitivity to temperature and a relatively strong Bohr shift are demonstrated, and the possible physiological-ecological pressures involved are discussed. The responses to pH and temperature (Hill's n ) of the shapes of the equilibrium curves have also been investigated; the significance of these responses is still obscure. A possibly significant difference in Bohr shifts is noted with P CO 2 -dependent variation in pH, and with a naturally occurring variation among individual serum pH values.