The significance of the linkage between the Bohr and Haldane effects in cephalopod bloods.

This study concerns the physiological implications of the theoretical identity between the Bohr and Haldane effects in the hemocyanin containing blood from the cephalopods Loligo forbesii and Sepia officinalis. The Bohr factor is for both species lower than -1.0. The functional Haldane coefficient (delta ctCO2/delta cHcO2)pH ranges from -2.0 to -0.9 mMCO2/mMO2 in S. officinalis and from -1.2 to -0.7 mMCO2/mMO2 in L. forbesii. This implies for S. officinalis that there may not be enough protons produced from aerobic metabolism to facilitate the release of O2 from HcO2 via the pH sensitivity of this binding. The amount of anaerobically produced protons are predictably of little consequence for release of Hc bound O2 in cephalopods since octopine as the primary product of anaerobic metabolism is a much weaker acid than lactic acid at physiological pH. It is proposed that during burst swimming powered by the ventilatory current, such as practiced by many squids, the overall requirement for ventilation may increase causing a reduced pCO2 and bring the functional Haldane effect below unity. This implies that more H+ are produced by aerobic metabolism than can be found to hemocyanin, hence a shift of the O2 equilibrium curve to the right and improved O2 unloading potential. The advantage of the very large (pH sensitivity) Bohr shift in benthic forms like S. officinalis, both tolerant of and frequently experiencing hypoxic water, may rest with a marked increase in O2 affinity and improved O2 loading in response to respiratory alkalosis produced by hyperventilation.