Temperature Sensitivity of Molluscan and Arthropod Hemocyanins

Abstract

The temperature sensitivity of hemocyaninoxygen affinity and cooperativity was measured at 5, 15, 25, and 35°C in a variety of manine molluscs and arthropods from different thermal environments. These environments included a subtidal habitat in which the temperature is generally less than 15°C and the diurnal temperature variation is small, and an intertidal habitat in which the temperature varies more than 30°C. The temperature sensitivity of P50 showed considerable variation (▵H = 0 to ▵H = -67 kJ/mol) depending on species and experimental temperatures. Sensitivity generally decreased as temperature increased. In several species temperature sensitivity was either absent or greatly reduced above 15°C. The horseshoe crab Limulus polyphemus showed a minimum temperature sensitivity between 15 and 25°C but higher sensitivity above and below this range. The hypothesis that a greater interaction between hemocyanin molecules and calcium ions at high temperatures offsets the temperature effect, resulting in a pi...