AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 1 93-R98, Copyright © 1981 by American Physiological Society
Effects of temperature acclimation on crayfish hemocyanin oxygen binding
P. S. Rutledge
Crayfish, Pacifastacus leniusculus, were acclimated to 10, 20, and 25
degrees C for 1 mo. Hemocyanin from animals at these three acclimation
temperatures showed distinctly different oxygen binding patterns. At any
particular set of test temperature and pH, hemocyanin from 10 degrees
C-acclimated animals had the lowest oxygen affinity and the greatest
cooperativity, whereas hemocyanin from 25 degrees C-acclimated animals had
the highest oxygen affinity and the lowest cooperativity. When tested at
their own acclimation temperature, and at normal hemolymph pH for that
temperature, all three hemocyanins showed oxygen pressure for
half-saturation of hemoglobin of 6-7 Torr. Thus acclimation keeps oxygen
affinity centered around a narrow range of values. The acclimation response
probably eliminates hemocyanin oxygen affinity as a major factor in the
decline of oxygen uptake ability in the crayfish above 20 degrees C. The
structural basis for the observed functional changes in the hemocyanin is
not yet clear.
