AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 1 99-105, Copyright © 1981 by American Physiological Society
Circulation, oxygen transport, and activity in the crayfish
P. S. Rutledge
Heart and ventilation frequencies, oxygen uptake rate, hemocyanin
concentration, and pre- and postbranchial PO2 and pH were measured in
unrestrained crayfish (Pacifastacus leniuculus) immediately following
routine and forced (maximum) activity. Experiments were performed at 20
degrees C, the temperature of maximum scope for activity in this species,
and at 10 and 25 degrees C. A procedure for using N-ethylmaleimide as an
anticoagulant in hemolymph sampling is described. Hemocyanin oxygen
saturation, oxygen content of pre- and postbranchial hemolymph, cardiac
output, and stroke volume were estimated from the measured parameters. PO2
of postbranchial hemolymph sampled immediately after routine activity was
low (9-12 Torr), accompanied by hemocyanin oxygen saturations of 55-75%.
Maximum forced activity for 10 min caused further reduction in these
values. Thus hemocyanin is apparently not usually saturated with oxygen in
these crayfish. Cardiac output, as estimated by the Fick principle, was
high (at 20 degrees C, 236 ml x kg-1 x min-1 for routine activity and 969
ml x kg-1 x min-1 for forced activity). Evidence is presented that
ventilation, rather than circulation, limits active oxygen uptake and scope
for activity both above and below 20 degrees C.
