Responses to respiratory stress in relation to blood pigment affinity in Goniopsis cruentata (Latreille) and (to a lesser extent) in Cardisoma guanhumi Latreille

Abstract

The crabs Goniopsis cruentata (Latreille) and Cardisoma guanhumi Latreille are shown to be metabolic regulators at environmental temperatures. Haemocyanin P 50 in Goniopsis shows strong correlation with maximum standard respiratory rates ( R max ) and critical oxygen tension ( P c ) and also with lethal oxygen tensions ( P L ), at different temperatures. The hypothesis that the P c represents that P o 2 at which the blood pigment fails to become saturated in the gills, though qualitatively in accord with these correlations, is irreconcilable with metabolic regulation in these animals. An alternative hypothesis is tentatively suggested from which, like the previous hypothesis, the experimental relationship P c ∝ ( R max ) ( P 50) can be derived. The new hypothesis leads to the conclusion that the P c reflects the initiation of anaerobiosis. Altogether, the evidence is thought to suggest that the graphical correlations are causal and that pigment affinity plays a determining role in the responses to respiratory stresses, both thermal and anoxic.