Haemolymph gas transport, acid-base regulation, and anaerobic metabolism during exercise in the land crab (Cardisoma carnifex) (original) (raw)

1981, Journal of Experimental Zoology

Haemolymph gases, acid-base status, and metabolite levels were studied in Cardisoma carnifu, at rest and after 10 minutes of mild (0.2 body lengths/second) or severe (exhausting, 0.5 Bl/second) exercise. 02 transport is very similar to that in aquatic crabs. At rest, arterial haemocyanin saturation is : 87Vo, venous saturation is :45Vo, and tissue utilization is :57Vo. During exercise, M6, rises 2-3-fold. P6,s fall so that O, transport is shifted onto the steep part of the dissociation curve, venous saturation decreases markedly while arterial saturation remains high, and cardiac output rises. These adjustments raise the Pe, gradient at the respiratory surface, tap the haemolymph 02 store, and maintain or increase the a-v 02 difference so that utilization reaches :82Vo. Postexercise acidosis augments these effects via the Bohr shift. Resting P66r's are low (-15 torr) for an air-breather, and Pase, changes minimally despite 2.5-5fold evaluations in Mcor. All haemolymph gas levels return to normal within 0.5-1.0 hours. Postexercise acidosis is largely metabolic, and smaller than in aquatic crabs. Lactate anions and protons enter the haemolymph in equivalent amounts and totally account for the metabolic acidosis. Elevated NHs and pymvic acid levels have negligible influence. During recovery, the metabolic acid load is reduced faster than the lactate load, resulting in alkalosis, possibly because of CaCO3 mobilization from the carapace. Exercise metabolism appears largely anaerobic, but changes in haemolymph lactate levels do not correlate with the 02 debt. However, the "excess lactate" concept which compengates for pyruvate elevation gives a good index of the debt. All changes are more marked after severe than after mild exercise, but the patterns are similar. In the previous paper (Wood and Randall, crabs with these observations on marine crabs '81), we have shown that the land crab Corraises a number of issues. disomacarnifexhasconsiderablerunningabil-Increaeed 02 delivery to the tissues during ity. Exercise is facilitated by marked increases exercise in aquatic crabe is facilitated by rein ventilation, 02 consumption, CO2 pro{u9ductions in both P-, and P"or. This taps the tion, and the acquisition of a substantial 02 haemolymph 02 stori:, increasles the diffusion debt. Basically similar effects were seen in gradient for 02 loading at the gills, and at the Cardisomaguanhami(Herreidetal.,'79).Very same time takes maximum advantage of the little is known about the role of haemolymph 02 transport properties of the respiratory piggas transport in these events, about the nature ment, haemocyanin. The extremely low in vivo of the 02 debt, or about the influence of the Per's, arterial saturations, and in vitro P5s's increased CO2 flux and anaerobic metabolism reported for C ardisoma guanhami at rest (Redon acid-base regulation in land crabs, though mond, '62, '68a; Young, '73) make it questionthese areas have been extensively studied in ablewhetherthisstrategycanbeimplemented marine brachyurans (Johansen et al., '70; by the exercising land crab. Mangum and Weiland,'75; McMahon et al., DespitetherelativeeaseofCO2excretionin '79; McDonald et al., '79). Comparison of the water, Canrcer magister suffers a significant very limited information available on land riseinP."orandassociatedrespiratoryacidosis