ANALYSIS OF HEMOLYMPH OXYGEN LEVELS AND ACID-BASE STATUS DURING EMERSION 'IN SITU' IN THE RED ROCK CRAB, CANCER PRODUCTUS.

Hemolymph samples were taken from small (< 100 g) individuals of Cancer productus following ca. 3 h air exposure (emersion) on the beach, `in situ', at Friday Harbor, Washington. Compared with crabs of similar size in sea water in the laboratory, these crabs emersed `in situ' had lower Pao2, and Pvo2, but no significant change in pH and a small, not significant, internal hypercapnia. Total CO2 (Cco2) content of the hemolymph was elevated by 70% (15.2 versus 9.0 mM), possibly as compensation for input of acid into the hemolymph. These responses are qualitatively similar to those resulting from similar treatment in the laboratory, but differ in the reduced magnitude of the internal hypercapnia and acidosis of the hemolymph. It is suggested that the particular conditions of emersion `in situ' permit some gas exchange with interstitial sea water. Interstitial sea water was found to be hypoxic (Po2 = 20-40 torr), which would limit oxygen supply yet permit CO2 excretion to continue, in agreement with the data.