. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. O2 UPTAKE AND TRANSPORT IN BUSYCON 85 o> CM O o 0. PH FIGURE 4. Buffer properties of oxygenated (open circles) and deoxygenated (open squares) blood taken from Busycon canaliculatum (22° C, 31%f salinity). observed change in pH. Whether the relatively large CO-> change is due to a slow rate of blood flow or, equally likely, to the special CO2 requirements of shell secretion, is not clear, but we suggest that the primary agent of the pH change is the exchange of a component of the CO2 sy
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. O2 UPTAKE AND TRANSPORT IN BUSYCON 85 o> CM O o 0. PH FIGURE 4. Buffer properties of oxygenated (open circles) and deoxygenated (open squares) blood taken from Busycon canaliculatum (22° C, 31%f salinity). observed change in pH. Whether the relatively large CO-> change is due to a slow rate of blood flow or, equally likely, to the special CO2 requirements of shell secretion, is not clear, but we suggest that the primary agent of the pH change is the exchange of a component of the CO2 system. When animals are held in hypoxic water (Po2 < 20 mm Hg) for 6 hr, pedal blood pH ( ± ) and PCo2 [ (± ) mm Hg] change very little (N = 6). Moreover, there is no increase in free Ca+2 content of the blood (Mangum and Lykkeboe, 1979), suggesting that the shell is not an important source of buffer under these conditions. When exposed to hypoxia for longer periods (12-24 hr), pedal blood pH dropped to to However, none of six animals in each of two experiments survived this experience, and no further measure- ments were attempted. Oxygen carrying capacity Numerous samples of blood from the pedal sinus of freely locomoting animals yielded values for oxygen carrying capacity that were unexpectedly low [ (± ) ml/100 ml, N = 58]. They were, however, consistent with predic- tions based on hemocyanin concentration [ (± ) ml/100 ml, N = 11]. Surprisingly, the values for samples taken from the nephridium of the same animals were 2 to 4 times higher. This apparent anomaly occasioned a more intensive study of the changes in hemocyanin levels in different parts of the circulatory system and in the water extruded from the shell as the animal withdraws, which was under- taken in the closely related species Busycon carcia because of its greater abundance (Mangum, 1979). Although fewer data are available for B. canaliculatum (Ta
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