BODY-FLUID VOLUMES IN THE AQUATIC SNAKE, ACROCHORDUS-GRANULATUS

Tracer dilution analysis was used to evaluate body fluid volumes in the marine file snake, Acrochordus granulatus. Relative blood volume (determined from the dilution of 51Cr-labeled red cells) averages 12.5% of wet body mass and is independent of size within the range of 69 to 191 g body mass. These volumes are slightly less than earlier estimates determined by exsanguination (Feder, 1980), but are nonetheless two-fold greater than blood volumes of many other reptiles. The blood of A. granulatus has high hematocrit values (mean, 50.1%) and thus confers an unusually large capacity for storage and transport of oxygen. Behavioral observations indicate that large oxygen stores extend aerobic dives and may be advantageous during prolonged diurnal submergence inside burrows. Extracellular fluid volumes (determined by dilution of NaSCN) are larger than those measured similarly in terrestrial snakes by an amount that reflects the relative differences in blood volume (mean ECFV = 48.8% body mass). Total body water (determined by desiccation) is ca. 75% of body mass, and is similar to that of terrestrial species. Thus, in comparison with other snakes, the blood volume A. granulatus appears to have expanded at the expense of the intracellualr fluid volume.