Ontogeny and Scaling of Hematocrit and Blood Viscosity in Western Fence Lizards, Sceloporus Occidentalis
Hematocrit, the volume fraction of blood composed of erythrocytes, influences the oxygen transport capacity of blood by affecting both the oxygen content and viscosity of the blood. In lizards, variation in locomotor performance also depends on hematocrit. Here, I report that hematocrit, total plasma protein, and consequently blood viscosity increase allometrically with body size in the Western Fence Lizard, Sceloporus occidentalis. Blood viscosity varied exponentially with hematocrit and was substantially higher at 15 C than at 30 C. Hematocrit was lower in hatchling lizards (<five weeks old) than in juveniles and adults and increased significantly between four and five weeks after hatching. The size-dependent variation in these hematological parameters may contribute to size-dependent variation in aerobic performance or may be part of another adaptive ontogenetic change (e.g., in the osmoregulatory system).Abstract
Scaling of hematocrit in field active lizards, S. occidentalis. See Table 1 for allometric equation fitted to data.
Relationship between hematocrit and viscosity in reconstituted samples of blood from S. occidentalis. Open circles were measured at 15 C; closed circles were measured at 30 C. See text for equations fitted to data.
Hematocrit during the first weeks post-hatching in S. occidentalis. Hematocrit is significantly higher at week five than in previous weeks. n = 6–10/sample period.
Contributor Notes
Department of Biology, Trinity College, Hartford, Connecticut 06106. E-mail: Kent.Dunlap@trincoll.edu.