Record Details

Smits, Allan W
Correlates of activity, diet, and body water flux in the chuckwalla lizard Sauromalus hispidus
Physiological Zoology
Journal Article
Sauromalus hispidus
Field measurements of body water balance were made in the insular, herbivorous lizard Sauromalus hispidus during a comparatively dry year when succulent annual plants were not available. Lizards fed selectively but irregularly on potassium-laden fruits of perennial cacti and lost an average of 21% of their body mass between April and August; decreases in total body water accounted for ca. 82% of this loss in mass. Fluid volumes in chuckwalla "accessory lymph sacs" decreased significantly (>50%) over the lizard's active season. Despite these net losses in body fluids and the osmotic load imposed by their food, measurements of total osmolality, ionic concentration, and erythrocyte content of the blood indicated that lizards maintained osmotic stability of their extracellular fluid. Reductions in the duration of daily activity presumably accounted for an extremely low requirement of body water (7.3 ml/kg-day), which is less than one-half that predicted and is the lowest rate of water turnover measured in any vertebrate at steady state.