title: Effect of hematocrit on behavioral thermoregulation of the toad Bufo marinus.
abstract: This study tested the hypothesis that the oxygen capacity of blood, indexed by hematocrit, affects the body temperature (Tb) selected by toads (Bufo marinus) in a thermal gradient. Anesthetized toads (Brevital sodium; 40 mg/kg im) were fitted with a cloacal thermistor and femoral artery cannula. After recovery, they were placed in a thermal gradient ranging from approximately 10 to 40 degrees C. Tb was measured for 24 h. Then 1-2 ml blood were withdrawn and replaced with an equal volume of either 0.66% saline or packed red cells from donor toads. Selected Tb was measured for the next 24 h. The mean Tb selected by B. marinus (n = 33) was 24.9 degrees C. Cross-sectional analysis showed no correlation between selected Tb and hematocrit. However, each toad rendered anemic showed a reduction of selected Tb (mean = 22.9 degrees C). The degree of Tb reduction was correlated with the hematocrit reduction, (r = 0.86; P = 0.013). Blood doping did not have a significant effect on selected Tb. The reduction of Tb could be adaptive by reducing oxygen consumption.
authors.affiliation: Oxygen Transport Program, Lovelace Medical Foundation, Albuquerque, New Mexico 87108.
authors.forename: S C
authors.initials: SC
authors.lastname: Wood
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001831:Body Temperature; D001833:Body Temperature Regulation; D002024:Bufo marinus / Q000502:physiology*; D006400:Hematocrit