Blood viscosity and hematology of American bullfrogs (Rana catesbeiana) at low temperature

(1) The purpose of this study was to evaluate hematological properties and blood viscosity in bullfrogs (Rana catesbeiana) submerged and exposed to prolonged low temperature. (2) Blood was collected from bullfrogs submerged in aerated water for 0, 20 or 50 days at 5degreesC, and those kept at 25degreesC. (3) No significant differences were found in hematocrit, hemoglobin, red blood cell count (RBCC), mean cell volume, apparent viscosity, plasma viscosity, or relative viscosity. (4) Plasma osmolality significantly decreased (P<0.001) in 5degreesC groups relative to the 25degreesC group. (5) Bullfrogs maintained a constant hematocrit, RBCC, and hemoglobin concentrations despite potential hemodilution, suggesting that bullfrogs could maintain a constant hematocrit during hibernation. (C) 2003 Elsevier Science Ltd. All rights reserved.