COMPARISON OF BLOOD-VISCOSITY IN RED-EARED SLIDERS (TRACHEMYS-SCRIPTA) ADAPTED TO COLD AND ROOM-TEMPERATURE

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees C, which may result in a profound bradycardia and a drop in blood pressure leading to very sl ow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigat e the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, col d environment (5 degrees C) or room-temperature environment (25 degree s C). At the end of 5 months treatment, hematocrit values, plasma prot ein concentration, and whole-blood viscosity values were determined fo r each turtle. Blood viscosity measurements were determined at five sh ear rates (3.75, 15, 30, 75, and 150 s(-1)) at 5 degrees C and 25 degr ees C for all animals. No significant differences were found in hemato crit or plasma protein values between cold-adapted and room temperatur e-adapted animals. Whole-blood viscosity between groups at any shear r ate at a temperature of 5 degrees C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to c old and room temperature occurred at a shear rate of 3.75 s(-1) at 25 degrees C. The whole-blood viscosity of red-eared sliders, whether ada pted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate , and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these an imals during hibernation. (C) 1998 Wiley-Liss, Inc.