Percentage contribution of increased heart rate to increased oxygen transport during activity in Pseudemys scripta, Terrapene ornata and other reptiles.

l. A new formula which correctly expresses the percentage contribution of increased heart rate to increased oxygen transport during activity is presented. 2. The percentage contribution is reported for the turtles Pseudemys scripta and Terrupene ornata at body temperatures of 1@-4O”C. 3. Corrected values for this parameter in reptiles studied at 30°C by other authors are also presented. SEVERAL recent physiological studies have included simultaneous measurements of metabolic rate and heart rate of resting and active reptiles. Bartholomew & Tucker (1963) presented an equation which they felt expressed the relative change of metabolism and heart rate during activity, a parameter which they termed the percentage contribution of increased heart rate to increased oxygen transport during activity. The equation which these authors derived from the Fick equation for this parameter is o/0 contribution = AHR-SHR+AOP-SOP SHR SOP (1) where AHR, SHR, AOP and SOP are active and standard heart rate and oxygen pulse, respectively. This equation, however, overestimates the percentage contribution because the denominator of the right-hand side of the equation ( AHR-SHR+AOP-SOP SHR SOP > does not represent the actual fractional change in oxygen transport during activity, i.e. metabolic scope (active metabolic rate minus standard metabolic rate) divided by standard metabolic rate. Consider the hypothetical case where SMR = 10, SHR = 5, SOP = 2, AMR = 40, AHR = 15, AOP = 2.67, * Present address: Department of Biology, The College of Wooster, Wooster, Ohio 44691, U.S.A. 649 6.50 ROBERT E. GATTEN, JR, in which SMR and AMR are standard and active metabolic rate, respectively. Note that metabolic rate equals heart rate times oxygen pulse at rest and during activity. According to Bartholomew & Tucker’s (1963) equation