Effects of temperature and body size upon heart rate and oxygen consumption in turtles

Abstract

Numerous scattered reports have given data on effects of temperature upon heart rates in reptiles. Reports have also been made on rates of oxygen consumption at different temperatures. However, few (with the exception of Adolph, '51) have attempted to correlate these phenomena even though Benedict, in his extensive study of reptile physiology ('32), has stated he believed that ''. . . the heart rate of the tortoise may furnish a significant hint as to its metabolic activity." Also, the size of the animals has usually not been considered in interpreting the data reported.It was the purpose of this investigation to attempt to determine the effects of temperature and body size upon heart rate and metabolic rate in two species of turtles, and to determine if a correlation exists between heart rate and metabolic rate in these animals. MATERIALS AND METHODSSix specimens of the Mobile cooter turtle, Pseudemys floridana mobilensis, were collected in the region of Lake Concordia, Louisiana, in May, 1957. Heart rates were taken of these animals of varying size at different temperatures between 10.5" and 35°C. The animals were initially cooled in a refrigerator and then gradually warmed to room temperature and heated under an incandescent lamp. Heart rates were recorded on a Sanborn Twin-Viso, Model 60, electrocardiograph. Channel 3 or, at times, channel 2 was found to give the best recordings. Leads were attached by means of copper alligator clamps to the plastron and epidermis ventral to the limbs. Electrode paste was liberally used. The animals were held immobile during the recording by strapping them with cord to a wooden platform. Results are given in figure 1.More extensive studies were done on specimens of the red-eared turtle, Pseudemys scripta elegans. These animals were collected in the region of Schriever, Louisiana, a short time previous to each study in which they were used. In July of 1957 heart rates were taken on a group of 10 animals varying in weight between 300 and 800 gm. Rates were recorded at 5 degree intervals ranging from 15" to 35°C. The method of recording rates was similar to that used with the cooter turtles. However, body temperatures were achieved in a slightly different manner: the animals were placed in a water bath at the desired temperature for several hours previous to having the heart rates taken. Results are given in figure 2.During March of 1958 oxygen consumption and heart rates at lo", 20°, and 30°Cwere determined in a series of 11 red-eared turtles ranging between 233 and 1,805 gm. Oxygen consumption was measured by placing the animal in a sealed desiccator which, in turn, was placed in a constanttemperature water bath. Soda lime within the desiccator absorbed COB. Each desiccator was connected by tubing to a gravity-type water spirometer containing 0,.

Ecology of the Basking Habit in Turtles

“…Lowe and Vance (1955) found the resistance time to the critical thermal maximum in Urosaurus ornatus varied inversely with the body size of the lizard. Size may affect body temperatures in a physiological fashion as well as by simple physical effect, since heart rates and other physiological processes in turtles that may affect thermal gradients have size correlates (Hutton et al 1960;Boyer 1963).…”

“…Effects of circulation on gradients of heat within turtles are unknown. They exhibit higher heart rates at higher temperatures (Hutton et al 1960;Kaplan and Taylor 1957;Rodbard and Feldman 1946;Wilbur and Lieb 1950) and higher blood pressure when the brain is warmed (Rodbard et al 1950).…”