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Physiological Responses to Temperature in the Alligator Lizard, Gerrhonotus Multicarinatus

Dawson, William R., Templeton, James R.
Ecology 1966 v.47 no.5 pp. 759-765
blood volume, breathing, heart rate, heat production, heat tolerance, lizards, mouth, oxygen, oxygen consumption, physiological response, temperature, tissues
The effects of temperature upon oxygen consumption, heart rate, breathing rate, and evaporative water loss of resting alligator lizards. (Gerrhonotus multicarinatus) were analyzed. The Q₁ ₀ for oxygen consumption remains constant at 3.1 between approximately 4°C and the upper level of thermal tolerance for this species, 39°—40°C. That for heart rate remains 2.3 between 10° and 39°—40°C, increasing to 7 between 10° and 5°C. The disparity in temperature coefficients for the two functions in the former range means that animals must meet the increased requirements for oxygen that develop with heating by increasing not only heart rate, but also stroke volume and/or the amount of oxygen withdrawn in the tissues from each volume of blood. Breathing rate bears a complex relation to temperature, showing rapid increases (Q₁ ₀°10) with temperature below 15° and above approximately 33°C. Within this thermal range it changes relatively little (Q₁0=1.4). At temperatures exceeding 38°C the lizards opened their mouths as if to pant, but the breathing rates and movements accompanying this activity were lower and more limited, respectively, than those found in panting iguanid lizards. Evaporative water loss by alligator lizards increases slowly with temperature between 25° and 30°C (Q₁ ₀=1.5). Between 30° and 35°C a marked upswing in the evaporation—temperature curve commences. However, even at 38°C, evaporative water loss dissipates only 66% of metabolic heat production. Loss by this route exceeds metabolic production of water at all temperatures studied.