Fred N. White

Redistribution of cardiac output in response to heating in Iguana iguana

Abstract 1. 1. In Iguana iguana and Tupinambis nigropunctatus heating resulted in lower arterial-venous oxygen differences than were seen in controls at a similar temperature. Oxygen pulse values changed in a similar manner. 2. 2. Ventricular systemic output increased as much as 2.3 times during heatigg when compared with values during non-heating, control conditions. 3. 3. In three iguanas right-to-left shunting or bypassing the pulmonary circuit in response to heating averaged 20.3 per cent of ventricular systemic output. In one tegu it averaged 8.3 per cent. 4. 4. Increased heart rate with sustained, increased or decreased stroke volume was responsible for the increase in observed ventricular output under conditions of heating.

PHYSIOLOGICAL AND ECOLOGICAL CORRELATES OF TUNNEL NESTING IN THE EUROPEAN BEE-EATER, MEROPS APIASTER'

Bee-eaters excavate tunnel nests to a depth sufficient to blunt the impact of wide variations in surface temperatures on the thermal environment in the nest chamber. Thermal environment of the inhabitants is maintained within or near their thermal neutral zone. High chamber humidity, minimal thermal stress, and succulent insect food combine to stabilize water balance of nestlings. Diffusion of gases through soil and along the nest tunnel can account for maintenance of tolerable levels of O₂ and CO₂; however, the absence of nest sanitation and presence of microorganisms causes significant periodic elevations in NH₃ and CO₂ and a decrease in chamber O₂. This latter circumstance is associated with windless conditions. Wind movements rapidly improve internal conditions by the formation of gas vortices which penetrate via the nest tunnel to the chamber while displacing chamber gas to the exterior. The piston effect of adult birds moving along the tunnels and thermally induced density currents further augment gas renewal. The combination of soil characteristics and nest design provides a generally equable and uniform microenvironment for the developing young, even though external conditions may vary widely.

Temperature and the Galapagos marine iguana—Insights inso reptilian thermoregulation

Abstract 1. 1. Marine iguanas regulate core temperature under increasing thermal loads. Regulation correlates with behavior. 2. 2. Elevated basking (EB) is initiated within a narrow range of body temperatures ( T b ). The principal exteroreceptor for adjusting body attitude appears to be the eyes. 3. 3. Panting can be induced when EB is prevented but occurs at a higher T b than was encountered under field conditions. Panting is an effective mechanism for stabilizing T b . 4. 4. EB minimizes radiant heating but cannot account for stability of T b under successively warmer conditions. Creation of a ventrally located heat sink and associated cardiovascular changes allow construction of a model which deficits the animal as a regulated “heat shunt”. 5. 5. Night cooling rate is attenuated by aggregating. 6. 6. Immature animals regulate T b by vertical shuttling in the thermal gradients of crevices. 7. 7. Major thermoregulatory interactants are discussed.

Temperature induced peripheral blood flow changes in lizards

SummaryThe influence of local temperature changes within the posterior portion of the body on dorsal aorta blood flow (

Thermoregulatory Behavior of the Northern Elephant Seal, Mirounga angustirostris

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Blood Flow in Turtles

), femoral arterial pressure (Pa), peripheral resistance (R), skin blood flow (

Metabolism and Oxygen Transport in the Innkeeper Urechis caupo

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