Peripheral circulation inAlligator mississippiensis effects of diving, fear, movement, investigator activities, and temperature

Summary

• 1. Cutaneous and skeletal muscle blood flows cease when alligators are forcibly submerged or when they are disturbed by the investigator. Contrary to previous reports, blood flow to the musculature and tail of freely diving alligators remains normal during submergence, as measured with¹³³Xe (Fig. 2). Cardiovascular adjustments previously reported for diving reptiles appear to be due largely to a psychogenic response (fear) induced by experimental manipulation.

• 2. Handling and experimental manipulation cause a statistically significant elevation in peripheral blood flow at the beginning of an experiment. Blood flow then gradually decreases and reaches a steady-state after 30 min. Muscles and skin are minimally perfused when at rest. Standard blood flows for muscle ranged from 0.004 to 0.049 ml·g⁻¹ min⁻¹ $(\bar X = 0.018)$ and for skin ranged from 0.006 to 0.039$(\bar X = 0.016)$.

• 3. Voluntary movement in the absence of disturbance results in a statistically significant increase in blood flow (Figs. 3 and 4). When alligators struggle against a restraint their muscles undergo isometric contraction and blood flow ceases (Fig. 3).

• 4. Skin blood flow is elevated at temperatures above 30°C during the early portion (<30 min) of experiments (Fig. 4). There are no differences in flows during heating, cooling or steady-state conditions at the same temperature.

• 5. Muscle blood flow is insensitive to temperature between 25°C and 35°C and increases in response to exercise.