Pulmonary Blood Flow at Rest and during Swimming in the Green Turtle, Chelonia mydas

Abstract

Miniature pulsed Doppler flow probes were implanted on the left pulmonary artery and left aorta of juvenile green turtles (Chelonia mydas) to measure the cardiovascular changes associated with intermittent ventilation at rest and its conversion to a continuous pattern during swimming at 0.4 m·s⁻¹. In resting turtles, respiratory frequency, tidal volume, and oxygen uptake were also measured and convection requirements and the oxygen-content difference across the lungs calculated. Respiration-related increases in heart rate and blood flow were most pronounced in resting turtles in which bursts of breaths, rather than single breaths, occurred in ventilatoryperiods. Hypoxia (10% O₂) produced continuous ventilation in resting turtles, and pulmonary blood flow was maintained at a high, steady level Increases in heart rate and both left pulmonary and left aortic blood flow were associated with the sevenfold increase in ventilation frequency observed during swimming. Most of the increase in left pulmonary flow during swimming could be attributed to an increase in cardiac output. However, left pulmonary flow increased more than left aortic flow, which suggests that pulmonary vascular resistance may have decreased during exercise.