Respiratory minute volume

Ecology

Biology

Ventilation (architecture)

Animal science

Treadmill

Tidal volume

Respiration

Heart rate

Anesthesia

Iguana

Thermodynamics

Physics

Blood pressure

Respiratory exchange ratio

Anatomy

Internal medicine

Respiratory system

Medicine

Chemistry

Journal of Experimental Biology

ABSTRACT The extent to which lizards ventilate their lungs during locomotion is controversial. Direct measurements of airflow across the nostrils suggest a progressive reduction in tidal volume and minute ventilation with increased running speed, while other studies have demonstrated that arterial remains constant during exercise. To resolve these conflicting findings, we measured minute ventilation and gas exchange rate in five specimens of Varanus exanthematicus and five specimens of Iguana iguana during treadmill locomotion at speeds between 0.14 and 1.11 m s−1 at 35 °C. These speeds are much lower than maximal running speeds, but are greater than the maximal aerobic speed. In both species, the ventilatory pattern during locomotion was highly irregular, indicating an interference between locomotion and lung ventilation. In Varanus exanthematicus, treadmill locomotion elicited a six- to eightfold increase in minute ventilation from a pre-exercise level of 102 ml kg−1 min−1, whereas the rate of oxygen uptake increased approximately threefold (from 3.9 to 12.6 ml kg−1 min−1). After exercise, both minute ventilation and gas exchange rate decreased immediately. Because minute ventilation increased more than did oxygen consumption, an increase in lung during exercise is predicted and, thus, Varanus exanthematicus appears effectively to ventilate its lungs to match the increased metabolic rate during locomotion at moderate speed. In Iguana iguana, both minute ventilation and gas exchange rate increased above resting values during locomotion at 0.28 m s−1, but both decreased with further increases in locomotor speed. Furthermore, following exercise, both minute ventilation and oxygen uptake rate increased significantly. Iguana iguana, therefore, appears to be unable to match the increased oxygen demand with adequate ventilation at moderate and higher speeds.

Ventilation and Gas Exchange in Lizards During Treadmill Exercise