Relationship of Gill Ventilation and Perfusion in Pacific Dogfish,Squalus suckleyi

Abstract

Unanesthetized specimens of Pacific dogfish, Squalus suckleyi, were used to study the relationships of oxygen uptake to ventilation and blood perfusion of the gills. Ventilation–perfusion ratios [Formula: see text] were determined over a wide range.In resting dogfish the [Formula: see text] ratios normally fell within the range of 10–20 at 6–10 C with a ventilation usually between 200 and 500 ml/min∙kg and a cardiac output between 20 and 40 ml/min∙kg. The extraction of oxygen from water varied from about 20 to 50% within that [Formula: see text] range, but at lower ratios the extraction was higher and sometimes exceeded 75%. When extraction was high the oxygen tension of expired water often fell below that of arterial blood thus indicating countercurrent gas exchange.The oxygen uptake varied almost directly with cardiac output over a wide range and with ventilation at low and normal water flows.Data are presented regarding the effectiveness of oxygen removal from water, oxygen uptake by blood, and overall transfer of oxygen from water to blood at various ventilations.In curarized dogfish the heart rate varied with changes of induced ventilation. The reflex nature of this cardiac and ventilatory coupling was revealed by its abolition when the fish were atropinized.