The partitioning of oxygen uptake from air and from water by the large obligate air-breathing teleost pirarucu (Arapaima gigas)

Pirarucu, weighing 2 to 3 kg, ventilated their gills 16to 24 times per minute and ventilated their lungs every 1to 2 min. Average oxygen uptake from water was 23 mg. h ' .kg-l; average oxygen uptake from air was 80 mgh-'.kg-'. That is, in normoxic water they obtain about 75% of their oxygen from air, and never less than 50% from air. In hypoxic water the fraction from air increases, ultimately to 100%in anoxic water.