Air breathing of the neotropical fishes Lepidosiren paradoxa, Hoplerythrinus unitaeniatus and Hoplosternum littorale during aquatic hypoxia.

The present study investigated the respiratory rates, frequency of air breathing and ability to extract oxygen from air compared to body mass of three neotropical air-breathing fishes (Lepidosiren paradoxa, Hoplerythrinus unitaeniatus and Hoplosternum littorale) with different accessory organs, under the same conditions of hypoxia (PO(2)<5 mm Hg) and temperature (25 degrees C), using the same apparatus. The results indicated a superior capacity of H. littorale (16.01 ml O(2) breath(-1) kg(-1)) compared to H. unitaeniatus (7.03 ml O(2) breath(-1) kg(-1)) and L. paradoxa (4.95 ml O(2) breath(-1) kg(-1)).