AIR-BREATHING DURING ACTIVITY IN THE FISHES AMIA-CALVA AND LEPISOSTEUS-OCULATUS

Many osteichthyan fishes obtain oxygen from both air, using a lung, an d water, using gills. Although it is commonly thought that fishes air- breathe to survive hypoxic aquatic habitats, other reasons may be more important in many species, This study was undertaken to determine the significance of air-breathing in two fish species while exercising in oxygen-rich water. Oxygen consumption from air and water was measured during mild activity in bowfin (Amia calva) and spotted gar (Lepisost eus oculatus) by sealing a fish in an acrylic flume that contained an air-hole, At 19-23 degrees C, the rate of oxygen consumption from air in both species was modest at rest, During low-level exercise, more th an 50 % of the oxygen consumed by both species was from the air (53.0/-22.9 % L. oculatus; 66.4+/-8.3 % A, calva).