Air-breathing behaviour of the African anabantoid fish Ctenopoma muriei

Frequency of aerial respiration in Ctenopoma muriei increased as dissolved oxygen (DO) decreased; breathing behaviour was spatially synchronous, and there was no difference in air-breathing frequency between populations from a high- and low-DO site. Although C. muriei survived without access to the surface, its loss of buoyancy and equilibrium under these conditions suggested that it is a functionally obligatory air breather. # 2005 The Fisheries Society of the British Isles Key words: Anabantidae; bimodal breather; synchronous air breathing; tropical freshwater fish. All air-breathing fishes are bimodal, and thus use a combination of aerial and aquatic respiration. This is partially because air-breathing fishes continue to rely on their gills for gas exchange, nitrogen excretion and ionic regulation (Claiborne, 1998; Gilmour, 1998; Karnaky, 1998). There is a large range, how-ever, in the use of aquatic respiration among air-breathing fishes. Fishes that regularly use aerial respiration over a range of dissolved oxygen (DO) levels are considered continuous air breathers (Graham, 1997). Continuous air breathers can be either obligatory or non-obligatory. Obligatory continuous air breather