RESPIRATION 



261 



sible for the fish to assume a pattern similar to that of the ground 

 on which it lies, but it is probable that the degree of expansion of the 

 chromatophores is adjusted to suit the amount of light reflected from 

 the ground; by increasing or decreasing the areas of dark skin, effects 

 approximately appropriate to various backgrounds are produced. 



Fig. 156. Special respiratory apparatus, A, in climbing perch (Anabas); b, Indian 

 catfish (Saccobranchus); c, African catfish (Clarias). (From Norman.) 



11. Aerial respiration and the air-bladder 



Many fishes are able to live outside the water. The excursions on to 

 the land vary from the wriggling of the eel through damp grass to the 

 life of the Indian climbing perch {Anabas) spent almost entirely on 

 land. In the eel there is no special apparatus for breathing air (though 

 oxygen may be taken in through the skin). The climbing perch is pro- 

 vided with special air chambers above the gills (Fig. 156) and even 

 when in water it comes to the surface to gulp air and will 'drown' if 

 prevented from doing so, even though it is placed in well-oxygenated 

 water. 



Many other fishes gulp air, especially those living in shallow tropical 

 waters, which readily become deoxygenated. There may be other 

 special mechanisms for gaseous interchange. In the Indian catfish 



