26 



VERTEBRATE RESPIRATION 



(a) Wrasse 



3 ;a 



(b) Dragonet 



Fig. 8. 



(a) Differential pressures recorded from several teleost fishes to 

 show the importance of the suction pump (shaded) in bottom-living 

 forms. The numbering corresponds to the four phases of Fig. 4c. Note 

 the absence of any reversal in the plaice. (After Hughes, G. M., 

 /. exp. Biol. Vol. 37, 1960.) (b)The ejection of the respiratory current 

 dorsally from the opercular cavities is illustrated for the gurnard and 

 dragonet. 



the latter fish most of the respiratory current enters the spiracles, 

 whose valves are well developed, and as they operate rhythmic- 

 ally produce the characteristic 'winking' movements of these 

 fish. 



In fishes which only spend part of their time on the bottom, 

 intermediate stages are found in the relative development of the 

 pressure and suction pumps. In the bony fishes these forms also 

 show an intermediate condition in the development of the 

 branchiostegal rays which form an important part of the highly 

 developed suction pumps of benthic forms. 



