AQUATIC RESPIRATION OF FISHES 



(a) 



17 



tube 



Water '^f > L^^Rubber_fc 



current 



ubing ^^ ■ 



Expiration Inspiration Inspiration Expirati 



(c) 



Buccal Opercular 

 cavity cavity 



Oral Gill Opercular 



valve resistance valve 



FT^ VTT^ 



(i) 



(ii) 



Suction 

 pump 



V^^^ -^ k { 



(iii) 



Pressure 

 pump 



V///////A 



f 



(iv) 



V///////M 



' % 



V////////A 



Fig. 4. 



Diagram of models to illustrate the mechanisms of ventilation in 

 fishes, (a) Lamprey when attached to its prey, inspiration being due 

 to the elastic recoil (spring) of the branchial skeleton, (b) Mechanism 

 in teleost fishes if a single pump, (c) The double pumping mechanism 

 which operates in bony and cartilaginous fishes. Water passes across 

 the gills in three phases. In phase 4 there may be some reversal in the 

 flow but this is a very brief part of the cycle, (c after Hughes, 1961.) 



close and the almost simultaneous contraction of both cavities 

 would force water out of the opercular openings. Flow of water 



