Contents 



Preface xi 



Acknowledgments xiii 



1. Introduction 1 



(a) The oxygen requirements of vertebrates 2 



(b) A comparison of air and water as respiratory 



media 4 



2. Aquatic Respiration of Fishes 8 



(a) Respiration in Cyclostomes 9 



(b) Bony fishes 13 



(i) Gill structure 13 



(ii) Counter-current principle 14 



(iii) The water flow across the gills 15 



(iv) Ventilation of the gills 16 



(v) Action of the skeletal and muscular 



systems during ventilation 19 



(c) Cartilaginous fishes 22 



(d) Ecological variations in the pattern of venti- 



lation 24 



3. Air-breathing in Fishes 29 



(a) Accessory respiratory organs 30 



(b) Lungs and the swimbladder of fishes 32 



(c) The swimbladder 33 



(i) Structure of the swimbladder 33 



(ii) Functions of the swimbladder 35 



(d) Respiration of lungfishes 39 



