RESPIRATION 



95 



monoxide, which combines readily with haemoglobin depresses 

 respiration by about a third at tensions above 0-1% (Dausend, 

 1931 (Fig. 29). 



It seems then that T. tuhifex is well adapted to utilize the 

 normally low tension of oxygen available at mud surfaces and that 

 it can survive complete air saturation of the water providing the 

 animal has reached maturity. Respiration rates are constant over a 

 wide range of oxygen tensions, falling only when oxygen reaches 



0-7 



0-6 



0-5 



o 0-4 



Q. 



3 



1 2 3 4 5 6 7 



Oxygen concentration 



Fig. 29. Tubifex oxygen consumption, (a) normal animal, (b) animal 

 treated with carbon monoxide, (c) difference between (a) and (b) 

 representing fraction of oxygen carried by haemoglobin (from 

 Dausend, 1931). 



a very low level at which time the haemoglobin of the blood system 

 takes over a greater fraction of the gaseous exchange. 



Ejfect of Carbon Dioxide 



The respiration of animals is aifected not only by the availability 

 of oxygen but also by the presence of large quantities of carbon 

 dioxide in the atmosphere. Little information is available regarding 

 the respiration of earthworms in the presence of heightened 

 concentrations of carbon dioxide though it is generally believed 



