RESPIRATION 109 



CO: O 2 is in the ratio 16:1 for E. foetida and 80:1 for P. veluttnus 

 with respect to cyanide sensitive systems. 



Estimates of the cytochrome oxidase activity in tissue homo- 

 genates reveals that E. foetida contains more than Peloscolex. 

 Homogenates from E. foetida have an oxygen consumption the 

 equivalent of 13-5 times the rate of the intact animal per g. Minced 

 tissues from Peloscolex respire only 2-5 times as fast as the normal 

 whole animal. The ratio of C0:02 that causes 50% reduction in 

 respiratory rates is now only 9-2: 1 for Eisenia and 21 : 6 for Pelo- 

 scolex. The inhibition of cytochrome oxidase by carbon monoxide 

 is almost completely suppressed by illumination of preparations 

 with blue light, unless haemoglobin is present in the homogenates 

 oi Peloscolex (^tX.xviCQ.1, 1955). 



Intermediate Metabolism 



The metabolic cycles and mechanisms of vertebrate tissues are 

 by now known. The series of reactions that go to make up the 

 tricarboxylic acid cycle, anaerobic glycolysis, the enzymes in- 

 volved and the end products are well known. This is not the case 

 with invertebrate animals in general and the oligochaetes in 

 particular. Very little experimental evidence is available and 

 although the indications are that basically the system is as for 

 vertebrates this must be subject to revision as further work 

 progresses. 



Anaerobic Metabolism and Glycolysis 



It is reasonably certain that special mechanisms have evolved in 

 the oligochaete metabolism. For example Tiibifex, living in mud, is 

 able to survive in the complete absence of oxygen for up to 60 

 hours. When air again becomes available the animal respires at a 

 greater rate than normal (Alsterberg, 1922). This must mean that 

 food substances are metabolized, possibly by glycolysis, metabolic 

 products accumulate, and these are oxidized when oxygen again 

 becomes available. Although it may be assumed that lactic acid is 

 formed and oxidized, there is as yet no direct evidence, and no one 

 has shown what tissue levels are reached in prolonged anaerobiosis. 

 It is known that glycogen disappears four times as rapidly in 

 anaerobic conditions as in the presence of oxygen, and is re- 

 synthesized when oxygen becomes available again, but no evidence 



