60 



LEECHES 



152 mm, 35% at 76 mm and 40% at 38 mm (Fig. 31). When 

 similar experiments were carried out with the leech Erpohdella 

 testacea it was found that after carbon monoxide treatment the 

 oxygen consumption fell by 45% in air-saturated water and by 

 25% in J air-saturated water (Mann, 1958). This suggests 



50 



50 100 



O2 tension, mmHg 



50 



1 2 3 4 5 6 



O2 concentration, ml/L 



Fig. 31. The percentage of oxygen carried by the haemoglobin 

 of an earthworm and a leech at various oxygen tensions. From 

 data in Johnson, 1942 and Mann, 1958. 



that in Erpohdella as in LumbricuSj the haemoglobin functions in 

 oxygen transport at all normal oxygen concentrations of the 

 environment. Haemoglobin appears to play no essential part in 

 acclimatization to low oxygen concentrations, as it does in the 

 Cladocera for instance, for E. testacea was able to acclimatize even 

 after the haemoglobin had been inactivated (Fig. 32). Many 

 leeches have a considerable ability to withstand anaerobic condi- 

 tions. Numerous examples are quoted by von Brand (1946). 

 Hirudo medicinalis, Haemopis sanguisuga, Helohdella stagnalis and 

 Erpohdella octoculata survived for about 5 days at room temperature 

 while Glossiphonia complanata was able to survive for 16 days at 

 14-16°C without oxygen. Putter showed that Hirudo survived 

 only 3-5 days if it had been recently fed but over 10 days 

 when starving. This may well have been because the oxygen 



