RESPIRATION 



TABLE 4.12 



Haemoglobin Concentration of the Blood of Marine Fishes 



(Selected values. Expressed in terms of iron per unit volume) 



181 



to the left of those of homoiotherms. The oxygen affinities of some in- 

 vertebrate haemoglobins are very high. 



Effect of C0 2 and Temperature on Dissociation Curve. The oxygen 

 affinities of haemoglobins are affected, sometimes greatly, by temperature, 

 CO 2 and pH. An appreciation of the normal functional role of haemo- 

 globin in a species is best obtained from the dissociation curve determined 

 under conditions of temperature and C0 2 tensions actually existing in the 

 animal and at its respiratory surfaces. 



In mammalian blood the addition of C0 2 reduces the affinity for oxygen, 

 and shifts the dissociation curve to the right — the Bohr effect. At low C0 2 

 tensions, such as encountered in normal sea water, loading tension (t t ) is 

 lower than in the tissues, where C0 2 tensions are high. The Bohr effect 

 therefore raises loading tension and facilitates unloading at sites where 

 2 is required. The same results are achieved by varying the pH. The 

 Bohr effect is quite pronounced in certain bloods (Figs. 4.17, 4.18). 

 Haemoglobins of marine teleosts are very sensitive to changes in C0 2 

 tension and pH. Among invertebrates the 2 affinities of Arenicola and 

 Thalassema haemoglobins are increased by C0 2 ; the blood of Urechis is 

 not affected by variance of C0 2 or pH over wide physiological ranges. 



A rise in temperature also shifts the haemoglobin dissociation curve to 

 the right, reducing affinity for 2 . In poikilotherms (fish, marine inverte- 



