RESPIRATION 



183 



in the tissues and, owing to the relative constancy of sea water, can but 

 rarely hinder loading in nature. Elasmobranch haemoglobin is less affected 

 by C0 2 than that of teleosts, but there is still a distinct acid effect within 

 physiological ranges of C0 2 tension, namely 1-2 mm Hg. 



Haemoglobins of sharks possess higher oxygen affinities than in rays. 

 In the skate Raja 66% of the oxygen is utilized or removed from the arter- 

 ial blood in passing through the tissues (74, 103, 105, 132, 135, 136, 153). 



Fig. 4.18. Bohr Effect on Haemoglobins of Various Marine Animals 



Ordinates, log p 50 (O a pressure in mm Hg at which Hb is half saturated). Curves: 

 1: mackerel blood {Scomber scombrus), 25 C C; 2: lamprey Petromyzon marinus, 20 C C; 

 3: porpoise Phocaena phocaena, 38°C; 4: echiuroid Urechis caupo, 19 C C; 5: lugworm 

 Arenicola marina, 20°C; 6: skate Raja ocellata, 10-4°C (from various sources). 



Haemoglobin in Invertebrates. Although restricted in occurrence, the 

 haemoglobins of marine invertebrates are of much theoretical interest and 

 are deserving of detailed study. They are probably as variously adapted 

 as those of vertebrates to their diverse functional roles, and further re- 

 search on their physiology will be aided by correlated studies on oxygen 

 consumption and ventilation of the species in question. 



Haemoglobin possesses strong affinity for carbon monoxide, which 

 blocks it as an oxygen carrier. In Nereis diversicolor, treatment with CO 



