304 



Comparative Animal Physiology 



TABLE 54. CHARACTERISTICS OF BLOODS CONTAINING HEMOCYANIN. 

 AND COPPER CONTENT OF SEA-WATER 



Copper content in mg./lOO cc. of blood (data from Dhere, quoted by Elvehjem"), per cent 



copper in purified hemocyanin (data from Hernler and Philippi, quoted by 



RedfieWO, and oxygen capacity (data from Redfield'" et al.). 



Sipunculus hemerythrin is pH 5.85. One molecule of oxygen combines with 

 three atoms of iron in hemerythrin. "- 



Hemocyanin. Hemocyanin is a protein with a prosthetic group containing 

 sulfur and copper; the prosthetic group is probably in part a polypeptide.'^^ 

 Table 54 gives the copper content of several hemocyanin bloods and of purified 

 hemocyanin. The copper content of molluscan hemocyanins is higher than 

 that of crustacean hemocyanins.'-'- ''^^ In general the copper content of the 

 blood, and hence its hemocyanin content in such active animals as Octopus, 

 Sepia, and Loligo, is much higher than that of the more sluggish forms (Table 

 54). Higher hemocyanin content is correlated with higher oxygen capacity. 

 The concentration of copper by hemocyanin-containing animals is remarkable, 

 since ocean water contains only 10 milligrams per cubic meter."" 



One molecule of oxygen combines with a quantity of hemocyanin contain- 

 ing 2 atoms of copper. The copper is normally cuprous, but it can be oxidized 

 by permanganate, and, unlike methemoglobin, methemocyanin can still be 

 oxygenated. Ferricyanid,e cannot be used to drive off Oo from hemocyanin, as 

 is done with hemoglobin. ^^ The affinity for CO is one-twentieth as great as 

 the affinity for 02.''^ The rate of dissociation of oxyhemocyanin, compared 

 with the rate of dissociation of oxyhemoglobin, is similar in Maja and slower 

 in Limnlus (Table 51)."'' 



Heipocyanin does not show sharp absorption bands like those of hemo- 



