174 THE BIOLOGY OF MARINE ANIMALS 



various bloods are shown in Table 4.9 (4, 5, 54, 58, 59, 61, 68, 69, 94, 124, 

 138, 141a, 148). 



Chlorocruorin. This is a greenish respiratory pigment related to haemo- 

 globin. It is confined to certain families of polychaetes — namely Chlor- 

 haemidae, Ampharetidae, Sabellidae and Serpulidae — in which it is 

 dissolved in the plasma, and it may coexist with haemoglobin in the same 

 species. In marine invertebrates the porphyrin-containing blood pigments, 

 haemoglobin and chlorocruorin, are restricted to relatively inactive 

 sedentary species, the majority of which live in tubes, burrows or crevices. 

 Their occurrence in such animals is often related to conditions of tem- 

 porary or permanent oxygen deficiency. 



The prosthetic group of the chlorocruorins is also a haem, but contains a 

 different porphyrin from haemoglobin. The affinity of chlorocruorin for 

 oxygen is on the basis of 1 molecule 2 per atom of Fe (27, 58, 125). 



Haemocyanin. This is a copper-containing pigment which appears light 

 blue in the oxygenated condition. It is found in the blood of some gastro- 

 pods, in cephalopods and in higher crustaceans, and is the most important 

 respiratory pigment of invertebrates, yielding to haemoglobin in vertebrates. 

 Some gastropods containing haemocyanin have myoglobin as well, e.g. 

 Busy con. 



The haemocyanins are copper-protein compounds in which the copper 

 is contained in a prosthetic group showing polypeptide characteristics. 

 The oxygen-combining capacity of haemocyanin is dependent upon its 

 copper content, 1 molecule of oxygen combining in proportion to 2 

 atoms of copper. The haemocyanin and copper contents of the blood of 

 various animals are given in Table 4.10. Haemocyanins differ in their 

 copper content, those of molluscs generally containing more copper than 

 arthropod haemocyanins. Copper in the haemolymph is predominantly 

 located in haemocyanin, and hence is indicative of haemocyanin content. 

 It has been pointed out that the high copper content of animals containing 

 haemocyanin demonstrates remarkable ability to concentrate this element. 

 The copper content of some haemolymphs may be as much as 3 x 10 5 

 times greater than that of sea water (1-10 jug Cu per 1.) (16, 130). 



Haemerythrin. Another iron-containing respiratory pigment found in 

 invertebrates is haemerythrin, which differs from haemoglobin in the 

 absence of a metallo-porphyrin group. It occurs in the polychaete Magelona, 

 in sipunculoids and priapuloids, and in the brachiopod Lingula. Haemery- 

 thrin is always enclosed in corpuscles, and appears pink when oxygenated. 

 It combines with oxygen in the ratio 3 Fe 2 ; the coloured prosthetic 

 group is not a porphyrin (34, 48, 93). 



Additional Pigments. Several other pigments of doubtful function 

 have been recognized among invertebrates. These include vanadium 

 chromogens found in blood and body fluids of ascidians; reddish naphtho- 

 quinones (echinochromes and related substances), found in tissues and 

 coelomic cells of echinoids (Chapter 11); and pinnaglobin, a manganese- 

 containing pigment found in the haemolymph of the lamellibranch Pinna. 



