480 



THE BIOLOGY OF MARINE ANIMALS 



pigment is a mixture of unstable chromoproteins, of which the prosthetic 

 groups behave like bile pigments (mesobiliviolin and mesobilierythrin). 

 The secretion of aplysiopurpurin is regarded as a means of defence, the 

 colouring material streaming through the water and forming a cloud be- 

 hind which the animal makes its escape (6, 7, 23, 51, 63, 78, 80). 



A few fishes with green and blue skin owe these colours solely to pig- 

 ments. The blue colours of wrasse (Labrus, Crenilabrus) are produced by 

 carotiproteins ; Fox ascribes the green colour of Odax to a porphyrin 

 pigment. Finally, the peculiar green colour of the bones of certain teleosts 

 (Belone belone and Zoarces viviparus) may be mentioned. The colour is 

 produced by bile pigments deposited in the skeleton (la, 17, 82). 



Quinones. Naphthoquinone pigments are characteristic of echinoids. 

 The first to be discovered was echinochrome, a purple pigment occurring 

 in elaeocytes in the perivisceral fluid of the urchins Paracentrotus lividus, 

 Echinus esculentus and Arbacia pustulosa. This pigment is widespread in 

 the body, occurring in the gut, ovaries, integument, shell and spines. In 

 addition, the shell and spines contain a deep red pigment, spinochrome, 

 closely allied to echinochrome. Recent work shows that these pigments 

 exist in several forms, in different species and in different parts of the same 

 animal. 



The variation in colour found within a species of echinoid often depends 

 upon the amounts of differently coloured spinochrome homologues 

 present. Thus, the colour range of test and spines in Paracentrotus lividus 

 is due to mixtures of spinochromes A and B in different proportions, the 

 violet variety containing relatively more of A, the olive-green variety 

 relatively more of B (Table 11.2). Moreover, the violet and olive-green 



TABLE 11.2 



Amounts of Spinochromes A and B in Spines and Tests of 

 Echinus esculentus and Paracentrotus lividus 



(From Goodwin and Srisukh (37).) 



colours encountered in the spines are due to the formation of salts between 

 the pigments and calcium in the skeleton, the normal colours of the pig- 

 ments being reddish. These substances differ from naphthoquinones of 

 vegetal origin, and they are probably synthesized by the sea urchin (17, 37, 

 48, 50, 58). 



