ANIMAL CAROTENOIDS 



pictus. At least 60 per cent, of the total carotenoids are carotenes, 

 mostly (i-carotene; a-carotene and echinenone were detected in L. pictus 

 and zeaxanthin in iS'. purpuratus. 



Table 2(). — Characteristic Echinoid Carotenoids 



Absorption spectra ynaxima {m\j..) 

 Pigment m.p. Carbon disulphide Light petroleum 



Echinenone ^'^ 178-179° 488-494 458-46U 



Pentaxanthin ^ 209-210^"^ 506, 474, 444 ' " — 



REFERENCES TO TABLE 28. 



1. Lederer, E. (1934), C. r. Soc. Biol., 117, 411 



2, Goodwin, T. W., and Taha, M. M. (1950), Biochem. J., 47, 244 



Formation and Function 



Only little is known about the formation of carotenoids but some 

 interesting correlations between the feeding habits of echinoderms 

 and their carotenoid make-up has been revealed by the work of Fox 

 and Scheer. ^ * The essentially herbivorous echinoids, crinoids and 

 holothuroids, contain on the average five times less carotenoids than do 

 the carnivores, the asteroids and the sphiaroids. The predominating 

 carotenoids of the carnivores are highly oxygenated whilst those of the 

 herbivores are predominantly hydrocarbon. The reasons for these 

 differences are not yet apparent. 



There is considerable correlation between sex and carotenoid dis- 

 tribution in the three echinoid species studied by Fox and Scheer. ^ * 

 Male Dendraster contain more carotenoids than do the females, the 

 increase being more marked in the xanthophyll fraction (3 times) 

 than in the carotene fraction (twice). The skin of both sexes contained 

 little and the intestines much pigment but the gonads show^ed marked 

 sexual differences. The concentration in the ovaries was three times 

 that in the testes, the pigments in both sexes being entirely carotenes. 

 In contrast the testicular tissue of S. purpuratus contained five times as 

 much pigment as did the ovarian tissue. This increased pigmentation 

 in the testes was due more to a preferential accumulation of carotenes 

 rather than of xanthophylls. There was also a sexual differentiation 

 in the intestines in this species ; the female gut contained three times 

 more xanthophylls and 4/3 more carotene than did the male gut. This 

 is the reverse of the situation in the gonads. 



The proportions of the total body carotenoids mobilized in the testes 

 and ovaries of Strongylocentrotus and Lytechinus are 17 and 25 per cent., 

 and 27 and 77 per cent, repectively. It is most interesting to find 

 that, in spite of the mobilization of carotenoids in testicular tissues, the 

 spermatozoa are colourless. 



165 



