CAROTENOIDS 



carotenoids were conserved. Once more a sexual differentiation was 

 noted, for the concentration of xanthophylls in all female tissues was 

 higher than in male tissues. In the case of epiphasic " non-carotene " 

 pigments the highest concentration was found in the male gonads, 

 although the female somatic tissue had a higher concentration than had 

 male somatic tissue. Scheer comments on his observations thus : 

 " the concentration of hypophasic pigments (xanthophylls) can be 

 considered to be a true secondary sex characteristic, while that of the 

 epiphasic pigment is apparently dependent only on the accumulation 

 of pigment in the testes, the composition being relatively uniform in 

 all other tissues." It is difficult to understand why a statistically signi- 

 ficant accumulation of epiphasic carotenoids in male gonads cannot 

 equally be considered of sexual significance. 



Scheer concluded his exhaustive survey by examining carotenoid 

 metabolism during spawning and his results again suggest the media- 

 tion of these pigments in reproduction. In the females the shed ova 

 contained carotenoids which were qualitatively and quantitatively the 

 same as in the female gonads ; however, the difference between the 

 carotenoid content of normal and spent females indicates a loss un- 

 accounted for by the shed ova. In the case of the males the sperma- 

 tozoa contained no carotenoids, but there was a suggestion of loss of 

 body carotenoids in fasted males after spawning ; the loss is in the 

 epiphasic and mytiloxanthin fractions and there was a small increase 

 in zeaxanthin almost exactly equal to the loss of mytiloxanthin. 



It will have been noted that a characteristic of molluscs is that 

 xanthophylls greatly predominate over carotenes. Although their 

 natural habits predispose to this condition, Scheer ^^ carried out an 

 experiment which indicated a definite predilection of M. californianus 

 for xanthophylls. He fed the mussels on Procentrotum mtcans, which has 

 a xanthophylls : carotenes ratio of 9 : 1 , and the resulting faeces con- 

 tained xanthophylls and carotenes in the ration of 6 : 1 ; thus, assuming 

 equal stability of the pigments in the intestinal tract, xanthophylls are 

 preferentially absorbed. 



CEPHALOPODA 



The most outstanding fact concerning carotenoids in this group is 

 their comparative absence. 



Lonnberg''^ examined three species, Sepiola scandica, Rossia 

 macrosoma, and Eledone cirrosa. Lutein (xanthophyll) was detected in 

 the eyes of all three species ; otherwise, apart from traces of (un- 

 specified) pigments in the mantle and testes, and large amounts in the 



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