CAROTENOIDS 



and those of Strain.^" The former claim that epoxides are not trans- 

 ferred to the yolk, whilst, as just stated, Strain found that violaxanthin 

 (a 5 : 6 - diepoxide) was not transferred but that flavoxanthin (a 5 : 8- 

 monoepoxide) was. Although it has not been directly proved, hens can 

 apparently accumulate astaxanthin, for those feeding on crab and lobster 

 shells produce very dark-red yolks, which are not acceptable in the 

 market. ^ ^ With regard to the yolk pigments of other birds, lutein 

 (xanthophyll) is the main pigment in the case of the canary (Serinus 

 canaria canaria) but it is absent from the eggs of black-headed gull 

 (Larus ridibundus) and the stork (Ciconia ciconia), its place being taken 

 by astaxanthin. 1**'^^ S. canaria does not store in its eggs dietary 

 lycopene, carotene, or violaxanthin. ^ * 



Skin, Fat, Liver, Eyes, etc. 



Palmer's pioneer work in the early 1920's proved that, in hens, 

 dietary xanthophylls but not carotenes occur in the blood plasma, fat, 

 and skin, especially of the shanks and claws. ^ ^ The main pigment is 

 lutein (xanthophyll) ^ ^ which, in these cases is esterified ; ^ ' recent 

 work has confirmed this. ^ ^' ^ * Flamingo fat contains a pigment very 

 similar to astaxanthin ; it has been named phoenicotterin but from 

 the data provided it is premature to consider it different from astaxan- 

 thin. ^^ Xanthophylls are stored in the liver of hens and turkeys,^' 

 and in the skin, fat, face and bills of 1 5 species of wild birds '^ ' [see 

 Table 47). Brockmann and Volker ^ ^ found astaxanthin in the red 

 wattles of pheasants but apart from the retina (see next section) Wald 

 and Zussmann ^ ^ could find no astaxanthin in any organ of the hen. 

 Lonnberg ^ ® found xanthophylls in the eyes of 27 species of wild birds 

 and Hollander and Owen^^ noted them in the irides of numerous 

 species of domestic hen but not in pigeons ; in fact, the iridial caro- 

 tenoids are so labile that alteration of diet can alter the eye colour of 

 hens. 3 



The carotenoids of the hen's retina have been examined in some 

 detail ; it was in 1877 that Capranica^^ described three types of oil 

 droplets in hens' retinas ; these were characterized by different 

 lipochromes, one greenish, one yellow, and one red, named chloro- 

 phane, xanthophane and rodophane respectively. In 1937-38 Wald 

 and Zussmann ^ ° fully investigated these globules and found that the 

 pigments present were carotenoids ; the greenish component is similar 

 to the bacterial carotenoid sarcinene {see p. 1 19), the yellow componentis 

 a mixture of lutein (xanthophyll) and zeaxanthin in the same ratio as 

 they occur in the egg, and the red component is astaxanthin. It should 

 be noted that von Studintz and his colleagues''' consider that the 



260 



