CAROTENOIDS 



occurring both as an ester and in the free state, and (iii), somewhat 

 surprisingly, a-carotene. The red carotenoid was the minor consti- 

 tuent but in the closely related scarlet C. cafer it was the major feather 

 constituent. The feathers of a suspected auratus cafer hybrid contained 

 an intermediate amount of the red substance. The difference between 

 the feather coloration of the two species, C. auratus and C. cafer^ is 

 thus merely quantitative. Kritzler ^ '» ^ ^ also found three carotenoids 

 (Rj, R2, and lutein (xanthophyll) ) in the display plumage of the African 

 bishop birds, Euplectes francisca?ius, E. orix, and E. nigroventis and the 

 head plumes of the woodpecker, Melanerpes erythrocephalus. The 

 three pigments in order of decreasing adsorption on alumina were 

 '* Ri," lutein (xanthophyll), and " Rg." M. erythrocephalus contains 

 more of Rj than do the bishop birds. Rj may be identical with canary- 

 xanthophyll. Volker^^-*^ reports the presence of unidentified caro- 

 tenoids in the yellow and red feathers of a number of parrot species, 

 but the yellow pigment of Melopsittacus undulatus is apparently not 

 a carotenoid. More recently, Volker*^ has reported the presence of 



Table 46. — Characteristic Avian Carotenoids 



Galloxanthin^ 



421, 400, 378 mix. (ethanol) 



422, 401, 380 mtx. (hexane) 

 427, 407, 387 m(z. (CHCI3) 

 446, 424 mfz. (CSg) 



None of these pigments has been isolated crystalline. 



REFERENCES TO TABLE 46. 



1. Brockmann, H. and V6lker, O. (1934), Hoppe-Seyl. Z.. 224, 193. 



2. Kritzler, H. (1943), Physiol. ZooL, 16, 241. 



3. Wald, G. (1943), y. gen. Physiol., 31, 377. 



262 



