STORAGE OF CAROTENOIDS AND OF VITAMINS A 495 



silkworm {Bonihyx mori) requires one gene to produce carotenoid pigmenta- 

 tion in the blood and serigenous gland from alimentary sources, and a 

 second gene to secrete silk containing the yellow (carotenoid) factor. 



The intestinal permeability for carotenes and for xanthophylls, and that 

 of the serigenous gland, differ in the various species.^^" The lemon strain 

 presents more permeability than do other races.^^** Carotene alone occurs 

 in the eggs of Melanoplus bivittatus,^^'^'^^^ Locusta migratoria migratorio- 

 ff/es,^™ Schislocerca gregaria,^^^ and also in the larvae of Lepidoptera in 

 general/^^ A sex difference is noted in Bomhyx mori, in that the hemo- 

 lymph of the male adults and larvae is colorless, and that of the females is 

 bright yellow. The pigment (carotene) in the hemolymph is transmitted 

 to the eggs, and acts as a protective coloring.^ ^^ 



b. In Vertebrates. Vitamin A appears to be present in all vertebrates. 

 In some cases, particularly in the case of freshwater fishes, the usual form 

 of the vitamin (vitamin Ai) may be in part or entirely replaced by vitamin 

 A2. Although /3-carotene and other carotenoids are sometimes stored in 

 the vertebrates, their presence is nowhere near as universal as is the case 

 with the lower forms. In contradistinction to the invertebrates, in which 

 almost all of the vitamin A stores may be localized in the eyes, the verte- 

 brates usually concentrate practically all of the vitamin A in the liver; 

 however, this vitamin is also present in the retina, as well as in other organs 

 such as the kidney and the lungs. ^^ In some cases, as, for example, the 

 chicken, considerable amounts of vitamin A may be concentrated in the 

 body fat, especially when the intake of the vitamin has been high. On the 

 other hand, the body fat of many animals (pig, goat, rat) contains no 

 detectable amounts of carotene or vitamin A. 



(a) Carotenoids and Vitamins A in Fishes. Although the carotenoid con- 

 tent of most fishes is overshadowed by their tremendous capacity to store 

 vitamin A, the carotenoids are of considerable importance in many species, 

 especially in those with conspicuous skin colors. Astaxanthin and similar 

 pigments account for the color in the numerous red fishes; it is believed 

 that this carotenoid is derived from the invertebrates which the fishes con- 

 sume. According to Goodwin,^^^ the xanthophylls in fishes are restricted 

 to lutein and a taraxanthin-like carotenoid, in addition to astaxanthin. 



Astaxanthin is found in the muscle of the North American salmon 



5'° C. Manunta, Atti soc. nat. e mat. Modena, 66, 104-113 (1936). 

 511 K. Geyer, Z. wiss. Zool, 105, 349-499 (1913). 

 "2 T. W. Goodwin, Biochem. J., 47, liv (1950). 



