494 IX. CAROTENOIDS AND VITAMINS A 



carotene and astaxanthin) and a blue component, which is a chromopro- 

 tein having mesobilinibin as the prosthetic group. In the gregarious pe- 

 riod of this insect's life, the insectoverdin disappears, while the astaxanthin 

 and /3-carotene are masked by either melanin or insectorubin.^"^ Good- 

 win^oT ^vas unable to demonstrate a variation in pigment metabolism as- 

 sociated with the breeding temperature. A certain degree of genetic con- 

 trol of carotenoids was reported in Locusta migratoria migratorioides.^^^ 



i". Resume of the Occurrence and Function of Carotenoids in Insecta. 

 /3-Carotene is the most widely distributed carotenoid pigment in insects, 

 while a-carotene is second in importance as far as occurrence is concerned. 

 Insects accumulate their carotenoids in three ways, namely (a) by indis- 

 criminate storage, (6) by preferential storage of one or two dietary ca- 

 rotenoids, or (c) by alteration of the absorbed dietary carotenoids before 

 storage. In the case of locusts, (b) and (c) occur simultaneously. In addi- 

 tion to jS-carotene, astaxanthin is an important carotenoid component in 

 the insects. 



Insofar as (c) is concerned, newly formed carotenoids usually arise by 

 oxidation of their precursors. This is the case with astaxanthin, which ap- 

 pears in the developing egg coincident with the disappearance of /3-carotene. 

 The fact that astaxanthin occurs in the integument but not in the hemo- 

 lymph, while |3-carotene is present only in the latter fluid, further supports 

 the concept that j8-carotene is the mother substance of astaxanthin. On 

 the other hand, oxidation is not the only transformation possible, since the 

 ladybird {Coccinella spp.) accumulates Ij^copene; the source of this hydro- 

 carbon, however, is uncertain. 



No clear-cut function has been assigned to the carotenoids as far as in- 

 sects are concerned. The presence of astaxanthin in the eyes of Schisto- 

 cera and Locusta suggests the possibility of its function in vision. In fact, 

 Wald^^^ is of the opinion that this is the chief reason for the occurrence of 

 astaxanthin in invertebrates in general. Another possible function of 

 carotenoids is in reproduction. The insect eggs usually contain j8-carotene, 

 which decreases as development proceeds. Thus, the carotenes and the 

 xanthophylls have been found in the eggs of the Chinese mulberry silk- 

 worm {Bomhyxmori)}^^ 



A generic factor must also be considered. A number of investigators, 

 including Manunta,^^^-^"^ Uda,^''^ and Gerould,^^- found that the Chinese 



50' T. W. Goodwin, Biochem. J., 49, 86-87 (1951). 



so* C. Maminta, Boll. soc. ital. biol. sper., 8, 1278-1284 (1933); 12, 31-32, 32-33, 33-34, 

 626-628(1927). 



503 H. Uda, Genetics, 4, 395-416 (1919). 



