Pteridines and Gene Homologies in the Eye Color Mutants of DROSOPHILA HYDEI and DROSOPHILA MELANOGASTER.

LUORESCENT pteridine compounds have been identified in Drosophila by HADORN and MITCHELL ( 195 1 ) , and FORREST and MITCHELL (1 954a,b, 1955). Variation in the accumulation of the various pteridines from species to species in the genus Drosophila has been discussed by RASMUSSEN and SCOSSIROLLI (1954), RASMUSSEN (1954, 1955), HUBBY and THROCKMORTON ( 1960), and THROCKMORTON ( 1962). HUBBY and THROCKMORTON ( 1960) and THROCKMORTON (1962) have made an extensive survey of pteridine patterns among various Drosophila species. They have demonstrated that the use of these patterns as taxonomic characteristics is justified, and that such biochemical characters can be very helpful both in taxonomic and evolutionary studies. Paper chromatographic and eleclrophoretic techniques have demonstrated the presence of pteridines in various specific organs including heads, bodies, testes, malpighian tubules, and in larval stages of numerous species of the genus. These authors have shown that differences in pteridine patterns between species occur in various organs of the fly, but with regard to the eyes (heads) , they found that the same pteridines were present in the same relative amounts in the wild-type eyes of all species. On the other hand HADORN and MITCHELL (195 1 ) and HADORN ( 1958) have shown locus specific alterations in pteridine patterns of the eyes for several eye color mutants in both Drosophila and Ephestia (even though the metabolic relationships between the various pteridines themselves, and between the pteridines and the eye pigments, are not well understood). In most eye color mutants, the pteridine pattern is only altered in the eyes, and not in any of the other organs, even though there are some mutants such as rosy2 (HADORN 1958), and white, whiteh, brown, brownzb, maroon-like, and rosy in the present study, in which both the bodies (chiefly due to the testes) and the heads show altered patterns. In the case of rosy2, HADORN showed that some of the changes were in opposite directions in different organs. Thus, it would appear that the pattern of a given genotype can be modified within the organs of an individual according to organ specific properties. At any rate, pteridines clearly seem to play a role in eye pigmentation and the pigmentation of other organs, but pteridine accumulation and excretion in larval stages indicate that some of them at least function in other capacities as well (HADORN and MITCHELL 1951).