Eye Pigment Relationships in Three Species Groups of Drosophila

Abstract

The system of pigment cells in the com-pound eyes of Drosophila melanogaster has been described by Nolte (1950), Gersh (1952) and Clayton (1952). In these cells the pigment granules are laid down and they carry deposits of two pigment components, a red and a brown. These pigments can be extracted differentially (Ephrussi and Herold, 1944; Nolte, 1952); the red pigment is extracted in an acidified ethyl alcohol (AEA) and the brown pigment in acidified methyl alcohol (AMA). Quantitative estimations of the two pigments have been made by means of spectrophotometric analysis of the two extracts, and a comparison has been made between the wild type and a large number of mutant strains (Nolte, 1952-1955). In a later study (Nolte, 1958b) the degree of dominance of wild type alleles of various mutant eye-color genes was investigated, and quantitative data were included for two South African strains of D. melanogaster; these were found to differ greatly from the data for the Canton-S strain which had mainly been used as a basis for the quantitative comparison of mutant strains of this species. This fact led to a consideration of the status of this quantitative characteristic in the various species and strains of Drosophila in South Africa. Since it then appeared that these pigment measurements might be useful characters for the analysis of natural populations, and could possibly be of interest in the tracing of phylogenies, the investigation was extended to include foreign species and strains. Since it is possible that the melanogaster and willistoni species groups are directly derived from the obscura group (Sturtevant, 1940), the investigation was extended to include species and mutant strains of these three groups of the subgenus Sophophora.