The Red Eye Pigment Content of the Drosophila affinis Subgroup Species

Abstract

The red eye pigments of Drosophila algonquin, D. azteca, D. melanogaster, D. narragansett, D. pseudoobscura, and D. tolteca were analyzed. The determinations confirm the close relationship of the D. obscura group species as compared to D. melanogaster. D. azteca and D. tolteca appear to be very closely related; whereas, D. pseudoobscura was shown to possess an appreciably lower amount of red eye pigment than the D. affinis subgroup species. A definite correlation was found to exist between the size of the eye and the red pigment contained therein, but the relationship varied from species to species. Instances of significantly great variability between strains of single species were found in D. affinis and D. melanogaster. The fact that the color of the eye of wild-type Drosophila is due to two pigments, red and brown, resulting from two different biosynthetic pathways has been established by several experimental techniques. The identification of the sequence involved in red pigment formation has been particularly difficult to elucidate and only in recent years has the mystery begun to be unveiled. A number of pteridines which are ostensive precursors of red pigment have been identified (Hadorn and Mitchell, 1951; Forrest and Mitchell, 1954, 1955; Forrest, Hatfield, and Van Baalen, 1959). Visconti, Hadorn, and Karrer (1957) isolated three red pigments from the eye of Drosophila melanogaster by paper chromatography. These pigments, apparently closely related to their pteridine precursors, have been named drosopterin, isodrosopterin, and neodrosopterin, and they may be extracted simultaneously and measured quantitatively. Members of the D. affinis subgroup are widely distributed geographically (Miller, 1958) and are very similar and closely related as evidenced by the mating experiments of Ensign (1960), Miller (1950a, 1950b), and Ensign and Miller (1957). Sulerud (1958) has indicated that the sex combs and tarsi of these species may be promising criteria for identification purposes and that overlapping of characteristics does occur although it is limited. The purpose of this study is to determine whether the red pigment content of the D. affinis subgroup might be used as an aid in establishing the relationships of the individual members which are considered. 1 This paper is taken from a master's thesis presented to the University of Nebraska and is contribution number 333 of the Zoology Department of the University of Nebraska.