Development of Eye Colors in Drosophila: Fat Bodies and Malpighian Tubes as Sources of Diffusible Substances

Abstract

From the work of Ephrussi and Beadle (see Ephrussi and Beadle [1] and Beadle and Ephrussi [2] for summaries) it is known that three diffusible substances are involved in the production of wild type eye color in Drosophila melanogaster. This paper is concerned with the normal sources of two of these, v+ and cn+ substances. Under certain conditions of genetic constitution these two substances may be produced by eye tissue itself [1,2]. Sturtevant's studies of mosaics of D. simulans indicated that v+ substance must have another normal source in the fly [3]; and it has been supposed, but not proved, that this was likewise true of cn+ substance. Tests for the production of v+ and cn+ substances by a given organ can be made conveniently by transplanting the organ in question into gentically vermilion (v) and cinnabar (cn) flies, respectively. Such tests can be made in the late larval stages as shown by positive results from certain eye transplants made at this time [1,2]. In practice, tests for these substances are more sensitive if test animals carrying an eye color "dilution" gene are used. The double recessive apricot vermilion (wa v) and apricot cinnabar (wa; cn) have been used extensively. In many of the tests reported here, vermilion brown (v; bw) and cinnabar brown (cn bw) are used. All of these double recessive eye colors are very light; there is only, at the most, a tinge of color. A positive test is indicated by a modification in the direction of apricot or brown; the maximum change is represented by phenotypes as dark as apricot or brown. In preliminary tests, effects are roughly graded as strong, medium, weak or none: "Strong" represents a complete or nearly complete change. In certain experiments an attempt was made to use a system of numerical grades.

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