The relation between tryptophan metabolism and phototaxis in the tan³ mutant of Drosophila melanogaster

Abstract

1) The relationship between phototaxis and tryptophan metabolism was investigated with a mutant “tan³” of D. melanogaster.
2) It has been found that “tan³” mutant flies, having little positive phototaxis, involve a little amounts of red and brown pigments in their eyes, as compared with those of wild type flies.
3) The amount of brown pigment in “tan³” mutant was increased by feeding the larvae with kynurenine or 3-hydroxykynurenine, and its positive phototaxis was simultaneously activated. These phenomena, however, have never been recognized by feeding the larvae with tryptophan. From these results, it was assumed that “tan³” might be a mutant having a very low metabolic activity between tryptophan and kynurenine.
4) The accumulation of cobalt was found in “tan³” eyes by feeding the larvae with kynurenine or 3-hydroxykynurenine, with an increase of brown pigment. This fact suggests that the cobalt-fuscanine named by Kikkawa and his coworkers may be produced in eye pigments and this metal containing pigment may take an important role in the activation of positive phototaxis.