Selection for Negative Phototactic Behavior in Y Mazes

Abstract

Phototaxis is a complex behavioral response to a light stimulus which results in locomotion or lack of locomotion with respect to the direction of the stimulus. For different species of Drosophila a polygenic inheritance of this behavioral trait has been demonstrated (for a review of the literature until 1976 see Grossfield, 1978). Nevertheless, the phototactic behavior of flies is clearly a function of the experimental design used. Rockwell and Seiger (1973) distinguished between three basic types that have been used to study photo-taxis in Drosophila. One measures the distribution of flies in a tube after a fixed interval of time or the rate of movement toward a directive light source (open-field apparatus). The second one determines the distribution of flies in an open arena partitioned by different light intensities and illuminated perpendicularly from above. In the last basic design flies arriving at the terminal tubes of a maze are counted according to the number of their light and dark choices at one or a certain number of consecutive T- or Y-shaped choice points (T or Y maze, Hirsch-Hadler maze). It is highly uncertain whether phototactic behavior tested or selected in one kind of these apparatus can be realized in this special design only or whether it can be reproduced in another one. The precise target of maze selection is not clearly known (Grossfield, 1978).

Supported by DFG grant Ko 701/2. Present addresses: ¹Institut für Humangenetik, ²Biometrie und Populationsgenetik, Justus-Liebig-Universität Giessen, Federal Republik of Germany.