Color Vision in Drosophila

Author: Harris, William Anthony

Year: 1976

Degree: Dissertation (Ph.D.)

Advisor: Benzer, Seymour

Committee Member: Unknown, Unknown

Option: Neurobiology; English

DOI: 10.7907/cbww-8k03

Abstract

In Chapter I an historical introduction to the study of invertebrate color vision is given, with emphasis on insects, especially Drosophila.

In Chapter II three mutations which eliminate specific types of photoreceptors in Drosophila are described. Of the 8 photoreceptors in each facet, two mutations delete the outer 6 (R1-6). The third eliminates R7, one of the two central photoreceptors. Double mutants were constructed in which only photoreceptor RB is present. The spectral sensitivities, photopigments, and behavioral properties of these mutants were investigated. R1-6 have two sensitivity peaks, near 350 and 470 nm. These receptors contain a rhodopsin with these absorption peaks. It interconverts with a metarhodopsin that absorbs around 570 nm. R7 is a UV-receptor, containing rhodopsin that absorbs around 370 nm and interconverts with a metarhodopsin which absorbs around 470 nm. R8 is a non-adapting blue-receptor with a third type of rhodopsin. The properties of these photopigments account for the different sensitivities and spectral adaptation phenomena of the various photoreceptors. All the photoreceptors have input into phototaxis. Spectral analysis of this behavior provides evidence for integration of the input from the different receptors.

In Chapter III experiments are described showing learning and color vision in Drosophila. Populations of Drosophila were trained by alternately exposing them to two odorants, one coupled with electric shock. On testing, the flies avoided the shock associated odor. Pseudoconditioning, excitatory states, odor preference, sensitization, habituation, and subjective bias have been eliminated as explanations. The selective avoidance can be extinguished by retraining. All flies in the population have equal probability of expressing this behavior. Memory persists for 24 hr. Another paradigm has been developed in which flies learn to discriminate between light sources of different color.

In Chapter IV the results of these experiments are discussed, relating them to previous work and future directions.

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