Twilight dominates over moonlight in adjusting Drosophila's activity pattern

Area of Science:

• Chronobiology
• Animal Behavior
• Sensory Neuroscience

Background:

• Light is the primary zeitgeber for Drosophila melanogaster circadian clock synchronization.
• Natural light conditions include twilight and moonlight, often simplified in laboratory settings.
• Previous studies show conflicting effects of simulated twilight and moonlight on fly activity.

Purpose of the Study:

• To investigate how Drosophila melanogaster integrates both twilight and moonlight cues.
• To determine the dominant light cue influencing circadian activity patterns.
• To identify the photoreceptor cells involved in mediating these responses.

Main Methods:

• Simulated natural light conditions (twilight and moonlight) were used to expose flies.
• Locomotor activity was monitored in wild-type and photoreceptor mutant flies.
• Specific photoreceptor mutants (including those for cells 7 and 8, and rhodopsin 6) were analyzed.

Main Results:

• Drosophila melanogaster integrates both twilight and moonlight cues.
• Twilight dominates over moonlight, anchoring activity peaks to dawn and dusk.
• Nocturnal activity is reduced in the presence of twilight.
• Photoreceptor cells 7 and 8 are crucial for wild-type activity peak phasing.
• Complex interactions among photoreceptor cells, particularly rhodopsin 6, regulate nocturnal activity.

Conclusions:

• Drosophila circadian clock is robust to integrated twilight and moonlight cues, with twilight being dominant.
• Compound eyes and specific photoreceptors (cells 7 and 8, rhodopsin 6) are essential for mediating activity responses to natural light.
• This study provides insights into the complex integration of light signals for circadian regulation in a model organism.