Abstract
Many insects show strong behavioral responses to short wavelength light. Drosophila melanogaster exhibit Cryptochrome- and Hyperkinetic-dependent blue and ultraviolet (UV) light avoidance responses that vary by time-of-day, suggesting that these key sensory behaviors are circadian regulated. Here we show mutant flies lacking core clock genes exhibit defects in both time-of-day responses and valence of UV light avoidance/attraction behavior. Non-genetic environmental disruption of the circadian clock by constant UV light exposure leads to complete loss of rhythmic UV light avoidance/attraction behavior. Flies with ablated or electrically silenced circadian lateral ventral neurons have attenuated avoidance response to UV light. We conclude that circadian clock proteins and the circadian lateral ventral neurons regulate both the timing and the valence of UV light avoidance/attraction. These results provide mechanistic support for Pittendrigh's "escape from light" hypothesis regarding the co-evolution of phototransduction and circadian systems.
Highlights
The ability to anticipate and adapt to daily environmental changes is critical for survival
We set out to test whether Drosophila long-term behavioral UV light responses are circadian regulated based on an earlier observation that wild-type Drosophila exhibit a peak of UV light avoidance behavior at midday under conditions of constant UV light intensity
To test the hypothesis that adult UV light avoidance behavior is circadian regulated, we measured this behavior in mutant flies lacking core circadian genes
Summary
The ability to anticipate and adapt to daily environmental changes is critical for survival. Rhythmic short wavelength light avoidance is crucial for avoiding heat, low humidity, and peak ultraviolet (UV) radiation at midday and minimizes a range of hazards from desiccation at organism level to DNA damage at molecular level. This is important for ectotherms like Drosophila that maintain their body temperature by behavioral adaptation [1]. Peak of UV avoidance in midday coincides with siesta rest in adult flies and flies show preference sleeping in dark environment over light environment during sleep [2]. The peak of midday avoidance coincides with peak UV light intensity in natural environments
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