Life at High Latitudes Does Not Require Circadian Behavioral Rhythmicity under Constant Darkness

High-latitude C. costata becomes arrhythmic under constant darkness, while low-latitude species remain rhythmic.

• Nearly all organisms have internal clocks to anticipate environmental changes, with circadian rhythms typically around 24 hours.
• High-latitude species, including some Drosophila, exhibit significant arrhythmic behavior under constant conditions.
• Subarctic Drosophila can extend their evening activity until dusk during long daylight periods.
• Clock network neurochemistry appears crucial for adaptations seen in high-latitude species.
• Analysis of Chymomyza species shows that those from low and high latitudes possess different clock mechanisms, affecting their rhythmicity.

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