Roles of PER immunoreactive neurons in circadian rhythms and photoperiodism in the blow fly, Protophormia terraenovae

Surgical ablation of specific brain areas in blow flies resulted in 55% of the flies exhibiting arrhythmic or obscure activity patterns under constant darkness.

• Five types of neurons associated with the circadian clock were identified in blow flies, including specific dorsal and ventral lateral neurons.
• Four large and four small ventral lateral neurons were found to express both pigment-dispersing factor (PDF) and period (PER).
• The percentage of flies showing rhythmic activity patterns decreased as the number of small PDF-expressing neurons decreased.
• Flies with ablated small PDF-expressing neurons failed to respond to changes in photoperiod, with diapause incidences of 48% under long-day and 55% under short-day conditions.
• These findings indicate that specific circadian clock neurons may play a role in both circadian rhythms and photoperiodic responses.

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