The circadian timing system in the brain of the fifth larval instar ofRhodnius prolixus(hemiptera)

The brain of larval Rhodnius prolixus exhibits a complex neuroarchitecture for its circadian timing system.

• Neurohormones are released with a circadian rhythm, suggesting the presence of a clock system in the larval brain.
• Larvae display a circadian locomotor rhythm, indicating synchronized activities with the clock system.
• Eight lateral clock neurons (LNs) in the proximal optic lobe contain the pigment-dispersing factor (PDF) and have specific axonal projections.
• LNs project to the accessory medulla and spread to the compound eye and anterior protocerebrum, forming extensive arborizations.
• A second group of clock cells, dorsal neurons (DNs), do not contain PDF and receive input from the LNs, integrating clock signals across the brain.
• The timing network's structure in larval insects is more intricate than previously reported and resembles that of adult insects.

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