Light and Temperature Cycles as Zeitgebers of Zebrafish (Danio rerio) Circadian Activity Rhythms

Zebrafish showed a diurnal activity pattern of 87% at 20 degrees C compared to 77% at 26 degrees C under light-dark cycles.

• Zebrafish were most active during the light phase of the day.
• Total activity increased at the warmer temperature of 26 degrees C.
• When exposed to temperature cycles, zebrafish synchronized their activity to the light phase regardless of whether the phases were in sync or out of sync.
• Under constant dim light conditions, zebrafish predominantly synchronized to temperature cycles, although their activity was less pronounced.
• Four out of six zebrafish groups previously trained to temperature cycles exhibited free-running activity rhythms when placed under constant conditions.

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