Circadian rhythmicity in Bulla gouldiana: Role of the eyes in controlling locomotor behavior

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Abstract
The eyes of Bulla express a circadian rhythm in optic nerve impulse frequency. Bulla also exhibit a circadian rhythm in locomotor behavior. In order to determine what role the ocular oscillators play in controlling rhythmic behavior, the eyes were removed and locomotor activity was recorded during free runs and while entrained to light‐dark cycles. We find that eye removal leads to a disorganization of the free‐running locomotor rhythm, suggesting that the ocular oscillators are involved in timing this behavior. Eyeless Bulla in the presence of light cycles exhibit locomotor rhythmicity but there is a switch from predominantly nocturnal to diurnal activity. While diurnal behavior in eyeless Bulla reveals the presence of extraocular photoreceptors, we presently find no evidence that a circadian pacemaker mediates this diurnal activity.