Circadian rhythmicity in the oviposition of the grasshopper Chorthippus curtipennis

Abstract

The pattern of oviposition in the grasshopper, Chorthippus curtipennis, shows a rhythm which is entrained by light/dark cycles and free runs under unvarying conditions of illumination. The physiological rhythm could be inverted in time through an inversion of the light/dark regime by 180°. The process of inversion is rapid and displays one transient before the new phase of the rhythm is achieved. The rhythmicity in oviposition persists even after the ocelli and/or the compound eyes are ablated and coated over with opaque material. A similar persistence of the rhythm is observed in grasshoppers with the whole head capsule painted, indicating that light still reaches some part of the central nervous system through an extracephalic path. Since oviposition is a complex physiological process the integration of the light/dark information probably takes place at a higher oscillatory nerve centre which regulates the rhythm via the neuro-secretory system.