A SPECIFIC AREA OF THE COMPOUND EYE IN THE CRICKET GRYLLUS-BIMACULATUS SENDS PHOTIC INFORMATION TO THE CIRCADIAN PACEMAKER IN THE CONTRALATERAL OPTIC LOBE

The circadian locomotor rhythm of the cricket Gryllus bimaculatus is p rimarily regulated by a pair of interacting optic lobe circadian pacem aker systems. The interaction involves phase-dependent modulation of t he free-running period and phase-dependent suppression of activity. Si nce photic information has been shown to be involved in the interactio n, we examined the regional difference in photoreception for the inter action within cricket compound eyes. The activity rhythm of animals re ceiving partial reduction of one compound eye combined with severance of the contralateral optic nerve split into entrained and free-running components under a 13-h light to 13-h dark cycle. All the animals ope rated on showed a phase-dependent suppression of activity, and most an imals showed a phase-dependent modulation of the period of the free-ru nning component. However, removal of the dorsocaudal area of the compo und eye resulted in a severe reduction of the amplitude of the phase-d ependent-period modulation. These results suggest that the dorsocaudal portion of the compound eye is a specific region receiving photic sig nals that are transmitted to the circadian pacemaker in the contralate ral optic lobe and that the phase-dependent suppression of activity is caused by a mechanism separate from that for the period modulation.