Photoreception in entrainment of rhythms and photoperiodic regulation of diapause in a hemipteran, Graphosoma lineatum.

The role of compound eyes in photoperiodic regulation of diapause and entrainment of circadian rhythms was studied in a hemipteran, Graphosoma lineatum. Bilateral removal of compound eyes resulted in the loss of locomotor rhythmicity under both 24-h light cycle and constant darkness. The arrhythmicity was associated with the loss of photoperiodic regulation of diapause. Females with removed compound eyes had similar incidence of oviposition under diapause preventing long-day photoperiod (light:dark [LD] 18:6) and diapause inducing short-day photoperiod (LD 12:12). By contrast, both locomotor rhythmicity and photoperiodic regulation of diapause were maintained after unilateral removal of compound eyes. The results suggest that the compound eye-optic lobe axis is involved in the transmission of light signals for both entrainment of rhythms in locomotor activity and photoperiodism. The compound eyes probably act as photoreceptors in both transmission chains. Sites of the clocks for the two phenomena are discussed.