The expression of locomotor circadian rhythm in male German cockroach is controlled by the pacemakers which is located in the optic lobes of brain. This pacemaker can be entrained by light through visual pathway to synchronize with environmental cycles. The compound eyes can receive light signals and convey the information to the pacemaker. In the electroretinography (ERG) recording, the amplitude of light-evoked responses has shown circadian rhythmicity. This rhythmitity is coincided with the locomotor circadian rhythm. Female German cockroaches don’t express locomotor, although their daily locomotor patterns were coincided with their ovarian development cycles. The female’s locomotor circadian rhythm was masked by the development of ovaries. This masking effect was also shown in the female’s ERG. This finding implys that the development of ovaries can mask the expression of circadian rhythm in the input pathway. An in situ hybridization of the clock gene, per, was employed to identify the pacemakers of locomotion and visual sensitivity.

Index terms: Blattella germmanica, ERG, circadian rhythm

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