| Summary: | 碩士 === 國立臺灣大學 === 昆蟲學研究所 === 88 === The expression of locomotor circadian rhythm in male German cockroach is controlled by the pacemakers which are located in the optic lobes of brain. These pacemakers can be entrained by light to synchronize with environmental cycles or displayed free-running in the constant condition. Some researches findings suggest that the pacemaker in the optic lobe may regulate the visual sensitivity. The compound eyes can receive light signals and convey the information to the pacemakers. The electroretinogram (ERG) has been proven to be a particularly useful as an easily recorded measurement of visual sensitivity. From the ERG recording, the amplitude of light-evoked responses have been shown circadian rhythmicity in male adults. This rhythmicity was coincided with the locomotor circadian rhythm. The peak of response was appeared in the subjective night, and the cycle of response was less than 24 h under DD condition. However, female German cockroaches don't express locomotor circadian rhythm. The female's locomotor circadian rhythm was masked by the development of ovaries. This masking effect was not shown in the female's ERG response. This finding implies that the development of ovaries can mask the locomotor rhythm, but not mask the circadian rhythm of visual sensitivity. By optic nerve severance, the ERG still showed circadian rhythm in amplitude under DD condition. The result suggests pacemaker of visual sensitivity that independent of the locomotor pacemaker is located in retina. The masking factor dose not interact on the locomotor pacemaker but on the output pathway.
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