斜紋夜盜蛾之日週律動表現

Abstract

日週律動在代謝，生理，以及行為上皆扮演了一個重要的角色。它使得昆蟲能夠利用外在的訊息調控內在的律動，以預期環境在一天內可能的變化，並使其內在的時鐘得以和環境的律動同步化，進而產生適時適地的活動。生殖在昆蟲的一生中是一項很重要的事件，而日周律動也在生殖中扮演了重要的角色，因為正確的時間和地點對於非群居的物種是很重要的。因此對於蛾類來說，費洛蒙的釋放與接收以及其他生殖的生理機制可假設亦受到日周律動的影響。在本研究中，先針對費洛蒙的吸引、交尾行為做出觀測與分析。利用Y型管嗅覺測試器，測試雄蟲對於定量性費洛蒙於16L：8D小時光照週期與全暗的環境在不同時間點的反應，結果指出雄蟲對性費洛蒙的反應是具有內在調控的律動行為；亦以16L：8D的光照週期以及全暗的環境中，進行交尾實驗，結果證實此行為亦受到內在時鐘調控。為了瞭解此律動的調控是否以觸角為中心，因此實驗以時鐘基因per為測試標的，透過定量聚合酶鏈鎖反應(Real-time PCR)的生物技術，了解per 基因在不同時間上的表現是否呈現律動性，且與行為上的表現一致，結果不論在觸角或是頭部的per基因表現量，皆呈現律動，但以頭部的表現與交尾行為以及對於費洛蒙反應的行為較為一致，因此可推測，斜紋夜蛾在生殖的相關行為上是受到位於頭部的中央神經系統控制，而非周圍階層，如觸角的控制。

Circadian clock plays an important role in metabolism, physiological process, and behavior in insects. It mediates insect to anticipate the daily changes of environmental conditions. Insects use external cues to entrain the clock, and then adjust its activities phase to accord with conditions. Reproduction is the most important event in insect life. Circadian rhythm is expressed in reproductive behavior. Since the timing is very important in solitary species, the release of sex pheromone, the response to sex pheromone, and any other physiological mechanisms of mating are hypothetically synchronizing under the control of circadian clock. In my study, I focus on the expression of circadian rhythm in attraction response of sex pheromone, and mating behavior in tobacco cutworm, Spodoptera litura. The mating observation was carried out under LD cycles and constant darkness to demonstrate its circadian control. The Y-tube olfactometer was used to monitor the daily fluctuation of attractiveness of sex pheromone. Furthermore, the expression of clock gene, period (per) mRNA was detected by real-time PCR to monitor the fluctuation pattern. Since the sex pheromone attraction and copulation occurred at night and subjective night, the mating behavior was demonstrated under the control of its circadian clock. The expression of per in antennae and head also show daily fluctuation, the time that presents the highest expression of per in head is more accord with the behavior level of circadian rhythm. These results hint that the mating behavior may control by head where the central nerve system is. It is not control by the peripheral level.