德國蜚蠊觸角電位圖譜之日週律動表現

Abstract

昆蟲體內的生物時鐘提供時間訊息讓個體能有效面對每日外在環境的變化。在傳統實驗方法上，要能明確獲得生物時鐘的相位變化需要至少10天以上的活動資料，或者是採用族群試驗的平均資料。而後經由資料的計算分析，我們才能分辨昆蟲體內時間訊息的變化模式。為了能夠縮短實驗所需的時間，或者在緊急狀況時能快速知道個體所處的時間相位，一個能快速與精確測定的應用方法是需要的。德國蜚蠊(Blattella germanica)雄性成蟲在活動行為上表現出日週律動；然而雌性成蟲的活動行為日週律動被與卵巢發育的相關機制所掩蓋，但是在其他的生理機制上，生物時鐘似乎表現出明顯的日週律動。觸角電位圖譜(electroantennogram, EAG)可成為一種有效、能快速監測時間相位，並且較其他方法更不會傷害受測體的測量方法。在德國蜚蠊的觸角電位圖譜記錄中，雄成蟲的EAG振幅大小表現出日週律動的現象，EAG振幅大小的規律性和活動行為的規律性相同。在持續黑暗的環境條件下，EAG的最大振幅出現在相對夜晚，週期長度(circadian period)小於24小時。同樣的，在16L:8D的試驗環境下，EAG的最大振幅也出現在夜晚。然而德國蜚蠊雌成蟲的EAG反應並沒有表現出日週律動，推測可能也受到卵巢發育的影響。德國蜚蠊對乙酸乙酯的濃度感度實驗中，EAG振幅的變化量並沒有隨著乙酸乙酯濃度增加而增加。利用EAG快速鑑定時間相位的實驗中，德國蜚蠊成蟲在相對白天與相對夜晚的EAG振幅大小比較量不顯著而無法表現出明顯的差異，推測其原因可能是由於不同的時間相位裡，EAG振幅也會有高低變化，而無法絕對判定在相對夜晚的EAG振幅大小一定高於在相對白天時的EAG振幅。因此，利用EAG快速鑑定時間相位的方法仍然需要進一步的探討。

Endogenous circadian clock is the timing device that insects use to anticipate the daily environmental changes. The traditional way to understand the phase changes of the circadian clock is to obtain long continuous data (at least 10 days worth of observation on locomotion) or a population data (such as timing of adult emergence). The circadian phase, then, can be known by calculating the data after the experiments. To shorten the long experimental time or an urgent need to know the phase, a rapid method to reveal the phase for the exact individual is an ideal way for the application of the knowledge of circadian clock. Adult males of the German cockroaches (Blattella germanica) express circadian rhythm in locomotion. Although adult females’ locomotor circadian rhythms are masked by the developing ovary, their circadian clocks are running and can be expressed in other overt rhythms. Since electroantennogram (EAG) is a quick, sensitive and a relatively non-intrusive method to monitor the phase of the circadian clock, the purpose in this study is to establish a basic reliable circadian pattern of EAG that corresponds to the overt rhythm of locomotion. Adult male German cockroaches have circadian rhythm of neuron activity in olfactory response by measuring EAG. By using ethyl acetate as the stimulus, the amplitude of EAG response fluctuates under constant darkness or light-dark cycle. The peak of response was at the subjective night. However, the EAG responses of adult females are arrhythmic. Dilution-responded curves of EAG indicate that waveforms of EAG response are similar when stimulated by different concentrations of ethyl acetate. The result indicates that adult males expressed EAG circadian rhythm and the masking effects on female’s locomotion may hinder the measurement of EAG response.