德國蜚蠊的日週期性溫度依變時鐘

Abstract

不只是光線，溫度也能夠同步德國蜚蠊 (Blattella germanica) 的日週期性時鐘。在經設計的行為實驗下，我們證實了在日週期性活動背後，存在特殊的溫度依變時鐘。溫度、光線時鐘分別受對應的環境時間訊息校正，不僅都能夠獨立觸發週期性的活動行為，還可以協同運作。若將德國蜚蠊雄蟲置於恆溫的條件下，一如其夜行性的特徵，都只能夠在暗期或相對暗期 (subjective night) 觀察到一個活動高峰。然而若在恆暗下施予週期性溫度變化 (30：20°C)，除了原來相對暗期 (對應：冷期) 的活動，還能夠在熱期 (對應：相對亮期) 發現新的高峰。溫度時鐘不僅能夠觸發兩個新的活動高峰 (在溫度轉換時)，還能與同時在自由律動中的光線時鐘在活動交會後重新協調。雖然兩個時鐘都有機會主導活動的走向，但考慮無光暗時間訊息的校正條件，光線時鐘顯然略勝一籌。本研究直接證明了日週期性系統實為分工合作的多個時鐘，而不僅僅是以元件應對溫度條件，為機制探討提供了迥異於當今研究的行為基礎。

Not only light, but also temperature can synchronize the circadian clock of German cockroach (Blattella germanica). By manipulating environmental conditions, we have proved a unique thermal clock underlying rhythmic locomotion behavior. Thermal and Photoperiodic clock may exert its own influence on the overt rhythm simultaneously, but can also couple forces for a proper phase. For male German cockroach, the locomotor circadian rhythm with only one peak of daily activity was found under constant temperature and LD or DD condition, which was restricted in scotophase or subjective night as a nocturnal animal does. However, a thermal cycle (30:20°C) under constant darkness, might switch the active phase from cold (subjective night) into warm (subjective day) phase, under which caused the presenting of multiple activity peaks. Two of the three peaks were triggered by the thermal clock at the transition of temperature, in the mean time, the photo clock kept a free-running rhythm, and would couple again with the thermal clock when activity peaks were getting closer. Although both clocks share the same opportunity in leading the activity pattern either in synchrony or free-running, the DD condition insinuate the power of photo clock. This finding provides direct evidence of a cooperative multiple-oscillator system for different zeitgebers, and also a novel behavioral basis from current studies on circadian mechanism.