由行為與Timeless基因來探討水蛭的生理時鐘

Abstract

大部分的生物都存在有生理時鐘，但是不同種類的生物生理時鐘週期會有明顯的差異。本文的實驗動物是水蛭(Helobdella robusta)欲用來探討生理時鐘的行為模式與基因表現。水蛭是一種冠輪動物(Lophotrochozoans)，屬於三類主要兩側對稱動物的一支。本研究著重在水蛭的外部行為觀察與內部生理時鐘相關基因Timeless homolog表現的探討。在外部行為觀察方面，發現水蛭在夜晚的活動比在白天的活動來的頻繁，所以推定水蛭有生理時鐘的存在。在內部基因表現方面，我發現水蛭的Timeless homolog基因表現量隨著時間改變，晚上的表現量較白天要高。至於這些基因之間彼此是如何來調控生理時鐘的變化則還不清楚，詳細機制探討需要未來更多的研究和數據來驗證。

Most of life forms have circadian clocks, but the details with respect to the mechanisms and the extents of influence vary between species. In this study, I studied the circadian rhythm in the behavior and gene expression of the leeches, Helobdella robusta. The leeches belong to Lophotrochozoa, one of the three major groups of bilaterally symmetric animals. This study focuses on behavioral observation first and also documents the temporal expression profile of a ‘circadian clock’ gene – Timeless homolog – in leech. In the behavior observation section, I found that the leeches are more active and having more walking distance during the night than during the day. In the summary, I found that the leeches have the circadian clock in the body. In the gene expression study, I found that the expression level of Timeless homolog is more during the night than during the day. However, the roles of Timeless homolog and other candidate genes in regulation of circadian behavior of the leeches are still unknown. More researches are needed for understanding the molecular and neural mechanism underlying the circadian behavior rhythm in the leech.