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  • 學位論文

光週期對於大頭金蠅生殖行為的影響

Chronobiological effect on reproductive behavior of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

指導教授 : 蕭旭峰

摘要


在法醫昆蟲學中最廣泛使用的辦案方式是以麗蠅在屍體上發育時間長短來推估最短死後間隔時間 (minimum postmortem-interval, mPMI),因此麗蠅出現以及產卵在屍體上的時間相當重要。一般認為,麗蠅是屬於日行性的昆蟲所以夜間行動或是產卵被認為是不會發生。也因如此,在計算最短死後間隔時間時,以夜間為產卵及發育時間起點是直接被忽略不計的。此研究希望從時間生物學 (Chronobiology)的角度來探討是否麗蠅內在的日夜節律是否有可能是夜間產卵的發生原因之一。藉由測量移動次數和模式來當作行為的指標並觀察麗蠅的日週律,此研究希望找出內在日週律對麗蠅的產卵行為有多少影響。本實驗使用麗蠅科(Calliphoridae),金蠅屬 (Chrysomya) 的大頭金蠅 (C. megacephala (Fabricius)),台灣最普遍在法醫昆蟲上會使用的物種來進行實驗。目前結果指出,麗蠅成蟲在一般光暗(12L:12D)下屬於完全日行性,在完全光照環境(LL)下會失去活動規律,以及在完全黑暗環境(DD)是會顯現內在日週律調整活動及休息的時間。麗蠅成蟲一個日週的長度大約是 1341分鐘/天 (22.35小時/天),在不同性別及雌蟲懷卵與否並沒有顯著差異。在三種不同的光照環境下,大頭金蠅的活量有顯著差異。雌蟲的活動量通常高於雄蟲,但在全光照及一般光照情況下交尾後的雄雌蟲沒有統計的顯著差異。在四次的野外實驗中,沒有觀察到有任何麗蠅的夜間活動或產卵行為,但是在實驗室環境下,麗蠅雌蟲在有光的夜間時間以及沒光的白天時間卻有產卵行為。在麗蠅自運日夜節律的情況下,產卵行為在活動以及休息時間皆有發生,可是休息時間的產卵有可能是意外發生。這代表內在日週率是麗蠅之產卵行為發生的重要因子,然而當光照存在時,內在日週律對產卵行為的影響會下降。

並列摘要


The most widely used entomological method of determining time since death (minimum postmortem-interval, mPMI) for Forensic Science has been the usage of blow fly’s (Diptera: Calliphoridae) developmental time on the deceased body (more specifically time since eggs laid), but the exact moment of oviposition is often only estimated. Since blow flies are known to be diurnal, oviposition at night has been considered impossible and left out in standard mPMI calculations. However, in recent years’ studies, a few cases of nocturnal oviposition were discovered, and there is not yet a clear explanation for them. It is in this study’s interest to look at this using chronobiology as a factor. Known as the periodic cycles of living organisms and their affinity to adapt, chronobiology is a factor that can rule over an animal’s behaviors, conforming them to a pattern. By monitoring the locomotion patterns and using it as an index of behavior, whether chronobiology plays an important factor in nocturnal oviposition or not, can be determined. Our current result indicates that the mate-finding and oviposition site-finding locomotion of C. megacephala show a free-running circadian rhythm under DD conditions (continuous darkness), arrhythmicity under LL (continuous light), and entrained to LD (12L12D) to be diurnal. The free-running length is around 1341 mins/day (22.35 hrs/day) for all flies with no significant difference between different sex or gravidity. There is a significant difference of daily locomotion amount between the three light conditions with LD being the highest, then DD and LL the least. Female flies showed higher locomotion amount than males with the exception to mated flies under LL and LD conditions. The activity pattern shared by both and male and female showed a peak of activity occuring right before rest phase. Under the observation study, C. megacephala did not arrive, or oviposit at night in the field conditions of Taipei on all four trials, but was able to oviposit in the lab under dark condition during daytime or artificially lighted condition during nighttime. Finally, under free-running condition (continuous darkness), C. megacephala was able to oviposit during its active period (subjective day) and rest period (subjective night) although it is suspected that the oviposition during rest period is accidental. This shows circadian rhythm is one of the important factors that affects the oviposition behavior of C. megacephala but its effect is eclipsed under the effect of light.

參考文獻


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