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  • 學位論文

視覺刺激對單隻雌性大頭金蠅產卵行為的影響

Effects of Visual Stimulation on the Oviposition Behavior of Single Female Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

指導教授 : 楊恩誠
共同指導教授 : 蕭旭峰(Shiuh-Feng Shiao)
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摘要


食腐性昆蟲幼蟲的發育狀況可以用來估算法醫昆蟲學中受害者或動物的死後間隔(post-mortem interval,PMI),研究麗蠅的產卵行為有助於提高估算PMI的準確性。某些昆蟲表現出多隻雌蟲在同一地點產卵的群聚產卵行為,藉此增加後代的生存優勢。一般情況下,只有單隻雌性麗蠅獨處時,雌蠅並不會產卵,如果提供單隻雌蠅視覺刺激,例如不同性別的同伴或不同物種,甚至其他非生物體後可誘發其產卵。推測麗蠅可能藉由視覺確認產卵的環境是否適合子代生存發育。為了釐清何種視覺因子為引發麗蠅產卵的必要條件,本研究以大頭金蠅 (Chrysomya megacephala (Fabricius)) 為材料,分別探討視覺刺激物的表面積、形狀、反射光譜及刺激物與背景的亮度對比。研究結果顯示,以2D平面的圖紙作為視覺刺激,確實能影響單隻雌性大頭金蠅的產卵行為,誘使原本不產卵的雌蠅產卵,且其卵數相當於正常情況下雌蠅產出的卵數。在改變圖紙形狀以及反射光譜的試驗結果中顯示,這兩個視覺因子並不是影響雌蠅產卵行為的主要因素。而改變圖紙的表面積能影響雌蠅的產卵行為,使用與實際蒼蠅大小差不多的圖紙做為標準,當圖紙表面積放大一倍以上時,雌蠅會選擇不產卵;若圖紙表面積縮小一倍或是與實際蒼蠅大小差不多時,雌蠅會有產卵行為且卵數為正常值。在改變圖紙亮度對比的試驗組中,當圖紙與豬肝的反射波長對比大於80% 時,單隻雌蠅會有產卵行為,反之則無。以此試驗結果進行推測,當環境中只有一隻雌性大頭金蠅時,若產卵基質上沒有任何刺激物,則雌蠅不會產卵;而當產卵基質上放置數個平面刺激物,其亮度對比大於80% 以及表面積與實際蒼蠅大小相似或較小時,單隻雌蠅會產卵。當產卵基質周遭沒有其他活體的情況下,推論雌蠅在選擇是否要產卵的依據,可能為產卵基質上有無卵、幼蟲或是同伴的屍體。

並列摘要


Developmental profile of necrophagous blow fly larvae is essential in helping to estimate the post-mortem interval (PMI) of victims or animals in forensic entomology. Oviposition behavior plays a vital role in the evolutionary adaptation for a species. Some insects show gregarious oviposition behavior, which means several females lay eggs at the same site or even in a cluster, thereby increasing the survival advantage of their offspring. Blow flies seem to exhibit this behavior, which implies blow flies rarely lay eggs when alone. Previous studies pointed out that after giving a single female fly visual stimuli, for example, companions of different genders or different species, or even other non-living objects can trigger oviposition. It is speculated that vision could be an essential cue for blow flies to recognize their oviposition sites. In this study, Chrysomya megacephala (Fabricius) is used as the material, and the surface area, shape, reflectance spectrum of the visual stimulus and the brightness contrast between the stimulus and the background will be discussed separately. The results of this experiment shows that using 2D pictures as visual stimuli can affect the oviposition behavior of a single female Chrysomya megacephala, make females that would not lay eggs lay eggs, and the number of eggs is also the number of eggs laid by females under normal circumstances. The experimental results of changing the shape and the reflection spectrum of the pictures show that these two visual factors are not the main factors affecting the oviposition behavior of female flies. However, changing the surface area of the pictures can affect the oviposition behavior of female flies. Use pictures that are about the size of the actual fly as a standard. When the surface area of the drawing is more than doubled, the female flies will choose not to lay eggs; if the surface area of the drawing is reduced by one time or it is about the same size as the actual fly, the female flies will have oviposition behavior and the number of eggs is normal. In the experimental group that changed the brightness contrast of the pictures, when the reflection wavelength contrast between the pictures and the pork liver was greater than 80%, a single female flies would have oviposition behavior, and vice versa. Based on the results of this experiment, if there is only one female Chrysomya megacephala in the surrounding environment, if there is no irritant on the oviposition substrate, the female fly will not lay eggs. When there are multiple 2D stimuli on the oviposition substrate, the brightness contrast is greater than 80% and the surface area is not too large, a single female fly will lay eggs. When there is no other living body around the oviposition substrate, it is inferred that the basis for the female fly to choose whether to lay eggs may be whether there are eggs, larvae or companion's dead body on the oviposition substrate.

參考文獻


Aggarwal A. 2005. Estimating the postmortem interval with the help of entomological evidence.
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Baldridge RS, Wallace SG, Kirkpatrick R. 2006. Investigation of nocturnal oviposition by necrophilous flies in central Texas. Journal of Forensic Sciences 51: 125-126.

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