大頭金蠅與紅顏金蠅之產卵偏好研究

The Oviposition Preference of Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae)

楊世綵(Shih-Tsai Yang)

指導教授 ： 蕭旭峰

國立臺灣大學/生物資源暨農學院/昆蟲學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01657

摘要

法醫昆蟲學常利用於屍體上取食之麗蠅幼蟲日齡來判定人類或動物之死後間隔時間 (post-mortem interval; PMI)。由於麗蠅成蟲之產卵行為直接影響到幼蟲之競爭、捕食等種內及種間之交互作用，進而可能使得幼蟲之存活率及生長速率改變，造成 PMI 估算時的誤差。本研究針對台灣平地至低海拔地區最優勢之食腐性麗蠅種類：大頭金蠅 (Chrysomya megacephala (Fabricius)) 與紅顏金蠅 (Chrysomya rufifacies (Macquart)) 進行成蟲之產卵偏好實驗。將新鮮或者經過處理的豬肝當作產卵基質，使用二選擇實驗裝置測試麗蠅雌蟲對不同狀態基質之產卵選擇。實驗結果顯示，大頭金蠅雌蟲顯著不偏好產卵於具紅顏金蠅幼蟲之產卵基質，而對具有同種或瘦葉帶綠蠅 (Hemipyrellia ligurriens (Wiedemann)) 幼蟲之產卵基質則不具特別的選擇性差異。紅顏金蠅則顯著偏好產卵於具大頭金蠅幼蟲或同種幼蟲之產卵基質。推論由於紅顏金蠅幼蟲在二齡之後具有兼捕食性 (facultatively predaceous)，而大頭金蠅之幼蟲可以做為其替代性的食物來源，因此紅顏金蠅雌蟲偏好產卵於具有大頭金蠅幼蟲處；大頭金蠅雌蟲則可能為避免其子代被捕食而演化出迴避紅顏金蠅幼蟲之產卵行為。另外，相較於較大之產卵基質，大頭金蠅與紅顏金蠅皆不偏好產卵於過小之產卵基質，推測乃因太小的產卵基質無法提供足夠之養分予其子代發育成長。而不具幼蟲之產卵基質，在一定程度內之腐敗程度對麗蠅之產卵偏好無顯著影響，不論供以放置二或四日之產卵基質與新鮮產卵基質做選擇，大頭金蠅雌蟲並無顯著之產卵偏好性。另外，於全暗環境下，兩種麗蠅對不同大小之產卵基質皆仍具顯著之產卵偏好差異；但大頭金蠅對原本顯著不偏好之具紅顏金蠅幼蟲之基質，竟表現出與無幼蟲基質相比無差異之產卵行為；而紅顏金蠅對原本偏好的具有同種幼蟲之產卵基質亦呈無偏好情形。若將遭紅顏金蠅幼蟲取食四日後移除幼蟲之產卵基質、與新鮮產卵基質供給大頭金蠅雌蟲選擇時，大頭金蠅亦無顯著之產卵偏好。根據前人研究，麗蠅雌蟲可能憑藉視覺或嗅覺以尋找、選擇產卵基質，但視覺可能是偵測產卵基質上幼蟲存在與否的最重要因子。因此在黑暗環境或移除幼蟲之情況下，麗蠅將此基質視為無幼蟲之狀態，故而在選擇該產卵基質與無幼蟲之基質時，呈現無偏好的情形。本研究期望能夠進一步增加台灣當地食腐性麗蠅之行為生態資料，進而對法醫昆蟲學及 PMI 之更精確估算有所助益。

關鍵字

法醫昆蟲學 ； 大頭金蠅,紅顏金蠅 ； 死後間隔時間 ； 產卵偏好

並列摘要

In forensic entomology, the age of necrophagous blow fly maggots that feed on the carcass are often used to estimate the post-mortem interval (PMI). The oviposition behavior of adults may influence the inter- or intraspecific interactions between larvae, such as competition or predation, may change the growth and survial rate of larvae, and then cause the bias of PMI estimation. Chrysomya megacephala and Chrysomya rufifacies are two most dominant necrophagous blow fly species in Taiwan. To understand the oviposition preference of these two species, the dual-choice device was used to test the females of the two species to choose their oviposition site. Results showed that when pork liver with or without larvae of C. rufifacies were provided, C. megacephala significantly preferred to lay eggs on the livers without larvae. Yet C. megacephala showed no preference when provided pork livers with or without conspecific larvae, or the larvae of Hemipyrellia ligurriens. These results probably indicated the C. megacephala has tried to escape from the facultatively predaceous larvae of C. rufifacies. At the same time, C. rufifacies showed significant oviposition preference on the pork liver with the larvae of C. megacephala or their conspecific ones when compared to those pork livers of no larva. This result implied the conspecific larvae or the larvae of C. megacephala could be a potentially alternative food resource of C. rufifacies which made the female prefer to lay eggs around. When considering about the size of oviposition media, both species significantly disliked the pork livers of relatively small size. This may because the females need to find enough food sources to meet the growth of their larvae. According to our results, both blow flies species showed no preference between the pork livers of differently decayed stage. In addition, there is one thing that deserved to be mentioned: the oviposition preferences of both species to those media with larvae were greatly disturbed under the dark environment. And if we removed the larvae which previously fed on the pork liver and let the females to choose, no oviposition preference was observed. But both species still showed preference to the larger media in the dark. This probably suggests the blow flies could use vision to recognize the larvae on the oviposition media. By knowing the factors that may influence the oviposition preference of blow flies, we can gather more useful information to contribute to the forensic entomology especially to the more accurate PMI estimation.

並列關鍵字

forensic entomology ； Chrysomya megacephala ； Chrysomya rufifacies ； post-mortem interval ； oviposition preference

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