載卵壓力和聚集效應對於大頭金蠅產卵行為的影響

Egg load and gregarious effects on Chrysomya megacephala (Diptera: Calliphoridae) oviposition

郭允(Yun Guo)

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(2018年)

https://doi.org/10.6342/NTU201801772

摘要

法醫昆蟲學上常利用屍體上出現的麗蠅幼蟲來推估人類或者動物的死後間隔時間 (post-mortem interval, PMI)。產卵行為會直接影響了幼蟲接下來的競爭、捕食、生長等，進而影響到死後間隔時間的推算。而在植食性和寄生性的昆蟲當中，個體需要去平衡壽命上的限制和卵的時效，讓整個的生殖行為能夠有最大化的效益。牠們通常會調整產卵行為和策略來因應本身數目有限的卵。在高載卵壓力 (egg load) 的情況之下，可能會促使雌蟲增加搜尋的頻率，來尋找更多的寄主或者產卵基質，或者讓牠們接受較低品質的寄主。而在麗蠅中，他們需要特定的物質像是屍體來產下後代，所以載卵壓力可能會影響麗蠅的產卵行為。然而在進行實驗設計之前，另一項的有關因子聚集效應 (gregarious effect) 也要納入考慮。聚集效應是麗蠅的產卵行為可以藉由其他同類的存在而被觸發。本研究以大頭金蠅 (Chrysomya megacephala (Fabricius)) 為材料，主要在探討載卵壓力和聚集效應對於大頭金蠅的產卵行為的影響，實驗分成四個部分。首先從解剖得知正常麗蠅的攜卵量，再針對不同共域雌蟲的數量測試是否聚集效應會影響平均產卵量，之後給予連續產卵刺激以進行生殖週期測試。之後在去除聚集效應的影響下，將單隻交配過的雌蟲給予連續性的產卵刺激，記錄日齡、產卵量，目的是以日齡作為載卵壓力的量化指標，隨著時間的增加，載卵壓力隨著增大，來測試雌蟲行為反應。而在生理攜卵量部分，得到平均每隻雌蟲的攜卵量為 263.4 ± 36.4 個。共域族群數量的測試結果為平均產卵量會隨著數量增加而提高，在數量到達 5隻以上則沒有顯著差異。另外在連續產卵刺激的生殖週期測試，其結果存在著三個週期，第一個週期平均單隻雌蟲產出 278.9 ± 48.1 個；第二個週期平均單隻雌蟲產出 258.9 ± 36.7 顆；第三個週期平均單隻雌蟲產出 92.7 ± 53.0 顆，產卵間隔平均 9.82 ± 1.03天。單隻雌蟲產卵測試的結果則是一半以上的組別，會在持續的刺激下超過20天以上才有產卵行為，後續進行檢查體內剩餘的攜卵量的結果顯示，不論是否出現產卵行為的單隻雌蟲，留在體內的殘存卵量占了絕大部分。總結來說，共域雌蟲的數量會影響產卵表現，而單隻雌蟲的結果有可能為載卵壓力的影響不及聚集效應來的顯著，導致未產出的卵佔大多數。

關鍵字

大頭金蠅 ； 生殖週期 ； 載卵壓力 ； 法醫昆蟲學 ； 產卵行為

並列摘要

In forensic entomology, the age of necrophagous blow fly maggots that appear on corpse are used to estimate the post-mortem interval (PMI). The oviposition behavior will directly influence competition, predation, growth, etc., which affect PMI calculation. Insect parasitoids and herbivores need to balance the risk of egg and time limitation in order to maximize reproductive success. They adjust their oviposition behavior in response to their limited eggs. High egg load pressure will trigger female to search more intensively, and therefore make them encounter more hosts or medium; or accept oviposition hosts of lower preference. In blow flies (Diptera: Calliphoridae), they need to find specific materials such as corpse to produce offspring, so the egg load will affect their oviposition behavior. However, another factor must to be taken into consideration, the gregarious effects. Gregarious effects, which means the blow fly oviposition can also be triggered by other companion individuals. In this study, we used Chrysomya megacephala (Fabricius) to measure egg load and gregarious effects. This study was divided into four stages. The first stage was the dissecting of female flies to obtain the egg amount, the second stage involved determing if female population size will affect the average oviposition quantity, then third gave the flies continuous oviposition stimulus to find the reproductive cycle. On the last stage, after seaparating females into single units, continunous oviposition stimulus was also applied to measure the behavior of single females. Fly age and oviposition quantity were recorded to quantify egg load. Results obtained by dissection indicated the average egg amount in a single female was 263.4 ± 36.4. Results from second stage revealed that as the amount of female increases, the average numbers of eggs laid also increased, but there was no significant difference when the female number increases past five. Continuous oviposition stimulus revealed three individual reproductive cycles. The first cycle produced 278.9 ± 48.1 eggs, the second cycle produced 258.9 ± 36.7 eggs, and the third cycle produced 92.7 ± 53.0 eggs, with a gap of 9.82 ± 1.03 days in between. In the final stage of the experiment, up to more than half of the groups would oviposit after 20 days of stimulus. After the experiement was over, dissection of the flies from this stage revealed that the amount of eggs laid is significantly lower than the residual eggs in the ovary. The conclusion from these results indicates number of female in a population affects oviposition behavior, and single female behavior is more heavily affected by gregarious effect than egg load, causing lower oviposition.

並列關鍵字

Chrysomya megacephala ； reproductive cycle ； egg load ； forensic entomology ； oviposition behavior

參考文獻

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