台灣索鐵線蟲 (Chordodes formosanus n. sp.) 之描述、寄主調查及對其寄主台灣斧螳 (Hierodula formosana)形態之影響

Description of Chordodes formosanus n. sp. (Nematomorpha), its host survey and effects on the morphology of the host mantid, Hierodula formosana

邱名鍾(Ming-Chung Chiu)

指導教授 ： 吳文哲

國立臺灣大學/生物資源暨農學院/昆蟲學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.03178

摘要

鐵線蟲隸屬於線形動物門 (phylum Nematomorpha)，這類節肢動物的寄生蟲具有獨特的生活史及特殊的寄主影響。全世界約有 300 餘種鐵線蟲，但在此之前台灣未曾有描述。本文中根據雄蟲尾部特徵、六種表皮結構、體表腹部縱向色素帶及粒線體 DNA 序列的分析，將台灣最普遍的鐵線蟲，台灣索鐵線蟲 (Chordodes formosanus n. sp.) 視為一新種，並描述了同種間頭部及尾部的形態變異。該種鐵線蟲感染台灣斧螳 (Hierodula formosana) 及寬腹螳螂 (H. patellifera)，發育為成蟲後離開寄主在水中交配繁殖，幼蟲孵化後感染水棲生物，該水棲生物稱為保幼寄主 (paratenic host)。在台北市立動物園中已觀察到鐵線蟲幼蟲感染搖蚊幼蟲 (Chironomus sp.) 的現象，並在搖蚊幼蟲全身包括腸壁、軀幹、尾足、肛管，及腹管中發現感染。鐵線蟲進入水棲昆蟲後，普遍認為能在昆蟲羽化後跟著上岸。這個現象也藉由解剖及聚合酵素鏈索反應 (polymerase chain reaction, PCR) 的偵測而證實：在台北市立動物園中，寶島缺叉石蛾 (Chimarra formosana) 及一未知種類的搖蚊科 (Chironomidae) 成蟲已確定受鐵線蟲感染。在上岸後，受感染的保幼寄主被捕食的同時也將鐵線蟲帶到最終寄主 (definitive host) 體內，鐵線蟲在最終寄主體內發育至成熟。寄主受鐵線蟲感染後形態出現變化。在比較正常台灣斧螳及受感染個體後發現，受感染的個體翅長縮短、雄蟲觸角變短且鞭節感覺毛密度下降。其中感覺器官的變化是首次在受到鐵線蟲感染的寄主中被發現。而雄蟲觸角感覺毛密度的下降造成該形態特徵趨近若蟲形態，因此有可能是寄生蟲感染後造成幼年化 (Juvenilization) 的結果。另外，感覺毛密度下降的現象也在落水的寬腹螳螂雄蟲身上被發現。

關鍵字

寄生關係 ； 台灣索鐵線蟲 ； 台灣斧螳 ； 寬腹螳螂 ； 寄主形態變化

並列摘要

Horsehair worms (Nematomorpha) are arthropod parasites. They are famous for their unique life cycles and host manipulations. About 300 extant species have been identified, but none in Taiwan been recorded. Based on the morphology of male’s tail, six types of areoles, vertical pigment line, and mitochondrial COI partial sequence, I described a new common horsehair worm species in Taiwan, Chordodes formosanus n. sp. and their morphological polymorphisms on the heads and tails. Chordodes formosanus parasitized with mantids Hierodula formosana and H. patellifera. When matured adult worms left their hosts, then mated and laid eggs in water. The hatched larvae infected paratenic hosts such as aquatic animals. The infection was detected in larval midges Chironomus sp. from Taipei Zoo. The horsehair worms were found in the host’s gut wall, trunk, posterior parapod, anal tubes, and ventral tubules. Logically, the horsehair worms land with aquatic insects’ imagoes. This was confirmed by the detection of infection in adult caddisflies (Chimarra formosana) and one unknown midge (Chironomidae) by using polymerase chain reaction (PCR). The horsehair worms invaded and developed inside the definitive host after the infected paratenic hosts were preyed. From the morphological comparison, the infected mantids, H. formosana, showed shorter wings in both sexes with shorter antennae and a reduction in the numbers of antennal sensilla in the infected males. This is the first discovery of a host’s sense organ change in the parasitism of horsehair worms. The reduced antennal sensilla made the infected male look similar to the nymph’s antennae. This may be the result of parasite-induced juvenilization. Additionally, the reduction in antennal sensilla was also observed in male H. patellifera fallen in water.

並列關鍵字

Parasitism ； Chordodes formosanus n. sp. ； Hierodula formosana ； H. patellifera ； Parasite-induced morphological change

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