植物外寄生性線蟲之演化及分類

Evolution and Classification of Plant-ectoparasitic Nematodes

陳殿義( D. Y Chen)

《植物病理學會刊》 9卷3期 (2000/09) Pp. 79-92

https://doi.org/10.6649/PPB.200009_9(3).0001

摘要

由寒武紀層(Cambrian)出土化石之古生物學研究，線蟲在六億年前之原生代(Proterozoic)時期即已存在。陸生植物在四億兩千萬年前出現後，植物根圈土壤中以取食細菌、真菌、藻類或捕食其他微生物之線蟲，逐漸演化出口針構造，進而對植物地下部根系及地上部之莖、葉及種子等產生寄生現象；而其寄生習性由兼行外寄生、移動性外寄生、固著性外寄生、移動性內寄生而至固著性內寄生是線蟲與植物共同演化之結果。線蟲至目前已知種類已超過一萬種以上，歸屬於線蟲門(Nematoda)之Adenophorea和Secernentea兩大綱分類系統中。其中Dorylaimida一目中之植物寄生性線蟲皆為地下部根系外寄生性線蟲，包括Logidorus spp., Xiphinema spp. (Dorylaimina, Longidoridae)及Trichodorus spp. (Diphtherophorina, Trichodoridae)等屬。而在 Tylenchida中外寄生性線蟲分屬於Tylenchoidea和Criconematoidea二個演化系統，前者包括Dolichodorus spp. (Dolichodoridae), Belonolaimus spp.,Tylenchorhynchus spp., Trophurus spp. (Belonolaimidae), Rotylenchulus spp. (Hoplolaimidae)等；後者之植物寄生性線蟲皆為外寄生，包括Criconema spp. Criconemoides spp., Hemicriconemoides spp.,Hemicycliophora spp. (Criconematidae), Paratylenchus spp., Gracilacus spp., Cacopaurus spp., Tylenchulus spp. (Tylenchulidae) 等。前述二個總科總共16屬之外寄生性線蟲中，除Rotylenchulus spp. 和 Belonolaimus spp. 之食道腺體 (esophageal glands) 呈腺葉狀 (gland lobes)且與腸 (intestine) 部分重疊外，其餘14屬線蟲之食道腺體皆為圓桶形、梨形或圓球形，且未與腸發生重疊。但隨著線蟲與寄生植物之寄生關係愈密切，由外寄生而至內寄生，食道腺體逐漸變大且加長，其形態由腺體球轉變為腺葉形態，而與腸之位置關係則由正面相接轉變為復部或背部之不同程度部分重疊，而此一演進過程於Tylenchoidea各科中相當明顯，為一平行演化之結果，由此可知線蟲之寄生習性何和食道腺體之發展有密切不可分之關係，可做為種系分類之基礎。此外在寄生線蟲中，除Trichodorus spp.,Tylenchorhynchus spp., Tylenchulus spp. 及 Paratylenchus spp. 等5屬線蟲外，其餘11屬線蟲之口針明顯比其他內寄生蟲為長，而此一特徵也決定了線蟲之外寄生習性。線蟲寄生習性之演進過程和生殖腺數目及生殖方式無明顯之相對關係。在Dorylaimoidea中，Longidorus spp. 和 Trichodorus spp. 皆為雙卵巢，而Xiphinema spp. 為單-雙卵巢兩種型式皆有，其中單卵巢型是保留後端生殖腺，與其他具單一生殖線蟲截然不同；在Tylenchoidea中之外寄生性線蟲，除Trophurus spp. 外，其餘皆具有雙卵巢；在Criconematoidea中，全部植物寄生蟲皆為外寄生且都只具有單一卵巢。若腺蟲由雙卵巢朝單一卵巢演化，則Criconematioidea顯然在此一方面比Tylenchoidea更早進化。另外有關各種線蟲生殖方式之研究資料尚屬欠缺，大部分局限於Heteroderidae (Heterodera spp., Meloidogyne spp.) 之內寄生性線蟲，因此很難據此特徵推論外寄生線蟲各分類層及內之種系演化關係。

關鍵字

植物外寄生性線蟲 ； 演化 ； 分類

並列摘要

According to the complexity of life forms found on fossils in Cambrian, nematodes have already existed in 600 million years ago. After following the appearance of terrestrial plant in 420 million years ago, the stylet of nematodes has evolved gradually by feeding on bacteria, fungi, algae, and other l1icroorganisms in the soils. Moreover, the evolution between nematodes and plants is attributed to the change of parasitic habit from facultative ectoparasite, migratory ectoparasite, sedentary ectoparasite, ligratory endoparasite, to sedentary endoparasite. The phylum Nematoda consists of more than 10,000 lematode species. Phylum Nematoda is divided into 2 classes – Adenophorea and Secernentea, which include all of plant-ectoparasitic nematode species. According to the system, all of root-ectoparasitic nematodes belong to the order Dorylaimida (class Adenophora), such as Longidorus spp., Xiphinema spp., hd Trichodorus spp. Ectoparasitic nematodes in the order Tylenchida (class Secernentea) have two superfamily, Tylenchoidea and Criconematoidea. In superfamily Tylenchoidea, Dolichodorus spp., Belonolaimus spp., Tylenchorhynchus spp., Trophurus spp., and Rotylenchulus spp. were involved. While superfamily Criconematoidea contains 7 genera, including Criconemoides spp., Hemicriconemoides spp., Hemicycliophora spp., Paratylenchus spp., Gracilacus spp., Cacopaurus spp., and Tylenchulus spp. Among he sixteen important genera of plant ectoparasitic nematodes, the esophageal glands of Rotylenchulus spp. And Belononlaimus spp. become gland lobes, and are overlapped with their intestine. The shape of esophageal glands of the other fourteen genera is round or pear-shape and is not overlapped with intestine. Moreover, the esophageal glands become larger, elongated and turn to gland lobes form, as well as intestine is graduated overlapped according to the levels of parasitism between plants and nematodes. This horizontal evolution process has occurred repeatedly within individual phyletic lines in Tylenchida. Indeed, the development of esophageal glands during the long period of evolution could be as the labels on the species/genera identification. Except Trichodorus spp., Tylenchorhynchus spp., Trophurus spp., Tylenchulus pp., and Paratylenchus spp., the rest of eleven genera of plant-ectoparasitic nematodes have longer stylet than those of endoparasitic nematodes. There is no apparent relationship between the evolution process of parasitic habit of nematodes and number of gonads or mode of reproduction. In superfamily Dorylaimoidea, ngidorus spp., and Trichodorus spp., female nematodes have two ovaries, whereas Xiphinema spp have ne or two. In superfamily Tylenchoidea, all plant-ectoparasitic nematodes have two ovaries except 1rophurus spp. In superfamily Criconematoidea, all plant parasitic nematodes are ectoparasite and have one ovary. If the evolution of ovary is from two toward one, superfamily Criconematoidea might be more pogress than superfamily Tylenchoidea. Up to now, the research data about the pattern of reproduction was mostly restricted on endoparasitic nematodes in Heteroderidae, Heterodera spp., and Meloidogyne spp. Therefore, more complete information regarding this issue was necessary to interpret the evolutionary Interrelationships of the plant-ectoparasitic nematodes in future.
Hemicyc/iophora spp., Paratylenchus spp., Gracilacus spp., Cacopaurus spp., and Tylenchulus spp. Among he sixteen important genera of plant ectoparasitic nematodes, the esophageal glands of Rotylenchulus spp. And Belonolaimus spp.

並列關鍵字

classification ； evolution ； plant-ectoparasitic nematode