Clark W C
Zoology Department, University of Canterbury, Christchurch, New Zealand.
Int J Parasitol. 1994 Dec;24(8):1117-29. doi: 10.1016/0020-7519(94)90186-4.
Circumstances that probably attended and influenced the adoption and development of the parasitic habit amongst the Nematoda are examined. Features that allowed early terrestrial nematodes to exploit discontinuous habitats such as decomposing organic matter, are considered to have been advantageous to microbivorous Secernentea that became parasites of animals and plants. This development followed the appearance of a land flora and that the Amphibia were the first vertebrate hosts of nematodes. Life cycles involving intermediate hosts were essential in drier environments and in a aquatic ones where intermediate hosts preserve the infective stages; keeps them "in circulation", and makes them attractive to predators. It is concluded that the parasitic habit was adopted repeatedly in both Secernentea and Adenophorea, though the latter did not diversify as much. Convergence is a common feature of nematode evolution, and the typical life history pattern of 5 stadia separated by 4 moults is often greatly modified by suppression, extension and diversification of stages and their roles. There is a need to examine the nematodes, especially of invertebrates in the remaining rain forests of Gondwanaland before they disappear.
本文研究了可能伴随并影响线虫寄生习性形成与发展的各种情况。早期陆生线虫能够利用诸如分解有机物等不连续栖息地的特征，被认为对那些后来成为动植物寄生虫的食微生物尾感器纲线虫具有优势。这种发展是在陆地植物群出现之后发生的，而且两栖动物是线虫的首批脊椎动物宿主。涉及中间宿主的生命周期在干燥环境以及中间宿主能保存感染阶段的水生环境中至关重要；中间宿主使感染阶段“循环传播”，并使其对捕食者具有吸引力。得出的结论是，寄生习性在尾感器纲和腺口纲中都曾多次出现，尽管后者的多样化程度较低。趋同是线虫进化的一个共同特征，典型的5个龄期由4次蜕皮分隔的生活史模式常常会因各阶段及其作用受到抑制、延长和多样化而发生很大改变。有必要在冈瓦纳大陆剩余雨林中的线虫尤其是无脊椎动物线虫消失之前对它们进行研究。
