Department of Zoology, School of Natural Sciences, National University of Ireland, Galway, Ireland.
Arthropod Struct Dev. 2012 May;41(3):231-43. doi: 10.1016/j.asd.2012.02.001. Epub 2012 Feb 24.
The forcipules of centipedes are the only known example in the animal kingdom of an evolutionary transition from walking legs to venom-injecting appendages. They provide a classic case of an evolutionary novelty under most (but not all) definitions of that concept. Although there is a reasonable literature on forcipules, and on the forcipular segment more generally, it is fragmentary and scattered. Also, many previous studies have been based on a single species and hence have no comparative component. Here, we build on this earlier literature by providing detailed qualitative and quantitative information on the forcipular segments of representatives of the five extant orders of centipedes. Our results reveal notable differences between the orders - as well as considerable variation within some of them. The pattern of inter-group differences can be used to infer, albeit cautiously, a major evolutionary trend from a presumed scutigeromorph-like last common ancestor (LCA), in which the forcipules were probably leg-like (as in present-day scutigeromorphs) to a more specialized claw-like structure with movement restricted to the horizontal plane. This morphological trend may reflect an ecological trend from open-habitat ambush predation to leaf-litter and subterranean predatory opportunism.
蜈蚣的铗状附肢是动物王国中唯一已知的、从步行足进化为注射毒液的附肢的例子。它们提供了一个经典的案例，说明了在大多数（但不是全部）该概念定义下的进化新颖性。尽管关于铗状附肢以及更一般的铗状节段有相当数量的文献，但这些文献是零散的。此外，许多先前的研究都是基于单一物种，因此没有比较的成分。在这里，我们在早期文献的基础上，提供了五个现存蜈蚣目代表物种的铗状节段的详细定性和定量信息。我们的结果揭示了不同目之间的显著差异——以及一些目内的相当大的变异。群体间差异的模式可以用来推断，尽管要谨慎，但从假定的 scutigeromorph 样的最后共同祖先（LCA）开始，就存在一个主要的进化趋势，在这个进化趋势中，铗状附肢可能是类似腿的结构（如现今的 scutigeromorph 目），到更专门的爪状结构，运动仅限于水平平面。这种形态趋势可能反映了从开阔栖息地伏击捕食到落叶和地下捕食机会主义的生态趋势。
