Polilov Alexey A, Beutel Rolf G
Lomonosov Moscow State University, Russia.
Arthropod Struct Dev. 2009 May;38(3):247-70. doi: 10.1016/j.asd.2008.11.003. Epub 2009 Feb 5.
We present the first morphological study of larvae and adults of Mikado sp. - one of the smallest known beetles and free-living insects (body length of adult is 390-455microm). Morphological and developmental consequences of miniaturisation in Mikado and insects in general are discussed. We used histological sectioning, scanning electron microscopy, laser confocal microscopy and 3D-computer reconstruction. For the first time we report that according to the morphometric data of Mikado sp., at least some ptiliid beetles have three larval stages. We studied the muscular system of adults and larval stages. It is shown that ptiliid beetles have nearly the complete set of muscles found in larger staphyliniform beetles. Developmental and size dependent changes in the relative volume of different organs are addressed. All organ systems change allometrically in the development of Mikado sp. as well as in comparison with larger representatives of Ptiliidae and closely related groups of beetles, such as Staphylinidae. We conclude that the factors limiting miniaturisation are the size of the neural system, associated with the number and size of neurons, the mass of the skeleton, the egg size (free-living insects), and consequently the volume of the reproductive system.
我们展示了对天皇蚁形甲幼虫和成虫的首次形态学研究——天皇蚁形甲是已知最小的甲虫和自由生活昆虫之一（成虫体长为390 - 455微米）。本文讨论了天皇蚁形甲以及一般昆虫小型化的形态学和发育学后果。我们使用了组织切片、扫描电子显微镜、激光共聚焦显微镜和三维计算机重建技术。我们首次根据天皇蚁形甲的形态测量数据报告，至少一些蚁形甲科甲虫有三个幼虫阶段。我们研究了成虫和幼虫阶段的肌肉系统。结果表明，蚁形甲科甲虫拥有在较大的隐翅虫形甲虫中发现的几乎完整的肌肉组。文中探讨了不同器官相对体积的发育和大小依赖性变化。在天皇蚁形甲的发育过程中，以及与蚁形甲科的较大代表和甲虫的近缘类群（如隐翅虫科）相比，所有器官系统都呈现异速生长变化。我们得出结论，限制小型化的因素包括与神经元数量和大小相关的神经系统大小、骨骼质量、卵的大小（自由生活昆虫），以及由此产生的生殖系统体积。
