Coulcher Joshua F, Edgecombe Gregory D, Telford Maximilian J
Laboratoire de Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique de Banyuls, Avenue du Fontaulé, 66650 Banyuls-sur-mer, France.
Department of Earth Sciences, The Natural History Museum, London SW7 5BD, United Kingdom.
Sci Rep. 2015 Oct 28;5:15757. doi: 10.1038/srep15757.
Pleurites are chitinous plates in the body wall of insects and myriapods. They are believed to be an adaptation to locomotion on land but their developmental and evolutionary origins are unclear. A widely endorsed explanation for their origin is through toughening pre-existing parts of the body wall; in contrast, the subcoxal theory suggests pleurites derive from a redeployment of the proximal-most section of the leg, the subcoxa. Here, by studying expression of appendage patterning genes in embryos and larvae of the beetle Tribolium castaneum, we provide the first molecular evidence for the existence of a cryptic subcoxal segment in developing legs. We follow this structure during development and show that the embryonic subcoxa later forms the pleurites of the larva as predicted by the subcoxal theory. Our data also demonstrate that subcoxal segments are present in all post-antennal appendages, including the first molecular evidence of a two-segmented mandible with a subcoxal segment in insects.
侧板是昆虫和多足纲动物体壁中的几丁质板。它们被认为是对陆地运动的一种适应，但其发育和进化起源尚不清楚。关于它们起源的一种广泛认可的解释是通过强化体壁中预先存在的部分；相比之下，亚基节理论认为侧板源自腿部最近端部分（亚基节）的重新部署。在这里，通过研究甲虫赤拟谷盗胚胎和幼虫中附肢模式基因的表达，我们提供了首个分子证据，证明发育中的腿部存在一个隐藏的亚基节。我们在发育过程中追踪这个结构，并表明胚胎亚基节后来如亚基节理论所预测的那样形成了幼虫的侧板。我们的数据还表明，亚基节段存在于所有触角后的附肢中，包括昆虫中具有亚基节段的双节下颚的首个分子证据。
