Department of Zoology, Faculty of Science, Charles University, Viničná 7, 128 44 Praha 2, Czech Republic.
Department of Zoology, Faculty of Science, Charles University, Viničná 7, 128 44 Praha 2, Czech Republic.
Curr Biol. 2017 Jan 23;27(2):263-269. doi: 10.1016/j.cub.2016.11.021. Epub 2017 Jan 12.
The appearance of wings in insects, early in their evolution [1], has been one of the more critical innovations contributing to their extraordinary diversity. Despite the conspicuousness and importance of wings, the origin of these structures has been difficult to resolve and represented one of the "abominable mysteries" in evolutionary biology [2]. More than a century of debate has boiled the matter down to two competing alternatives-one of wings representing an extension of the thoracic notum, the other stating that they are appendicular derivations from the lateral body wall. Recently, a dual model has been supported by genomic and developmental data [3-6], representing an amalgamation of elements from both the notal and pleural hypotheses. Here, we reveal crucial information from the wing pad joints of Carboniferous palaeodictyopteran insect nymphs using classical and high-tech techniques. These nymphs had three pairs of wing pads that were medially articulated to the thorax but also broadly contiguous with the notum anteriorly and posteriorly (details unobservable in modern insects), supporting their overall origin from the thoracic notum as well as the expected medial, pleural series of axillary sclerites. Our study provides support for the formation of the insect wing from the thoracic notum as well as the already known pleural elements of the arthropodan leg. These results support the unique, dual model for insect wing origins and the convergent reduction of notal fusion in more derived clades, presumably due to wing rotation during development, and they help to bring resolution to this long-standing debate.
昆虫翅膀的出现，早在其进化早期，就是促成其非凡多样性的关键创新之一。尽管翅膀引人注目且至关重要，但这些结构的起源一直难以解决，是进化生物学中的“可恶之谜”之一。一个多世纪的争论将问题归结为两种相互竞争的选择——一种观点认为翅膀是胸板的延伸，另一种观点则认为它们是从体壁侧面衍生而来的附肢。最近，基因组和发育数据支持了一种双重模式[3-6]，代表了来自胸板和侧板假说的元素融合。在这里，我们使用经典和高科技技术揭示了石炭纪古翅目昆虫若虫的翅垫关节的关键信息。这些若虫有三对翅垫，与胸部内侧关节相连，但与前胸和后胸也广泛相连（现代昆虫中不可见），这支持了它们的起源于胸部胸板，以及预期的腋侧板的中侧、侧板系列。我们的研究为昆虫翅膀的形成提供了支持，这既来自于胸部胸板，也来自于已经知道的节肢动物腿的侧板元素。这些结果支持昆虫翅膀起源的独特、双重模式，以及在更衍生的类群中胸板融合的趋同简化，这可能是由于发育过程中的翅膀旋转所致，它们有助于解决这一长期存在的争议。
