Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, Guandong Province, China; Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
Curr Biol. 2023 Jul 24;33(14):2888-2896.e2. doi: 10.1016/j.cub.2023.06.014. Epub 2023 Jun 28.
The extensive biodiversification of butterflies and moths (Lepidoptera) is partly attributed to their unique mouthparts (proboscis [Pr]) that can span in length from less than 1 mm to over 280 mm in Darwin's sphinx moths. Lepidoptera, similar to other insects, are believed to inhale and exhale respiratory gases only through valve-like spiracles on their thorax and abdomen, making gas exchange through the narrow tracheae (Tr) challenging for the elongated Pr. How Lepidoptera overcome distance effects for gas transport to the Pr is an open question that is important to understanding how the Pr elongated over evolutionary time. Here, we show with scanning electron microscopy and X-ray imaging that distance effects on gas exchange are overcome by previously unreported micropores on the Pr surface and by superhydrophobic Tr that prevent water loss and entry. We find that the density of micropores decreases monotonically along the Pr length with the maxima proportional to the Pr length and that micropore diameters produce a Knudsen number at the boundary between the slip and transition flow regimes. By numerical estimation, we further show that the respiratory gas exchange for the Pr predominantly occurs via diffusion through the micropores. These adaptations are key innovations vital to Pr elongation, which likely facilitated lepidopteran biodiversification and the radiation of angiosperms by coevolutionary processes.
蝴蝶和蛾类（鳞翅目）的广泛生物多样化部分归因于它们独特的口器（喙 [Pr]），其长度从不到 1 毫米到达尔文的天蛾中超过 280 毫米不等。与其他昆虫一样，鳞翅目被认为仅通过胸部和腹部的瓣膜状气门吸入和呼出呼吸气体，这使得通过狭窄的气管（Tr）进行气体交换对于长喙来说具有挑战性。鳞翅目如何克服距离效应对 Pr 的气体输送是一个悬而未决的问题，对于理解 Pr 如何在进化过程中延长具有重要意义。在这里，我们通过扫描电子显微镜和 X 射线成像显示，Pr 表面以前未报道的微孔和超疏水 Tr 克服了距离效应对气体交换的影响，防止了水分流失和进入。我们发现，微孔的密度沿着 Pr 的长度单调下降，最大值与 Pr 的长度成正比，并且微孔直径在滑移和过渡流区之间的边界产生了努森数。通过数值估计，我们进一步表明，Pr 的呼吸气体交换主要通过微孔的扩散来进行。这些适应性是 Pr 伸长的关键创新，这可能通过共同进化过程促进了鳞翅目生物多样化和被子植物的辐射。
