Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing
Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing
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DOI：
10.1073/pnas.1519459113
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发表时间：
2016-02-02
影响因子：
11.1
通讯作者：
Federle, Walter
中科院分区：
文献类型：
--
作者：
Labonte, David;Clemente, Christofer J.;Federle, Walter
当体表提供身体体积时，器官功能依赖于尺寸。较大的生物体可以发展出强烈折叠的内表面，以增强扩散，但在许多情况下，区域不能折叠，因此它们的扩大受到解剖学的限制，这对较大的动物来说是一个问题。在这里，我们研究了225种攀缘动物的粘附垫面积的异速生长，覆盖超过7个数量级的重量。在所有的类群，粘合垫面积表现出极端积极的异速生长和缩放与重量，这意味着一个200倍的相对垫面积从螨增加到壁虎。然而，异速生长缩放系数垫面积系统地降低与分类水平，并接近等距进化历史时占，这表明，实现这种相对垫面积的增加所需的实质性解剖变化是有限的系统发育的限制。使用比较系统发育的方法，我们发现，偏离等距几乎完全是由节肢动物和脊椎动物之间的大小校正垫面积的巨大差异。为了减轻密切相关的类群内的重量特异性粘附的预期降低，其中垫面积接近等距缩放，几个类群的数据表明，垫的粘附强度增加较大的动物。远亲类群的相对垫面积的调整和密切相关的群体的粘附强度的变化相结合，有助于解释如何攀登与胶粘垫已经演变成动物的体重变化超过7个数量级。我们的研究结果说明了基于粘附的攀爬的尺寸限制，对大规模生物启发粘合剂具有深远的影响。
Organismal functions are size-dependent whenever body surfaces supply body volumes. Larger organisms can develop strongly folded internal surfaces for enhanced diffusion, but in many cases areas cannot be folded so that their enlargement is constrained by anatomy, presenting a problem for larger animals. Here, we study the allometry of adhesive pad area in 225 climbing animal species, covering more than seven orders of magnitude in weight. Across all taxa, adhesive pad area showed extreme positive allometry and scaled with weight, implying a 200-fold increase of relative pad area from mites to geckos. However, allometric scaling coefficients for pad area systematically decreased with taxonomic level and were close to isometry when evolutionary history was accounted for, indicating that the substantial anatomical changes required to achieve this increase in relative pad area are limited by phylogenetic constraints. Using a comparative phylogenetic approach, we found that the departure from isometry is almost exclusively caused by large differences in size-corrected pad area between arthropods and vertebrates. To mitigate the expected decrease of weight-specific adhesion within closely related taxa where pad area scaled close to isometry, data for several taxa suggest that the pads' adhesive strength increased for larger animals. The combination of adjustments in relative pad area for distantly related taxa and changes in adhesive strength for closely related groups helps explain how climbing with adhesive pads has evolved in animals varying over seven orders of magnitude in body weight. Our results illustrate the size limits of adhesion-based climbing, with profound implications for large-scale bio-inspired adhesives.