Neumann Dietrich, Woermann Dietrich
Zoological Institute, University of Cologne/Germany, D50923 Koeln, Cologne, Germany.
Naturwissenschaften. 2009 Aug;96(8):933-41. doi: 10.1007/s00114-009-0551-8. Epub 2009 May 13.
The intertidal midge Clunio, which reproduces on exposed rocky seashores, becomes enclosed in an irregularly shaped air bubble during short submersion by incoming waves. This water-repellent property of Clunio's cuticle is caused by a complete cover of hydrophobic microtrichia offering an effective surf tolerance. These microtrichia not only trap a thin air layer above the cuticle but also maintain a larger air bubble between the insect's ventral side and legs. The effectiveness of the water repellence was quantitatively characterised on the basis of a known model (Crisp and Thorpe, Discuss Faraday Soc 3:210-220, 1948). The parameters of the model are the contact angle theta (>90 degrees) at the contact line of air/water/microtrichia and the distance between individual microtrichia and their radius. When the microtrichia are 1.1 microm apart and have a radius of 0.1 microm and an estimated contact angle theta of 140 degrees, the air layer is stable against hydrostatic pressures of up to 3 m water column. As shown by a modified version of the model, considerably larger air bubbles can be trapped by the microtrichia cover of the legs up to distances of 0.5 mm from the body. The widely spaced (about 8 microm apart) and longer setae of Clunio are not involved in the formation of air layers and air bubble.
潮间带蠓虫克吕尼奥在裸露的岩石海岸繁殖，在被涌浪短暂淹没时会被包裹在一个形状不规则的气泡中。克吕尼奥角质层的这种防水特性是由一层完整的疏水微毛造成的，这些微毛提供了有效的冲浪耐受性。这些微毛不仅在角质层上方捕获一层薄空气层，还在昆虫腹侧和腿部之间维持一个更大的气泡。基于一个已知模型（克里斯普和索普，《法拉第学会讨论》3:210 - 220，1948年）对防水效果进行了定量表征。该模型的参数是空气/水/微毛接触线处的接触角θ（>90度）以及单个微毛之间的距离及其半径。当微毛间距为1.1微米，半径为0.1微米，估计接触角θ为140度时，空气层在高达3米水柱的静水压力下是稳定的。如该模型的一个修改版本所示，腿部的微毛覆盖层能够捕获距离身体达0.5毫米远的大得多的气泡。克吕尼奥间距很宽（约8微米）且较长的刚毛不参与空气层和气泡的形成。
