Morphological and mechanical properties of flexible resilin joints on damselfly wings (<i>Rhinocypha</i> spp.)

Resilin functions as an elastic spring that demonstrates extraordinary extensibility and elasticity. Here we use combined techniques, laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) to illuminate the structure and study the function of wing flexibility in damselflies, focusing on the genus Rhinocypha. Morphological studies using LSCM and SEM revealed that resilin patches and cuticular spikes were widespread along the longitudinal veins on both dorsal and ventral wing surfaces. Nanoindentation was performed by using atomic force microscopy (AFM), where the wing samples were divided into three sections (membrane of the wing, mobile and immobile joints). The resulting topographic images revealed the presence of various sizes of nanostructures for all sample sections. The elasticity range values were: membrane (0.04 to 0.16 GPa), mobile joint (1.1 to 2.0 GPa) and immobile joint (1.8 to 6.0 GPa). The elastomeric and glycine-rich biopolymer, resilin was shown to be an important protein responsible for the elasticity and wing flexibility.节弹性蛋白（Resilin）作为一种弹性弹簧，展现出超凡的延展性与弹性。本研究采用激光扫描共聚焦显微镜（laser scanning confocal microscopy，LSCM）与扫描电子显微镜（scanning electron microscopy，SEM）联用技术，以蜻蛉的黑丽翅蜻属（Rhinocypha）类群为研究对象，解析其翅翼结构并探究翅翼柔性的功能机制。通过LSCM与SEM开展的形态学研究显示，节弹性蛋白斑块与角质棘突在翅翼背、腹两面的纵脉沿线广泛分布。本研究利用原子力显微镜（atomic force microscopy，AFM）对翅翼样本进行纳米压痕实验，将样本划分为三个区域：翅膜、活动关节与非活动关节。所得形貌图像显示，所有样本区域均存在多种尺寸的纳米结构。各区域的弹性模量区间分别为：翅膜0.04~0.16 GPa、活动关节1.1~2.0 GPa、非活动关节1.8~6.0 GPa。这种富含甘氨酸的弹性生物聚合物——节弹性蛋白，被证实是赋予翅翼弹性与柔性的关键蛋白质。