有鳞目动物鳞片表面超微结构的适应性进化

爬行动物鳞片的微结构是对环境的一种适应。本研究运用扫描电子显微镜观察了北草蜥(Takydromus septentrionalis)、脆蛇蜥(Dopasia harti)和王锦蛇(Elaphe carinata)头部、背部和腹部鳞片的微皮纹结构及感受器特征。结果表明,3个物种的微皮纹和感受器存在种间差异。北草蜥和王锦蛇背部及腹部微皮纹均为狭长带状,脆蛇蜥为不规则多边形。北草蜥和王锦蛇颔片上有感受器,北草蜥无。脆蛇蜥腹部微皮纹上无小齿状凸起,北草蜥和王锦蛇有,与北草蜥相比王锦蛇的小齿状凸起更宽更长。王锦蛇的眼部微皮纹为向上竖起的脊,而其他部位的鳞片为具有小齿状凸起的狭长带状结构。本研究共收集整理17科99种的背鳞微皮纹数据和8科25种的感受器数据,对微皮纹特征和感受器形态进行祖先重建发现,狭长带状背鳞微皮纹主要存在于蜥蜴科(Lacertidae)、游蛇科(Colubridae)和石龙子科(Scincidae)中,而鬛蜥科(Agamidae)、蛇蜥科(Anguidae)、蟒蛇科(Boidae)以及蝰蛇科(Viperidae)的大多为多边形;较原始的感受器形态为无感觉毛的透镜状,这一结构在有鳞目动物进化中发生多次演化。本研究发现蛇蜥的鳞片表面微结构更接近于蛇类动物。因此,有鳞类动物鳞片微皮纹特征和皮肤感受器的形态是对其所处环境多重压力的优化选择。     

Surface structure and frictional properties of the skin of the Amazon tree boa <Emphasis Type="Italic">Corallus hortulanus</Emphasis> (Squamata,Boidae)

The legless locomotion of snakes requires specific adaptations of their ventral scales to maintain friction force in different directions. The skin microornamentation of the snake Corallus hortulanus was studied by means of scanning electron microscopy and the friction properties of the skin were tested on substrates of different roughness. Skin samples from various parts of the body (dorsal, lateral, ventral) were compared. Dorsal and lateral scales showed similar, net-like microornamentation and similar friction coefficients. Average friction coefficients for dorsal and lateral scales on the epoxy resin surfaces were 0.331 and 0.323, respectively. In contrast, ventral scales possess ridges running parallel to the longitudinal body axis. They demonstrated a significantly lower friction coefficient compared to both dorsal and lateral scales (0.191 on average). In addition, ventral scales showed frictional anisotropy comparing longitudinal and perpendicular direction of the ridges. This study clearly demonstrates that different skin microstructure is responsible for different frictional properties in different body regions.     

Morphology and frictional properties of scales of Pseudopus apodus (Anguidae,Reptilia)

In the lizard family Anguidae different levels of limb reduction exist up to a completely limbless body. The locomotion patterns of limbless anguid lizards are similar to the undulating and concertina movements of snakes. Additionally, anguid lizards frequently use a third mode of locomotion, called slide-pushing. During slide-pushing the undulating moving body slides on the ground, while the posterior part of the body is pressed against the substrate. Whereas the macroscopic and microscopic adaptations of snake scales to limbless locomotion are well described, the micromorphology of anguid lizard scales has never been examined. Therefore we studied the macro- and micromorphology of the scales of Pseudopus apodus, an anguid lizard with a snakelike body. In addition, we measured the frictional properties of Pseudopus scales. Our data show that the microstructures of the ventral scales of this anguid lizard are less developed than in snakes. We found, however, a rostro-caudal gradient in macroscopic structuring. Whereas the ventral side of the anterior body was nearly unstructured, the tail had macroscopic longitudinal ridges. Our frictional measurements on rough substrates revealed that the ridges provide a frictional anisotropy: friction was higher in the lateral than in the rostral direction. The observed frictional properties are advantageous for a tail-based slide-pushing locomotion, for which a tail with a high lateral friction is most effective in generating propulsion.