Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA.
Functional Morphology Lab, Department of Biology, University of Antwerp, Wilrijk, Belgium.
J Anat. 2019 Aug;235(2):346-356. doi: 10.1111/joa.13003. Epub 2019 May 17.
The skin surface structure of squamate reptiles varies greatly among species, likely because it plays a key role in a range of tasks, such as camouflage, locomotion, self-cleaning, mitigation of water loss and protection from physical damage. Although we have foundational knowledge about squamate skin morphology, we still know remarkably little about how intraspecific variation in skin surface structure translates to functional variation. This gap in our understanding can be in part traced back to: (i) our lack of knowledge on how body size determines skin surface structure; and (ii) the lack of means to perform high-throughput and detailed analysis of the three-dimensional (3D) anatomy of reptilian skin surfaces in a non-destructive manner. To fill this gap, we explored the possibilities of a new imaging technique, termed gel-based stereo-profilometry, to visualize and quantify the 3D topography of reptilian skin surface structure. Using this novel approach, we investigated intra-specific and intra-individual variation in the skin surface morphology of a focal lizard species, Anolis cristatellus. We assessed how various characteristics of surface topography (roughness, skew and kurtosis) and scale morphology (area, height, width and shape) scale with body size across different body regions. Based on an ontogenetic series of A. cristatellus males, we show that skin roughness increases with body size. Skin patches on the ventral body region of lizards were rougher than on the dorsum, but this was a consequence of ventral scales being larger than dorsal scales. Dorsal surface skew and kurtosis varied with body size, but surfaces on the ventral skin showed no such relationship. Scale size scaled isometrically with body size, and while ventral scales differed in shape from dorsal scales, scale shape did not change with ontogeny. Overall, this study demonstrates that gel-based stereo-profilometry is a promising method to rapidly assess the 3D surface structure of reptilian skin at the microscopic level. Additionally, our findings of the explanatory power of body size on skin surface diversity provide a foundation for future studies to disentangle the relationships among morphological, functional and ecological diversity in squamate reptile skin surfaces.
爬行动物的皮肤表面结构在物种间差异很大，这可能是因为它在一系列任务中发挥着关键作用，例如伪装、运动、自我清洁、减少水分流失和防止物理损伤。尽管我们对爬行动物皮肤形态有了基本的了解，但我们仍然对皮肤表面结构的种内变异如何转化为功能变异知之甚少。这种理解上的差距部分可以追溯到：（i）我们缺乏关于身体大小如何决定皮肤表面结构的知识；（ii）缺乏以非破坏性方式对爬行动物皮肤表面的三维（3D）解剖结构进行高通量和详细分析的手段。为了填补这一空白，我们探索了一种新的成像技术，即基于凝胶的立体形貌测量法，以可视化和量化爬行动物皮肤表面结构的 3D 形貌。使用这种新方法，我们研究了焦点蜥蜴物种 Anolis cristatellus 的皮肤表面形态的种内和个体内变异。我们评估了表面形貌（粗糙度、偏度和峰度）和鳞片形态（面积、高度、宽度和形状）的各种特征如何随身体大小在不同身体区域发生变化。基于 Anolis cristatellus 雄性的个体发育系列，我们表明皮肤粗糙度随身体大小而增加。蜥蜴腹侧身体区域的皮肤比背部更粗糙，但这是由于腹侧鳞片比背侧鳞片大的结果。背侧表面偏度和峰度随身体大小而变化，但腹侧皮肤表面没有这种关系。鳞片大小与身体大小呈等比例变化，虽然腹侧鳞片的形状与背侧鳞片不同，但形状不随个体发育而变化。总的来说，这项研究表明，基于凝胶的立体形貌测量法是一种很有前途的方法，可以快速评估爬行动物皮肤的微观 3D 表面结构。此外，我们发现身体大小对皮肤表面多样性的解释力为未来的研究提供了基础，可以厘清爬行动物皮肤表面形态、功能和生态多样性之间的关系。
