Evolutionary Biomechanics, Zoological Institute and Museum, University of Greifswald, Greifswald, Germany.
Zoological Museum, Zoological Institute and Museum, University of Greifswald, Greifswald, Germany.
J Morphol. 2024 Feb;285(2):e21670. doi: 10.1002/jmor.21670.
Silk production is a prominent characteristic of spiders. The silk is extruded through spigots located on the spinnerets, which are single- to multimembered paired appendages at the end of the abdomen. Most extant spiders have three pairs of spinnerets, and in between either a cribellum (spinning plate) or a colulus (defunct vestigial organ), dividing these spiders into cribellate and ecribellate species. Previous research has shown that cribellate and ecribellate spiders differ not only in the composition of their spinning apparatus but also in the movements of their spinnerets during silk spinning. The objective of this study was to determine whether the differences in spinneret movements are solely due to variations in spinneret shape or whether they are based on differences in muscular anatomy. This was accomplished by analyzing microcomputed tomography scans of the posterior abdomen of each three cribellate and ecribellate species. It was found that the number of muscles did not generally differ between cribellate and ecribellate species, but varied considerably between the species within each of these two groups. Muscle thickness, particularly of the posterior median spinneret, varied slightly between groups, with cribellate spiders exhibiting more robust muscles, possibly to aid in the combing process during cribellar thread production. Interestingly, the vestigial colulus still possesses muscles, that can be homologized with those of the cribellum. This exploration into spinneret anatomy using microcomputed tomography data reveals that despite being small appendages, the spider spinnerets are equipped with a complex musculature that enables them to perform fine-scaled maneuvers to construct different fiber-based materials.
丝的生产是蜘蛛的一个显著特征。丝通过位于纺器上的喷丝孔挤出，纺器是腹部末端的单对到多对配对附肢。大多数现存的蜘蛛有三对纺器，在它们之间要么是一个筛器（纺丝盘），要么是一个科尔卢斯（已失去功能的残余器官），将这些蜘蛛分为筛器蜘蛛和无筛器蜘蛛。以前的研究表明，筛器蜘蛛和无筛器蜘蛛不仅在纺丝器的组成上有所不同，而且在纺丝过程中纺器的运动方式也有所不同。本研究的目的是确定纺器运动的差异是否仅仅是由于纺器形状的变化，还是基于肌肉解剖结构的差异。这是通过分析三种筛器蜘蛛和无筛器蜘蛛的后腹部的微计算机断层扫描来完成的。结果发现，筛器蜘蛛和无筛器蜘蛛的肌肉数量通常没有差异，但在这两个组内的每个物种之间差异很大。肌肉厚度，特别是后中纺器的肌肉厚度，在组间略有差异，筛器蜘蛛的肌肉更结实，可能有助于在筛丝生产过程中的梳理过程。有趣的是，已失去功能的科尔卢斯仍然拥有肌肉，这些肌肉可以与筛器的肌肉同源。这项使用微计算机断层扫描数据对纺器解剖结构的探索表明，尽管纺器是小的附肢，但蜘蛛的纺器配备了复杂的肌肉系统，使它们能够进行精细的操作，以构建不同的纤维基材料。
