3D is not just a tool - a study of the anal capsule in Craterostigmus tasmanianus Pocock (1902) (Chilopoda, Arthropoda)

Craterostigmus tasmanianus Pocock, 1902, is a chilopod distinguished, among other features, by a unique structure known as the anal capsule. Morphological questions regarding the anal capsule pertain to the homology of its functional components when compared to other chilopods, as well as the morpho-functional mechanisms involved in its opening and closing. Additionally, there has been ongoing debate about the precise location of the anus on the anal capsule. Some studies have suggested that the anus is located at the posterior end of the capsule, while others have proposed a position in the middle of the ventral side of the capsule. To address these questions, μCT and cLSM scans were conducted on the anal capsule of C. tasmanianus and the posterior segments of Scutigera coleoptrata (Linnaeus, 1758). The resulting data were processed using 3D visualization software. Different muscle groups were identified, and the cuticle was analyzed to determine the presence of resilin, a highly elastic component in arthropod cuticles. Based on the findings, hypotheses were formulated regarding the morpho-functional mechanisms of movement and the homology of the anal capsule structures in C. tasmanianus and S. coleoptrata. The analysis also resolved the question of anus location, confirming that it is situated at the posterior end of the anal capsule.