Morphological Changes in Thoracic Internal Structures of Asiophrida xanthospilota (Coleoptera: Chrysomelidae) During Pupal Period.

The thorax, which serves as the primary center of locomotion for insects, consists of a highly intricate skeletomuscular system. The thoracic morphological transformations during the pupal stage reveal the developmental formation of locomotor systems. Asiophrida xanthospilota is not only capable of flight but is also an exceptional jumper. In this study, we employed micro-CT and 3D reconstruction to document the thoracic internal anatomy of this species on pupal days 1, 2, 4, 6, 8, 10, and 12, with the goal of achieving a more comprehensive understanding of their locomotion mechanisms. In A. xanthospilota, a membrane connecting the occiput and metaphragma is present from pupal days 2 to 8, serving as the attachment site for the notal muscles. Morphological changes in some endoskeletal structures during development result in corresponding shifts in the origins or insertions of associated muscles. On the first day, most muscles are present in the pro- and mesothorax, while the metathorax contains comparatively few, a pattern likely linked to the primary reliance on jumping locomotion of the species. Some muscles that appear only during the early and middle pupal stages might function in structural support. Muscular morphology undergoes diverse changes that are difficult to generalize. On day 4, the muscles show a comparatively small relative volume, which might reflect experimental error or other underlying factors. In addition, the gut and nerve remain largely unchanged. It should be noted that the stroma within the thoracic cavity might have hindered the precise identification of muscles.