Bäumler Fabian, Gorb Stanislav N, Büsse Sebastian
Functional Morphology and Biomechanics, Institute of Zoology, Kiel University, Kiel, Schleswig-Holstein, Germany.
Cytology and Evolutionary Biology, Institute of Zoology and Museum, University of Greifswald, Greifswald, Mecklenburg-Vorpommern, Germany.
J Morphol. 2024 Dec;285(12):e70013. doi: 10.1002/jmor.70013.
Insect legs, as primarily locomotory devices, can show a tremendous variety of morphological modifications providing a multitude of usages. The prehensile raptorial forelegs of praying mantises (Mantodea) are a prominent example of true multifunctionality since they are used for walking while being efficient prey-capturing and grasping devices. Although being mostly generalist arthropod predators, various morphological adaptations due to different environmental conditions occur across Mantodea. Recently, the general mantodean morphology, and particularly their raptorial forelegs, received an increased interest. Yet, knowledge about the evolutionary transition from walking to prey-grasping legs is still scarce. From evolutionary and functional perspectives, the question arises: what changes were necessary to achieve the strongly modified raptorial forelegs-while keeping walking ability-and how does the foreleg morphology differ from the remaining four walking legs? In this context, we investigated the musculature of the raptorial forelegs in seven phylogenetically distant mantodeans, including pterothoracic legs in four of them, using high-resolution microcomputed tomography and dissection. To understand the results from an evolutionary perspective, we additionally examined all three pairs of unmodified walking legs of the closest sister group-Blattodea. We updated the knowledge of blattodean morphology, revealing differences in cuticle structures of the coxal articulation of the first pair of legs between the two orders and a shared musculature set-up in all pairs of legs among later-branching mantodeans. Interestingly, the early branching species Metallyticus splendidus and Chaeteessa sp. show several muscular characteristics, otherwise found exclusively in one or the other order, with a few procoxal muscles showing an intermediate state between the two orders. Studying the evolutionary transition from a walking leg to a raptorial leg will help to understand the character evolution of this highly specialized biomechanical system from a purely locomotory appendage to a multi-functional device with all related amenities and constraints.
昆虫的腿作为主要的运动器官，可呈现出极为多样的形态变化，具有多种用途。螳螂（螳螂目）用于抓握的捕捉式前腿就是真正多功能性的一个突出例子，因为它们在用于行走的同时，也是高效的猎物捕获和抓握工具。尽管螳螂大多是多食性节肢动物捕食者，但由于不同环境条件，整个螳螂目出现了各种形态适应。最近，螳螂的总体形态，尤其是它们的捕捉式前腿，受到了更多关注。然而，关于从行走腿到猎物抓握腿的进化转变的知识仍然匮乏。从进化和功能的角度来看，问题出现了：在保持行走能力的同时，实现高度特化的捕捉式前腿需要哪些变化？前腿形态与其余四条行走腿有何不同？在此背景下，我们使用高分辨率微型计算机断层扫描和解剖方法，研究了七种系统发育关系较远的螳螂捕捉式前腿的肌肉组织，其中四种还包括胸部腿。为了从进化角度理解研究结果，我们还检查了最亲近的姐妹类群——蜚蠊目的所有三对未特化的行走腿。我们更新了蜚蠊目形态学的知识，揭示了两个目之间第一对腿的髋节关节角质层结构的差异，以及在分支较晚的螳螂类群中所有腿对共享的肌肉组织设置。有趣的是，早期分支物种华丽金属螳和Chaeteessa sp.表现出一些肌肉特征，这些特征在其他情况下仅在一个或另一个目中发现，一些前髋部肌肉呈现出两个目之间的中间状态特征。研究从行走腿到捕捉腿的进化转变，将有助于理解这个高度特化的生物力学系统从单纯的运动附肢到具有所有相关便利和限制的多功能装置的特征进化。
