Exposing the drives of the insect mandibular apparatus: Examination of muscle fibre composition, contraction properties and innervation patterns in mandible muscles of cockroaches and related carnivorous and xylophagous insect species

昆虫是最大的类群，提供了动物生物量的主要部分，在许多陆地生态系统中发挥着主导作用。许多物种，包括一些与经济相关的害虫物种，都使用咬口器。在所有这些物种中，成对的下颌是最强壮的部分，负责咬住较大的食物，并将其减少为较小的可消化部分。了解昆虫可以通过其下颌施加的力量的大小，对于了解行为和生态过程至关重要。然而，对昆虫下颌器的生理学研究和了解仍然很少。在与一个专家团队的合作中，我之前检查了美国蟑螂的下颌器官。这项研究是第一个成功地测量非特化昆虫下颌全角度范围内咬合力的方法。然而，完全理解咬合生理学需要对下颌器官主要亚单位的功能有深入的了解。除了下颌骨的形状和杠杆比率外，收缩的动力和下颌更近的肌肉的神经元控制在很大程度上决定了昆虫的咬合能力。肌肉通常由具有不同收缩特性的纤维组成。这些纤维在肌肉中的分布与激活模式一起影响肌肉力量产生的数量和过程。因此，这项应用旨在揭示美洲蟑螂下颌肌中肌肉纤维的分布和收缩特性以及激活和神经支配模式。为了进行比较，将对包括蟑螂、白蚁和螳螂在内的双翅目超级目相关但适应不同的物种进行类似的检查。该提案提供了一个机会来研究一种相对简单但迄今未被探索的发动机系统，该系统在高度受控的条件下具有有限数量的驱动肌肉和部件。生理学方法和比较方法都将使人们能够深入了解决定昆虫头部被膜形状和结构的基本原理，以及下颌肌不同部分之间的相互作用。此外，对杂食性、食木性和肉食性物种的比较考虑将揭示对不同食性的功能适应，并将为从功能上理解昆虫咀嚼器官的进化铺平道路。

Insects are the largest phylum, provide a major part of the animal biomass and play a dominant role in many terrestrial ecosystems. Many species, including a number of economically relevant pest species, employ biting mouthparts. In all these species the paired mandibles are the strongest parts responsible for biting and reducing larger food items into smaller digestible pieces. To understand the magnitude of force insects can exert through their mandibles is pivotal to understand behavioural and ecological processes. Yet the physiology of the mandibular apparatus of insects is still poorly examined and understood. In collaboration with a team of specialists I previously examined the mandibular apparatus of the American cockroach. This study was the first successful approach to measure bite forces over the full angular range of non-specialized insect mandibles. However, full understanding of bite physiology requires insight in the functionality of the major subunits of the mandibular apparatus. Alongside the shape and lever ratio of the mandibles contraction dynamics and neuronal control of the mandible closer muscles largely determine the biting capabilities of an insect. Muscles do usually consist of fibres with different contraction properties. The distribution of these fibres within the muscle in conjunction with activation patterns affects the amount and course of the muscles force generation. This application, therefore, intends to reveal distribution and contraction properties of muscle fibres as well as activation and innervation patterns in the mandible muscles of the American cockroach. Aiming at comparative considerations, similar examinations will be conducted in related but differently adapted species from the superorder Dyctioptera comprising cockroaches, termites and mantids. The proposal provides the opportunity to examine a comparably simple, but so far underexplored motor system with a limited number of driving muscles and components under highly controlled conditions. Both the physiological and the comparative approach will permit insights into basic principles determining shape and structure of insect head capsules and the interplay of the different compartments of the mandible muscles. Moreover, the comparative consideration of omnivorous, xylophagous and carnivorous species will reveal functional adaptations to different feeding habits and will pave the way to a functional understanding of the evolution of the insect masticatory apparatus.