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

昆虫是最大的动物门，提供了动物生物量的主要部分，并在许多陆地生态系统中发挥主导作用。许多物种，包括一些经济上相关的害虫物种，使用咬口器。在所有这些物种中，成对的下颌骨是负责咬和将较大的食物分解成较小的可消化碎片的最强部分。了解昆虫通过下颌骨施加的力的大小对于理解行为和生态过程至关重要。然而，对昆虫下颌器官的生理学研究和了解仍然很少。在与一组专家的合作中，我先前检查了美国蟑螂的下颌器官。这项研究是第一个成功的方法来测量咬合力在整个角度范围内的非专业昆虫下颌骨。然而，咬生理学的充分理解需要在下颌骨装置的主要亚基的功能的洞察力。除了下颌骨的形状和杠杆比，下颌骨收缩动力学和神经元控制更紧密的肌肉在很大程度上决定了昆虫的叮咬能力。肌肉通常由具有不同收缩特性的纤维组成。这些纤维在肌肉内的分布与激活模式一起影响肌肉力量产生的量和过程。因此，本申请旨在揭示美洲大蠊下颌肌中肌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，将对来自Dyctioptera总目的相关但适应性不同的物种（包括蟑螂、白蚁和螳螂）进行类似的检查。该提案提供了一个机会，以检查一个非常简单的，但迄今为止，在高度控制的条件下，驱动肌肉和组件的数量有限的未充分开发的运动系统。无论是生理和比较的方法将允许洞察的基本原则，确定形状和结构的昆虫头囊和下颌骨肌肉的不同隔间的相互作用。此外，杂食性，食木性和肉食性物种的比较考虑将揭示不同的食性功能的适应，并将铺平道路的功能理解的昆虫咀嚼器的进化。

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.