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

• Applicant: Dr. Tom Weihmann
• Subject Area: Animal Physiology and Biochemistry ; Cognitive, Systems and Behavioural Neurobiology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2016 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 317341888

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.

• DFG Programme: Research Grants