Biomechanics of the insect bite apparatus
File(s)
Author(s)
Puffel, Frederik
Type
Thesis
Abstract
In this thesis, I investigate the morphology and biomechanics of the insect bite apparatus using polymorphous leaf-cutter ants as study organism. I first quantify the key morphological determinants of bite force and discuss the spatial constraints of muscle geometry imposed by the insect exoskeleton. Across the substantial size-range of leaf-cutter ant workers, the bite force capacity increases with a strong positive allometry, driven by a disproportional increase in the volume of the mandible closer muscle combined with a muscle fibre arrangement that enables high volume-specific muscle forces. Second, I derive and validate a biomechanical model that links the geometry of the musculoskeletal bite apparatus to changes of the mandibular opening angle. I then deploy this model to extract the force-length properties of the mandible closer muscle via in-vivo bite force measurements. Third, based on these results and the previously extracted morphological parameters, I predict the scaling relationship between maximum bite force and body mass, and compare this prediction to direct force measurements. Leaf-cutter ants generate among the highest weight-specific bite forces ever reported for any animal, displaying an exceptional level of morphological and physiological adaptation to the high mechanical demands of herbivory. Fourth, I turn my attention to ontogenetic changes of the bite apparatus, from freshly-eclosed adults to fully-matured foragers. In the week following eclosion, the bite apparatus undergoes a considerable biomechanical development, driven by substantial muscle growth and increasing head capsule rigidity. As a result, young leaf-cutter ants are likely incapable of engaging in any colony tasks involving leaf-cutting. Fifth, although fully-matured foragers can generate much larger bite forces than callows, their mandibles require significantly higher forces to cut the same material. These mandibular cutting forces are largely size-independent, and for callows, they approach a theoretical minimum for the tested material, suggesting geometric adaptations for high mandible ‘sharpness’. The results of this work add important aspects to the discussion on age- and size-related foraging behaviour in social insects, and more generally, underline the importance
of biomechanics in insect herbivory.
of biomechanics in insect herbivory.
Version
Open Access
Date Issued
2022-12
Date Awarded
2023-05
Copyright Statement
Creative Commons Attribution Licence
License URL
Advisor
Labonte, David
Masouros, Spyridon
Sponsor
Cusanuswerk
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)