Meeting Abstract

P2-2   -   Mechanical efficiency of cutting in Atta cephalotes leaf-cutter ants Walthaus, OK*; Kang, V; Imirzian, N; Labonte, D; Imperial College London, UK; Imperial College London, UK; Imperial College London, UK; Imperial College London, UK lkw120@ic.ac.uk

Leaf-cutter ants cut fragments from fruits and leaves to grow a fungus used as crop. Cutting leaves requires the application of a force. This force is generated by muscle, in a process that consumes chemical energy. Leaf-cutting is therefore both mechanically challenging and metabolically costly. The ratio between mechanical and metabolic energy requirements defines the efficiency of the cutting process. How does this efficiency depend on worker size, and the mechanical properties of the material which is cut? In this study, we addressed this question with a three-pronged approach. First, we established an “artificial leaf” system based on polymers, providing us with full control over the relevant structural and mechanical properties of the cut material. Second, we use a custom-built fibre optic force sensor setup to measure the steady-state force required to cut these “leaves” with mandibles from ants of different sizes, so deriving the mechanical power requirements of cutting. Third, we quantified the metabolic power requirements of cutting using flow-through respirometry. The resulting understanding of how the efficiency of leaf cutting varies with both the material properties of the substrate and with worker size will enable detailed predictions about energetically optimal forager size-distributions as a function of food source properties, which can be tested experimentally in behavioural assays.