Meeting Abstract

P2-3    3D shape analysis of polymorphic leafcutter ant mandibles Imirzian, N*; Puffel, F; Labonte, D; Imperial College London; Imperial College London; Imprial College London n.imirzian@imperial.ac.uk

Ants iconically divide up tasks in a colony and worker ants typically show little morphological specialization for these tasks. The exception are polymorphic species, such as leafcutter ants, that have evolved workers whose mass can vary 200-fold within one colony. Size and task preference appear to correlate, with the largest workers primarily engaged in defense, the medium sized foraging and leaf cutting, and the smallest involved in nest care. Our research seeks to answer whether worker task preference correlates with size-independent shape changes and if this alters performance at different tasks. We focus on mandibles, as they are relevant across the size range: soldiers need strong mandibles for defense, foragers must cut many leaves, and the smallest workers must delicately handle brood and fungal material. Most existing studies compare linear measurements of body parts, but such a dimensional reduction risks missing important information on morphological specialization. We investigated mandible shape change across the worker size range by conducting a morphometric analysis of high-resolution micro-CT scans of Atta vollenweideri workers. Instead of using landmark points to compare shape, we determined the atlas or mean mandible shape to compute the deformation required to morph each surface mesh to the atlas. This method reduces the bias of selecting landmark points while allowing us to map fine scale change, better emphasizing the difference between morphs within a species. Performing shape morphing between workers also offers predictions on the pathways leading to the observed morphology. We identify significant shape variation across the size range and are investigating how this might alter task performance. Landmark-free 3D shape analysis enhances our understanding of worker specialization in a leafcutter colony and may provide insight into advantages of evolving a polymorphic workforce.