Constructing motion spaces of ant mandibles from microCT scans using vector embeddings.

Recent advances in microCT scanning technology allow for a large amount of high-fidelity geometric data to be collected across the tree of life. However, these high fidelity 3D scanning methods have rarely been utilized to shed light on the motion or kinematic state space of animals. This imaging methodology is particularly promising for organisms that operate at a scale difficult to record with standard motion capture solutions. Taking ants as a motivating example, we set out to characterize the range of three-dimensional kinematics of ant mandibles across several ant families and among several Hymenopteran clades for a broader phylogenetic context. We make use of microCT scan data of both closed and open states of the mandible of preserved specimens to generate three-dimensional models of both the head and the mandible for a phylogenetically and morphologically broad sample. With these models, we are able to perform three-dimensional interpolation between these open and closed states. Interpolation is done by considering the mandibles as vector embeddings in three-dimensional space. These kinematic predictions are made biologically relevant through collision checking of the mandible geometry against the head geometry. Using the vector embedding representation, we are further able to quantify range-of-motion for use in a comparative framework. Our methodology opens up a new avenue of research based on high-fidelity scanning methods and gives new insight into the kinematics of small-scale organisms.