Abstract
Quadrupeds and hexapods are known by their ability to adapt their locomotive patterns to their functions in the environment. Computational modeling of animal movement can help to better understand the emergence of locomotive patterns and their body dynamics. Although considerable progress has been made in this subject in recent years, the strengths and limitations of kinematic simulations at the scale of small moving animals are not well understood. In response to this, this work evaluated the effects of modeling uncertainties on kinematic simulations at small scale. In order to do so, a multibody model of a Messor barbarus ant was developed. The model was built from 3D scans coming from X-ray micro-computed tomography. Joint geometrical parameters were estimated from the articular surfaces of the exoskeleton. Kinematic data of a free walking ant was acquired using high-speed synchronized video cameras. Spatial coordinates of 49 virtual markers were used to run inverse kinematics simulations using the OpenSim software. The sensitivity of the model’s predictions to joint geometrical parameters and marker position uncertainties was evaluated by means of two Monte Carlo simulations. The developed model was four times more sensitive to perturbations on marker position than those of the joint geometrical parameters. These results are of interest for locomotion studies of small quadrupeds, octopods, and other multi-legged animals.
Highlights
Legged locomotion is the most common form of terrestrial animal movement (Christensen et al, 2021)
Specimen 1 was used to build a 3D model from micro-computed tomography (Section 2.2). 3D models of body segments were used to extract joint geometrical parameters and to create a multibody model (Section 2.3 and Section 2.4)
It can be noticed that the trochanter/femur joint is the one with the wider range of motion, while the thorax/coxa joints exhibit the smallest one
Summary
Legged locomotion is the most common form of terrestrial animal movement (Christensen et al, 2021). Even if quadrupedal and hexapodal forms of locomotion have evolved independently (Blickhan and Full, 1987), they present similarities. Both quadrupeds and hexapods can adapt their locomotive patterns according to their objective (Hoyt and Taylor, 1981; Nirody, 2021). Insects change smoothly the inter-leg coordination patterns based on their locomotion speed (Ambe et al, 2018). In the metachronous gait (or direct wave gait), hexapods propagate swinging movements from the hind legs to the forelegs, as quadrupeds do in the walking gait (Ambe et al, 2018). Hexapods move their diagonal legs in phases, as quadrupeds do in the trotting gait
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