The biomechanics of ultra-stretchable nerves.

When digging in the ground during egg laying the female locust extends her abdomen to 2-3 times of its original length. How the abdominal nervous system accommodates such extreme elongation remains unknown. We characterized and quantified the system's biomechanical response using controlled ex vivo elongation and force measurements. The microstructure of the nerves was studied using histology and high-resolution confocal microscopy. Although the nervous system of sexually mature females demonstrated fully reversible hyper-extensibility of up to 275%, the elongation observed in premature females and males was much more limited. The unique extension dynamics of the different groups were captured by their very different force-displacement curves. Confocal microscopy suggested that elongation is not owing to undulations of the nervous system structure. Thus, the exceptional resistance to deformation and rupture presents the female locust abdominal nervous system as a valuable model for understanding the functionality and pathology related to nerve extension and reversible elongation.