A simple 1-D physical model for the crawling nematode sperm cell

We develop a one-dimensional physical model of the crawling movement of simple cells: The sperm of a nematode, Ascaris suum. The model is based on the assumptions that polymerization and bundling of the cytoskeletal filaments generate the force for extension at the front, and that energy stored in the gel formed from the filament bundles is subsequently used to produce the contraction that pulls the rear of the cell forward. The model combines the mechanics of protrusion and contraction with chemical control, and shows how their coupling generates stable rapid migration, so that the cell length and velocity regulate to constant values.