VideoLab: Swimming in Sand
Physics can model organisms running or crawling on solids, and those flying and swimming through fluids. Yet the desert-dwelling sandfish lizard moves through sand -- a solid- and fluid-like medium. Using high-speed x-ray imaging, Maladen et al. discovered that, although the sandfish uses its legs to run on top of sand and to bury itself underneath (movie 1), once subsurface, sandfish use undulatory locomotion (movie 2), slithering through sand with its unused limbs tucked close to its body (movie 3).