在沙漠中生活的沙鱼蜥（Scincus scincus，如上图）就像它的名字一样生活。它们能够钻到沙丘的下面，并且在沙下“游泳”，从而避开天敌和炎热，同时悄悄靠近猎物。但是这种10厘米长的爬行动物究竟如何穿越这些沙粒的表层呢？
据美国《科学》杂志在线新闻报道，高速X射线成像结果显示，这种蜥蜴会缩拢它们的四肢，并通过Z字型地左右摇摆身体来推动自己在沙子上前进，其像鱼或蛇一样摆动身体前行的速度能够达到每秒钟15厘米。这一发现将帮助科学家搞清沙漠中的其他居民——例如蝎子和蛇——是如何在沙子下行动的。研究人员在7月17日出版的美国《科学》杂志上报告了这一发现。（生物谷Bioon.com）
生物谷推荐原始出处：
Science 17 July 2009:DOI: 10.1126/science.1172490
Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard
Ryan D. Maladen,1 Yang Ding,2 Chen Li,2 Daniel I. Goldman1,2,*
The desert-dwelling sandfish (Scincus scincus) moves within dry sand, a material that displays solid and fluidlike behavior. High-speed x-ray imaging shows that below the surface, the lizard no longer uses limbs for propulsion but generates thrust to overcome drag by propagating an undulatory traveling wave down the body. Although viscous hydrodynamics can predict swimming speed in fluids such as water, an equivalent theory for granular drag is not available. To predict sandfish swimming speed, we developed an empirical model by measuring granular drag force on a small cylinder oriented at different angles relative to the displacement direction and summing these forces over the animal movement profile. The agreement between model and experiment implies that the noninertial swimming occurs in a frictional fluid.
1 Interdisciplinary Bioengineering Program, Georgia Institute of Technology, Atlanta, GA 30332, USA.
2 School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA.
