Pattishall Abigail, Cundall David
Biological Sciences, Lehigh University, 31 Williams Drive, Bethlehem, PA 18015-3126, USA.
Zoology (Jena). 2008;111(1):48-61. doi: 10.1016/j.zool.2007.04.002. Epub 2007 Nov 13.
Video records of swimming water snakes show that during moderate to rapid swimming, the rear half to two-thirds of the trunk is compressed laterally, approaching the body form of some sea snakes. Body form of swimming snakes differed significantly from their shape when resting on a flat surface or when anesthetized and suspended in water. The extent of lateral flattening is positively correlated with swimming speed, a relationship generally supported by tests of trunk models in a flow tank. In Nerodia, the ability to temporarily flatten the trunk depends on kinetic costovertebral joints, a large compressible body cavity, and the absence of ventral skeletal support - features found in most snakes. Histological studies and manipulations of partially dissected preserved specimens showed that the resting angle of the ribs is maintained by localized elastic hypertrophy of the costovertebral capsular ligament. Trunk form during swimming in Nerodia is proposed to arise from anteromedial movement of the distal rib powered by deep muscles acting in concert with those proposed to generate undulation of the vertebral column.
对水蛇游泳的视频记录显示，在中速到快速游泳时，躯干后半部到三分之二会向侧面压缩，接近一些海蛇的身体形态。游泳时蛇的身体形态与它们趴在平面上或被麻醉并悬浮在水中时的形状有显著不同。侧面扁平的程度与游泳速度呈正相关，这一关系在水槽中对躯干模型的测试中得到了普遍支持。在水游蛇属中，暂时使躯干变扁平的能力取决于动肋椎关节、一个可大幅压缩的体腔以及没有腹侧骨骼支撑——大多数蛇都有这些特征。组织学研究以及对部分解剖的保存标本的操作表明，肋骨的静止角度由肋椎关节囊韧带的局部弹性肥大维持。水游蛇属游泳时的躯干形态被认为是由远端肋骨向前内侧移动产生的，这一移动由深层肌肉协同作用驱动，这些深层肌肉被认为与产生脊柱波动的肌肉共同作用。
