Tucker J B, Mackie J B
Tissue Cell. 1975;7(4):601-12. doi: 10.1016/0040-8166(75)90029-4.
Microtubules at the tip of a resting (non-feeding) tentacle are arranged helically in two concentric tube-shaped arrays. The pitches of the helical paths followed by tubules in the two arrays differ. At the start of feeding these microtubules bend along their longitudinal axes and splay outwards and downwards away from the tentacle tip as it 'everts'. Tubules in the two arrays slide across each other as this occurs. Comparison of the fine structure of the tips of feeding and resting tentacles with a dynamic model of the microtubular framework indicates that movement of the tubules is not brought about by active sliding of the tubules against each other or by the action of contractile elements attached along the lengths of the tubules. The tips of microtubules forming the inner tube may be pulled downwards by contractile elements in the tentacular pellicle; these tubules apparently push those in the outer tube to their new position. The pattern of configurational changes in a tentacle tip at the start of feeding appears to be largely defined by the elastic resistance of the microtubules to bending, and the ways in which tubules are packed and linked together and attached to the pellicle.
静息（非摄食）触手尖端的微管呈螺旋状排列，形成两个同心管状阵列。两个阵列中微管遵循的螺旋路径螺距不同。在摄食开始时，这些微管沿其纵轴弯曲，并在触手“外翻”时从触手尖端向外和向下展开。此时，两个阵列中的微管相互滑动。将摄食和静息触手尖端的精细结构与微管框架的动态模型进行比较表明，微管的运动不是由微管相互之间的主动滑动或沿着微管长度附着的收缩元件的作用引起的。形成内管的微管尖端可能被触手薄膜中的收缩元件向下拉动；这些微管显然将外管中的微管推到它们的新位置。摄食开始时触手尖端的构型变化模式似乎很大程度上由微管对弯曲的弹性阻力以及微管的堆积、连接方式以及与薄膜的附着方式所决定。
