Initiation of bends in the microtubular axostyle of Pyrsonympha.

The motile axostyle of Pyrsonympha, a symbiotic protozoan occupying the hindgut of termites, is a cytoplasmic bundle of microtubules capable of initiating and propagating bends. In vivo, bends are always initiated at the anterior end of the cell. The early events to bend initiation are described using quantitative data from cinemicrographic recordings. In addition, the conplicated array of structures at the site of bend initiation is described using electron microscopy of serial thin sections through the anterior end of the cell. Bend initiation is postulated to represent a mechanical event associated with one or more of the specialized structures associated specifically with the anterior end of the axostyle.