Subpellicular microtubules of Euplotes eurystomus: their geometry relative to cell form, surface contours and ciliary...

There is a layer of microtubules (MT) beneath the innermost pellicular membrane of the ciliated protozoan Euplotes eurystomus. These MT have been revealed for scanning electron microscopic study by chemical dissection techniques. In much of the body of this ciliate, these MT are oriented parallel to its long axis. Those directed towards cirri, which are complex ciliary structures of the ventral surface, either abut or bend around the cirral base. MT adjacent to or closely associated with the ciliary feeding structures (membranelles of the adoral zone of membranelles or AZM) are oriented parallel to the long axis of the AZM. Some of the MT within the oral cavity have quite complex paths. The various orientations of these subpellicular MT are discussed and evaluated for hypothetical functions of cytoskeletal support, cell shaping and organelle movement. Each of these roles is considered to be theoretically possible.