Shape instabilities in single-component, saturated fatty acid membrane tubes have been investigated using phase contrast microscopy. These tubes were created in the course of a Langmuir monolayer collapse transition. Two types of shape instabilities were observed: (i) the excitation of a bending mode of a single tube, and (ii) topological changes of an assembly of tubes. The development of tube bending was accompanied by a shape transition from extended amphiphilic globules to confined ones that were transported in the tube. The evolution of bending instability has been analyzed as a balance among the bending energy, the surface tension energy of the tube, and the hydrodynamic dissipation energy by the surrounding fluid. Topological changes of an assembly of tubes were initiated by the formation of a membrane passage connecting two opposing tubes and followed by tube fusion and breaking. These changes were interpreted as a result of surface tension-gradient driven molecules transport on the tube surface.