CHANGES IN MICROTUBULES OF CILIA AND FLAGELLA FOLLOWING NEGATIVE STAINING WITH PHOSPHOTUNGSTIC ACID

¹ Department of Zoology and Laboratories for Reproductive Biology, University of North Carolina, Chapel Hill, North Carolina 27514, and the Marine Biological Laboratory, Woods Hole, Mass. 02543

1. Variability in the macerating action of 1% aqueous phosphotungstic acid, pH 6.8, is exemplified in microtubules of flatworm and rhynchocoel cilia, from one grid square to another of the same preparation and within a single grid square. The central singlets appear to be the most susceptible and are often completely absent, even in cases where the binding matrix is still present around the doublets. Maceration usually, but not always, begins at the distal tip of a cilium and proceeds towards the basal plate; it is evident along the lengths of doublets as partial or complete loss of one subtubule, as breaks and bends, and as fraying into the component protofibrils, with disappearance of the white line marking the wall between the subtubules.

2. Cortical singlet microtubules of a spermatozoon were thrown into a helical configuration by the action of PTA, while the flagellar microtubules of the same spermatozoon were unaffected.

3. After treatment with 1% PTA at pH 8.3, the central singlets of cilia (but not the doublets) were semi-fused along most of their lengths, and had a beaded appearance; there were breaks in the doublets but otherwise they appeared to be unaffected.

4. Ciliary rootlets were rarely seen, but when present had a clear 790 Å major repeating pattern and a longitudinal fibrous substructure.