ELECTRON MICROSCOPICAL OBSERVATIONS ON MUCOCYSTS OF CILIATE TETRAHYMENA ROSTRATA

Electron-microscopic observations on the occurrence of mucoid trichocysts or mucocysts in the hymenostome ciliate Tetrahymena rostrata are reported for the first time. In this cyst-forming species of the genus Tetrahymena there are numerous mucocysts in the cytoplasm in all stages in the life history. Measuring 0.5-2.0 [mu] in length and 0.2-0.5 [mu] in width, their matrix is quite homogeneous except for a possibly unique central axial structure which is distinctly more electrondense. At the tips there is an indistinct paracrystalline structure with a periodicity of about 80-90 A. The organelles are compared with what are presumably homologous structures in other ciliates, and their probable role in the physiological life cycle of the species T. rostrata is discussed.