Tetrahymena has only one type of extrusome, the mucocyst
(mu). Mucocysts form two rows along the longitudinal axis of
the cell. One row is in line with the kinety (the primary meridian)
and a second row, parallels the kinety halfway between two kineties
(the secondary meridian). Mucocysts orient with their long axis more
or less perpendicular to the cell surface and extend to the plasma
membrane through gaps in the septum between alveoli. This section
shows cross-sectioned pores (arrows) passing between alveoli
through this septum. m, mitochondria; per, peroxisome.
EM taken on 8/16/67 by R. Allen with Philips 200 TEM. Neg. 12,400X.
Bar = 0.5µm. Part published in Poste and Nicolson (eds.), Membrane
Fusion, p.731, Elsevier/North Holland Biomed. Press, 1978.