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The cytoproct ridge at higher magnification. The unique system of
thick fibers extends from each side of the ridge toward the center of
the ridge. These thickened fibers are not found in any other part of
the cell’s surface. Also extending from the ridge tip are single
microtubules (arrowheads) that extend down into the cytosol.
These microtubules may make contact with the surface of the
approaching vacuole’s membrane and help to pull the vacuole membrane
and the plasma membrane together to promote their fusion. The role of
the thickened fibers is unclear, they may cross link to prevent the
cytoproct from an untimely opening under stress. A few vesicles get
trapped in the ridge. al, alveolus. EM taken on 6/1/84 by R.
Allen with Zeiss 10A TEM. Neg. 19,800X. Bar = 0.2µm.
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