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When a spent vacuole has fused with the single membrane along the
midline of the ridge the lips of the cytoproct (cyp) split
apart and form a wide gap. The membrane of the spent vacuole is now
continuous with the plasma membrane and quickly undergoes vesiculation
into vesicles that are released back into the cytosol. No membrane is
released into the surrounding environment. The cytoproct lips are
covered by extensions of alveoli (al) up to their tips.
Complete defecation is insured by the retrieval of all of the spent
vacuole membrane until the lips are pulled back together at the tip of
the ridge and all DV-IV membrane has been removed from the cytoproct.
No other expulsion force is needed for expelling the vacuole contents.
EM taken on 5/25/82 by R. Allen with Hitachi HU11A TEM. Neg. 6,500X.
Bar = 1µm.
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