en.wikipedia.org/wiki/Contractile_vacuole
1 correction found
it expels the water through a pore in the cytoplasm which can be opened and closed
The pore is not in the cytoplasm. In Paramecium, discharge occurs at an excretory pore where the vacuole membrane fuses with the plasma membrane/cell surface.
Full reasoning
This sentence misplaces the excretory pore anatomically. The cytoplasm is the cell interior; the discharge pore is a specialized opening at the cell surface. Classic work on Paramecium describes expulsion through the excretory canal/pore, with the vesicular and cell membranes resealing after discharge. Later work likewise states that the vacuole membrane fuses with the plasma membrane at the pore region and the pore opens. So the pore is associated with the plasma membrane/cell surface, not "in the cytoplasm."
2 sources
- THE MECHANISM OF THE NEPHRIDIAL APPARATUS OF PARAMECIUM MULTIMICRONUCLEATUM I. Expulsion of Water from the Vesicle - PMC
Abstract: "At onset of expulsion... the membrane across the basal opening of the excretory canal is ripped along one semicircular portion of the excretory pore... A constriction of the vesicular and cell membranes at the base of the excretory canal reseals the opening."
- Development of periodic tension in the contractile vacuole complex membrane of paramecium governs its membrane dynamics.
Abstract snippet: "The vacuole membrane then fuses with the plasma membrane at the pore region and the pore opens."