The cytoproct or cell anus of Paramecium caudatum was studied, using light optics and electron microscopy, at known times before, during and following food vacuole egestion. This was accomplished by microscopically observing single cells, fixing these cells at specific times and finally serial sectioning these individually processed cells. The cytoproct, at rest, is a long narrow ridge along the posterior suture. It contains 2 uniquely positioned components which identify this structure as the cytoproct: piles of fibres along the inside surfaces of the ridge, and microtubules passing from the epiplasm at the summit of the ridge down into the cytoplasm. The plasma membrane is continuous over the top of the ridge. The cortical basal bodies adjacent to the ridge have bundles of microtubules passing into the cytoplasm from an opaque plaque at their proximal ends. These 2 sets of microtubules may function in guiding the food vacuoles to the cytoproct. A model is presented in which motive forces generated between the microtubules and the food vacuole membrane bring the food vacuole to the cytoproct and, in addition, pull the cytoproct lips apart so that the food vacuole membrane and plasma membrane come into contact and fuse together, thus opening the food vacuole to the outside. The plasma membrane increases in area between the parting lips, possibly, as the result of intercalation of membrane vesicles into the plasma membrane at the top of the ridge. Immediately after this opening is formed the food vacuole membrane changes from a smooth topography to a highly convoluted one. The membrane is engulfed through a process of endocytosis resulting in an accumulation of membranous fragments in the cytoplasm below the cytoproct. The endocytic forces probably bring about the restitution of the cytoproct ridge by pulling the lips back together as the membrane is engulfed. A filamentous meshwork underlying the food vacuole membrane may be active in this endocytic process.
The Cytoproct of Paramecium Caudatum: Structure and Function, Microtubules, and Fate of Food Vacuole Membranes
RICHARD D. ALLEN, R. W. WOLF; The Cytoproct of Paramecium Caudatum: Structure and Function, Microtubules, and Fate of Food Vacuole Membranes. J Cell Sci 1 May 1974; 14 (3): 611–631. doi: https://doi.org/10.1242/jcs.14.3.611
Download citation file:
JCS Journal Meeting 2023: Imaging Cell Dynamics
Our 2023 Journal Meeting on ‘Imaging Cell Dynamics’ will be held from 14-17 May 2023 in Lisbon, Portugal. Due to popular demand, we can currently only accept applications for online attendance. Apply now to attend this meeting virtually. Registration deadline: 31 March.
Call for papers: Cell and Tissue Polarity
We are welcoming submissions for our next special issue, which will focus on ‘Cell and tissue polarity’ and will be guest edited by David Bryant. Submission deadline: 15 July.
Editorial: Publishing where it matters
Editor-in-Chief Michael Way outlines Journal of Cell Science’s plans for the upcoming year and introduces Seema Grewal as our new Executive Editor.
preLights 5th Birthday webinar
preLights, our preprint highlighting service, is celebrating its 5th birthday this year. To mark the occasion, join us online on 14 March 2023 at 16:00 GMT for a discussion, led by four preLights alumni, on how to identify and navigate the challenges and opportunities while shaping your career as an early-career researcher.
Cell Scientists to Watch
As a community-focused journal, Journal of Cell Science is keen to support the next generation of cell biologists. Check out Cell Scientists to Watch, our interview series featuring talented researchers who have recently set up their own labs.