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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4210

Timothy W. Mislan and Harriett E. Smith-Somerville; Food Vacuole Morphology and Membrane Retrieval in the Microstomal Form of Tetrahymena vorax. J.Protozool. 33(2):172-179, 1986

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After formation, food vacuoles in the microstomal cell type of Tetrahymena vorax labeled with either India ink or cationized ferritin (CF) undergo three morphological stages during processing: a initial condensation with a size decrease, the appearance of a clear halo around the condensed marker that apparently results from expansion of the vacuole, and the disppearance of the halo region. These stage correspond generally to three of the four stages described previously for Tetrahymena. Fusion of older vacuoles prior to egestion may represent a fourth stage in vacuole processing. The developing vacuole has small coated regions of the membrane; two populations of vesicles, small coated vesicles and larger vesicles with electron-dense cores, are adjacent to it. During the initial condensation, tubular invaginations with CF project from the vacuole. After the disappearance of the halo, much of the vacuolar surface appears to be multilayered with extensive folds containing CF. Labeled flattened or curved disks and closed rings occur in the cytoplasm often adjacent to labeled vacuoles and in the vicinity of the cytoproct. The appearance of labeled disks and rings is identical to both labeled and unlabeled vesicles adjacent to the cytopharynx, additional support to the hypothesis that, like Paramecium, vesicles retrieved from food vacuoles during processing as well as after fusion with the cytoproct may be reused for vacuole formation.