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The nascent digestive vacuole (nfv) forms as the membrane of
flattened vesicles (disc) fuse (arrowhead) with the
single membrane of the cytopharynx between the lamellae
(arrows, 2 microtubules forming a lamella) that are connected
along their length to the membrane at the cytopharynx. Another portion
of the forming vacuole is associated with the ends of the 4 element-
(4 mt) and 2 element- (2 mt) microtubular ribbons that
come from the oral ribs. These ribbons are covered with specialized
cytoplasm (sc) and do not take part in moving discoidal
vesicles to the vesicle fusion region. One feature of the nascent
vacuole in Tetrahymena that I have never observed in
Paramecium is the presence of coated pits (cop)
extending from the vacuole membrane. Finally, vesicles previously
called lysosomes, which to me resemble the late endosomes, acidosomes
(ac), of Paramecium, dock at the growing vacuole. For a
review of the literature of phagocytosis in Tetrahymena see
Nilsson, Biochemistry and Physiology of Protozoa, 2nd ed., Academic
Press, pp. 339-379, 1979; Sattler and Staehelin, J. Ultrastructure
Res. 66:132-150, 1979; and Baumert et al., Eur. J. Protistol.
34:291-300, 1998. EM taken on 8/15/67 by R. Allen with Philips 200
TEM. Neg 19,200X. Bar = 0.5µm.
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