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CHAPTER 7 Miscellaneous Protozoa
163
Cilia
Contractile
vacuole
Cyst wall
Micronucleus
Macronucleus
A
Size range: 43-66 m
B
Average size: 52-55 m
FIGURE 7-6 A, Balantidium coli cyst. B, Balantidium coli cyst. (B, from Mahon CR, Lehmann DC, Manuselis G: Textbook
of diagnostic microbiology, ed 4, St Louis, 2011, Saunders.)
TABLE 7-1
Balantidium coli
Trophozoite: Typical
Characteristics at a Glance
Parameter Description
Size range 28-152 µm in length, 22-123 µm
wide
Motility
Rotary, boring
Number of nuclei Two
Kidney-shaped macronucleus
Small spherical micronucleus
Other features One or two visible contractile
vacuoles
Cytoplasm may contain food
vacuoles and/or bacteria
Small cytostome present
Layer of cilia around organism
boring motility. The trophozoite contains two
nuclei.
A small dotlike nucleus (micronucleus) is
located adjacent to a large, often kidney bean–
shaped nucleus known as a macronucleus. The
micronucleus is often not readily visible, even in
stained preparations, whereas the macronucleus
may often appear as a hyaline mass, especially in
unstained preparations. Two contractile vacuoles
are located in the granular cytoplasm, although
sometimes only one is readily visible, as in Figure
7-5A. In addition, the cytoplasm may also contain
food vacuoles, as well as ingested microbes
TABLE 7-2
Balantidium coli Cyst:
Typical Characteristics at
a Glance*
Parameter Description
Size range 43-66 µm
Number and Two
appearance of Kidney-shaped macronucleus
nuclei
usually present
Small spherical micrcnucleus;
may not be observable
Other features One or two visible contractile
vacuoles in young cysts
Double cyst wall
Row of cilia visible in between
cyst wall layers of young
cysts
*Mature cysts typically only reveal macronucleus on examination.
The other structures are usually not apparent.
(bacteria). The trophozoite is equipped with a
small cytostome. A layer of cilia surrounds
the organism, which serves as its means of
locomotion.
Cysts. Averaging in size from 52 to 55 µm,
the subspherical to oval B. coli cyst may measure
from 43 to 66 µm (Fig. 7-6; Table 7-2). Although
the cyst technically contains the macronucleus
and micronucleus, the micronucleus may not
be observed in wet or permanent preparations.
One or two contractile vacuoles may be visible,