diploid micronucleus. The diploid micronucleus undergoes two mitotic divisions, so each cell has four micronuclei,
and two of the four combine to form a new macronucleus. The chromosomes in the macronucleus then replicate
repeatedly, the macronucleus reaches its polyploid state, and the two cells separate. The two cells are now genetically
different from each other and from their previous versions.
Protozoan conjugation is illustrated in thisanimation
(https://openstaxcollege.org/l/22proconjanim).Figure 5.13 This specimen of the ciliateBalantidium coliis a trophozoite form isolated from the gut of a primate.B.
coliis the only ciliate capable of parasitizing humans (scale bar = 5 μm). (credit: modification of work by Kouassi
RYW, McGraw SW, Yao PK, Abou-Bacar A, Brunet J, Pesson B, Bonfoh B, N’goran EK & Candolfi E)
Figure 5.14 Parameciumhas a primitive mouth (called an oral groove) to ingest food, and an anal pore to excrete it.
Contractile vacuoles allow the organism to excrete excess water. Cilia enable the organism to move.
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Chapter 5 | The Eukaryotes of Microbiology 195