LESSON 2
PHYLUM PROTOZOO: CILIATA, PIROPLASMASIOA AND SPOROZOA
Section I. CLASS CILIATA
2-1.
GENERAL DESCRIPTION
These organisms use small, hair-like structures called cilia (singular: cilium) for
locomotion. The outer envelope of the organism is a tough but flexible area called the
pellicle. Food absorption is carried out by gathering food particles with the cilia and
forcing them down the gullet (cytostome), where a vacuole is produced which surrounds
the food. Digestion is accomplished by internal enzymes. Excretion of the unused food
is accomplished by expulsion through the anal pore (cytopyge).
2-2.
RESPIRATION AND REPRODUCTION
Hydrostasis with the environment is controlled by a pair of contractile vacuoles.
Respiration is performed by diffusion through the cell membrane. Reproduction may be
attained by simple cell division or by a complex exchange of genetic material between
two individuals. There is only one member of this class which is pathogenic to man:
Balantidium coli.
Figure 2-1. Typical ciliate.
MD0842
2-2