Section III CLASS ZOOMASTIGOPHORA
These organisms move by means of rotation of a whiplike organelle called a
flagellum (plural: flagella). The flagella can also be used for gathering and sorting food.
Respiration, food absorption, and excretion can be performed by osmosis and active
transport across the cell membrane. Some species have organelles for the purpose of
food ingestion (gullet or cytostome), and for excretion (cytopyge). Encystation may be
used by these organisms in response to adverse environment and/or for reproduction.
The parasitic members of this class are divided into two groups: the lumen flagellates,
which inhabit the body orifices, the intestines and the bladder; and the blood and tissue
flagellates. There are many members of this class which are pathogenic to man.
These include lumen flagellates such as Giardia lamblia and members of the
Trichomonas species and blood and tissue flagellates from the Trypanosoma and
Figure 1-20. Typical flagellate.