Life cycle stage

• During its lifecycle, protozoa generally pass through several stage, that differ in structure and activity.

a. Trophozoite

• Active, feeding, multiplying stage of most protozoa.
• In case of hemoflagellates, teron amastigote, promastigote, epimastigote and frymastigote are used to demonstrate trophozoite stages.
• In some amoebas and apicomplexa, multiple fission (merogony, schizogony) occurs. In this type of division, large number of daughter cells are produced.
• Cells under schizogony are called schizonts meronts. These schizonts nuclei arrange themselves peripherally, with membrane of daughter cells beneath the cell surface of mother cell. Merozoites are formed resulting from fission of multinucleate schizont.

b. Sporozoite

• Infective stage of some protozoa.
• Motile spore-like stage in lifecycle of some parasitic sporozoans.
• In a sexual form of reproduction in sub-phylum sporozoan, called as schizogony. Trophozoite grows in a large size while nucleus divides repeatedly. This structure is called schizont. These schizonts when mature acquire a portion of cytoplasm so that schizont is filled with large number of elongated separate organism called merozoites.