Phylum Apicomplexa - Protozoan

Characteristic set of organelles (apical complex) asssociated with the anterior end present in some developmental stages. Cilia and flagella absent except for flagellated microgametes in some groups; cysts often present; all species parasitic.

• Class - Perkinsea

Small group parasitic in Oysters.

• Class - Sporozoa

Spores or oocysts present that contain infective sporozoites that result from sporogony; locomotion of mature organism by body flexion, gliding or undulation of longitudinal ridges; flagella present only in microgametes of some species; pseudopods ordinarily absent, wherever present they are used for feeding not locomotion; one or two host life cycles.

Examples: Monocysris, Gregarina, Toxoplasma, Plasmodium.