Toxoplasmea

(invertebrate zoology) A class of the protozoan subphylum Sporozoa composed of small, crescent-shaped organisms that move by body flexion or gliding and are characterized by a two-layered pellicle with underlying microtubules, micropyle, paired organelles, and micronemes.

A class of the subphylum Sporozoa. The organisms are small and crescent-shaped. They move by body flection or gliding and have no flagella or pseudopodia. Characteristic structures are the two-layered pellicle and underlying longitudinal microtubules, micropyle, a conoid, paired organelles, and micronemes.

The most distinguishing characteristic of the Toxoplasmea is the unique means of reproduction. Electron microscope studies indicate that endodyogeny is the sole method. Endodyogeny is an internal budding wherein two daughter cells are produced within a mother cell which is destroyed in the process.

Only two stages are known in the life cycle most animals. One stage, the proliferative form or trophozoite, occurs singly or in groups within host cells. The other stage, the so-called cysts, consists of a large number of organisms which, with minor differences, are structurally similar to the proliferative forms. See also Sporozoa; Toxoplasmida.