endodyogeny

Endodyogeny is a form of asexual reproduction used by certain intracellular protozoan parasites in the phylum Apicomplexa, most notably Toxoplasma gondii and Neospora caninum. In this mode of replication, two daughter cells develop within the cytoplasm of the mother parasite and eventually replace it.

The process begins with division of the parental nucleus, followed by the formation of two daughter buds inside the maternal cytoplasm. Each bud acquires organelles and cytoplasm and grows to mature size. As development proceeds, the original maternal cell is consumed, and the two mature daughter cells are released to continue the life cycle and infect new host cells.

Endodyogeny is distinct from schizogony, in which multiple rounds of nuclear division produce numerous daughter cells before cytokinesis. It differs from a simple binary fission process, which yields two daughter cells through a single division event; in endodyogeny the two daughters form within the mother and the mother is replaced rather than simply split.

The mode is characteristic of intracellular replication during host infection. In Toxoplasma gondii tachyzoites, endodyogeny supports rapid intrahost expansion during acute infection, allowing parasites to multiply within a range of host cell types, including fibroblasts and macrophages. The method illustrates the diversity of intracellular reproductive strategies among apicomplexan parasites, alongside related internal budding processes such as endopolygeny that can produce more than two daughters.