extrusome

Extrusomes are membrane-bound organelles found in eukaryotic cells that are capable of discharging material contained within to the exterior of the cell. Due to the diversity in structure and function, it is unlikely that different types of extrusomes are homologous.

Some notable extrusomes include mucocysts, which discharge a mucous mass sometimes used in cyst formation, and trichocysts, which discharge a fibrous rod. Nematocysts, the stinging structure found in Cnidarian animals, could be considered extrusomes as well, though those functions are performed by differentiated cells rather than organelles. Other extrusomes include the ancoracyst, a specialized extrusome found in the Provoran eukaryote Ancoracysta twista used to immobilize prey.