The name "epixenosomes" comes from the ancient Greek επι ξενον σομα, meaning "external alien body", referring to their extracellular position on the host.

The extrusive apparatus ejects its contents when triggered; this process helps to defend the ciliate host against predators.

[3] External signals of unknown origin are detected by the membrane receptors located at the top of the organism.

The consequent activation of the adenylate cyclase-cAMP system triggers the ejection of the extrusive apparatus, with the formation of a hollow tube, about 40 μm long, terminating in a head mainly consisting of the apical portion of the epixenosome (the region containing DNA).

Experiments with antitubulin drugs and immunocytochemical analyses at the optical and electron microscopical level suggested that these tubules consist of tubulin, which is a eukaryotic protein.