 Algae-free (aposymbiotic) individuals are known, and a species that lacks algal symbionts, "Climacostomum gigas" Meunier 1907, has been identified, but not confirmed in recent literature.In its cortex, "Climacostomum virens" has colorless granules structurally similar to the defensive pigmentocysts found in its fellow Heterotrichs, "Stentor coreuleus" and "Blepharisma japonicum".When "Climacostomum" is threatened by a predator, such as the ciliate "Dileptus margaritifer," these cortical cysts release a defensive cytotoxin called Climacostol.