What is "climacostomum"

Climacostomum is a genus of unicellular ciliate protists, belonging to the class Heterotrichea.

The genus has one well-described species, Climacostomum virens, which usually carries a symbiotic alga, a variety of Chlorella that can be cultivated outside its host. 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. This substance has been synthesized in the laboratory and found to be highly toxic to certain species of ciliates. It is believed that this toxicity is accomplished by the inhibition of mitochondrial respiration. It has been shown to have toxic effects on certain human cancer cells.