[1] 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.

[11] Peck et al. report that these are not contained within a membrane, but are in direct contact with the host's cytoplasm; however, other observers have noted the presence of perialgal vacuoles around the algae.

[9] In a detailed study of its physical characteristics, published in 1972, Arthur J. Repak placed Climacostomum with the genus Fabrea in a new family he named Climacostomidae.

[7] Recently, molecular analyses have shown that, while the Heterotrichea as a whole are a monophyletic group, the taxon Climacostomidae is paraphyletic, the genus Fabrea being more closely related to the ciliates Eufolliculina and Maristentor than to Climacostomum.