Species of Coleps can grow up to 250 µm in length, but are usually under 100 µm in their longest axis. Coleps can be taxonomically distinguished by the ornamentation of the ectoplasmic plates which make up their test. These plates are located outside alveolar vesicles of the cell cortex, and contain both organic and inorganic components, the latter of which is mostly amorphous calcium carbonate.
Coleps feeds on bacteria, algae, flagellates, living and dead ciliates, animal and plant tissues. Coleps uses toxicysts, which are organelles containing poison that it uses to capture its prey from its oral area. It extrudes tube-like structures to force toxicysts into its prey and wait until its prey becomes paralyzed. These toxicysts, however, takes about 5–10 minutes to be effective on the prey of the Coleps and it separates itself from the prey during this time. If there are numerous Coleps hunting for the same prey, some Coleps will cling to its prey until the toxicysts become effective and fragment the prey, consuming only a few parts.
- Carey, Philip G. (1992). Marine Interstitial Ciliates : An Illustrated Key. London ; New York: Chapman Hall. pp. 44–47. ISBN 0-412-40610-1.
- Lemloh, Marie-Louise; Marin, Frédéric; Herbst, Frédéric; Plasseraud, Laurent; Schweikert, Michael; Baier, Johannes; Bill, Joachim; Brümmer, Franz (2013). "Genesis of amorphous calcium carbonate containing alveolar plates in the ciliate Coleps hirtus (Ciliophora, Prostomatea)". Journal of Structural Biology. 181 (2): 155–161. doi:10.1016/j.jsb.2012.12.001. PMID 23228488.
- Buonanno, Federico; Anesi, Andrea; Guella, Graziano (January 2014). "Chemical Offense by Means of Toxicysts in the Freshwater Ciliate, Coleps hirtus". Eukaryotic Microbiology. 61 (3): 293–304. doi:10.1111/jeu.12106. PMID 24512001.
- Wickham, Stephen A.; Gugenberger, Eva (November 2008). "Evaluating inducible morphological defences in the common freshwater ciliate, Coleps hirtus". Journal of Plankton Research. 30 (11): 1315–1321. doi:10.1093/plankt/fbn076. Retrieved 12 February 2015.
- “A comical beastie” at Microscopy-UK