Carchesium sp.

Let’s talk about Carchesium, creatures that look like flowers under the microscope when moving their heads and crown of petals happily in the water. Every aquarist regularly cleans the aquarium by changing the water and wiping the glass with a soft sponge. Protozoal micro-organisms, algae, micro-worms, and other creatures form communities that continuously grow on the glass and decorative items of our aquarium. This unsightly dirt, that we mercilessly scrub off, may conceal secrets that are only revealed under a microscope. Let’s dive into it!

What are Carchesium sp.?

Carchesium sp. are sessile infusoria of the family Vorticellidae belonging to the order of Sessilidae, which proliferate and form colonies resembling bouquets of flowers. The peculiarity of their lifestyle is that they can only swim freely for a short time after birth, until they attach themselves, contrary to their free-living relatives of the family Mobilida, which remain mobile. Carchesium need a substrate to which they attach with a stalk. This stalk contains the myoneme, a special contractile fibril that individual cells or the entire colony can rapidly contract when danger occurs.


The shape of the infusoria resembles a drinking cup, which the ancient Greeks called Carchesium, where the name of the whole genus of protozoa comes from.


They are completely harmless to fish: Carchesium are single-celled microorganisms that actually fulfill a useful function in the aquarium. Through the movement of the cilia at the opening of the mouth, the peristome, they create a flow of water, which sucks tiny organic material like fish feces, food remnants, algae and bacteria towards it. Thus the sessile infusoria help in the breakdown of organic matter, dwelling not only on the aquarium glasses but also in the filtration system, contributing to the purification and improvement of the water quality in the aquarium.


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