Cercomonad

Cercomonads are small flagellates, widespread in aqueous habitats and especially common in soils. The cells are generally around 10 &mu;m in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do not use them for locomotion, which usually takes place by gliding along surfaces. Most members have two smooth flagella, one directed forward and one trailing under the cell, inserted at right angles near its anterior. The nucleus is connected to the flagellar bases and accompanied by a characteristic paranuclear body.

Genetic studies place the cercomonads among the core Cercozoa, a diverse group of amoeboid and flagellate protozoans. They are divided into two families. The Heteromitidae tend to be relatively rigid, and produce only temporary pseudopods. The Cercomonadidae are more plastic, and when food supplies are plentiful may become amoeboid and even multinucleate. The classification of genera and species continues to undergo revision. Some genera have been merged, like Cercomonas and Cercobodo, and some have been moved to other groups.