Freshwater ciliate Colpidium campylum (400x)
These are freshwater ciliates of the species Colpidium campylum, characterized by its kidney-shaped cell. The cilia of this protozoan are arranged in rows, and inside you can see the two nuclei that are characteristic of many other ciliates, a more or less central macronucleus, and one micronucleus, slightly smaller.
Because it feeds on bacteria, Colpidium campylum is a microorganism involved in the process of self-purification of water. When the concentration of bacteria is very high in the water, and consequently food is abundant, the population of this protozoan multiplies. So, this species is regarded as a test-microorganism and is used in bioassays with a broad range of applications for single toxicants and contaminant mixtures, such as effluents.
[Protozoa - Ciliophora - Hymenostomatida - Tetrahymenidae - Colpidium - Colpidium campylum Stokes]
Technique: Interference Contrast.
References: [1] - [2] - [3]
Photo credit: ©Proyecto Agua | Locality: from a water sample collected in the Ebro river as it passes through Logroño river, La Rioja, Spain (2008)