Blepharisma is a ciliate protozoan that looks something like Paramecium (the genus of common ciliates named in many submissions to our contest). The cell is about 200 µ in length and has many vacuoles, including a very large contractile vacuole at the posterior end.

Blepharisma is covered with short cilia, except in the oral groove, where there are both longer membranelles (cilia bundles) and an undulating membrane running along a portion of the groove.

The pink pigment is held in small vesicles below the membrane surface. If cultures of Blepharisma are left in the light for extended periods, the pink pigments fade away, whereas, the color of Blepharisma left in the dark is intensified. The role of the pigment is not yet understood.

Blepharisma can often be found in stagnant pond water cultures. They usually eat bacteria, but may become cannibalistic when the bacteria food supply is short, in which case the color becomes more intense.

To learn more about ciliates, see our program, Branches on the Tree of Life: Protists. For a rich overview of freshwater biology, see our program: The Biology of Lakes Ponds, Streams and Wetlands.