Choanoflagellates

Choanoflagellates are 5-10 micron, colorless flagellates which have a distinct collar. They may be solitary or colonial, may possess either a chitinous or siliceous lorica, and may live free in the water, or attached to substrates such as the setae (spines) of the Chaetoceros affinis in this photograph. They are divided into three groups, each recognized as a family. Choanoflagellates feed on bacteria, and are common contaminants of Chaetoceros cultures. On several occasions I have maintained balanced "community cultures" of Chaetoceros, choanoflagellates and bacteria for extended periods of time.

More information about choanoflagellates can be found in:

Sieburth, J.McN. (1979) - Sea Microbes. New York: Oxford University Press, Inc., pp. 377-379.

Yellow arrows denote individual choanoflagellate cells. The collars are barely visible on the two cells at lower left.