9 Cryptomonads

Cryptomonads, their name literally meaning “hidden single cells,” are among the most inconspicuous of the algae. There are several reasons for this. First, cryptomonads are relatively small flagellates, ranging from 3 to 50 µm in length. In addition, cryptomonads are readily eaten by a wide variety of herbivores and so they tend to be found in low numbers. Further, they are often most numerous in cold or deep habitats that people sample less often than warmer surface waters. Finally, cryptomonad cells tend to burst when subjected to environmental shock or preservatives, and thus may not persist for long in water samples. Despite their low profile, cryptomonads are important in both natural systems and aquaculture operations as high-quality food for zooplankton (Chapter 3). In addition, evolutionary biologists recognize the relevance of cryptomonad cell structure to our understanding of secondary endosymbiosis (see Chapter 7). This chapter surveys the relationships, cell biology, reproduction, ecology, and diversity of cryptomonads.