Euglenophyceae

(botany) The single class of the plant division Euglenophyta.

A class coextensive with the division Euglenophycota, comprising unicellular colorless or photosynthetic flagellates with very distinctive cytological characters. In protozoological classification, these organisms constitute an order, Euglenida, of the class Phytomastigophora. Although photosynthetic euglenoids are like Chlorophycota in containing chlorophyll a and b, in most other respects they are so different from those algae as to suggest an independent phylogenetic origin of their pigments. About 1000 species have been described and classified into about 40 genera and 6 orders. See also Euglenida.

Most euglenoids are free-swimming and have two flagella, one of which may be nonemergent, arising from an anterior invagination known as a reservoir. Photosynthetic euglenoids contain one to many grass-green chloroplasts, which vary from minute disks to expanded plates or ribbons. Colorless euglenoids depend on osmotrophy or phagotrophy for nutrient assimilation.

Euglenoids are found most commonly in fresh water rich in organic matter, but they also occur in marine or brackish habitats, on mud or sand, and in ice or snow. A few species prefer very acidic water.