Euglenophyta include mostly unicellular flagellates (Figure 1.39) although colonial species are
common. They are widely distributed, occurring in freshwater, brackish and marine waters, most
soils, and mud. They are especially abundant in highly heterotrophic environments. The flagella
arise from the bottom of a cavity called reservoir, located in the anterior end of the cell. Cells
can also ooze their way through mud or sand by a process known as metaboly, a series of
flowing movements made possible by the presence of the pellicle, a proteinaceous wall which
lies inside the cytoplasm. The pellicle can have a spiral construction and can be ornamented.
The members of this division share their pigmentation with prochlorophytes, green algae, and
land plants, because they have chlorophylls a and b, β- and γ-carotenes, and xanthins. However,
plastids could be colorless or absent in some species. As in the Dinophyta the chloroplast envelope
consists of three membranes. Within the chloroplasts, the thylakoids are usually in groups of three,
without a girdle lamella and pyrenoids may be present. The chloroplast DNA occurs as a fine skein
of tiny granules. |
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FIGURE 1.39 Unicell of Euglena mutabilis. (Bar: 10 µm.) |
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