EUGLENIDA

Most euglenids occur in fresh water, but a few marine and brackish-water species are known. the majority are noncolonial, but some colonial forms exist. Euglenids come in a wide variety of shapes elongate, spherical, ovoid, or leaf shaped. This group includes organisms such as the familiar genus euglena, which has been used extensively in research laboratories and is commonly studied in introductory biology and invertebrate zoology courses.

the phyla Euglenida and Kinetoplastida appear to be closely related, even though many euglenids are photosynthetic and most kinetoplastics are parasitic heterotrophs.

The morphological features they share include linked microtubules underying the cell mmebrane, discoidal cristae in a single large mitochondrion, flagella containing a lattice like supportiverod, and a similar pattern of mitosis. molecular studies, using sequences from the gene for ribosomal DNA, also indicate that these are closely related proups. Euglenids are commonly found in bodies of water rich in decaying organic matter. As such, some of them are useful indicator organism of water quality. Some species of euglena have been used in experiments for waste water treatment and have been reported to extract heavy metals such as magnesium, iron, and zinc from sludge. Other euglenids, however, are environmental pest, and some have been shown to produce toxic substances which have been associated with diseases in trout fry. Others are responsible for toxic blooms, which have caused massive destruction of fishes and molluscs in Japan.