EUGLENIDS
CHARACTERISTICS	They are single-celled organisms. They carry out all of life´s functions using only the organelles found in the “typical” eukaryotic cells of animals. Euglenoids detect light using a pigmented eyespot or stigma red and paraflagellar body located at the base of the flagellum emerging. All have two flagella euglenoids rooted basal bodies located in a small reservoir at the front of the cell. In Euglena, a flagellum is very short and does not protrude from the cell, while the other is relatively long, and often readily visible under light microscopy. Euglena lacks a cell wall. Instead, has a film formed by a layer of protein on the support of a substructure of microtubules, spiral strips disposed around the cell.
FORM	They are often discoidal in shape but can also be ovate, lobate, elongate, U-shaped, or ribbon-shaped.
HABITAT	Most euglenids occur in fresh water, but a few marine and brackish- water species are known. Freshwater euglenoids have a contractile vacuole.  The majority  are  noncolonial but some colonial forms exist. It usually live in quiet ponds or puddles Species of  Euglena. They are often abundant in quiet, inland waters, where they may bloom in numbers sufficient to color the surface of ponds and ditches green or red.
SUPPORT AND LOCOMOTION	: the shape of euglenids is maintained by a pellicle consisting of interlocking strips of protein lying beneath the cell membrane. the stripes that can sometimes be seen on a euglenid are the seams between the long protein strips winding around the cell. often the pellicle is suported by regularly arranged microtubules lying just underneath it. the rigidity of the pellicle is variable. some have protein strips that are fused together into a rigid pellicle, while others have protein strips that are articulated to produce a flexible pellicle. those euglenids with a flexible pellicle undergo euglenoid movement, or metaboly, in which the cell undulates as it rapidly extends and contracts . although this type of  movement is not fully understood it is thought to be accomplished by the sliding of microtubules againsr t the protein strips. a few euglenids secrete a lorica, or envelope exterior to the cell membrane . the lorica is formed by the mucous secretions of small organelles called mucocysts membrane along the seams between the protein strips of the pellicle. secretions of mucocysts are also used to form protective coverings when environmental conditions become unfavorable locomtion in euglenids is primarily by flagella. they have two flagella but one may be very short or represented by just a kinetosome. the flagella originate in an invagination at the anterior end of the cell called a reservior. the longer, anteriorly directed flagellum propels the cell through the water or across surfaces. the shorter flagellum either trails behind for does not emerge from the reservoir at all. both flagella have a single row of hairs on their surface and a lattice-like supporting rod, called the paraxonemal rod, lying adjacent to the microtubules within the shaft.
NUTRITION	Euglenids are quite variable in their nutrition. Aproximately one- third have chloroplasts and are photo-autotrophic. these are positively phototaxic and have a swelling near the base of the anterior flagellum that acts as a photoreceptor. the chloroplasta is surrounded by three membranes and has thylakoids that are arranged in stacks of three- the photosynthetic pigments include: chlorophylls a and b, phycobilins,  ß- carotene and the xanthophylls neoxanthin and diadinoanthin. When feeding as a heterotroph, the Euglena surrounds a particle of food and consumes it by phagocytosis. The cytoplasm of Euglena and other euglenoids contains many paramylon starch storage granules.
REPRODUCTION	Asexual reproduction in euglenids is by longitudinal cell division. Division occurs along the longitudinal plane. Sexual reproduction has been reported in one species, but this has not been confirmed.
ECOLOGY	Euglenids are commonly found in bodies of water rich in decaying organic matter. As such some of them are useful indicator organisms of water quality. some species of euglena have been used in experiments for waste metals such as magnesium, iron and zinc from sludge.  Other euglenids, however, are environmental pests and some have been shown to produce toxic substances which have been associated with diseases in trout fry.

flexible movement in Euglena

 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.