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Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. [1] [2] Species of Euglena are found in fresh water and salt water.
Euglenaceae show the most morphological diversity within the class Euglenophyceae. [3] They are mostly single-celled organisms, except for the genus Colacium.They are free-living or sometimes inhabiting the digestive tracts of animals. [1]
The term continues to be used in a loose way to describe single-celled protists (that is, eukaryotes that are not animals, plants, or fungi) that feed by heterotrophy. [9] Traditional textbook examples of protozoa are Amoeba, Paramecium, Euglena and Trypanosoma. [10]
Euglena gracilis is a freshwater species of single-celled alga in the genus Euglena. It has secondary chloroplasts , and is a mixotroph able to feed by photosynthesis or phagocytosis . It has a highly flexible cell surface, allowing it to change shape from a thin cell up to 100 μm long to a sphere of approximately 20 μm.
[36] [37] Protozoa, like plants and animals, can be considered heterotrophs or autotrophs. [33] Autotrophs like Euglena are capable of producing their energy using photosynthesis, while heterotrophic protozoa consume food by either funneling it through a mouth-like gullet or engulfing it with pseudopods, a form of phagocytosis. [33]
Later, various biologists described additional characteristics for Euglena and established different classification systems for euglenids based on nutrition modes, the presence and number of flagella, and the degree of metaboly.
Euglenales consists mostly of freshwater organisms, in contrast to its sister Eutreptiales which is generally marine. Cells have two flagella, but only one is emergent; the other is very short and does not emerge from the cell, so cells appear to have only one flagellum. [3]
A protist (/ ˈ p r oʊ t ɪ s t / PROH-tist) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus.Protists do not form a natural group, or clade, but are a polyphyletic grouping of several independent clades that evolved from the last eukaryotic common ancestor.