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Euglena

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Taxonomic lineage

cellular organisms - Eukaryota - Euglenozoa - Euglenida - Euglenales - Euglenaceae - Euglena -

Phylogeny

In 1786, Műller described small green flagellate he called Cercaria viridis. Subsequently, Ehrenberg (1830) renamed C. viridis to Euglena viridis, which is now recognized as the type species of the genus Euglena. There are about 65 species in the genus Euglena, and E. viridis and E. gracilis are most studied among them.

Euglena spp. belong to a large taxonomic group of unicellular organisms Euglenozoa that contain colorless and pigmented organisms. Among those are osmotrophs that lack a feeding apparatus and are able to absorb molecules directly from eutrophic environments, e.g., Distigma and Rhabdomonas, parasites such as Trypanosoma, Leishmania, Giardia , and phagotrophs that hunt and ingest particulate food, including bacteria and other unicellular organisms living in these environments. Among phagotrophs there are bacterivores that feed on bacteria (Petalomonas, Ploeotia and Entosiphon) and eukaryovores, e.g., Dinema, Peranema and Urceolus) that feed on eukaryotes. Many are also be capable of photosynthesis.

Typical Euglena are fusiform (have spindle-like shape of the cell that is wide in the middle and tapers at both ends) or cylindrical. They have two flagella (hence their common name Flagellates), with the second flagellum often being rudimentary. They also have one or more chloroplasts and feed osmotrophically and/or autotrophically (by photosynthesis, i.e., food is produced from inogranic substances and light).

For hundreds of years, zoologists claimed these fascinating organisms to be animals, while botanists regarded them as plants.

Photosynthetic euglenids are a clade of chimeric cells that are derived from a relatively recent endosymbiosis with green algal prey cells.

Photosynthetic euglenids adopted distinct flagellar beat patterns (e.g. a lasso or figure-eight beat pattern that pulls the cell forward), allowing them to stay in the water column above the substrate.

Photosynthetic euglenids have an enlarged flagellar pocket (reservoir), a photosensory swelling at the base of dorsal (emergent) flagellum and a carotenoid-based structure involved in phototaxis (stigma or eyespot).


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Brief facts

Euglena cell anatomy

Cell size varies widely within genus. Length ranges are 34-78 and width 5-24 μm.

Euglena cell anatomy

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Reproduction

There are no confirmed reports of sexual reproduction (production of haploid gametes and their union) in Euglena.

The following methods of asexual reproduction are reported in euglenoids:

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Life stages

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References and other resources


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