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Euglenids (euglenoids, or euglenophytes, formally Euglenida, ICZN, or Euglenophyceae, ICBN) are one of the best-known groups of flagellates, which are Excavate Eukaryotes of the phylum Euglenophyta and their cell structure is typical of that group. They are commonly found in freshwater, especially when it is rich in organic materials, with a few marine, and endosymbiotic members. Most euglenids are unicellular. Many euglenids have chloroplasts and produce energy through photosynthesis, but others feed by phagocytosis, or strictly by diffusion. This group is known to contain carbohydrate paramylon.

Euglenoids descend from an ancestor that took up green algae by secondary endosymbiosis.^[2]

Structure and locomotion

Euglenoids are distinguished mainly by the presence of a pellicle (periplast), which is composed of proteinaceous strips underneath the cell membrane, supported by dorsal and ventral microtubules. This varies from rigid to flexible, and gives the cell its shape, often giving it distinctive striations. In many euglenids the strips can slide past one another, causing an inching motion called metaboly. Otherwise they move using the flagella.

History and classifications

The euglenoids were first defined by Otto Bütschli in 1884 as the flagellate order Euglenida, as an animal. Botanists subsequently created the algal division Euglenophyta; thus they were classified as both animals and plants, as they share characteristics with both. This conflict is an example of why the kingdom Protista was adopted. However, they retained their double-placement until the flagellates were split up, and both names are still used to refer to the group. Their chlorophyll are not masked with accessory pigments.

Classification and nutrition

The classification of euglenoids is still variable, as groups are being revised to conform with their molecular phylogeny. To some extent, however, the results support the traditional groups based on differences in nutrition and number of flagella; at any rate these provide a starting point for considering euglenid diversity.

As with other Euglenozoa, the primitive mode of nutrition is phagocytosis. Prey such as bacteria and smaller flagellates are ingested through a cytostome, supported by microtubules. These are often packed together to form two or more rods, which function in ingestion, and in Entosiphon form an extendable siphon. Most phagotrophic euglenids have two flagella, one leading and one trailing. The latter is used for gliding along the substrate. In some, such as Peranema, the leading flagellum is rigid and beats only at its tip.

Osmotrophic euglenoids

A prolonged absence of light or exposure to harmful chemicals may cause atrophy and absorption of the chloroplasts without otherwise harming the organism. There are a number of species where a chloroplast's absence was formerly marked with separate genera such as Astasia (colourless Euglena) and Hyalophacus (colourless Phacus). Since they lack a developed cytostome, these forms feed exclusively by absorption.

References

^ lee, R.E. (2008). Phycology, 4th edition. Cambridge University Press. ISBN 978-0-521-63883-8.
^ Keeling PJ (2009). "Chromalveolates and the evolution of plastids by secondary endosymbiosis". J. Eukaryot. Microbiol. 56 (1): 1–8. doi:10.1111/j.1550-7408.2008.00371.x. PMID 19335769.

3. Agwata S.Nyamoki:BSc Aqua/11 B

4.NCERT.Biology text:plusone/2.2.3

Bibliography

Ciugulea, I. & Triemer, R. E. (2010) A Color Atlas of Photosynthetic Euglenoids. Michigan State University Press, East Lansing, MI, 204 p., [1].
Wołowski, K & Hindák, F. (2005). Atlas of Euglenophytes. Cracow: VEDA Publishing House of the Slovak Academy of Sciences, 136 p., [2].

External links

The Euglenoid Project
Tree of Life: Euglenida

English Journal

An overview on kinetoplastid paraflagellar rod.

Maharana BR1, Tewari AK2, Singh V3.
Journal of parasitic diseases : official organ of the Indian Society for Parasitology.J Parasit Dis.2015 Dec;39(4):589-95. doi: 10.1007/s12639-014-0422-x. Epub 2014 Feb 7.
Kinetoplastids, the evolutionary ancient organisms exhibit a rich and diverse biology which epitomizes many of the fascinating topics of recent interest and study. These organisms possess a multifunctional organelle, the flagellum containing a canonical 9 + 2 axoneme which is involved in vital rol
PMID 26688619

Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis.

Giometto A1, Altermatt F2, Maritan A3, Stocker R4, Rinaldo A5.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2015 Jun 2;112(22):7045-50. doi: 10.1073/pnas.1422922112. Epub 2015 May 11.
Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to
PMID 25964338

Characterization and physiological role of two types of chloroplastic fructose-1,6-bisphosphatases in Euglena gracilis.

Ogawa T1, Kimura A1, Sakuyama H1, Tamoi M2, Ishikawa T3, Shigeoka S1.
Archives of biochemistry and biophysics.Arch Biochem Biophys.2015 Jun 1;575:61-8. doi: 10.1016/j.abb.2015.04.002. Epub 2015 Apr 20.
The chloroplastic fructose-1,6-bisphosphatase (FBPase) is a late-limiting enzyme in the Calvin cycle. In the present study, we isolated and characterized the cDNAs encoding two types of chloroplastic FBPase isoforms (EgFBPaseI and II) from Euglena gracilis. The Km values of recombinant EgFBPaseI and
PMID 25906744

Japanese Journal

湛水期間中の水田水生生物群集の生息場所について

山崎真嗣,濱田千裕,神本宣親,籾井隆志,木村眞人
Edaphologia (74), 1-10, 2004-02-28
NAID 110003891286

Seasonal Variations in the Community Structure of Aquatic Organisms in a Paddy Field under a Long-Term Fertilizer Trial

Yamazaki Masatsugu,Hamada Yukihiro,Ibuka Takeo,Momii Takashi,Kimura Makoto
Soil science and plant nutrition 47(3), 587-599, 2001-09
… The frequency of the presence of Chlorococcales, Lemanaceae, Euglenida, Oligotrichida, Pharyngophorida, Sessilida, Turbellaria, Podocopida, and Cyclopoida was significantly different among the plots, while the maximum population density was significantly different for Cladocera and Cyclopoida among the plots. …
NAID 110001718654

落水後の水田水生生物群集の生息場所について

山崎真嗣,濱田千裕,神本宣親,籾井隆志,木村眞人
Edaphologia (68), 23-31, 2001-08-31
愛知県安城農業技術センター内の水田において,水稲収穫後の水田土壌,刈株,およびコンバインによる収穫後放置された稲わらの部位に休眠状態で留まった水生生物群集の組成を調査した.調査は1998年10月から1999年3月まで実施した.水生生物群集は,主として目(order)のレベルで分類された.その結果,36種類の水生生物が確認された.水生生物群集の種類数が最も豊富であったのは刈株直下の表層土壌であった. …
NAID 110003946371

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★リンクテーブル★

リンク元	「Euglena」「ミドリムシ目」「ユーグレナ目」

「Euglena」

Euglenids; Temporal range: Eocene (53.5Ma) - recent
Scientific classification
Domain:	Eukaryota
(unranked):	Excavata
Phylum:	Euglenozoa
Class:	Euglenida; Stein, 1878, Simpson, 1997
Major groups
	Phototrophs; Euglenales; Eutreptiales; Osmotrophs; Rhabdomonadales; Phagotrophs; ?Heteronematales; ?Sphenomonadales
Synonyms
	Euglenoidina Bütschli, 1884, Blochmann, 1886; Euglenoidea Lankester, 1885, Hartmann & Chagas, 1910; Euglenophyceae Schoenichen, 1925; Euglenophyta Pascher, 1931; Euglenoida Cavalier-Smith, 1993;