Euglenids (euglenoids, or euglenophytes, formally Euglenida/Euglenoida, ICZN, or Euglenophyceae, ICBN) are one of the best-known groups of flagellates, which are excavateeukaryotes 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. Many euglenids feed by phagocytosis, or strictly by diffusion. A monophyletic group consisting of the mixotrophic Rapaza viridis (1 species) and the two groups Eutreptiales (24 species) and Euglenales (983 species) have chloroplasts and produce their own food through photosynthesis.[3][4][5] This group is known to contain the carbohydrate paramylon.
Euglenids split from other Euglenozoa more than a billion years ago. The plastids in all extant photosynthetic species is the result from secondary endosymbiosis between a phagotrophic eukaryovorous euglenid and a Pyramimonas-related green alga.[6]
Euglenoids are distinguished mainly by the presence of a type of cell covering called a pellicle. Within its taxon, the pellicle is one of the euglenoids' most diverse morphological features.[7] The pellicle 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 their flagella.
The euglenids 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. Conflicts of this nature are exemplary 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 chlorophylls are not masked with accessory pigments.
Nutrition
The classification of euglenids is still variable, as groups are being revised to conform with their molecular phylogeny. Classifications have fallen in line with the traditional groups based on differences in nutrition and number of flagella; these provide a starting point for considering euglenid diversity. Different characteristics of the euglenids' pellicles can provide insight into their modes of movement and nutrition.[8]
As with other Euglenozoa, the primitive mode of nutrition is phagocytosis. Prey such as bacteria and smaller flagellates is 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
Osmotrophic euglenids are euglenids which have undergone osmotrophy.
Due to a lack of characteristics that are useful for taxonomical purposes, the origin of osmotrophic euglenids is unclear, though certain morphological characteristics reveal a small fraction of osmotrophic euglenids is derived from phototrophic and phagotrophic ancestors.[9]
A prolonged absence of light or exposure to harmful chemicals may cause atrophy and absorption of the chloroplasts without otherwise harming the organism. A number of species exists where a chloroplast's absence was formerly marked with separate genera such as Astasia (colourless Euglena) and Hyalophacus (colourless Phacus). Due to the lack of a developed cytostome, these forms feed exclusively by osmotrophic absorption.
Reproduction
Although euglenids share several common characteristics with animals, which is why they were originally classified as so, no evidence has been found of euglenids ever using sexual reproduction. This is one of the reasons they could no longer be classified as animals.
For euglenids to reproduce, asexual reproduction takes place in the form of binary fission, and the cells replicate and divide during mitosis and cytokinesis. This process occurs in a very distinct order. First, the basal bodies and flagella replicate, then the cytostome and microtubules (the feeding apparatus), and finally the nucleus and remaining cytoskeleton. Once this occurs, the organism begins to cleave at the basal bodies, and this cleavage line moves towards the center of the organism until two separate euglenids are evident.[10] Because of the way that this reproduction takes place and the axis of separation, it is called longitudinal cell division or longitudinal binary fission.[11]
^. Archived from the original on 2020-07-13. Retrieved 2019-10-27.
^Zakryś, B; Milanowski, R; Karnkowska, A (2017). "Evolutionary Origin of Euglena". Adv Exp Med Biol. Advances in Experimental Medicine and Biology. 979: 3–17. doi:10.1007/978-3-319-54910-1_1. ISBN978-3-319-54908-8. PMID 28429314.
^Leander, Brian S.; Farmer, Mark A. (2001-03-01). "Comparative Morphology of the Euglenid Pellicle. II. Diversity of Strip Substructure". Journal of Eukaryotic Microbiology. 48 (2): 202–217. doi:10.1111/j.1550-7408.2001.tb00304.x. ISSN 1550-7408. PMID 12095109. S2CID 2109559.
^Leander, Brian Scott (May 2001). "Evolutionary morphology of the euglenid pellicle". University of Georgia Theses and Dissertations.
^Busse, Ingo; Preisfeld, Angelika (14 April 2018). "Systematics of primary osmotrophic euglenids: a molecular approach to the phylogeny of Distigma and Astasia (Euglenozoa)". International Journal of Systematic and Evolutionary Microbiology. 53 (2): 617–624. doi:10.1099/ijs.0.02295-0. PMID 12710635.
Ciugulea, I. & Triemer, R. E. (2010) A Color Atlas of Photosynthetic Euglenoids. Michigan State University Press, East Lansing, MI, 204 p., [2].
Leander, B. S., Triemer, R. E., & Farmer, M. A. (2001). Character evolution in heterotrophic euglenids. European Journal of Protistology, 37(3), 337-356, [3].
Leander, B.S., Lax, G., Karnkowska, A., Simpson, A.G.B. (2017). Euglenida. In: Archibald, J.M., Simpson, A.G.B., Slamovits, C. (Eds.). Handbook of the Protists. Springer, pp. 1–42. doi:10.1007/978-3-319-32669-6_13-1
Leedale, G. F. (1978). Phylogenetic criteria in euglenoid flagellates. BioSystems 10: 183–187, [4].
Wołowski, K & Hindák, F. (2005). Atlas of Euglenophytes. Cracow: VEDA Publishing House of the Slovak Academy of Sciences, 136 p., [5].
External links
Data related to Euglenoidea at Wikispecies
Tree of Life: Euglenida
January 31, 2023
euglenid, euglenoids, euglenophytes, formally, euglenoida, iczn, euglenophyceae, icbn, best, known, groups, flagellates, which, excavate, eukaryotes, phylum, euglenophyta, their, cell, structure, typical, that, group, they, commonly, found, freshwater, especia. Euglenids euglenoids or euglenophytes formally Euglenida Euglenoida 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 Many euglenids feed by phagocytosis or strictly by diffusion A monophyletic group consisting of the mixotrophic Rapaza viridis 1 species and the two groups Eutreptiales 24 species and Euglenales 983 species have chloroplasts and produce their own food through photosynthesis 3 4 5 This group is known to contain the carbohydrate paramylon EuglenidsTemporal range Eocene 53 5Ma recent 1 Euglena viridis by EhrenbergScientific classificationDomain Eukaryota unranked ExcavataPhylum EuglenozoaClass EuglenophyceaeSchoenichen 1925Major groups 2 Phototrophs in general Euglenales Euglenina Eutreptiales Eutreptiina Euglenamorphales EuglenamorphinaChemotrophs Rhabdomonadales RhabdomonadinaPhagotrophs Heteronematales Heteronematina Sphenomonadales SphenomonadinaSynonymsEuglenoidina Butschli 1884 Blochmann 1886 Euglenoidea Lankester 1885 Euglenida Stein 1878 sensu Simpson 1997 Euglenoida Cavalier Smith 1993Euglenids split from other Euglenozoa more than a billion years ago The plastids in all extant photosynthetic species is the result from secondary endosymbiosis between a phagotrophic eukaryovorous euglenid and a Pyramimonas related green alga 6 Contents 1 Structure 2 Classification 3 Nutrition 3 1 Osmotrophic euglenoids 4 Reproduction 5 Gallery 6 References 7 Bibliography 8 External linksStructure EditEuglenoids are distinguished mainly by the presence of a type of cell covering called a pellicle Within its taxon the pellicle is one of the euglenoids most diverse morphological features 7 The pellicle 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 their flagella Classification Edit Diagnostic drawings of euglenids 1 2 Ascoglena sp Euglenales 3 4 Cryptoglena sp idem 5 9 14 15 24 25 27 29 Trachelomonas spp id 10 Eutreptia sp Eutreptiales 11 20 Astasia spp Euglenales 12 Distigma sp Eutreptiales 13 Menoid i um sp Rhabdomonadales 16 18 Colacium sp Euglenales 19 26 Petalomonas spp Sphenomonadales 21 Sphenomonas sp id 22 23 Euglenopsis sp Euglenales 30 Peranema sp Heteronematales Further information Wikispecies Euglenida The euglenids were first defined by Otto Butschli 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 Conflicts of this nature are exemplary 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 chlorophylls are not masked with accessory pigments Nutrition EditThe classification of euglenids is still variable as groups are being revised to conform with their molecular phylogeny Classifications have fallen in line with the traditional groups based on differences in nutrition and number of flagella these provide a starting point for considering euglenid diversity Different characteristics of the euglenids pellicles can provide insight into their modes of movement and nutrition 8 As with other Euglenozoa the primitive mode of nutrition is phagocytosis Prey such as bacteria and smaller flagellates is 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 Edit Osmotrophic euglenids are euglenids which have undergone osmotrophy Due to a lack of characteristics that are useful for taxonomical purposes the origin of osmotrophic euglenids is unclear though certain morphological characteristics reveal a small fraction of osmotrophic euglenids is derived from phototrophic and phagotrophic ancestors 9 A prolonged absence of light or exposure to harmful chemicals may cause atrophy and absorption of the chloroplasts without otherwise harming the organism A number of species exists where a chloroplast s absence was formerly marked with separate genera such as Astasia colourless Euglena and Hyalophacus colourless Phacus Due to the lack of a developed cytostome these forms feed exclusively by osmotrophic absorption Reproduction EditAlthough euglenids share several common characteristics with animals which is why they were originally classified as so no evidence has been found of euglenids ever using sexual reproduction This is one of the reasons they could no longer be classified as animals For euglenids to reproduce asexual reproduction takes place in the form of binary fission and the cells replicate and divide during mitosis and cytokinesis This process occurs in a very distinct order First the basal bodies and flagella replicate then the cytostome and microtubules the feeding apparatus and finally the nucleus and remaining cytoskeleton Once this occurs the organism begins to cleave at the basal bodies and this cleavage line moves towards the center of the organism until two separate euglenids are evident 10 Because of the way that this reproduction takes place and the axis of separation it is called longitudinal cell division or longitudinal binary fission 11 Gallery Edit Euglena sp Euglenales Phacus sp Euglenales Trachelomonas sp Euglenales Euglenoid cultures in Petri dishes Cell diagram Astasia sp Euglenales Euglena Astasia and Phacus spp Euglenales Euglena Phacus and Lepocinclis spp Euglenales Anisonema Petalomonas Notosolenus Scytomonas and Tropidoscyphus spp Sphenomonadales Heteronema Dinema and Entosiphon spp Heteronematales References Edit Lee R E 2008 Phycology 4th edition Cambridge University Press ISBN 978 0 521 63883 8 Leedale G F 1967 Euglenoid Flagellates Prentice Hall Englewood Cliffs 242 p 1 Dynamic evolution of inverted repeats in Euglenophyta plastid genomes Secondary Endosymbioses Algaebase Subclass Euglenophycidae Archived from the original on 2020 07 13 Retrieved 2019 10 27 Zakrys B Milanowski R Karnkowska A 2017 Evolutionary Origin of Euglena Adv Exp Med Biol Advances in Experimental Medicine and Biology 979 3 17 doi 10 1007 978 3 319 54910 1 1 ISBN 978 3 319 54908 8 PMID 28429314 Leander Brian S Farmer Mark A 2001 03 01 Comparative Morphology of the Euglenid Pellicle II Diversity of Strip Substructure Journal of Eukaryotic Microbiology 48 2 202 217 doi 10 1111 j 1550 7408 2001 tb00304 x ISSN 1550 7408 PMID 12095109 S2CID 2109559 Leander Brian Scott May 2001 Evolutionary morphology of the euglenid pellicle University of Georgia Theses and Dissertations Busse Ingo Preisfeld Angelika 14 April 2018 Systematics of primary osmotrophic euglenids a molecular approach to the phylogeny of Distigma and Astasia Euglenozoa International Journal of Systematic and Evolutionary Microbiology 53 2 617 624 doi 10 1099 ijs 0 02295 0 PMID 12710635 Euglenida tolweb org Retrieved 2017 03 30 Reproduction Euglena Retrieved 2017 03 31 Bibliography EditCiugulea I amp Triemer R E 2010 A Color Atlas of Photosynthetic Euglenoids Michigan State University Press East Lansing MI 204 p 2 Leander B S Triemer R E amp Farmer M A 2001 Character evolution in heterotrophic euglenids European Journal of Protistology 37 3 337 356 3 Leander B S Lax G Karnkowska A Simpson A G B 2017 Euglenida In Archibald J M Simpson A G B Slamovits C Eds Handbook of the Protists Springer pp 1 42 doi 10 1007 978 3 319 32669 6 13 1 Leedale G F 1978 Phylogenetic criteria in euglenoid flagellates BioSystems 10 183 187 4 Wolowski K amp Hindak F 2005 Atlas of Euglenophytes Cracow VEDA Publishing House of the Slovak Academy of Sciences 136 p 5 External links Edit Data related to Euglenoidea at Wikispecies The Euglenoid Project Tree of Life Euglenida Retrieved from https en wikipedia org w index php title Euglenid amp oldid 1131382172, wikipedia, wiki, book, books, library,
