pectinate muscles function

pectinate muscles function


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Euglena sp.jpg
Scientific classification
> Euglenozoa [1] [2]

Ehrenberg , 1830

Euglena is a genus of single cell flagellate eukaryotics . It is the best known and most widely studied member of the class Euglenoidea , a diverse group containing some 54 genera and at least 800 species. [3] [4] Species of Euglena are found in freshwater and salt water. They are often abundant in quiet inland waters where they may bloom in numbers sufficient to color the surface of ponds and ditches green (E. viridis) or red ( E. sanguinea ). [5]

The species Euglena gracilis has been used extensively in the laboratory as a model organism . [6]

Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy , like plants. However, they can also take nourishment heterotrophically , like animals. Since Euglena have features of both animals and plants, early taxonomists, working within the Linnaean three-kingdom system of biological classification, found them difficult to classify. [7] [8] It was the question of where to put such “unclassifiable” creatures that prompted Ernst Haeckel to add a third living kingdom (a fourth kingdom in toto) to the Animale, Vegetabile (and Lapideum meaning Mineral) of Linnaeus : the Kingdom Protista . [9]


  • 1 Form and function
  • 2 Reproduction
  • 3 Historical background and early classification
  • 4 Recent phylogeny and classification
  • 5 Human consumption
  • 6 Video gallery
  • 7 See also
  • 8 References
  • 9 External links

Form and function[ edit ]

When feeding as a heterotroph, Euglena takes in nutrients by osmotrophy , and can survive without light on a diet of organic matter, such as beef extract , peptone , acetate , ethanol or carbohydrates . [10] [11] When there is sufficient sunlight for it to feed by phototrophy , it uses chloroplasts containing the pigments chlorophyll a and chlorophyll b to produce sugars by photosynthesis . [12] Euglena’s chloroplasts are surrounded by three membranes, while those of plants and the green algae (among which earlier taxonomists often placed Euglena) have only two membranes. This fact has been taken as morphological evidence that Euglena’s chloroplasts evolved from a eukaryotic green alga. [13] Thus, the intriguing similarities between Euglena and the plants would have arisen not because of kinship but because of a secondary endosymbiosis . Molecular phylogenetic analysis has lent support to this hypothesis, and it is now generally accepted. [14] [15]

Diagram of Euglena

Euglena chloroplasts contain pyrenoids , used in the synthesis of paramylon , a form of starch energy storage enabling Euglena to survive periods of light deprivation. The presence of pyrenoids is used as an identifying feature of the genus, separating it from other euglenoids, such as Lepocinclis and Phacus . [16]

All euglenoids have two flagella rooted in basal bodies located in a small reservoir at the front of the cell. In Euglena, one flagellum is very short, and does not protrude from the cell, while the other is relatively long, and often easily visible with light microscopy. In some species, the longer, emergent flagellum is used to help the organism swim.

Like other euglenoids, Euglena possess a red eyespot , an organelle composed of carotenoid pigment granules. The red spot itself is not thought to be photosensitive . Rather, it filters the sunlight that falls on a light-detecting structure at the base of the flagellum (a swelling, known as the paraflagellar body), allowing only certain wavelengths of light to reach it. As the cell rotates with respect to the light source, the eyespot partially blocks the source, permitting the Euglena to find the light and move toward it (a process known as phototaxis ). [17]

Spiral pellicle strips

Euglena lacks a cell wall . Instead, it has a pellicle made up of a protein layer supported by a substructure of microtubules , arranged in strips spiraling around the cell. The action of these pellicle strips sliding over one another, known as metaboly, gives Euglena its exceptional flexibility and contractility. [17] The mechanism of this euglenoid movement is not understood, but its molecular basis may be similar to that of amoeboid movement . [18]

In low moisture conditions, or when food is scarce, Euglena forms a protective wall around itself and lies dormant as a resting cyst until environmental conditions improve.

Reproduction[ edit ]

Euglena reproduce asexually through binary fission , a form of cell division . Reproduction begins with the mitosis of the cell nucleus , followed by the division of the cell itself. Euglena divide longitudinally, beginning at the front end of the cell, with the duplication of flagellar processes, gullet and stigma. Presently, a cleavage forms in the anterior , and a V-shaped bifurcation gradually moves toward the posterior , until the two halves are entirely separated. [19]

Reports of sexual conjugation are rare, and have not been substantiated. [20]

Historical background and early classification[ edit ]

Cercaria viridis (= E. viridis) from O.F. Müller ‘s Animalcula Infusoria. 1786

Species of Euglena were among the first protists to be seen under the microscope.

In 1674, in a letter to the Royal Society, the Dutch pioneer of microscopy Antoni van Leeuwenhoek wrote that he had collected water samples from an inland lake, in which he found “animalcules” that were “green in the middle, and before and behind white.” Clifford Dobell regards it as “almost certain” that these were Euglena viridis, whose “peculiar arrangement of chromatophores…gives the flagellate this appearance at low magnification.” [21]

Twenty-two years later, John Harris published a brief series of “Microscopical Observations” reporting that he had examined “a small Drop of the Green Surface of some Puddle-Water” and found it to be “altogether composed of Animals of several Shapes and Magnitudes.” Among them, were “oval creatures whose middle part was of a Grass Green, but each end Clear and Transparent,” which “would contract and dilate themselves, tumble over and over many times together, and then shoot away like Fish.” [22]

In 1786, O.F. Müller gave a more complete description of the organism, which he named Cercaria viridis, noting its distinctive color and changeable body shape. Müller also provided a series of illustrations, accurately depicting the undulating, contractile movements (metaboly) of Euglena’s body. [23]

Euglena from Félix Dujardin ‘s Histoire Naturelle des Zoophytes, 1841

In 1830, C. G. Ehrenberg renamed Müller’s Cercaria Euglena viridis, and placed it, in keeping with the short-lived system of classification he invented, among the Polygastrica in the family Astasiaea: multi-stomached creatures with no alimentary canal, variable body shape but no pseudopods or lorica. [24] [25] By making use of the newly invented achromatic microscope, [26] Ehrenberg was able to see Euglena’s eyespot, which he correctly identified as a “rudimentary eye” (although he reasoned, wrongly, that this meant the creature also had a nervous system). This feature was incorporated into Ehrenberg’s name for the new genus, constructed from the Greek roots “eu-” (well, good) and glēnē (eyeball, socket of joint). [27]

Ehrenberg did not notice Euglenas flagella, however. The first to publish a record of this feature was Félix Dujardin , who added “filament flagelliforme” to the descriptive criteria of the genus in 1841. [28] Subsequently, the class Flagellata (Cohn, 1853) was created for creatures, like Euglena, possessing one or more flagella. While “Flagellata” has fallen from use as a taxon, the notion of using flagella as a phylogenetic criterion remains vigorous. [29]

Recent phylogeny and classification[ edit ]

Euglena movement, known as metaboly

In 1881, Georg Klebs made a primary taxonomic distinction between green and colorless flagellate organisms, separating photosynthetic from heterotrophic euglenoids. The latter (largely colorless, shape-changing uniflagellates) were divided among the Astasiaceae and the Peranemaceae , while flexible green euglenoids were generally assigned to the genus Euglena. [30]

As early as 1935, it was recognized that this was an artificial grouping, however convenient. [31] In 1948, Pringsheim affirmed that the distinction between green and colorless flagellates had no taxonomic justification, although he acknowledged its practical appeal. He proposed something of a compromise, placing colorless, saprotrophic euglenoids in the genus Astasia, while allowing some colorless euglenoids to share a genus with their photosynthesizing cousins, provided they had structural features that proved common ancestry. Among the green euglenoids themselves, Pringsheim recognized the close kinship of some species of Phacus and Lepocinclis with some species of Euglena. [30]

The idea of classifiying the euglenoids by their manner of nourishment was finally abandoned in the 1950s, when A. Hollande published a major revision of the phylum, grouping organisms by shared structural features, such as the number and type of flagella. [32] If any doubt remained, it was dispelled in 1994, when genetic analysis of the non-photosynthesizing euglenoid Astasia longa confirmed that this organism retains sequences of DNA inherited from an ancestor that must have had functioning chloroplasts. [33]

In 1997, a morphological and molecular study of the Euglenozoa put Euglena gracilis in close kinship with the species Khawkinea quartana, with Peranema trichophorum basal to both. [34] Two years later, a molecular analysis showed that E. gracilis was, in fact, more closely related to Astasia longa than to certain other species recognized as Euglena. In 2015, Dr Ellis O’Neill and Professor Rob Field have sequenced the transcriptome of Euglena gracilis, which provides information about all of the genes that the organism is actively using. They found that Euglena gracilis has a whole host of new, unclassified genes which can make new forms of carbohydrates and natural products. [35] [36]

The venerable Euglena viridis was found to be genetically closer to Khawkinea quartana than to the other species of Euglena studied. [32]
Recognizing the polyphyletic nature of the genus Euglena, Marin et al. (2003) have revised it to include certain members traditionally placed in Astasia and Khawkinea. [16]

Human consumption[ edit ]

Starting in 2005, Tokyo-based Euglena Company has started marketing Euglena-based food and beverage products, based on their provision of both plant- and animal-based nutrients. [37] While the fitness of euglena for human consumption had long been surmised, Euglena Co. was the first to develop a technique to cultivate and farm the microorganism in large enough quantities to be commercially viable. [38] The company’s main production facility is located on Ishigaki Island , Okinawa , due to favorable climate conditions.

Euglena Company is also experimenting with the use of Euglena as a potential fuel source. [39]

Video gallery[ edit ]

File:Euglena sp.ogv Play media

Red Euglena sp.

File:Euglena mutabilis.ogv Play media

Euglena mutabilis, showing metaboly, paramylon bodies and chloroplasts

File:Euglena sanguinea.ogv Play media

Euglena sanguinea

File:Euglena metaboly and swimming movement.ogv Play media

Euglena, moving by metaboly and swimming

See also[ edit ]

  • Elysia chlorotica
  • Kleptoplasty

References[ edit ]

  1. ^ Adl, SM; Simpson, AG; Lane, CE; Lukeš, J; Bass, D (2012). “The Revised Classification of Eukaryotes” . Journal of Eukaryotic Microbiology. 59 (5): 429–493. doi : 10.1111/j.1550-7408.2012.00644.x . PMC   3483872 . PMID   23020233 .

  2. ^ Guiry, MD; Guiry, GM. “Algaebase Taxonomy Browser” . Algaebase. National University of Ireland. Retrieved 2015-05-11.
  3. ^ “The Euglenoid Project: Alphabetic Listing of Taxa” . The Euglenoid Project. Partnership for Enhancing Expertise in Taxonomy. Retrieved Sep 20, 2014.
  4. ^ “The Euglenoid Project for Teachers” . The Euglenoid Project for Teachers. Partnerships for Enhancing Expertise in Taxonomy. Retrieved Sep 20, 2014.
  5. ^ Wolosski, Konrad. “Phylum Euglenophyta” . In John, David M.; Whitton, Brian A.; Brook, Alan J. The Freshwater Algal Flora of the British Isles: an Identification Guide to Freshwater and Terrestrial Algae. p. 144. ISBN   978-0-521-77051-4 .
  6. ^ Russell, A. G.; Watanabe, Y; Charette, JM; Gray, MW (2005). “Unusual features of fibrillarin cDNA and gene structure in Euglena gracilis: Evolutionary conservation of core proteins and structural predictions for methylation-guide box C/D snoRNPs throughout the domain Eucarya” . Nucleic Acids Research. 33 (9): 2781–91. doi : 10.1093/nar/gki574 . PMC   1126904 . PMID   15894796 .
  7. ^ Margulis, Lynn (2007). “Power to the Protoctists” . In Margulis, Lynn; Sagan, Dorion. Dazzle Gradually: Reflections on the Nature of Nature. White River Junction: Chelsea Green. pp. 29–35. ISBN   978-1-60358-136-3 .
  8. ^ Keeble, Frederick (1912). Plant-animals: a study in symbiosis . London: Cambridge University Press. pp. 103–4. OCLC   297937639 .
  9. ^ Solomon, Eldra Pearl; Berg, Linda R.; Martin, Diana W., eds. (2005). “Kingdoms or Domains?” . Biology (7th ed.). Belmont: Brooks/Cole Thompson Learning. pp. 421–7. ISBN   978-0-534-49276-2 .
  10. ^ Leadbeater, Barry S. C.; Green, John C. (2002-09-11). Flagellates: Unity, Diversity and Evolution . CRC Press. ISBN   9780203484814 .
  11. ^ Pringsheim, E. G.; Hovasse, R. (1948-06-01). “The Loss of Chromatophores in Euglena Gracilis” . New Phytologist. 47 (1): 52–87. doi : 10.1111/j.1469-8137.1948.tb05092.x .
  12. ^ Nisbet, Brenda (1984). Nutrition and Feeding Strategies in Protozoa. p. 73. ISBN   0-7099-1800-3 .
  13. ^ Gibbs, Sarah P. (1978). “The chloroplasts of Euglena may have evolved from symbiotic green algae”. Canadian Journal of Botany. 56 (22): 2883–9. doi : 10.1139/b78-345 .
  14. ^ Henze, Katrin; Badr, Abdelfattah; Wettern, Michael; Cerff, Rudiger; Martin, William (1995). “A Nuclear Gene of Eubacterial Origin in Euglena gracilis Reflects Cryptic Endosymbioses During Protist Evolution” . Proceedings of the National Academy of Sciences of the United States of America. 92 (20): 9122–6. Bibcode : 1995PNAS…92.9122H . doi : 10.1073/pnas.92.20.9122 . JSTOR   2368422 . PMC   40936 . PMID   7568085 .
  15. ^ Nudelman, Mara Alejandra; Rossi, Mara Susana; Conforti, Visitacin; Triemer, Richard E. (2003). “Phylogeny of euglenophyceae based on small subunit rDNA sequences: Taxonomic implications”. Journal of Phycology. 39 (1): 226–35. doi : 10.1046/j.1529-8817.2003.02075.x .
  16. ^ a b Marin, B; Palm, A; Klingberg, M; Melkonian, M (2003). “Phylogeny and taxonomic revision of plastid-containing euglenophytes based on SSU rDNA sequence comparisons and synapomorphic signatures in the SSU rRNA secondary structure”. Protist. 154 (1): 99–145. doi : 10.1078/143446103764928521 . PMID   12812373 .
  17. ^ a b Schaechter, Moselio (2011). Eukaryotic Microbes. San Diego: Elsevier/Academic Press. p. 315. ISBN   978-0-12-383876-6 .
  18. ^ O’Neill, Ellis (2013). An exploration of phosphorylases for the synthesis of carbohydrate polymers (PhD thesis) . University of East Anglia. pp. 170–171.
  19. ^ Gojdics, Mary (1934). “The Cell Morphology and Division of Euglena deses Ehrbg”. Transactions of the American Microscopical Society. 53 (4): 299–310. doi : 10.2307/3222381 . JSTOR   3222381 .
  20. ^ Lee, John J. (2000). An Illustrated Guide to the Protozoa: organisms traditionally referred to as protozoa, or newly discovered groups. 2 (2nd ed.). Lawrence, Kansas: Society of Protozoologists. p. 1137.
  21. ^ Dobell, Clifford (1960) [1932]. Antony van Leeuwenhoek and his ‘Little Animals’. New York: Dover. p. 111. ISBN   0-486-60594-9 .
  22. ^ Harris, J. (1695). “Some Microscopical Observations of Vast Numbers of Animalcula Seen in Water by John Harris, M. A. Kector of Winchelsea in Sussex, and F. R. S” . Philosophical Transactions of the Royal Society of London. 19 (215–235): 254–9. Bibcode : 1695RSPT…19..254H . doi : 10.1098/rstl.1695.0036 . JSTOR   102304 .
  23. ^ Müller, Otto Frederik; Fabricius, Otto (1786). Animalcula Infusoria, Fluvia Tilia et Marina . Hauniae, Typis N. Mölleri. pp. 126, 473.
  24. ^ Ehrenberg, C. Organisation, Systematik und geographisches Verhältnifs der Infusionsthierchen. Vol. II. Berlin, 1830. pp 58-9
  25. ^ Pritchard, Andrew (1845). A history of Infusoria, living and fossil: arranged according to ‘Die Infusionsthierchen’ of C.G. Ehrenberg . London: Whittaker. p. 86. hdl : 2027/uc2.ark:/13960/t5fb4z64c .
  26. ^ “Notes and Queries” . Notes and Queries. 12 (13): 459. July–December 1855.
  27. ^ “Merriam-Webster online dictionary” . Encyclopædia Britannica. Retrieved 6 July 2005.
  28. ^ Dujardin, Félix (1841). Histoire Naturelle des Zoophytes. Infusoires, comprenant la Physiologie et la Classification de ces Animaux, et la Manière de les Étudier a l’aide du Microscope . Paris. p. 358.
  29. ^ Cavalier-Smith, Thomas; Chao, Ema E.-Y. (2003). “Phylogeny and Classification of Phylum Cercozoa (Protozoa)”. Protist. 154 (3–4): 341–58. doi : 10.1078/143446103322454112 . PMID   14658494 .
  30. ^ a b Pringsheim, E. G. (1948). “Taxonomic Problems in the Euglenineae”. Biological Reviews. 23 (1): 46–61. doi : 10.1111/j.1469-185X.1948.tb00456.x . PMID   18901101 .
  31. ^ Schwartz, Adelheid (2007). “F. E. Fritsch, the Structure and Reproduction of the Algae Vol. I/II. XIII und 791, XIV und 939 S., 245 und 336 Abb., 2 und 2 Karten. Cambridge 1965 (reprinted): Cambridge University Press 90 S je Band”. Zeitschrift für allgemeine Mikrobiologie. 7 (2): 168–9. doi : 10.1002/jobm.19670070220 .
  32. ^ a b Linton, Eric W.; Hittner, Dana; Lewandowski, Carole; Auld, Theresa; Triemer, Richard E. (1999). “A Molecular Study of Euglenoid Phylogeny using Small Subunit rDNA”. The Journal of Eukaryotic Microbiology. 46 (2): 217–23. doi : 10.1111/j.1550-7408.1999.tb04606.x . PMID   10361741 .
  33. ^ Gockel, Gabriele; Hachtel, Wolfgang; Baier, Susanne; Fliss, Christian; Henke, Mark (1994). “Genes for components of the chloroplast translational apparatus are conserved in the reduced 73-kb plastid DNA of the nonphotosynthetic euglenoid flagellate Astasia longa”. Current Genetics. 26 (3): 256–62. doi : 10.1007/BF00309557 . PMID   7859309 .
  34. ^ Montegut-Felkner, Ann E.; Triemer, Richard E. (1997). “Phylogenetic Relationships of Selected Euglenoid Genera Based on Morphological and Molecular Data”. Journal of Phycology. 33 (3): 512–9. doi : 10.1111/j.0022-3646.1997.00512.x .
  35. ^ The potential in your pond published on August 14, 2015 by the “John Innes Centre”
  36. ^ O’Neill, Ellis C.; Trick, Martin; Hill, Lionel; Rejzek, Martin; Dusi, Renata G.; Hamilton, Christopher J.; Zimba, Paul V.; Henrissat, Bernard; Field, Robert A. (2015). “The transcriptome of Euglena gracilis reveals unexpected metabolic capabilities for carbohydrate and natural product biochemistry”. Molecular Biosystems. 11 (10): 2808–21. doi : 10.1039/C5MB00319A .
  37. ^
  38. ^
  39. ^ NHK World, Rising, 26 June 2015

External links[ edit ]

Wikispecies has information related to Euglena
Look up euglena in Wiktionary, the free dictionary.
  • The Euglenoid Project
  • Tree of Life web project: Euglenida
  • Protist Images: Euglena
  • Euglena at Droplet – Microscopy of the Protozoa
  • Images and taxonomy
  • Constantopoulos, George; Bloch, Konrad (1967). “Effect of Light Intensity on the Lipid Composition of Euglena gracilis” . The Journal of Biological Chemistry. 242 (15): 3538–42.
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Taxon identifiers
  • Wikidata : Q236001
  • Wikispecies : Euglena
  • EoL : 11704
  • GBIF : 3209628
  • iNaturalist : 203631
  • ITIS : 9620
  • NCBI : 3038
  • WoRMS : 8012

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  • Euglenozoa genera
  • Taxa named by Christian Gottfried Ehrenberg
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      Euglena Cells

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      Regina Bailey

      Regina Bailey is a science writer and educator who has covered biology for ThoughtCo since 1997. Her writing is featured in Kaplan AP Biology 2016.

      Updated January 26, 2018

      What Are Euglena?


      Euglena are eukaryotic protists. They are photoautotrophs with cells containing several chloroplasts. Each cell has a noticeable red eyespot.
      Gerd Guenther/Science Photo Library/Getty Images

      Euglena are tiny protist organisms that are classified in the Eukaryota Domain and the genus Euglena. These single-celled eukaryotes have characteristics of both plant and animal cells . Like plant cells , some species are photoautotrophs (photo-, – auto , – troph ) and have the ability to use light to produce nutrients through photosynthesis . Like animal cells , other species are heterotrophs ( hetero -, – troph ) and acquire nutrition from their environment by feeding on other organisms. There are thousands of species of Euglena that typically live in both fresh and salt water aquatic environments . Euglena can be found in ponds, lakes, and streams, as well as in waterlogged land areas like marshes.

      Euglena Taxonomy

      Due to their unique characteristics, there has been some debate as to the phylum in which Euglena should be placed. Euglena have historically been classified by scientists in either the phylum Euglenozoa or the phylum Euglenophyta. Euglenids organized in the phylum Euglenophyta were grouped with algae because of the many chloroplasts within their cells. Chloroplasts are chlorophyll containing organelles which enable photosynthesis. These euglenids get their green color from the green chlorophyll pigment. Scientists speculate that the chloroplasts within these cells were acquired as a result of endosymbiotic relationships with green algae. Since other Euglena do not have chloroplasts and the ones that do obtained them through endosymbiosis, some scientists contend that they should be placed taxonimically in the phylum Euglenozoa. In addition to photosynthetic euglenids, another major group of non-photosynthetic Euglena known as kinetoplastids are included in the Euglenozoa phylum. These organisms are parasites that can cause serious blood and tissue diseases in humans, such as African sleeping sickness and leishmaniasis (disfiguring skin infection). Both of these diseases are transmitted to humans by biting flies .

      Euglena Cell Anatomy

      Euglena Cell

      Euglena Cell Anatomy.
      Claudio Miklos/Public Domain Image

      Common features of photosynthetic Euglena cell anatomy include a nucleus, contractile vacuole, mitochondria, Golgi apparatus, endoplasmic reticulum, and typically two flagella (one short and one long). Unique characteristics of these cells include a flexible outer membrane called a pellicle that supports the plasma membrane. Some euglenoids also have an eyespot and a photoreceptor, which aid in the detection of light.

      Euglena Cell Anatomy

      Structures found in a typical photosynthetic Euglena cell include:

      • Pellicle: flexible membrane that supports the plasma membrane
      • Plasma membrane : thin, semi-permeable membrane that surrounds the cytoplasm of a cell, enclosing its contents
      • Cytoplasm : gel-like, aqueous substance within the cell
      • Chloroplasts : chlorophyll containing plastids that absorbs light energy for photosynthesis
      • Contractile Vacuole : structure that removes excess water from the cell
      • Flagellum : cellular protrusion formed from specialized groupings of microtubules that aid in cell movement
      • Eyespot: This area (typically red) contains pigmented granules that aid in the detection of light. It is sometimes called a stigma.
      • Photoreceptor or Paraflagellar Body: This light sensitive region detects light and is located near the flagellum. It assists in phototaxis (movement toward or away from light).
      • Paramylon: This starch-like carbohydrate is composed of glucose produced during photosynthesis. It serves as a food reserve when photosynthesis is not possible.
      • Nucleus : membrane bound structure that contains DNA
        • Nucleolus: structure within the nucleus that contains RNA and produces ribosomal RNA for the synthesis of ribosomes
      • Mitochondria : organelles that generate energy for the cell
      • Ribosomes : Consisting of RNA and proteins , ribosomes are responsible for protein assembly.
      • Reservoir: inward pocket near the anterior of the cell where flagella arise and excess water is dispelled by the contractile vacuole
      • Golgi Apparatus : manufactures, stores, and ships certain cellular molecules
      • Endoplasmic Reticulum : This extensive network of membranes is composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). It is involved in protein production.
      • Lysosomes : sacs of enzymes that digest cellular macromolecules and detoxify the cell

      Some species of Euglena possess organelles that can be found in both plant and animal cells. Euglena viridis and Euglena gracilis are examples of Euglena that contain chloroplasts as do plants . They also have flagella and do not have a cell wall , which are typically characteristic of animal cells. Most species of Euglena have no chloroplasts and must ingest food by phagocytosis. These organisms engulf and feed on other unicellular organisms in their surroundings such as bacteria and algae.

      Euglena Reproduction

      Euglenoid Protozoans

      Euglenoid Protozoans.
      Roland Birke/Photographer’s Choice/Getty Images

      Most Euglena have a life cycle consisting of a free-swimming stage and a non-motile stage. In the free-swimming stage, Euglena reproduce rapidly by a type of asexual reproduction method known as binary fission . The euglenoid cell reproduces its organelles by mitosis and then splits longitudinally into two daughter cells . When environmental conditions become unfavorable and too difficult for Euglena to survive, they can enclose themselves within a thick-walled protective cyst. Protective cyst formation is characteristic of the non-motile stage.

      In unfavorable conditions, some euglenids can also form reproductive cysts in what is known as the palmelloid stage of their life cycle. In the palmelloid stage, Euglena gather together (discarding their flagella) and become enveloped in a gelatinous, gummy substance. Individual euglenids form reproductive cysts in which binary fission occurs producing many (32 or more) daughter cells. When environmental conditions once again become favorable, these new daughter cells become flagellated and are released from the gelatinous mass.

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