Description of Petalomonas

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Sphenomonadine euglenids, colourless, phagotrophic and/or osmotrophic, rigid, fusiform or triangular, flattened cells, usually very flat and leaf-shaped, mostly with strong ribs or keels; no special ingestion organelle visible by light microscopy but some species, at least, have a simple feeding apparatus visible by electron-microscopy; canal opening subapical with one emergent flagellum, directed anteriorly, straight, during swimming; second flagellum non-emergent; paramylon abundant; freshwater and marine, mainly benthic, in mud sediments, cosmopolitan; Scytomonas was purportedly distinguished by having a single flagellum and no reduced second flagellum in the reservoir although a reduced basal body may have been overlooked; cells assigned to Scytomonas have a simple feeding pocket and are known to indulge in sexuality - two cells fuse as isogametes, one flagellum is lost and the zygote swims by means of the other; the gamete nuclei fuse but meiosis and further stages have not been seen, type species P. abscissa (Dujardin, 1841) Stein, 1859.
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Petalomonas

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Petalomonas is a genus of phagotrophic, flagellated euglenoids.[1] Phagotrophic euglenoids are one of the most important forms of flagellates in benthic aquatic systems, playing an important role in microbial food webs.[2] The traits that distinguish this particular genus are highly variable, especially at higher taxa.[2] However, general characteristics such as a rigid cell shape and single emergent flagellum can describe the species among this genus.

History of knowledge

Petalomonas was first describe by Dr. Friedrich Stein, a zoologist at the University of Prague, in 1859.[3]

Habitat and ecology

Petalomonas is a cosmopolitan genus, most abundant in fresh water with a few species observed in marine environments.[1][4] These euglenoids mainly reside in muddy sediments as benthic organisms.[5] The cells are phagotrophic, feeding on bacteria, and/or osmotophic, assimilating nutrients from its surroundings.[1][6]

Description

These non-metabolic, colourless cells range in size from 8–45 um, with a general flattened, leaf-like shape.[1] The posterior end is rounded or truncate and the anterior end is narrowed; however, cells can span from ovoid, to fusiform or triangular, to elongately oval.[1][4] A distinguishing feature of the euglenoids is the presence of proteinaceous pellicle strips that are underlined with microtubules.[7] In Petalomonas, cells are covered with approximately a dozen thickly, fused pellicle strips making the cell very rigid and possibly resistant to surface ice crystal formation that can disrupt the cell.[7] These pellicle strips, unlike most euglenoids, are lacking grooves or troughs; however, species specific pellicle features, such as pleat-like thickenings at the joints of pellicle strips, that characterize P. cantuscygni, can distinguish certain species.[5] Strong ribs or keels are also evident in these cells, which can be arranged spirally or relatively straight, ranging in width.[1][4] Some species may contain furrows that vary in size and depth, and can be located dorsally and/or ventrally on the body of the cell.[4] The cells also have an abundance of paramylon bodies, typically used for the storage of starch, that are observed in all species.[1][4]

The feeding structure, not visible under light microscopy, is relatively simple consisting of a pocket-like cavity ending with a cytostome, lined with microtubules for phagocytosis.[8][5] The cells within this genus are also defined by one emergent flagellum extending from a sub-apical opening, directed anteriorly when swimming.[1][7][4] The movement of this flagellum is very minimal with some vibration at the tip; however, some species are observed to have vigorously, whipping flagellum that result in rapid rotation and oscillation of the cell body.[4] These euglenoids have also been observed to glide forward using the body, while the flagellum is used to contact the substrate.[7][4] The nucleus is located centrally to the left side of the cell.[4]

Life history

In euglenoids, sexual reproduction is unknown; however, asexual reproduction has been observed to occur in this genus through longitudinal fission, where the division occurs very quickly, starting at the anterior end of the cell.[6]

List of species

References

  1. ^ a b c d e f g h Guiry, M. D.; Guiry, G. M. (2002). “Petalomonas F.Stein 1859”. Retrieved February 10, 2019, from [1]
  2. ^ a b Lax, G.; Simpson, A. G. (2013). “Combining Molecular Data with Classical Morphology for Uncultured Phagotrophic Euglenids (Excavata): A Single-Cell Approach”. Journal of Eukaryotic Microbiology. 60 (6): 615-625. doi:10.1111/jeu.12068
  3. ^ Stein, F. (1859). Der Organismus der Infusionsthiere nach eigenen Forschungen in systematischer Reihenfolge bearb. von Friedrich Stein. doi:10.5962/bhl.title.3933
  4. ^ a b c d e f g h i Shawhan, F. M.; Jahn, T. L. (1947). “A Survey of the Genus Petalomonas Stein (Protozoa: Euglenida)”. Transactions of the American Microscopical Society. 66 (2): 182. doi:10.2307/3223249
  5. ^ a b c Cavalier-Smith, Thomas; Chao, Ema E.; Vickerman, Keith (2016). “New phagotrophic euglenoid species (new genus Decastava; Scytomonas saepesedens; Entosiphon oblongum), Hsp90 introns, and putative euglenoid Hsp90 pre-mRNA insertional editing”. European Journal of Protistology. 56: 147-170. doi:10.1016/j.ejop.2016.08.002
  6. ^ a b Esson, H. J.; Leander, B. S. (2006). “A model for the morphogenesis of strip reduction patterns in phototrophic euglenids: Evidence for heterochrony in pellicle evolution”. Evolution Development, 8 (4): 378-388. doi:10.1111/j.1525-142x.2006.00110.x
  7. ^ a b c d Larsen, Jacob; Patterson, David J. (1990). "Some flagellates (Protista) from tropical marine sediments”. Journal of Natural History, 24 (4): 801-937. doi:10.1080/00222939000770571
  8. ^ Breglia, Susana A.; Yubuki, N.; Leander, Brian S. (2013). “Ultrastructure and Molecular Phylogenetic Position of Heteronema scaphurum: A Eukaryovorous Euglenid with a Cytoproct”. Journal of Eukaryotic Microbiology. 2: 107-120. doi: 10.1111/jeu.12014
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Petalomonas: Brief Summary

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Petalomonas is a genus of phagotrophic, flagellated euglenoids. Phagotrophic euglenoids are one of the most important forms of flagellates in benthic aquatic systems, playing an important role in microbial food webs. The traits that distinguish this particular genus are highly variable, especially at higher taxa. However, general characteristics such as a rigid cell shape and single emergent flagellum can describe the species among this genus.

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Classification

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This authority places the genus under the family Sphenomonadidae
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bibliographic citation
Guiry, M.D. & Guiry, G.M. (2020). AlgaeBase. <em>World-wide electronic publication, National University of Ireland, Galway.</em> Hayward, P.J.; Ryland, J.S. (Ed.). (1990). The marine fauna of the British Isles and North-West Europe: 1. Introduction and protozoans to arthropods. Clarendon Press: Oxford, UK. ISBN 0-19-857356-1. 627 pp.
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