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Scientific classification

F. Stein, 1859

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[edit]

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

Habitat and ecology[edit]

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]


These non-metabolic, colourless cells range in size from 8-45um, 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[edit]

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[edit]

  • P. abscissa (Dujardin) Stein
  • P. acuminata Hollande
  • P. africana Bourrelly
  • P. alata (A.C. Stokes) A.C. Stokes
  • P. applanata Skuja
  • P. arcuata Hollande
  • P. asymmetrica Schawhan & Jahn
  • P. bicarinata Shawhan & Jahn
  • P. calycimonadoides Christen
  • P. calycimonoides W.J.Lee & D.J.Patterson
  • P. cantuscygni J.Cann & N.Pennick
  • P. carinata A.C.Stokes
  • P. christenii W.J.Lee & D.J.Patterson
  • P. conchata Christen
  • P. curvata Skuja
  • P. dentata Christen
  • P. dilatata Hollande
  • P. dorsalis Stokes
  • P. dubosqui Hollande
  • P. excavata Skuja
  • P. gibbera Christen
  • P. gigas Skuja
  • P. hyalina Christen
  • P. inflexa G.A.Klebs
  • P. intorta W.J.Lee & D.J.Patterson
  • P. involuta Skuja
  • P. irregularis Skuja
  • P. iugosa W.J.Lee & D.J.Patterson
  • P. klebsii Christen
  • P. klinostoma Skuja
  • P. labrum W.J.Lee & D.J.Patterson
  • P. lata Christen
  • P. mediocanellata F. Stein
  • P. messikommeri Christen
  • P. micra R.E.Norris
  • P. minor Larson & D.J. Patterson
  • P. minuta Hollande
  • P. minutula Christen
  • P. mira Awerinzew
  • P. ornata Skvortzov
  • P. ovata Skvortzov
  • P. ovum Matvienko
  • P. paludosa Christen
  • P. pentacarinata Péterfi
  • P. phacoides Skuja
  • P. plana W.J.Lee & D.J.Patterson
  • P. platyrhyncha Skuja
  • P. pluteus Christen
  • P. praegnans Skuja
  • P. pringsheimii Christen
  • P. prototheca Skuja
  • P. punctato-striata Skuja
  • P. pusilla Skuja
  • P. quadrilineata Penard
  • P. quinquecarinata Hollande
  • P. quinquemarginata Shawhan & Jahn
  • P. robusta Christen
  • P. septemcarinata Shawhan & Jahn
  • P. sexlobata Klebs
  • P. simplex Christen
  • P. sinica Skvortzov
  • P. sinuata F.Stein
  • P. sphagnicola Tschermak-Woess
  • P. sphagnophila Christen
  • P. spinifera (Lackey) W.J.Lee & D.J.Patterson
  • P. splendens Hollande
  • P. steinii Klebs
  • P. stellata Skvortzov
  • P. sulcata A.C.Stokes
  • P. tenuis Christen
  • P. triangula Z.X.Shi
  • P. tricarinata Skuja
  • P. triquetra Skvortzov
  • P. variabilis Christen
  • P. ventritracta Skuja
  • P. virgata W.J.Lee & D.J.Patterson
  • P. vulgaris Skuja
  • P. wuhanica Z.Shi


  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