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Cryptophyceae Pascher 1913

Description of Cryptomonads

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Circumscription: Biflagellated autotrophic, mixotrophic and heterotrophic flagellates, flagella inserting in an anterior groove/channel lines with refractile ejectisomes. Variously coloured photosynthetic compartments, in some taxa at least, formed from secondary symbioses with eukaryotes, the symbiont being located in a membrane-bound compartment and provided with a reduced nucleus (the nucleomorph). Two genera of heterotrophs, one (Goniomonas) possibly primitively so. Ultrastructural identity: Mitochondria cristae flattened, mitochondrion often extensive. Coiled ribbon extrusomes (eiectisomes) associated with flagellar pocket (gullet) and with cell surface. Geometrically positioned plates of fibrous cytoskeletal material underlie the membrane. Plastidic taxa with plastid inside a fold of the nuclear envelope and with nucleomorph where studied. No eyespot. Both flagella with stiff bipartite hairs. Small scales may be attached to cell body. Flagella insert into near parallel basal bodies, usually with multilamellate root structure (rhizostyle) in addition to several microtubular roots. Nuclear division with spindle developing from basal bodies and penetrating the dividing nucleus, the membrane of which completely breaks down. Synapomorphy: Flagellar groove/channel with associated ejectisomes and/or double row of flagellar hairs on both flagella and/or cortical plates.
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Algae: Protists with Chloroplasts

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The algae are a polyphyletic and paraphyletic group of organisms. They are defined in differing ways, but are usually considered to be the photosynthetic organisms excepting plants. Using the term 'plants' in its most restrictive fashion, the algae are then photosynthetic organisms excepting the sister group to the Charales (i.e. the land plants). Such a definition allows inclusion of photosynthetic prokaryotes such as the cyanobacteria. The definition applied here is that the algae is that artificial subset of the photosynthetic eukaryotes which excludes the sister group to the Charales (land plants).

The algae are the dominating primary producers in aquatic ecosystems, on unstable substrates (muds and sands) and in intertidal marine habitats. Algae are commonly exploited as foodstuffs, food additives, toothpastes, etc.

The ability for eukaryotes to carry out photosynthesis was made possible by one or more symbiotic associations between heterotrophic eukaryotes and photosynthetic prokaryotes (or their descendents). There were several primary symbioses between eukaryotes and blue green algae. In one lineage, the photosynthetic organism lost much of its genetic independence and became functionally and genetically integrated as chloroplasts within the host cell. Modern chloroplasts, also called plastids, are bounded by two or more membranes, and most usually lie free in the cytoplasm, but in some cases they may be located within a fold of the nuclear envelope, or may be associated with the cytoplasm and residual nucleus of a eukaryotic endosybiont. The descendents of some of these primary plastids have gone on to form further associations. At least two types of protists (chloroarachniophytes and cryptomonads) have acquired 'plastids' by forming symbioses with eukaryotic algae. This are referred to as secondary symbioses.

Algae are distinguished on a number of different characteristics. The most important ones are:

  • the colour of the plastids (more correctly the combination of photosynthetic pigments that are present in the plastid)
  • the presence of flagella (and if so how many, how do they insert in the cell and how do they beat)
  • is the cell surrounded by extracellular material? If so, what is that material - organic or inorganic, a continuous wall or a layer of scales)
  • are the cells motile or not?
  • do they occur singly, in colonies, filaments or exhibit differentiation that would allow them to satisfy the criterion of multicellularity?

Algal protists occur in 8 lineages. These are summarised below.

Groups of Algae

ALVEOLATES

Contains some algae, autotrophic dinoflagellates, diverse, Peridinium, Symbiodinium, Ceratium

unicellular, colonial, syncytial; free-living, symbiotic and parasitic

MAJOR PIGMENTS:chlorophylls a and c, some symbionts

CHLORARACHNIOPHYTES

A few genera of amoeboid organisms all with symbiotic algae, Chlorarachnion

syncytial, free-living

MAJOR PIGMENT:Chlorophyll b

CRYPTOMONADS

About 12 genera of flagellates, Cryptomonas

single cells, rarely forming colonies, some are endobiotic

MAJOR PIGMENTS:Chlorophylls a and c, phycobilins

EUGLENIDS

about half of the genera (35) contain members with green chloroplasts, flagellates, Euglena, Trachelomonas

single cells

MAJOR PIGMENT:Chlorophyll b

GLAUCOPHYTES

Several genera of flagellated and non-flagellated protists with similar phycobilin-rich symbionts, e.g. Glaucocystis, Cyanophora

flagellated and non-flagellated cells

MAJOR PIGMENT:Phycobilin

HAPTOPHYTES

Diverse, with many genera, all or all bar one genera with plastids, with naked species and those with scales (coccolithophores)

single cells, some are endosymbionts

MAJOR PIGMENTS:Chlorophylls a and c

RED ALGAE (Rhodophyta)

All species are regarded as algal

free-living and parasitic, single celled, and multicellular

MAJOR PIGMENTS:Phycobilins

STRAMENOPILES

Most but not all stramenopiles are algae, the group includes diatoms, brown algae, synurophytes and other 'chrysophytes'

single celled, colonial and multicellular, free-living and parasitic

MAJOR PIGMENTS:Chlorophylls a and c

VIRIDAEPLANTAE

The green algae, all but a few genera are algal, prasinophytes, chlorophyta (e.g. volvocalean algae, conjugatopohytes, Ulvales, Charales)

single celled, colonial and multicellular, free-living

MAJOR PIGMENT:Chlorophyll b

Genera of algal protists for which no clear ultrastructuralidentityhas been developed (after Patterson, 1999):

  • Adinomonas
  • Archaeosphaerodiniopsis
  • Aurospora
  • Berghiella
  • Bjornbergiella
  • Boekelovia
  • Camptoptyche
  • Chalarodora
  • Chlamydomyxa
  • Copromonas
  • Cyanomastix
  • Dinoasteromonas
  • Dinoceras
  • Glaucocystopsis
  • Goniodinium
  • Heteromastix
  • Hillea
  • Histiophysis
  • Isoselmis
  • Melanodinium
  • Meringosphaera
  • Monodus
  • Nephrodinium
  • Pachydinium
  • Peliainia
  • Petasaria
  • Phialonema
  • Pleuromastix
  • Pseudoactiniscus
  • Strobilomonas
  • Syncrypta
  • Tetragonidium
  • Thaulirens
  • Thaumatodinium
  • Thylakomonas
  • Triangulomonas
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Algae: Protists with Chloroplasts. Authored by David J. Patterson. Tree of Life; accessed August 13, 2013
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Cryptomonad

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The cryptomonads (or cryptophytes)[2] are a group of algae,[3] most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella.

Some may exhibit mixotrophy.[4]

Characteristics

Cryptomonads are distinguished by the presence of characteristic extrusomes called ejectisomes or ejectosomes, which consist of two connected spiral ribbons held under tension.[5] If the cells are irritated either by mechanical, chemical or light stress, they discharge, propelling the cell in a zig-zag course away from the disturbance. Large ejectisomes, visible under the light microscope, are associated with the pocket; smaller ones occur underneath the periplast, the cryptophyte-specific cell surrounding.[6][7]

Cryptomonads have one or two chloroplasts, except for Chilomonas, which has leucoplasts and Goniomonas (formerly Cyathomonas) which lacks plastids entirely. These contain chlorophylls a and c, together with phycobiliproteins and other pigments, and vary in color (brown, red to blueish-green). Each is surrounded by four membranes, and there is a reduced cell nucleus called a nucleomorph between the middle two. This indicates that the plastid was derived from a eukaryotic symbiont, shown by genetic studies to have been a red alga.[8] However, the plastids are very different from red algal plastids: phycobiliproteins are present but only in the thylakoid lumen and are present only as phycoerythrin or phycocyanin. In the case of "Rhodomonas" the crystal structure has been determined to 1.63Å;[9] and it has been shown that the alpha subunit bears no relation to any other known phycobiliprotein.

A few cryptomonads, such as Cryptomonas, can form palmelloid stages, but readily escape the surrounding mucus to become free-living flagellates again. Some Cryptomonas species may also form immotile resting stages with rigid cell walls (cysts) to survive unfavorable conditions. Cryptomonad flagella are inserted parallel to one another, and are covered by bipartite hairs called mastigonemes, formed within the endoplasmic reticulum and transported to the cell surface. Small scales may also be present on the flagella and cell body. The mitochondria have flat cristae, and mitosis is open; sexual reproduction has also been reported.

Classification

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Cryptophytes under SEM
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Cryptophytes under light microscope
Further information: Wikispecies:Cryptophyceae

The first mention of cryptomonads appears to have been made by Christian Gottfried Ehrenberg in 1831,[10] while studying Infusoria. Later, botanists treated them as a separate algae group, class Cryptophyceae or division Cryptophyta, while zoologists treated them as the flagellate protozoa order Cryptomonadina. In some classifications, the cryptomonads were considered close relatives of the dinoflagellates because of their (seemingly) similar pigmentation, being grouped as the Pyrrhophyta. There is considerable evidence that cryptomonad chloroplasts are closely related to those of the heterokonts and haptophytes, and the three groups are sometimes united as the Chromista. However, the case that the organisms themselves are closely related is not very strong, and they may have acquired plastids independently. Currently they are discussed to be members of the clade Diaphoretickes and to form together with the Haptophyta the group Hacrobia. Parfrey et al. and Burki et al. placed Cryptophyceae as a sister clade to the Green Algae.[11][12]

One suggested grouping is as follows: (1) Cryptomonas, (2) Chroomonas/Komma and Hemiselmis, (3) Rhodomonas/Rhinomonas/Storeatula, (4) Guillardia/Hanusia, (5) Geminigera/Plagioselmis/Teleaulax, (6) Proteomonas sulcata, (7) Falcomonas daucoides.[13]

Katablepharids

Main article: Katablepharid

The katablepharids, a group of heterotrophic flagellates, have been considered as part of the Cryptophyta since katablepharids were described in 1939.

References

  1. ^ Reviers, B. de. (2006). Biologia e Filogenia das Algas. Editora Artmed, Porto Alegre, p.15.
  2. ^ Barnes, Richard Stephen Kent (2001). The Invertebrates: A Synthesis. Wiley-Blackwell. p. 41. .mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}ISBN 978-0-632-04761-1.
  3. ^ Khan H, Archibald JM (May 2008). "Lateral transfer of introns in the cryptophyte plastid genome". Nucleic Acids Res. 36 (9): 3043–53. doi:10.1093/nar/gkn095. PMC 2396441. PMID 18397952.
  4. ^ "Cryptophyta - the cryptomonads". Archived from the original on 2011-06-10. Retrieved 2009-06-02.
  5. ^ Graham, L. E.; Graham, J. M.; Wilcox, L. W. (2009). Algae (2nd ed.). San Francisco, CA: Benjamin Cummings (Pearson). ISBN 9780321559654.
  6. ^ Morrall, S.; Greenwood, A. D. (1980). "A comparison of the periodic sub-structures of the trichocysts of the Cryptophyceae and Prasinophyceae". BioSystems. 12: 71–83. doi:10.1016/0303-2647(80)90039-8.
  7. ^ Grim, J. N.; Staehelin, L. A. (1984). "The ejectisomes of the flagellate Chilomonas paramecium - Visualization by freeze-fracture and isolation techniques". Journal of Protozoology. 31 (2): 259–267. doi:10.1111/j.1550-7408.1984.tb02957.x.
  8. ^ Douglas, S.; et al. (2002). "The highly reduced genome of an enslaved algal nucleus". Nature. 410 (6832): 1091–1096. doi:10.1038/35074092. PMID 11323671.
  9. ^ Wilk, K.; et al. (1999). "Evolution of a light-harvesting protein by addition of new subunits and rearrangement of conserved elements: Crystal structure of a cryptophyte phycoerythrin at 1.63Å resolution". PNAS. 96: 8901–8906. doi:10.1073/pnas.96.16.8901. PMC 17705.
  10. ^ Novarino, G., 2012. Cryptomonad taxonomy in the 21st century: The first 200 years. In: Phycological Reports: Current advances in algal taxonomy and its applications: phylogenetic, ecological and applied perspective. Institute of Botany, Polish Academy of Sciences, Kraków, pp. 19-52, [1].
  11. ^ Parfrey, Laura Wegener; Lahr, Daniel J. G.; Knoll, Andrew H.; Katz, Laura A. (2011-08-16). "Estimating the timing of early eukaryotic diversification with multigene molecular clocks". Proceedings of the National Academy of Sciences. 108 (33): 13624–13629. doi:10.1073/pnas.1110633108. ISSN 0027-8424. PMC 3158185. PMID 21810989.
  12. ^ Burki, Fabien; Kaplan, Maia; Tikhonenkov, Denis V.; Zlatogursky, Vasily; Minh, Bui Quang; Radaykina, Liudmila V.; Smirnov, Alexey; Mylnikov, Alexander P.; Keeling, Patrick J. (2016-01-27). "Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista". Proc. R. Soc. B. 283 (1823): 20152802. doi:10.1098/rspb.2015.2802. ISSN 0962-8452. PMC 4795036. PMID 26817772.
  13. ^ "Cryptomonads". Retrieved 2009-06-24.

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Cryptomonad: Brief Summary

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The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella.

Some may exhibit mixotrophy.

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