Editing Cryptomonad

{{short description|Group of algae and colorless flagellates}}
{{redirect|Cryptophyte||Cryptophyte (disambiguation)}}
{{Automatic taxobox
| name = Cryptomonads
| image = Rhodomonas_salina_CCMP_322.jpg
| image_caption =  ''Rhodomonas salina''
| taxon = Cryptomonada
| authority = [[Thomas Cavalier-Smith|Cavalier-Smith]], 2004 stat. nov. 2015<ref name="Cavalier-Smith 2018">{{cite journal|doi=10.1007/S00709-017-1147-3 |title=Kingdom Chromista and its eight phyla: A new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences |date=2018 |last1=Cavalier-Smith |first1=Thomas |journal=Protoplasma |volume=255 |pages=297–357 |pmid=28875267 |pmc=5756292 }}</ref>
|display_parents=6
| subdivision_ranks = Classes & orders
| subdivision_ref = <ref name="Cavalier-Smith 2018"/>
| subdivision = 
* [[Goniomonadea]]
** [[Hemiarmida]]
** [[Goniomonadida]]
* [[Cryptophyceae]]
** [[Cryptomonadales]]
** [[Tetragonidiales]]
}}

The '''cryptomonads''' (or '''cryptophytes''')<ref>Barnes, Richard Stephen Kent (2001). ''The Invertebrates: A Synthesis''. Wiley-Blackwell. p. 41. {{ISBN|978-0-632-04761-1}}.</ref> are a [[Class (biology)|superclass]] of [[algae]],<ref name="pmid18397952">{{cite journal |author=Khan H, Archibald JM |title=Lateral transfer of introns in the cryptophyte plastid genome |journal=Nucleic Acids Res. |volume=36 |issue=9 |pages=3043–53 |date=May 2008 |pmid=18397952 |pmc=2396441 |doi=10.1093/nar/gkn095 |url=}}</ref> most of which have [[chloroplast|plastids]]. They are traditionally considered a [[Division (taxonomy)|division]] of [[algae]] among [[phycologist]]s, under the name of '''Cryptophyta'''.<ref>{{cite journal|doi=10.1016/j.protis.2004.12.003 |title=The Katablepharids are a Distant Sister Group of the Cryptophyta: A Proposal for Katablepharidophyta Divisio Nova/Kathablepharida Phylum Novum Based on SSU rDNA and Beta-Tubulin Phylogeny |date=2005 |last1=Okamoto |first1=N. |last2=Inouye |first2=I. |journal=Protist |volume=156 |issue=2 |pages=163–179 |pmid=16171184 }}</ref> They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around [[1 E-5 m|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 [[flagellum|flagella]]. Some may exhibit [[mixotrophy]].<ref name="urlCryptophyta - the cryptomonads">{{cite web|url=http://www.life.umd.edu/labs/delwiche/PSlife/lectures/Cryptophyta.html/wwwtax.cgi?mode=Info&id=412159&lvl=1|title=Cryptophyta - the cryptomonads|access-date=2009-06-02|url-status=dead|archive-url=https://web.archive.org/web/20110610151135/http://www.life.umd.edu/labs/delwiche/PSlife/lectures/Cryptophyta.html/wwwtax.cgi?mode=Info&id=412159&lvl=1|archive-date=2011-06-10}}</ref> They are classified as superclass '''Cryptomonada''', which is divided into two classes: heterotrophic [[Goniomonadea]] and phototrophic [[Cryptophyceae]]. The two groups are united under three shared morphological characteristics: presence of a [[periplast]], [[ejectisomes]] with secondary scroll, and mitochondrial [[cristae]] with flat tubules.<ref>{{cite book | last = Cavalier-Smith| first = Thomas| title  =Organelles, Genomes, and Eukaryote Phylogeny | year = 2004| pages = 87–88}}</ref> Genetic studies as early as 1994 also supported the hypothesis that ''Goniomonas'' was sister to Cryptophyceae.<ref>{{Citation |last=McFadden, Gilson, & Hill |year=1994 |title=Goniomonas: rRNA sequences indicate that this phagotrophic flagellate is a close relative of the host component of cryptomonads |journal=European Journal of Phycology |volume=29 |issue=1 |pages=29–32 |doi=10.1080/09670269400650451}}</ref> A study in 2018 found strong evidence that the common ancestor of Cryptomonada was an autotrophic protist.<ref>{{Citation |last=Cenci |year=2018 |title=Nuclear genome sequence of the plastid-lacking cryptomonad Goniomonas avonlea provides insights into the evolution of secondary plastids |journal=BMC Biology  |volume=16 |issue=1 |pages=137 |doi=10.1186/s12915-018-0593-5|pmid=30482201 |pmc=6260743 |doi-access=free }}</ref>
==Characteristics==
Cryptomonads are distinguished by the presence of characteristic [[extrusome]]s called [[ejectosome]]s, which consist of two connected spiral ribbons held under tension.<ref name="Graham">{{cite book |last1=Graham |first1=L. E. |last2=Graham |first2=J. M. |last3=Wilcox |first3=L. W. |year=2009 |title=Algae |edition=2nd |publisher=Benjamin Cummings (Pearson) |location=San Francisco, CA |isbn=9780321559654 }}</ref> 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 ejectosomes, visible under the light microscope, are associated with the pocket; smaller ones occur underneath the [[periplast]], the cryptophyte-specific cell surrounding.<ref name="MorrallGreenwood">{{cite journal |last1=Morrall |first1=S. |last2=Greenwood |first2=A. D. |year=1980 |title=A comparison of the periodic sub-structures of the trichocysts of the Cryptophyceae and Prasinophyceae |journal=BioSystems |volume=12 |issue= 1–2|pages=71–83 |doi= 10.1016/0303-2647(80)90039-8|pmid=6155157 }}</ref><ref name="GrimStaehelin">{{cite journal |last1=Grim |first1=J. N. |author2-link=Lucas Andrew Staehelin|last2=Staehelin |first2=L. A. |year=1984 |title=The ejectisomes of the flagellate ''Chilomonas paramecium'' - Visualization by freeze-fracture and isolation techniques |journal=[[Journal of Protozoology]] |volume=31 |issue=2 |pages=259–267 |doi=10.1111/j.1550-7408.1984.tb02957.x |pmid=6470985 }}</ref>

Except for the class ''[[Goniomonadea]]'', which lacks plastids entirely,<ref>[https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-018-0593-5 Nuclear genome sequence of the plastid-lacking cryptomonad ''Goniomonas avonlea'' provides insights into the evolution of secondary plastids]</ref> and ''Cryptomonas paramecium'' (previously called ''[[Chilomonas]] paramecium''), which has [[leucoplast]]s, cryptomonads have one or two chloroplasts. These contain [[chlorophyll]]s ''a'' and ''c'', together with [[phycobiliprotein]]s 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 [[eukaryote|eukaryotic]] symbiont, shown by genetic studies to have been a [[red alga]].<ref name="Douglas2002">{{cite journal |last=Douglas |first=S. |year=2002 |title=The highly reduced genome of an enslaved algal nucleus |journal=[[Nature (journal)|Nature]] |volume=410 |issue=6832 |pages=1091–1096 |doi=10.1038/35074092 |pmid=11323671|display-authors=etal|doi-access=free |bibcode=2001Natur.410.1091D }}</ref> 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 1.63{{Space|1|thin}}Å;<ref name="Wilk1999">{{cite journal |last=Wilk |first=K. |year=1999 |title=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. |journal=PNAS |volume=96 |issue=16 |pages=8901–8906 |doi=10.1073/pnas.96.16.8901|pmid=10430868 |display-authors=etal|pmc=17705 |doi-access=free }}</ref> 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 [[wikt:palmelloid|palmelloid]] stages, but readily escape the surrounding mucus to become free-living flagellates again. Some ''[[Cryptomonas]]'' species may also form immotile [[microbial cyst]]s—resting stages with rigid cell walls 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 [[mitochondrion|mitochondria]] have flat [[crista]]e, and [[mitosis]] is open; [[sexual reproduction]] has also been reported.

[[File:2023 Cryptomonad.svg|thumb|upright=2|center|{{center|'''Representation of a cryptomonad'''}} {{ordered list| Anterior flagellum ([[Mastigoneme|mastigonemes]] on both faces)|
Posterior flagellum (mastigonemes on one face)|
[[Contractile vacuole]], regulates the quantity of water inside a cell|
Vestibulum|
[[Basal body|Basal bodies]]|
Gullet (furrow or crypt)|
[[Mitochondria|Mitochondrion]], creates [[Adenosine triphosphate|ATP]] (energy) for the cell|
Maupa's bodies|
Ejectisomes|
Starch granule|
[[Golgi apparatus]], packages proteins|
[[Nucleomorph]], a small, vestigial eukaryotic nucleus|
[[Pyrenoid]], center of [[carbon fixation]]|
Periplastidial compartment|
[[Thylakoid]], site of the [[light-dependent reactions]] of [[photosynthesis]]|
[[Plastid]] membranes (4, secondary)|
Nucleus|
[[Nucleolus]]|
Lipid globules|
}}]]

==Classification==
[[File:CSIRO ScienceImage 6743 SEM Cryptophyte.jpg|thumb|Cryptophytes under [[Scanning electron microscope|SEM]]]]
[[File:CSIRO ScienceImage 7234 microalgal cultures.jpg|thumb|Cryptophytes under [[light microscope]] ]]
{{further|Wikispecies:Cryptophyceae}}

The first mention of cryptomonads appears to have been made by [[Christian Gottfried Ehrenberg]] in 1831,<ref>{{cite journal |last=Novarino |first=G. |date=2012 |title=Cryptomonad taxonomy in the 21st century: The first 200 years |journal=Phycological Reports: Current Advances in Algal Taxonomy and Its Applications: Phylogenetic, Ecological and Applied Perspective |pages=19–52 |url= https://www.researchgate.net/publication/265520014 |access-date=2018-10-16}}</ref> 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 [[dinoflagellate]]s because of their (seemingly) similar pigmentation, being grouped as the [[Pyrrhophyta]]. Cryptomonad chloroplasts are closely related to those of the [[heterokont]]s and [[haptophyte]]s, and the three groups were united by Cavalier-Smith as the [[Chromista]]. However, the case that the organisms themselves are closely related was counter-indicated by the major differences in cell organization ([[ultrastructural identity]]), suggesting that the three major lineages assigned to the chromists had acquired plastids independently, and that chromists are polyphyletic. The perspective that cryptomonads are primitively heterotrophic and secondarily acquired chloroplasts, is supported by molecular evidence.<ref>{{cite journal|pmid=30482201|pmc=6260743 |date=2018 |last1=Cenci |first1=U. |last2=Sibbald |first2=S. J. |last3=Curtis |first3=B. A. |last4=Kamikawa |first4=R. |last5=Eme |first5=L. |last6=Moog |first6=D. |last7=Henrissat |first7=B. |last8=Maréchal |first8=E. |last9=Chabi |first9=M. |last10=Djemiel |first10=C. |last11=Roger |first11=A. J. |last12=Kim |first12=E. |last13=Archibald |first13=J. M. |title=Nuclear genome sequence of the plastid-lacking cryptomonad Goniomonas avonlea provides insights into the evolution of secondary plastids |journal=BMC Biology |volume=16 |issue=1 |page=137 |doi=10.1186/s12915-018-0593-5 |doi-access=free }}</ref>   Parfrey et al. and Burki et al. placed Cryptophyceae as a sister clade to the [[Green algae|Green Algae]],<ref>{{cite journal|author-link1=Laura Wegener Parfrey|last1=Parfrey|first1=Laura Wegener|last2=Lahr|first2=Daniel J. G.|last3=Knoll|first3=Andrew H.|last4=Katz|first4=Laura A.|author-link4=Laura A. Katz|title=Estimating the timing of early eukaryotic diversification with multigene molecular clocks|journal=Proceedings of the National Academy of Sciences of the United States of America|date=August 16, 2011|volume=108|issue=33|pages=13624&ndash;13629|doi=10.1073/pnas.1110633108|pmid=21810989|pmc=3158185|bibcode=2011PNAS..10813624P |doi-access=free}}</ref> or green algae plus [[glaucophytes]].<ref>{{Cite journal|last1=Burki|first1=Fabien|last2=Kaplan|first2=Maia|last3=Tikhonenkov|first3=Denis V.|last4=Zlatogursky|first4=Vasily|last5=Minh|first5=Bui Quang|last6=Radaykina|first6=Liudmila V.|last7=Smirnov|first7=Alexey|last8=Mylnikov|first8=Alexander P.|last9=Keeling|first9=Patrick J. |date=2016-01-27 |title=Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista |journal=Proc. R. Soc. B |language=en |volume=283 |issue=1823 |pages=20152802 |doi=10.1098/rspb.2015.2802 |issn=0962-8452 |pmid=26817772 |pmc=4795036}}</ref>  The sister group to the cryptomonads is likely the kathablepharids (also referred to as katablepharids), a group of flagellates that also have ejectisomes.<ref>{{cite journal|doi=10.3389/fevo.2020.00140 |doi-access=free |title=Mitochondrial Genomes of Hemiarma marina and Leucocryptos marina Revised the Evolution of Cytochrome c Maturation in Cryptista |date=2020 |last1=Nishimura |first1=Yuki |last2=Kume |first2=Keitaro |last3=Sonehara |first3=Keito |last4=Tanifuji |first4=Goro |last5=Shiratori |first5=Takashi |last6=Ishida |first6=Ken-Ichiro |last7=Hashimoto |first7=Tetsuo |last8=Inagaki |first8=Yuji |last9=Ohkuma |first9=Moriya |journal=Frontiers in Ecology and Evolution |volume=8 }}</ref>

One suggested grouping is as follows: (1) ''[[Cryptomonas]]'', (2) ''[[Chroomonas]]/[[Komma caudata|Komma]]'' and ''[[Hemiselmis]]'', (3) ''[[Rhodomonas]]/[[Rhinomonas]]/[[Storeatula]]'', (4) ''[[Guillardia]]/[[Hanusia]]'', (5) ''[[Geminigera]]/[[Plagioselmis]]/[[Teleaulax]]'', (6) ''[[Proteomonas sulcata]]'', (7) ''[[Falcomonas daucoides]]''.<ref name="urlCryptomonads">{{cite web |url=http://tolweb.org/Cryptomonads/2396 |title=Cryptomonads |access-date=2009-06-24}}</ref>

==References==
{{reflist|20em}}

==External links==
* [http://tolweb.org/Cryptomonads/2396 Tree of Life: Cryptomonads]
* [http://www.algaebase.org/browse/taxonomy/?id=97243 Phylum Cryptophyta at AlgaeBase]

{{Life on Earth}}
{{Eukaryota|D.}}
{{Cryptista}}
{{Taxonbar|from=Q21281984}}

[[Category:Cryptomonads| ]]
[[Category:Cryptista]]
[[Category:Taxa named by Thomas Cavalier-Smith]]