Editing Cryptomonad (section)

==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|
}}]]