Editing Diatom (section)

==Morphology==
[[File:2023 Diatom.svg|thumb|upright=1.9|{{center|'''Representation of a diatom'''}} {{ordered list| Central nodule|Striae; pores, punctae, spots or dots in a line on the surface that allow nutrients in, and waste out, of the cell |
[[Areolae (diatom)|Areola]]; hexagonal or polygonal boxlike perforation with a sieve present on the surface of diatom |[[Raphe]]; slit in the valves  |Polar nodule; thickening of wall at the distal ends of the raphe <ref>Taylor, J. C., Harding, W. R. and Archibald, C. (2007). ''An Illustrated Guide to Some Common Diatom Species from South Africa''. Gezina: Water Research Commission. {{ISBN|9781770054844}}.</ref><ref>Mishra, M., Arukha, A.P., Bashir, T., Yadav, D. and Prasad, G.B.K.S. (2017) "All new faces of diatoms: potential source of nanomaterials and beyond". ''Frontiers in microbiology'', '''8''': 1239. {{doi|10.3389/fmicb.2017.01239}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=16 October 2017 }}.</ref>|[[Frustule]]; hard and porous cell wall |[[Pyrenoid]]; center of [[carbon fixation]] |[[Plastid]] membranes (4, secondary red) |Inner membranes |[[Thylakoid]]; site of the [[light-dependent reactions]] of [[photosynthesis]] |[[Oil body]]; storage for triacylglycerols <ref>{{cite journal|journal=Philosophical Transactions of the Royal Society B|last=Maeda|first=Yoshiaki|url=https://doi.org/10.1098/rstb.2016.0408|title=Structure and properties of oil bodies in diatoms|date=2017-07-17|volume=372|issue=1728|doi=10.1098/rstb.2016.0408 |pmid=28717018 |pmc=5516117 }}</ref>|[[Mitochondria|Mitochondrion]]; creates [[Adenosine triphosphate|ATP]] (energy) for the cell |[[Vacuole]]s; vesicle of a cell that contains fluid bound by a membrane |Cytoplasmic strand; holds the nucleus |Protoplasmic bridge| Epivalve|[[Cell nucleus|Nucleus]]; holds the genetic material |[[Endoplasmic reticulum]], the transport network for molecules going to specific parts of the cell||[[Golgi apparatus]]; modifies [[protein]]s and sends them out of the cell |Epicingulum|Hypocingulum|Hypovalve|[[Microtubule]] centre}}]]

[[File:3D-animation of the diatom Corethron sp.ogg|thumb|upright=1.8| {{center|'''3D-animation of the diatom ''Corethron'' sp.'''<br />Displays overlays from four fluorescent channels}}(a) Green: [DiOC6(3) fluorescence] - stains cellular membranes indicating the core cell bodies<br />(b) Cyan: [PLL-A546 fluorescence] - generic counterstain for visualising eukaryotic cell surfaces<br />(c) Blue: [Hoechst fluorescence] - stains DNA, identifies nuclei<br />(d) Red: [chlorophyll autofluorescence] - resolves chloroplasts{{hsp}}<ref name="Colin 2017">Colin, S., Coelho, L.P., Sunagawa, S., Bowler, C., Karsenti, E., Bork, P., Pepperkok, R. and De Vargas, C. (2017) "Quantitative 3D-imaging for cell biology and ecology of environmental microbial eukaryotes". ''eLife'', '''6''': e26066. {{doi|10.7554/eLife.26066.002}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=16 October 2017 }}.</ref><br /><small> {{center|The animation starts by overlaying all available fluorescent channels, and then clarifies the visualisation by switching channels on and off}}</small>]]Diatoms are generally 20 to 200 micrometers in size,<ref>University College London (2002) [https://www.ucl.ac.uk/GeolSci/micropal/diatom.html#:~:text=Diatoms%20are%20commonly%20between%2020,by%20bands%20into%20long%20chains). Diatoms] {{Webarchive|url=https://web.archive.org/web/20110927231912/http://www.ucl.ac.uk/GeolSci/micropal/diatom.html#:~:text=Diatoms%20are%20commonly%20between%2020,by%20bands%20into%20long%20chains). |date=27 September 2011 }} ''Micropalaeontology Unit''.</ref> with a few larger species. Their yellowish-brown [[chloroplast]]s, the site of photosynthesis, are typical of [[heterokont]]s, having four [[cell membrane]]s and containing [[biological pigment|pigments]] such as the [[carotenoid]] [[fucoxanthin]]. Individuals usually lack [[flagellum|flagella]], but they are present in male [[gamete]]s of the centric diatoms and have the usual heterokont structure, including the hairs ([[mastigoneme]]s) characteristic in other groups.

Diatoms are often referred as "jewels of the sea" or "living opals" due to their optical properties.<ref>{{cite journal |doi=10.1038/nnano.2007.152 |pmid=18654305 |title=Biomimetics of photonic nanostructures |journal=Nature Nanotechnology |volume=2 |issue=6 |pages=347–53 |year=2007 |last1=Parker |first1=Andrew R. |last2=Townley |first2=Helen E. |bibcode=2007NatNa...2..347P }}</ref> The biological function of this [[structural coloration]] is not clear, but it is speculated that it may be related to communication, camouflage, thermal exchange and/or UV protection.<ref>{{cite journal |doi=10.1016/j.tibtech.2008.11.003 |pmid=19167770 |title=The Glass Menagerie: Diatoms for novel applications in nanotechnology |journal=Trends in Biotechnology |volume=27 |issue=2 |pages=116–27 |year=2009 |last1=Gordon |first1=Richard |last2=Losic |first2=Dusan |last3=Tiffany |first3=Mary Ann |last4=Nagy |first4=Stephen S. |last5=Sterrenburg |first5=Frithjof A.S. }}</ref>

Diatoms build intricate hard but porous cell walls called [[frustule]]s composed primarily of [[silica]].<ref name="Horner2002" />{{rp|25–30}} This siliceous wall<ref name="Corning Museum of Glass">{{cite web|title=Glass in Nature|url=http://www.cmog.org/article/glass-nature|publisher=The Corning Museum of Glass|access-date=19 February 2013|archive-url=https://web.archive.org/web/20130307120741/http://www.cmog.org/article/glass-nature|archive-date=7 March 2013|url-status=dead}}</ref> can be highly patterned with a variety of pores, ribs, minute spines, marginal ridges and elevations; all of which can be used to delineate genera and species.

The cell itself consists of two halves, each containing an essentially flat plate, or valve, and marginal connecting, or girdle band. One half, the ''hypotheca'', is slightly smaller than the other half, the ''epitheca''. Diatom morphology varies. Although the shape of the cell is typically circular, some cells may be triangular, square, or elliptical. Their distinguishing feature is a hard mineral shell or frustule composed of opal (hydrated, polymerized silicic acid).{{clear}}
[[File:Diatomeas-Haeckel.jpg|thumb|upright=1.3|right|Selections from [[Ernst Haeckel]]'s 1904 {{lang|de|[[Kunstformen der Natur]]}} (''Art Forms of Nature''), showing pennate (left) and centric (right) frustules.]]

Diatoms are divided into two groups that are distinguished by the shape of the frustule: the ''centric diatoms'' and the ''pennate diatoms''.

Pennate diatoms are bilaterally symmetric. Each one of their valves have openings that are slits along the [[raphe]]s and their shells are typically elongated parallel to these raphes. They generate cell movement through cytoplasm that streams along the raphes, always moving along solid surfaces.

Centric diatoms are radially symmetric. They are composed of upper and lower valves – ''epitheca'' and ''hypotheca'' – each consisting of a valve and a girdle band that can easily slide underneath each other and expand to increase cell content over the diatoms progression. The cytoplasm of the centric diatom is located along the inner surface of the shell and provides a hollow lining around the large vacuole located in the center of the cell. This large, central vacuole is filled by a fluid known as "cell sap" which is similar to seawater but varies with specific ion content. The cytoplasmic layer is home to several organelles, like the chloroplasts and mitochondria. Before the centric diatom begins to expand, its nucleus is at the center of one of the valves and begins to move towards the center of the cytoplasmic layer before division is complete. Centric diatoms have a variety of shapes and sizes, depending on from which axis the shell extends, and if spines are present.

[[File:Shape classification of diatom frustules.png|thumb|upright=1.3|left| {{center|Shape classification of diatom frustules. The images are 3D models. The actual sizes of the frustules are about 10–80&nbsp;μm.<ref name="Zhang 2012" />}}]]
[[File:Structure of diatom frustules.png|thumb|upright=1.3|right|{{center|Structure of a centric diatom frustule <ref name="Zhang 2012">{{cite journal|last1=Zhang|first1=D.|last2=Wang|first2=Y.|last3=Cai|first3=J.|last4=Pan|first4=J.|last5=Jiang|first5=X.|last6=Jiang|first6=Y.|year=2012|title=Bio-manufacturing technology based on diatom micro- and nanostructure|journal=Chinese Science Bulletin|volume=57|issue=30|pages=3836–3849|doi=10.1007/s11434-012-5410-x|bibcode=2012ChSBu..57.3836Z|doi-access=free}}</ref>}}]]
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