View source for Radiolaria

{{Short description|Phylum of single-celled organisms}}
{{automatic taxobox
| image              = Radiolaria.jpg
| image_caption      = Radiolaria illustration from the [[Challenger Expedition|''Challenger'' expedition]] 1873–76
| image_upright      = 1.2
| fossil_range       = {{fossilrange|542|0|[[Cambrian]] – Recent}}
| taxon              = Radiolaria
| authority          = [[Thomas Cavalier-Smith|Cavalier-Smith]], 1987
| subdivision_ranks  = Classes
| subdivision        = * [[Polycystine]]a
** [[Nassellaria]]
** [[Spumellaria]]
** [[Collodaria]]
* [[Acantharea]]
* [[Taxopodida]] (''[[Sticholonche]]'')
*<small>''Excluded:'' [[Phaeodaria]] (now in [[Cercozoa]])</small>
}}
{{plankton sidebar|taxonomy}}

The '''Radiolaria''', also called '''Radiozoa''', are unicellular eukaryotes of diameter 0.1–0.2&nbsp;mm that produce intricate [[mineral]] [[skeleton]]s, typically with a central capsule dividing the [[cell (biology)|cell]] into the inner and outer portions of [[endoplasm]] and [[Ectoplasm (cell biology)|ectoplasm]]. The elaborate mineral skeleton is usually made of [[Silicon dioxide|silica]].<ref>{{cite journal | last1 = Smalley | first1 = I.J. | year = 1963 | title = Radiolarians:construction of spherical skeleton | journal = Science | volume = 140 | issue = 3565 | pages = 396–397 | doi = 10.1126/science.140.3565.396 | pmid = 17815802 | bibcode = 1963Sci...140..396S | s2cid = 28616246 }}</ref> They are found as [[zooplankton]] throughout the global ocean. As zooplankton, radiolarians are primarily [[heterotroph]]ic, but many have photosynthetic [[endosymbiont]]s and are, therefore, considered [[mixotroph]]s. The skeletal remains of some types of radiolarians make up a large part of the cover of the ocean floor as [[siliceous ooze]]. Due to their rapid change as species and intricate skeletons, radiolarians represent an important diagnostic [[fossil]] found from the [[Cambrian]] onwards.

==Description==
Radiolarians have many needle-like [[pseudopod]]s supported by bundles of [[microtubule]]s, which aid in the radiolarian's buoyancy. The [[cell nucleus]] and most other [[organelle]]s are in the endoplasm, while the ectoplasm is filled with frothy [[vacuole]]s and [[lipid]] droplets, keeping them buoyant. The radiolarian can often contain [[symbiotic]] algae, especially [[zooxanthellae]], which provide most of the cell's energy. Some of this organization is found among the [[heliozoa]], but those lack central capsules and only produce simple scales and spines.

Some radiolarians are known for their resemblance to [[regular polyhedra]], such as the [[icosahedron]]-shaped ''Circogonia icosahedra'' pictured below.

==Taxonomy==
The radiolarians belong to the supergroup [[Rhizaria]] together with ([[amoeboid]] or [[flagellate]]) [[Cercozoa]] and (shelled amoeboid) [[Foraminifera]].<ref name=Pawlowski2009>{{cite journal |vauthors=Pawlowski J, Burki F |title=Untangling the phylogeny of amoeboid protists |journal=J. Eukaryot. Microbiol. |volume=56 |issue=1 |pages=16–25 |year=2009 |pmid=19335771 |doi=10.1111/j.1550-7408.2008.00379.x |doi-access=free }}</ref> Traditionally the radiolarians have been divided into four groups—[[Acantharea]], [[Nassellaria]], [[Spumellaria]] and [[Phaeodarea]]. Phaeodaria is however now considered to be a Cercozoan.<ref name=Yuasa2005>{{cite journal |vauthors=Yuasa T, Takahashi O, Honda D, Mayama S |title=Phylogenetic analyses of the polycystine Radiolaria based on the 18s rDNA sequences of the Spumellarida and the Nassellarida |journal=European Journal of Protistology |volume=41 |issue=4 |pages=287–298 |year=2005 |doi= 10.1016/j.ejop.2005.06.001 }}</ref><ref name=Nikolaev2004>{{cite journal |vauthors=Nikolaev SI, Berney C, Fahrni JF, etal |title=The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=101 |issue=21 |pages=8066–71 |date=May 2004 |pmid=15148395 |pmc=419558 |doi=10.1073/pnas.0308602101 |doi-access=free }}</ref> Nassellaria and Spumellaria both produce siliceous skeletons and were therefore grouped together in the group [[Polycystina]]. Despite some initial suggestions to the contrary, this is also supported by molecular phylogenies. The Acantharea produce skeletons of [[strontium sulfate]] and is closely related to a peculiar genus, ''[[Sticholonche]]'' ([[Sticholonche|Taxopodida]]), which lacks an internal skeleton and was for long time considered a [[heliozoa]]n. The Radiolaria can therefore be divided into two major lineages: Polycystina (Spumellaria + Nassellaria) and Spasmaria (Acantharia + Taxopodida).<ref name="Krabberød2011">{{cite journal |vauthors=Krabberød AK, Bråte J, Dolven JK, etal |title=Radiolaria divided into Polycystina and Spasmaria in combined 18S and 28S rDNA phylogeny |journal=PLOS ONE |volume=6 |issue=8 |pages=e23526 |year=2011 |pmid=21853146 |pmc=3154480 |doi=10.1371/journal.pone.0023526 |bibcode=2011PLoSO...623526K |doi-access=free }}</ref><ref name=Cavalier-Smith1993>{{cite journal |author=Cavalier-Smith T |title=Kingdom protozoa and its 18 phyla |journal=Microbiol. Rev. |volume=57 |issue=4 |pages=953–94 |date=December 1993 |pmid=8302218 |pmc=372943 |url=|doi=10.1128/mmbr.57.4.953-994.1993}}</ref>

There are several higher-order groups that have been detected in molecular analyses of environmental data. Particularly, groups related to Acantharia<ref name=Decelle2011>{{cite journal |vauthors=Decelle J, Suzuki N, Mahé F, de Vargas C, Not F |title=Molecular phylogeny and morphological evolution of the Acantharia (Radiolaria) |journal=Protist |volume=163 |issue=3 |pages=435–50 |date=May 2012 |pmid=22154393 |doi=10.1016/j.protis.2011.10.002 }}</ref> and Spumellaria.<ref name=Not2007>{{cite journal |vauthors=Not F, Gausling R, Azam F, Heidelberg JF, Worden AZ |title=Vertical distribution of picoeukaryotic diversity in the Sargasso Sea |journal=Environ. Microbiol. |volume=9 |issue=5 |pages=1233–52 |date=May 2007 |pmid=17472637 |doi=10.1111/j.1462-2920.2007.01247.x |bibcode=2007EnvMi...9.1233N }}</ref> These groups are so far completely unknown in terms of morphology and physiology and the radiolarian diversity is therefore likely to be much higher than what is currently known.

The relationship between the Foraminifera and Radiolaria is also debated. Molecular trees support their close relationship—a grouping termed Retaria.<ref name=Cavalier-Smith1999>{{cite journal |author=Cavalier-Smith T |title=Principles of protein and lipid targeting in secondary symbiogenesis: euglenoid, dinoflagellate, and sporozoan plastid origins and the eukaryote family tree |journal=J. Eukaryot. Microbiol. |volume=46 |issue=4 |pages=347–66 |date=July 1999 |pmid=18092388 |doi=10.1111/j.1550-7408.1999.tb04614.x |s2cid=22759799 }}</ref> But whether they are sister lineages or whether the Foraminifera should be included within the Radiolaria is not known.

{| class="wikitable"
|-
! Class
! Order
! Image
! Families
! Genera
! Species
! Description
|-
! rowspan=3 style="background:rgb(110,110,170)" | [[Polycystinea|<span style="color:white;">Polycystinea</span>]]
! style="background:rgb(150,80,150)" |[[Nassellaria|<span style="color:white;">Nassellaria</span>]]
| [[File:Mikrofoto.de-Radiolarien-3.jpg|140px]]
| align=center | 
| align=center | 
| align=center | 
| valign="top" | ...
|-
! style="background:rgb(150,80,150)" |[[Spumellaria|<span style="color:white;">Spumellaria</span>]]
| [[File:Haeckel Spumellaria detail.png|140px]]
| align="center" |
| align="center" | 
| align="center" | 
| valign="top" | ...
|-
! style="background:rgb(150,80,150)" |[[Collodaria|<span style="color:white;">Collodaria</span>]]
| [[File:Acrosphaera spinosa 2.jpg|140px]]
| align="center" |
| align="center" | 
| align="center" | 
| valign="top" | ...
|-
! style="background:rgb(110,110,170)" |[[Acantharea|<span style="color:white;">Acantharea</span>]]
! style="background:rgb(150,80,150)" |
|[[File:Acantharian radiolarian Xiphacantha (Haeckel).jpg|140px]]
| align="center" | 
| align="center" | 
| align="center" | 
| valign="top" | ...
|-
! style="background:rgb(110,110,170)" |[[Sticholonchea|<span style="color:white;">Sticholonchea</span>]]
! style="background:rgb(150,80,150)" |[[Taxopodida|<span style="color:white;">Taxopodida</span>]]
|[[File:Sticholonche.png|140px]]
| align="center" | 1
| align="center" | 1
| align="center" | 1
| valign="top" | ...
|}

==Biogeography==
[[File:Radiolarian biogeography with observed and predicted responses to temperature change.webp|thumb|upright=2| {{center|Radiolarian biogeography with observed and predicted responses to temperature change}} <small>The color polygons in all three panels represent generalized radiolarian biogeographic provinces, as well as their relative water mass temperatures (cooler colors indicate cooler temperatures, and vice versa). Globe image adapted from NASA Blue Marble: Next Generation imagery. Ocean floor bathymetry from Google Earth seafloor elevation profile (5°N–74°S, at 120°W).</small>]]

In the diagram on the right, '''a''' Illustrates generalized radiolarian provinces{{hsp}}<ref>Boltovskoy, D., Kling, S. A., Takahashi, K. & BjØrklund, K. (2010) "World atlas of distribution of recent Polycystina (Radiolaria)". ''Palaeontologia Electronica'', '''13''': 1–230.</ref><ref>Casey, R. E., Spaw, J. M., & Kunze, F. R. (1982) "Polycystine radiolarian distribution and enhancements related to oceanographic conditions in a hypothetical ocean". ''Am. Assoc. Pet. Geol. Bull.'', '''66''': 319–332.</ref> and their relationship to water mass temperature (warm versus cool color shading) and circulation (gray arrows). Due to high-latitude water mass submergence under warm, stratified waters in lower latitudes, radiolarian species occupy habitats at multiple latitudes, and depths throughout the world oceans. Thus, marine sediments from the tropics reflect a composite of several vertically stacked faunal assemblages, some of which are contiguous with higher latitude surface assemblages. Sediments beneath polar waters include cosmopolitan deep-water radiolarians, as well as high-latitude endemic surface water species. Stars in ('''a''') indicate the latitudes sampled, and the gray bars highlight the radiolarian assemblages included in each sedimentary composite. The horizontal purple bars indicate latitudes known for good radiolarian (silica) preservation, based on surface sediment composition.<ref>{{cite journal |doi = 10.1144/SP358.10|title = The deep-sea microfossil record of macroevolutionary change in plankton and its study|year = 2011|last1 = Lazarus|first1 = David B.|journal = Geological Society, London, Special Publications|volume = 358|issue = 1|pages = 141–166|bibcode = 2011GSLSP.358..141L|s2cid = 128826639}}</ref><ref name=Trubovitz2020>{{cite journal |doi = 10.1038/s41467-020-18879-7|title = Marine plankton show threshold extinction response to Neogene climate change|year = 2020|last1 = Trubovitz|first1 = Sarah|last2 = Lazarus|first2 = David|last3 = Renaudie|first3 = Johan|last4 = Noble|first4 = Paula J.|journal = Nature Communications|volume = 11|issue = 1|page = 5069|pmid = 33093493|pmc = 7582175|bibcode = 2020NatCo..11.5069T}} [[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].</ref> 

Data show that some species were extirpated from high latitudes but persisted in the tropics during the late [[Neogene]], either by migration or range restriction ('''b'''). With predicted global warming, modern [[Southern Ocean]] species will not be able to use migration or range contraction to escape environmental stressors, because their preferred cold-water habitats are disappearing from the globe ('''c'''). However, tropical endemic species may expand their ranges toward midlatitudes. The color polygons in all three panels represent generalized radiolarian biogeographic provinces, as well as their relative water mass temperatures (cooler colors indicate cooler temperatures, and vice versa).<ref name=Trubovitz2020/>

<gallery mode="packed" style="float:left" heights="200px">
File:Circogoniaicosahedra ekw.jpg|''Circogonia icosahedra'', radiolarian species shaped like a [[regular icosahedron]]
File:Anthocyrtium hispidum Haeckel - Radiolarian (34986365113).jpg|''Anthocyrtium hispidum Haeckel''
</gallery>

{{clear}}

==Radiolarian shells==
{{multiple image
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 | header            = Radiolarian shapes
 | header_align      = center
 | header_background = 
 | footer            = &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Drawings by [[Ernst Haeckel|Haeckel]] 1904 (click for details)
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 | background color  = 
 | image1    = Haeckel Phaeodaria 1.jpg
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 | image2    = Haeckel Stephoidea edit.jpg
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{{further|Protist shell#Radiolarians}}

Radiolarians are unicellular predatory [[#Marine protists|protists]] encased in elaborate globular shells (or "capsules"), usually made of silica and pierced with holes. Their name comes from the Latin for "radius". They catch prey by extending parts of their body through the holes. As with the silica frustules of diatoms, radiolarian shells can sink to the ocean floor when radiolarians die and become preserved as part of the ocean sediment. These remains, as [[#Marine microfossils|microfossils]], provide valuable information about past oceanic conditions.<ref name=Wassilieff2006b>Wassilieff, Maggy (2006) [http://www.TeAra.govt.nz/en/photograph/5138/radiolarian-fossils "Plankton - Animal plankton"], ''Te Ara - the Encyclopedia of New Zealand''. Accessed: 2 November 2019.</ref>

<gallery mode="packed" heights="150px" style="float:left;">
File:Mikrofoto.de-Radiolarien 6.jpg|Like diatoms, radiolarians come in many shapes
File:Theocotylissa ficus Ehrenberg - Radiolarian (34638920262).jpg|Also like diatoms, radiolarian shells are usually made of silicate
File:Acantharian radiolarian Xiphacantha (Haeckel).jpg|However [[acantharian]] radiolarians have shells made from [[strontium sulfate]] crystals
</gallery>

[[File:Animation of radiolarian diversity.gif|thumb|upright=2| {{center|Animation of radiolarian diversity{{hsp}}<ref>Kachovich, Sarah (2018) [https://blogs.egu.eu/divisions/ts/2018/07/03/minds-over-methods-linking-microfossils-to-tectonics/ "Minds over Methods: Linking microfossils to tectonics"] Blog of the Tectonics and Structural Geology Division of the European Geosciences Union.</ref>}}]]

<gallery mode="packed" heights="150px" style="float:left;">
File:Spherical radiolarian 2.jpg|Cutaway schematic diagram of a spherical radiolarian shell
File:Cladococcus abietinus.jpg| ''Cladococcus abietinus''
</gallery>

{{Quote box
 |title = 
 |quote = So I set to work on seeking a solution to the Morphogenesis Equations on a sphere. The theory was that a spherical organism was subject to diffusion across its surface membrane by an alien substance, eg sea-water. The Equations were:

:<math>\frac{\partial \mathbf{U}}{\partial t} =  \phi(\nabla^2) \mathbf{U} +  G \mathbf{U}^2 - H\mathbf{U}V, </math>

:<math>V = \mathbf{U}^2</math>

The function <math>\mathbf{U}</math>, taken to be the radius vector from the centre to any point on the surface of the membrane, was argued to be representable as a series of normalised [[Legendre polynomials|Legendre functions]]. The algebraic solution of the above equations ran to some 30 pages in my Thesis and are therefore not reproduced here. They are written in full in the book entitled “Morphogenesis” which is a tribute to Turing, edited by P. T. Saunders, published by North Holland, 1992.<ref>{{cite book | last1=Turing | first1=Alan | last2=Saunders | first2=P. T. | title=Morphogenesis | publisher=North-Holland | publication-place=Amsterdam | date=1992 | isbn=978-0-08-093405-1 | oclc=680063781 | language=eo}}</ref>

The algebraic solution of the equations revealed a family of solutions, corresponding to a parameter n, taking values 2, 4. 6.

When I had solved the algebraic equations, I then used the computer to plot the shape of the resulting organisms. Turing told me that there were real organisms corresponding to what I had produced. He said that they were described and depicted in the records of the voyages of HMS Challenger in the 19th Century.

I solved the equations and produced a set of solutions which corresponded to the actual species of Radiolaria discovered by [[HMS Challenger (1858)|HMS ''Challenger'']] in the 19th century. That expedition to the Pacific Ocean found eight variations in the growth patterns. These are shown in the following figures. The essential feature of the growth is the emergence of elongated "spines" protruding from the sphere at regular positions. Thus the species comprised two, six, twelve, and twenty, spine variations.
 |source = [[Bernard Richards]], 2006{{hsp}}<ref>[[Bernard Richards|Richards, Bernard]] (2006) [https://web.archive.org/web/20060816084810/http://rutherfordjournal.org/article010109.html "Turing, Richards and Morphogenesis"], ''[[The Rutherford Journal]]'', Volume 1.</ref>
 |align = right
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 |border = 
}}

{{clear left}}

===Diversity and morphogenesis===
[[Bernard Richards]], worked under the supervision of [[Alan Turing]] (1912–1954) at Manchester as one of Turing's last students, helping to validate [[Turing pattern|Turing’s theory]] of [[morphogenesis]].<ref>{{citation| last=Richards | first=Bernard | year=1954 | title=The Morphogenesis of Radiolaria | work=MSc thesis | publisher=[[The University of Manchester]] | location=Manchester, UK }}</ref><ref>{{cite journal| last=Richards | first=Bernard | year=2005 | title=Turing, Richards and morphogenesis | journal=[[The Rutherford Journal]] | volume=1 | url=http://www.rutherfordjournal.org/article010109.html }}</ref><ref name=Richards2017>{{cite book| last=Richards | first=Bernard | year=2017 | chapter=Chapter 35 – Radiolaria: Validating the Turing theory | editor-last1=Copeland | editor-first1=Jack |editor-link1=Jack Copeland  |display-editors=etal| title=[[The Turing Guide]] | pages=383–388 }}</ref><ref name="copeland17">{{cite book| authorlink=Jack Copeland | last1=Copeland | first1=Jack | authorlink2=Jonathan Bowen | last2=Bowen | first2=Jonathan | last3=Sprevak | first3=Mark | authorlink4=Robin Wilson (mathematician) | last4=Wilson | first4=Robin |display-authors=et al | title=[[The Turing Guide]] | publisher=[[Oxford University Press]] | year=2017 | isbn=978-0198747833 | pages=478 | chapter=Notes on Contributors }}</ref>

"Turing was keen to take forward the work that [[D’Arcy Thompson]] had published in [[On Growth and Form]] in 1917".<ref name=Richards2017 />

{{clear left}}

{{multiple image
 | align = left
 | direction = horizontal
 | header            = Turing and radiolarian morphology
 | header_align      =
 | header_background = 
 | footer            = Computer simulations of [[Turing pattern]]s on a sphere<br/>closely replicate some radiolarian shell patterns<ref>{{cite journal | last1 = Varea | first1 = C. | last2 = Aragon | first2 = J.L. | last3 = Barrio | first3 = R.A. | year = 1999 | title = Turing patterns on a sphere | journal = Physical Review E | volume = 60 | issue = 4| pages = 4588–92 | doi = 10.1103/PhysRevE.60.4588 | pmid = 11970318 | bibcode = 1999PhRvE..60.4588V }}</ref>
 | footer_align      = center
 | footer_background = #f4ffdd
 | caption_align = center
 | background color  = 
 | image1    = Spherical radiolarian.jpg
 | width1    = 208
 | alt1      = 
 | caption1  = Shell of a spherical radiolarian
 | image2    = Radiolarians - Actinomma sol (33732012006).jpg
 | width2    = 111
 | alt2      = 
 | caption2  = Shell micrographs
 }}

{{ external media
| float  = left
| width  = 280px
| video1 = [https://www.youtube.com/watch?v=5rxwn6vT9JE Radiolarian geometry]
| video2 = [https://www.youtube.com/watch?v=tl_onFMjJWA Ernst Haeckel's radiolarian engravings]
}}

<gallery mode=packed style=float:left heights=160px caption="Spine  variations in radiolarians as discovered by HMS ''Challenger'' in the 19th century and drawn by Ernst Haeckel">
File:Cromyatractus tetracelyphus.jpg| ''Cromyatractus tetracelyphus'' with 2 spines
File:Circopus sexfurcus.jpg| ''Circopus sexfurcus'' with 6 spines
File:Circopurus octahedrus.jpg| ''Circopurus octahedrus'' with 6 spines and 8 faces
File:Circogonia icosahedra.jpg| ''Circogonia icosahedra'' with 12 spines and 20 faces
File:Circorrhegma dodecahedra.jpg| ''Circorrhegma dodecahedra'' with 20 (incompletely drawn) spines and 12 faces
File:Cannocapsa stethoscopium.jpg| ''Cannocapsa stethoscopium'' with 20 spines
</gallery>
{{clear}}

The gallery shows images of the radiolarians as extracted from drawings made by the German zoologist and polymath [[Ernst Haeckel]] in 1887.


* {{Cite journal | last1 = Turing | first1 = Alan | author-link = Alan Turing| title = The Chemical Basis of Morphogenesis | journal = Philosophical Transactions of the Royal Society of London B | volume = 237 | issue = 641 | pages = 37–72 | doi = 10.1098/rstb.1952.0012 | url = http://www.dna.caltech.edu/courses/cs191/paperscs191/turing.pdf| jstor = 92463| date = 1952 | bibcode = 1952RSPTB.237...37T| s2cid = 120437796 }}
* [[Bernard Richards|Richards, Bernard]] (2005-2006) [http://rutherfordjournal.org/article010109.html "Turing, Richards and Morphogenesis"], ''[[The Rutherford Journal]]'', Volume 1.

==Fossil record==
{{multiple image
 | align = right
 | direction = horizontal
 | width     = 500
 | header            = Fossil radiolarian
 | header_align      = center
 | header_background = 
 | background color  = 
 | image1    = Micro-CT model of radiolarian, Triplococcus acanthicus.png
 | alt1      = 
 | caption1  = {{center|'''[[X-ray microtomography]] of ''Triplococcus acanthicus'''''}} This is a [[microfossil]] from the [[Middle Ordovician]] with four nested spheres. The innermost sphere is highlighted red. Each segment is shown at the same scale.<ref name=Kachovich2019>Kachovich, S., Sheng, J. and Aitchison, J.C., 2019. Adding a new dimension to investigations of early radiolarian evolution. Scientific reports, 9(1), pp.1-10. {{doi|10.1038/s41598-019-42771-0}}. [[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].</ref>
}}

The earliest known radiolaria date to the very start of the [[Cambrian]] period, appearing in the same beds as the first [[small shelly fauna]]—they may even be terminal Precambrian in age.<ref name=Chang2018>{{cite journal |last1=Chang |first1=Shan |last2=Feng |first2=Qinglai |last3=Zhang |first3=Lei |title=New Siliceous Microfossils from the Terreneuvian Yanjiahe Formation, South China: The Possible Earliest Radiolarian Fossil Record |journal=Journal of Earth Science |date=14 August 2018 |volume=29 |issue=4 |pages=912–919 |doi=10.1007/s12583-017-0960-0|bibcode=2018JEaSc..29..912C |s2cid=134890245 }}</ref><ref name=Zhang2019>{{cite journal |last1=Zhang |first1=Ke |last2=Feng |first2=Qing-Lai |title=Early Cambrian radiolarians and sponge spicules from the Niujiaohe Formation in South China |journal=Palaeoworld |date=September 2019 |volume=28 |issue=3 |pages=234–242 |doi=10.1016/j.palwor.2019.04.001|s2cid=146452469 }}</ref><ref name="Braun2007"/><ref name="Maletz2017">{{cite journal |last1=Maletz |first1=Jörg |title=The identification of putative Lower Cambrian Radiolaria |journal=Revue de Micropaléontologie |date=June 2017 |volume=60 |issue=2 |pages=233–240 |doi=10.1016/j.revmic.2017.04.001|bibcode=2017RvMic..60..233M }}</ref> They have significant differences from later radiolaria, with a different silica lattice structure and few, if any, spikes on the [[Test (biology)|test]].<ref name= Braun2007>{{the Rise and Fall of the Ediacaran Biota |author=A. Braun |author2=J. Chen |author3=D. Waloszek |author4=A. Maas |chapter=First Early Cambrian Radiolaria|pages=143–149|doi=10.1144/SP286.10}}</ref> About ninety percent of known radiolarian species are extinct. The skeletons, or tests, of ancient radiolarians are used in [[Biostratigraphy|geological dating]], including for [[oil exploration]] and determination of [[Paleoclimatology|ancient climates]].<ref>Zuckerman, L.D., Fellers, T.J., Alvarado, O., and Davidson, M.W. [http://micro.magnet.fsu.edu/micro/gallery/radiolarians/radiolarians.html "Radiolarians"], Molecular Expressions, Florida State University, 4 February 2004.</ref>

Some common radiolarian fossils include ''[[Actinomma]]'', ''[[Heliosphaera]]'' and ''[[Hexadoridium]]''.

{{clear}}

==See also==
* [[Radiolarite]]

==References==
{{Reflist}}
{{refbegin}}
* {{cite journal | last1 = Zettler |first1=Linda A.
| title = Phylogenetic relationships between the Acantharea and the Polycystinea: A molecular perspective on Haeckel's Radiolaria
| journal = Proc. Natl. Acad. Sci. U.S.A.
| year = 1997 | volume = 94 | pages = 11411–6 | doi = 10.1073/pnas.94.21.11411
| pmid = 9326623 | last2 = Sogin | first2 = ML | last3 = Caron | first3 = DA | issue = 21 | pmc = 23483
|bibcode=1997PNAS...9411411A
|doi-access=free
}}
* {{cite journal |vauthors=López-García P, Rodríguez-Valera F, Moreira D | title = Toward the monophyly of Haeckel's radiolaria: 18S rRNA environmental data support the sisterhood of polycystinea and acantharea
| journal = Mol. Biol. Evol.
| date = January 2002 | volume = 19 | issue = 1 | pages = 118–121 | pmid = 11752197 | doi=10.1093/oxfordjournals.molbev.a003976 | doi-access =  }}
* {{cite journal |vauthors=Adl SM, Simpson AG, Farmer MA, etal | title = The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists
| journal = J. Eukaryot. Microbiol.
| year = 2005 | volume = 52 | issue = 5 | pages = 399–451
| doi = 10.1111/j.1550-7408.2005.00053.x | pmid = 16248873 | doi-access = free }}
*{{cite book
|last= Haeckel
|first= Ernst
|title= Art Forms from the Ocean: The Radiolarian Atlas of 1862
|year= 2005 |url=https://books.google.com/books?id=aAkEnwEACAAJ
|publisher= Prestel Verlag
|location= Munich; London
|isbn= 978-3-7913-3327-4}}
{{refend}}

==External links==
{{Commons category|Radiolaria}}
{{Wikispecies|Radiolaria}}
*<ref>{{Cite book|title=Handbook of the Protists|last1=Boltovskoy|first1=Demetrio|last2=Anderson|first2=O. Roger|last3=Correa|first3=Nancy M.|chapter=Radiolaria and Phaeodaria |date=2016|publisher=Springer International Publishing|isbn=978-3-319-32669-6|editor-last=Archibald|editor-first=John M.|pages=1–33|language=en|doi=10.1007/978-3-319-32669-6_19-1|editor-last2=Simpson|editor-first2=Alastair G. B.|editor-last3=Slamovits|editor-first3=Claudio H.|editor-last4=Margulis|editor-first4=Lynn|editor4-link=Lynn Margulis|editor-last5=Melkonian|editor-first5=Michael|editor-last6=Chapman|editor-first6=David J.|editor-last7=Corliss|editor-first7=John O.}}</ref>[http://hoopermuseum.earthsci.carleton.ca/2001_radiolarians_bb/ Radiolarians]
*{{cite journal |first=C. |last=Brodie |title=Geometry and Pattern in Nature 3: The holes in radiolarian and diatom tests |journal=Micscape |date=February 2005 |issue=112 |issn=1365-070X |url=http://www.microscopy-uk.org.uk/mag/artfeb05/cbdiatoms.html}}
*[http://www.radiolaria.org/ Radiolaria.org]
*{{cite book |first=Ernst |last=Haeckel |title=Die Radiolarien (''Rhizopoda radiaria'') |location=Berlin |year=1862 |url=http://caliban.mpiz-koeln.mpg.de/~stueber/haeckel/radiolarien/ |access-date=2007-09-07 |archive-url=https://web.archive.org/web/20090619000841/http://caliban.mpiz-koeln.mpg.de/~stueber/haeckel/radiolarien/ |archive-date=2009-06-19 }}
*[http://www.pirx.com/droplet/radiolaria.html Radiolaria—Droplet]
*[http://tolweb.org/Radiolaria/139596 Tree Of Life—Radiolaria]

{{Eukaryota}}
{{Rhizaria}}
{{Life on Earth}}

{{Taxonbar|from1=Q107920|from2=Q21446955}}
{{Authority control}}

[[Category:Radiolarians|*]]
[[Category:Amoeboids]]
[[Category:Extant Cambrian first appearances]]
[[Category:Bikont subphyla]]
[[Category:Taxa named by Thomas Cavalier-Smith]]