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The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral , typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The elaborate mineral skeleton is usually made of Silicon dioxide. They are found as zooplankton throughout the global ocean. As zooplankton, radiolarians are primarily , but many have photosynthetic and are, therefore, considered . 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.
Some radiolarians are known for their resemblance to regular polyhedra, such as the icosahedron-shaped Circogonia icosahedra pictured below.
There are several higher-order groups that have been detected in molecular analyses of environmental data. Particularly, groups related to Acantharia and Spumellaria. 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. But whether they are sister lineages or whether the Foraminifera should be included within the Radiolaria is not known.
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).
{\partial t} = \phi(\nabla^2) \mathbf{U} + G \mathbf{U}^2 - H\mathbf{U}V,
The function , 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 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.
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 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.
"Turing was keen to take forward the work that D’Arcy Thompson had published in On Growth and Form in 1917".
The gallery shows images of the radiolarians as extracted from drawings made by the German zoologist and polymath Ernst Haeckel in 1887.
Some common radiolarian fossils include Actinomma, Heliosphaera and Hexadoridium.
Radiolarian shells
Radiolarians are unicellular predatory 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 microfossils, provide valuable information about past oceanic conditions.Wassilieff, Maggy (2006) "Plankton - Animal plankton", Te Ara - the Encyclopedia of New Zealand. Accessed: 2 November 2019.
(1992). 9780080934051, North-Holland. ISBN 9780080934051
|source = [[Bernard Richards]], 2006[[Richards, Bernard|Bernard Richards]] (2006) [https://web.archive.org/web/20060816084810/http://rutherfordjournal.org/article010109.html "Turing, Richards and Morphogenesis"], ''The Rutherford Journal'', Volume 1.
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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 of morphogenesis. (2025). 9780198747833, Oxford University Press. ISBN 9780198747833
Fossil record
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. They have significant differences from later radiolaria, with a different silica lattice structure and few, if any, spikes on the test. About ninety percent of known radiolarian species are extinct. The skeletons, or tests, of ancient radiolarians are used in Biostratigraphy, including for oil exploration and determination of Paleoclimatology.Zuckerman, L.D., Fellers, T.J., Alvarado, O., and Davidson, M.W. "Radiolarians", Molecular Expressions, Florida State University, 4 February 2004.
See also
External links
(2025). 9783319326696, Springer International Publishing. ISBN 9783319326696 Radiolarians
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