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48-438: Acantharea The Acantharia are a group of radiolarian protozoa , distinguished mainly by their strontium sulfate skeletons. Acantharians are heterotrophic marine microplankton that range in size from about 200 microns in diameter up to several millimeters. Some acantharians have photosynthetic endosymbionts and hence are considered mixotrophs . Acantharian skeletons are composed of strontium sulfate , SrSO 4 , in

96-481: A heterotrophic host organism, are believed to have led to eukaryotes acquiring photosynthesis and to the evolution of plants . Lichens represent an association between one or more fungal mycobionts and one or more photosynthetic algal or cyanobacterial photobionts. The mycobiont provides protection from predation and desiccation, while the photobiont provides energy in the form of fixed carbon. Cyanobacterial partners are also capable of fixing nitrogen for

144-434: A central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm . The elaborate mineral skeleton is usually made of silica . They are found as zooplankton throughout the global ocean. As zooplankton, radiolarians are primarily heterotrophic , but many have photosynthetic endosymbionts and are, therefore, considered mixotrophs . The skeletal remains of some types of radiolarians make up

192-458: 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. Radiolarians have many needle-like pseudopods supported by bundles of microtubules , which aid in the radiolarian's buoyancy. The cell nucleus and most other organelles are in

240-433: 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: The function U {\displaystyle \mathbf {U} } , 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

288-463: Is divided into two regions: the endoplasm and the ectoplasm . The endoplasm, at the core of the cell, contains the main organelles , including many nuclei, and is delineated from the ectoplasm by a capsular wall made of a microfibril mesh. In symbiotic species, the algal symbionts are maintained in the endoplasm. The ectoplasm consists of cytoplasmic extensions used for prey capture and also contains food vacuoles for prey digestion. The ectoplasm

336-447: Is important in the development, maintenance, and evolution of terrestrial and aquatic ecosystems , for example in biological soil crusts , soil formation , supporting highly diverse microbial populations in soil and water , and coral reef growth and maintenance. When one organism lives within another symbiotically it’s called endosymbiosis . Photosymbiotic relationships where microalgae and/or cyanobacteria live within

384-535: Is known about the evolutionary history of sponge photosymbiois due to a lack of genomic data. However, it has been shown that photosymbiotes are acquired vertically (transmission from parent to offspring) and/or horizontally (acquired from the environment). Photosymbiotes can supply up to half of the host sponge’s respiratory demands and can support sponges during times of nutrient stress. Members of certain classes in phylum Cnidaria are known for photosymbiotic partnerships. Members of corals (Class Anthozoa ) in

432-636: Is likely there have been several gains and losses of photosymbiosis as most genera include both photosymbiotic and non-photosymbiotic species. The second, Sacoglossa , removes chloroplasts from macroalgae when feeding and sequesters them into their digestive tract at which point they are called kleptoplasts . Whether these kleptoplasts maintain their photosynthetic capabilities depends on the host species ability to digest them properly. In this group, functional kleptoplasy has been acquired twice, in Costasiellidae and Plakobranchacea . Photosymbiosis

480-547: Is present in the egg masses of the species, causing them to appear green and providing oxygen and carbohydrates to the embryos. Similarly, little is known about the evolution of symbiosis in amphibians, but there appears to be multiple origins. Photosymbiosis has evolved multiple times in the protist taxa Ciliophora , Foraminifera , Radiolaria , Dinoflagellata , and diatoms . Foraminifera and Radiolaria are planktonic taxa that serve as primary producers in open ocean communities. Photosynthetic plankton species associate with

528-427: Is relatively uncommon in chordate species. One such example of photosymbiosis is in ascidians , the sea squirts. In the genus Didemnidae , 30 species establish symbiotic relationships. The photosynthetic ascidians are associated with cyanobacteria in the genus of Prochloron as well as, in some cases, the species Synechocystis trididemni . The 30 species with a symbiotic relationship span four genera where

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576-405: Is surrounded by a periplasmic cortex , also made up of microfibrils , but arranged into twenty plates, each with a hole through which one spicule projects. The cortex is linked to the spines by contractile myonemes , which assist in buoyancy control by allowing the ectoplasm to expand and contract, increasing and decreasing the total volume of the cell. The way that the spines are joined at

624-630: Is therefore believed that the cysts help acantharians sink into deep water. Genetic data and some imaging suggests that non-cyst-forming acantharians may also sink to deep water to release swarmers. Releasing swarmer cells in deeper water may improve the survival chances of juveniles. Study of these organisms has been hampered mainly by an inability to "close the lifecycle" and maintain these organisms in culture through successive generations. Radiolaria The Radiolaria , also called Radiozoa , are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons , typically with

672-439: Is thought to take place by formation of swarmer cells (formerly referred to as "spores"), which may be flagellate , and cysts have been observed to release these swarmers. Non-encysted cells have also been seen releasing swarmers in laboratory conditions. Not all life cycle stages have been observed, however, and no one has witnessed the fusion of swarmers to produce a new acantharian. Cysts are often found in sediment traps and it

720-562: Is very scarce in seawater and the crystals dissolve after the acantharians die. The arrangement of the spines is very precise, and is described by what is called the Müllerian law in terms of lines of latitude and longitude – the spines lie on the intersections between five of the former, symmetric about an equator, and eight of the latter, spaced uniformly. Each line of longitude carries either two tropical spines or one equatorial and two polar spines, in alternation. The cell cytoplasm

768-498: The icosahedron -shaped Circogonia icosahedra pictured below. The radiolarians belong to the supergroup Rhizaria together with ( amoeboid or flagellate ) Cercozoa and (shelled amoeboid) Foraminifera . Traditionally the radiolarians have been divided into four groups— Acantharea , Nassellaria , Spumellaria and Phaeodarea . Phaeodaria is however now considered to be a Cercozoan. Nassellaria and Spumellaria both produce siliceous skeletons and were therefore grouped together in

816-479: 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. Bernard Richards , 2006  Bernard Richards , worked under

864-551: 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. So I set to work on seeking a solution to the Morphogenesis Equations on

912-560: The Radiolarian group Acantharia , photosynthetic species inhabit surface waters whereas non-photosynthetic species inhabit deeper waters. Photosynthetic Acantharia are associated with similar microalgae as the Foraminifera groups, but were also found to be associated with Phaeocystis , Heterocapsa , Scrippsiella, and Azadinium which were not previously known to be involved in photosynthetic relationships. In addition, several of

960-569: The Symbiodinium are hosted extracellularly, which is relatively rare. The only known freshwater bivalve with a symbiotic relationship are in the genus Anodonta which hosts the chlorophyte Chlorella in the gills and mantle of the host. In bivalves, photosymbiosis is thought to have evolved twice, in the genus Anodonta and in the family Cardiidae. However, how it has evolved in Cardiidae could have occurred through different gains or losses in

1008-431: 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

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1056-584: The acantharians. Symbiotic Holacanthida acantharians host diverse symbiont assemblages, including several genera of dinoflagellates ( Pelagodinium , Heterocapsa, Scrippsiella, Azadinium ) and a haptophyte ( Chrysochromulina ). Clade E & F acantharians have a more specific symbiosis and primarily host symbionts from the haptophyte genus Phaeocystis , although they sometimes also host Chrysochromulina symbionts. Clade F acantharians simultaneously host multiple species and strains of Phaeocystis and their internal symbiont community does not necessarily match

1104-823: The alignment of ribosomal RNA genes, although the groups are mostly polyphyletic. Holacanthida seems to have evolved first and includes molecular clades A, B, and D. Chaunacanthida evolved second and includes only one molecular clade, clade C. Arthracanthida and Symphacanthida, which have the most complex skeletons, evolved most recently and constitute molecular clades E and F. Many acantharians, including some in clade B (Holacanthida) and all in clades E & F (Symphiacanthida and Arthracanthida), host single-celled algae within their inner cytoplasm (endoplasm). By participating in this photosymbiosis , acantharians are essentially mixotrophs : they acquire energy through both heterotrophy and autotrophy. The relationship may make it possible for acantharians to be abundant in low-nutrient regions of

1152-762: The capacity to withstand higher levels of reactive oxygen species (ROS), the conversion of sugars to polypols that help withstand dedication, and the downregulation of fungal virulence . However, it is still unclear whether these are derived or ancestral traits. Currently described photobiont species number about 100, far less than the 19,000 described species of fungal mycobionts, and factors such as geography can predominate over mycobiont preference. Phylogenetic analyses in lichenized fungi have suggested that, throughout evolutionary history, there has been repeated loss of photosymbionts, switching of photosymbionts, and independent lichenization events in previously unrelated fungal taxa. Loss of lichenization has likely led to

1200-589: The center of the cell varies and is one of the primary characteristics by which acantharians are classified. The skeletons are made up of either ten diametric or twenty radial spicules. Diametric spicules cross the center of the cell, whereas radial spicules terminate at the center of the cell where they either form a tight or flexible junction depending on species. Acantharians with diametric spicules or loosely attached radial spicules are able to rearrange or shed spicules and form cysts. The morphological classification system roughly agrees with phylogenetic trees based on

1248-663: The chlorophyte Tetraselmis convolutae while others have a symbiotic relationship with the dinoflagellates Symbiodinium , Amphidinium klebsii, or diatoms in the genus Licomorpha. In freshwater systems, photosymbiosis is present in platyhelminths belonging to the Rhabdocoela group. In this group, members of the Provorticidae , Dalyeliidae , and Typhloplanidae families are symbiotic. Members of Provorticidae likely feed on diatoms and retain their symbionts. Typhloplanidae have symbiotic relationships with

1296-513: The chlorophytes in the genus Chlorella . Photosymbiosis is taxonomically restricted in Mollusca . Tropical marine bivalves in the Cardiidae family form a symbiotic relationship with the dinoflagellate Symbiodinium . This family boasts large organisms often referred to as giant clams and their large size is attributed to the establishment of these symbiotic relationships. Additionally,

1344-440: The coexistence of non-lichenized fungi and lichenized fungi in lichens. Sponges (phylum Porifera) have a large diversity of photosymbiote associations. Photosymbiosis is found in four classes of Porifera ( Demospongiae , Hexactinellida , Homoscleromorpha , and Calcarea ), and known photosynthetic partners are cyanobacteria, chloroflexi , dinoflagellates , and red ( Rhodophyta ) and green (Chlorophyta) algae. Relatively little

1392-405: 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

1440-429: The congeners are primarily non-symbiotic, suggesting multiple origins of photosymbiosis in ascidians. In addition to sea squirts, embryos of some amphibian species ( Ambystoma maculatum , Ambystoma gracile , Ambystoma jeffersonium, Ambystoma trigrinum , Hynobius nigrescens , Lithobates sylvaticus , and Lithobates aurora ) form symbiotic relationships with the green alga in the genus of Oophila. This algae

1488-420: The coral fossil record, understanding the evolutionary history of the symbiosis is difficult.   In basal bilaterians , photosymbiosis in marine or brackish systems is present only in the family Convolutidae . In the group Acoela there is limited knowledge on the symbionts present, and they have been vaguely identified as zoochlorella or zooxanthella . Some species have a symbiotic relationship with

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1536-449: The endoplasm, while the ectoplasm is filled with frothy vacuoles 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

1584-703: The family. In gastropods , photosymbiosis can be found in several genera. The species Strombus gigas hosts Symbiodinium which is acquired during the larval stage, at which point it is a mutualistic relationship. However, during the adult stage, Symbiodinium becomes parasitic as the shell prevents photosynthesis. Another group of gastropods, heterobranch sea slugs, have two different systems for symbiosis. The first, Nudibranchia , acquire their symbionts through feeding on cnidarian prey that are in symbiotic relationships. In Nudibranchs, photosymbiosis has evolved twice, in Melibe and Aeolidida . In Aeolidida it

1632-562: The form of mineral celestine crystal. Celestine is named for the delicate blue colour of its crystals, and is the heaviest mineral in the ocean. The denseness of their celestite ensures acantharian shells function as mineral ballast , resulting in fast sedimentation to bathypelagic depths . High settling fluxes of acantharian cysts have been observed at times in the Iceland Basin and the Southern Ocean , as much as half of

1680-575: The fungal partner. Recent work suggests that non-photosynthetic bacterial microbiomes associated with lichens may also have functional significance to lichens. Most mycobiont partners derive from the ascomycetes , and the largest class of lichenized fungi is Lecanoromycetes . The vast majority of lichens derive photobionts from Chlorophyta (green algae). The co-evolutionary dynamics between mycobionts and photobionts are still unclear, as many photobionts are capable of free-living, and many lichenized fungi display traits adaptive to lichenization such as

1728-515: The global establishment of coral reefs . Corals are likewise adapted to eject damaged photosymbionts that generate high levels of toxic reactive oxygen species, a process known as bleaching . The identity of the Symbiodinium photosymbiont can change in corals, although this depends largely on the mode of transmission: some species vertically transmit their algal partners through their eggs, while other species acquire environmental dinoflagellates as newly-released eggs. Since algae are not preserved in

1776-481: 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). Radiolarians are unicellular predatory protists encased in elaborate globular shells (or "capsules"), usually made of silica and pierced with holes. Their name comes from

1824-741: 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 ( Taxopodida ), which lacks an internal skeleton and was for long time considered a heliozoan . The Radiolaria can therefore be divided into two major lineages: Polycystina (Spumellaria + Nassellaria) and Spasmaria (Acantharia + Taxopodida). 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

1872-457: The oceans and may also provide extra energy necessary to maintain their elaborate strontium sulfate skeletons. It is hypothesized that the acantharians provide the algae with nutrients (N & P) that they acquire by capturing and digesting prey in return for sugar that the algae produces during photosynthesis. It is not known, however, whether the algal symbionts benefit from the relationship or if they are simply being exploited and then digested by

1920-421: The orders Hexacorallia and Octocorallia form well-characterized partnerships with the dinoflagellate genus Symbiodinium . Some jellyfish (class Scyphozoa ) in the genus Cassiopea (upside-down jellyfish) also possess Symbiodinium. Certain species in the genus Hydra (class Hydrozoa ) also harbor green algae and form a stable photosymbiosis. The evolution of photosymbiosis in corals was likely critical for

1968-594: 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. 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

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2016-803: 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. In the diagram on the right, a Illustrates generalized radiolarian provinces  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

2064-510: The relative availability of potential symbionts in the surrounding environment. The mismatch between internal and external symbiont communities suggests that acantharians can be selective in choosing symbionts and probably do not continuously digest and recruit new symbionts, and maintain symbionts for extended periods of time instead. Adults are usually multinucleated. Earlier diverging clades are able to shed their spines and form cysts, which are often referred to as reproductive cysts. Reproduction

2112-565: The supervision of Alan Turing (1912–1954) at Manchester as one of Turing's last students, helping to validate Turing’s theory of morphogenesis . "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. The earliest known radiolaria date to

2160-511: The symbiotes of dinoflagellates, diatoms, rhodophytes , chlorophytes , and cyanophytes that can be transferred both vertically and horizontally . In Foraminifera, benthic species will either have a symbiotic relationship with Symbiodinium or retain the chloroplasts present in algal prey species. The planktonic species of Foraminifera associate primarily with Pelagodinium . These species are often considered indicator species due to their bleaching in response to environmental stressors. In

2208-436: The total gravitational organic carbon flux. The strontium sulfate crystals are secreted by vacuoles surrounding each spicule or spine. Acantharians are unique among marine organisms for their ability to biomineralize strontium sulfate as the main component of their skeletons. However, unlike other radiolarians whose skeletons are made of silica, acantharian skeletons do not fossilize , primarily because strontium sulfate

2256-839: 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 geological dating , including for oil exploration and determination of ancient climates . Some common radiolarian fossils include Actinomma , Heliosphaera and Hexadoridium . Photosymbiosis Examples of photosymbiotic relationships include those in lichens , plankton , ciliates , and many marine organisms including corals , fire corals , giant clams , and jellyfish . Photosymbiosis

2304-406: 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

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