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Acantharea
Acantharea species
Scientific classification
Domain:	Eukaryota
(unranked):	Rhizaria
Phylum:	Radiolaria
Class:	Acantharea Haeckel 1881 emend.

The Acantharea are a group of radiolarian^[1] protozoa, distinguished mainly by their skeletons.

Structure

These are composed of strontium sulfate crystals, which do not fossilize, and take the form of either ten diametric or twenty radial spines. The central capsule is made up of microfibrils arranged into twenty plates, each with a hole through which one spine projects, and there is also a microfibrillar cortex linked to the spines by myonemes. These assist in flotation, together with the vacuoles in the ectoplasm, which often contain zooxanthellae.

Classification by spine arrangment

The arrangement of the spines is very precise, and is described by what is called the Müllerian law. This is easiest to describe 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 way that the spines are joined together at the center of the cell varies and is one of the primary characteristics by which acanthareans are classified.

• Holacanthida - diametric spines, simply crossed
• Symphyacanthida - radial spines, with free bases
• Chaunacanthida - radial spines, with articulated bases
• Arthracanthida - radial spines, with pyramidal bases packed together

The axopods are fixed in number.

Life cycle

Adults are usually multinucleated. Reproduction is thought to take place by formation of swarmer cells (formerly referred to as "spores"), which may be flagellate. All life cycle stages have not been observed, and study of these organisms has been hampered mainly by an inability to maintain these organisms in culture through successive generations.

References

Definition from Wiktionary, a free dictionary

Translingual

Etymology

Alternative spellings

• Acantharia

Proper noun

Wikipedia has an article on:

Acantharea

Wikipedia

Acantharea

1. a taxonomic class, within phylum Radiolaria (or within subclass Spasmaria) - those radiolarians whose skeletons are made of celestite rather than silica

Wikispecies has information on:

Acantharea

Wikispecies

See also

• See Wikipedia for further classification

From Wikispecies

Taxonavigation

Main Page
Cladus: Eukaryota
Supergroup: Rhizaria
Phylum: Retaria
Subphylum: Radiozoa
Classis: Acantharea
Ordines: Arthracanthida - Chaunacanthida - Holacanthida - Symphyacanthida - Incertae sedis - Unassigned Genera

Name

Acantharia Haeckel, 1881, emend. Mikrjukov, 2000 (sic!)

References

• Protist classification at micro*scope (CC)
• Thomas Cavalier-Smith: Protist phylogeny and the high-level classification of Protozoa, Europ. J. Protistol. 39: 338-348 (2003).

Alternative classifications

Honigberg et al. (1964)

In Classis Actinopodea
Subclass Acantharia

• Ordo Acanthometrida
• Ordo Acanthophractida

John O. Corliss (1984)

From The kingdom Protista and its 45 phyla

In Regnum Protista, Assemblage "Actinopods"
Phylum Acantharia Haeckel, 1876

Cavalier-Smith (1993)

From Regnum Protozoa and its 18 phyla

In Phylum Radiozoa, Subphylum Spasmaria
Classis Acantharea Haeckel, 1881 stat. nov.

• Subclass Holacanthia
• Subclass Euacanthia

David J. Patterson (1999)

From The Diversity of Eukaryotes

In Eukaryotes
Clade Acantharea