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Anthozoa

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Title: Anthozoa  
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Subject: Coral, Sea anemone, Antipathes, Ivell's sea anemone, Planula
Collection: Anthozoa, Ediacaran First Appearances
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Anthozoa

Anthozoa
Temporal range: 570–0 Ma
Є
O
S
D
C
P
T
J
K
Pg
N
Late Ediacaran to Recent
Stony corals
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Subkingdom: Eumetazoa
Phylum: Cnidaria
Class: Anthozoa
Ehrenberg, 1834
Subclasses

Octocorallia
Hexacorallia
Ceriantharia

Anthozoa is a class within the phylum Cnidaria. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows. Some anthozoans can also reproduce asexually through budding. More than 6,100 species have been described.[1]

The name comes from the Greek words άνθος (ánthos; "flower") and ζώα (zóa; "animals"), hence ανθόζωα (anthozoa) = "flower animals", a reference to the floral appearance of their perennial polyp stage.

Contents

  • Biology and anatomy 1
  • Phylogeny 2
  • Paleontology 3
  • References 4
  • External links 5

Biology and anatomy

Like those of other cnidarians, the individual polyps have a cylindrical body crowned by a ring of tentacles surrounding the mouth. The mouth leads into a tubular pharynx which descends for some distance into the body before opening into the gastrovascular cavity that fills the interior of the body and tentacles. Unlike other cnidarians, however, the cavity is subdivided by a number of radiating partitions, or mesenteries. The gonads are also located within the cavity walls.[2]

All cnidarian species can feed by catching prey with nematocysts; sea anemones are capable of catching fish and corals of catching plankton. Some of the species also harbour a type of algae, dinoflagellates called zooxanthellae, in a symbiotic relationship; the reef building corals known as hermatypic corals rely on this symbiotic relationship particularly. The zooxanthellae benefit by using nitrogenous waste and carbon dioxide produced by the host or, and the cnidarian gains photosynthetic capability and increased calcium carbonate production in hermatypic corals.[3]

Anemones and certain species of coral live in isolation; however, most corals form colonies of genetically identical polyps. These closely resemble anemones in structure, although they are generally much smaller. Stony coral are found in most seas.

Phylogeny

 Hexacorallia 

Actiniaria


Antipatharia


Corallimorpharia


Scleractinia


Zoantharia


 Octocorallia 

Alcyonacea


Helioporacea


Pennatulacea


 Ceriantharia 

Penicilaria


Spirularia


Phylogeny of Anthozoa[4]
Giant green anemone, likely Anthopleura xanthogrammica, Southern California.

Anthozoa is subdivided into three subclasses Octocorallia, Hexacorallia and Ceriantharia which form monophyletic groups and generally show reflections on symmetry of polyp structure respectively.[4] Historically Ceriantipatharia was thought to be a separate subclass but the two orders it comprised, Antipatharia is now considered part of Hexacorallia and Ceriantharia an independent subclass. The extant orders are shown to the right.[4][5]

Hexacorallia includes coral reef builders the stony corals (Scleractinia), sea anemones (Actiniaria), and zoanthids (Zoantharia). Genetic studies of ribosomal DNA has shown Ceriantharia to be a monophyletic group and the oldest, or basal, order among them.[6]

Classification according to the World Register of Marine Species :[7]

Octocorallia comprises the sea pens (

  • Data related to Anthozoa at Wikispecies

External links

  1. ^
  2. ^
  3. ^ Contribution to the BUFUS Newsletter, Field excursion to Milne Bay Province - Papua New Guinea, Madl and Yip 2000
  4. ^ a b c
  5. ^ a b
  6. ^
  7. ^
  8. ^
  9. ^
  10. ^
  11. ^

References

These are all corals and correspond to the fossil record time line shown below; they comprise the majority of the fossils of Anthozoa due to their calcareous skeleton being preserved.

  • Numidiaphyllida †
  • Kilbuchophyllida †
  • Heterocorallia †
  • Rugosa
  • Heliolitida †
  • Tabulata
  • Cothoniida †
  • Tabuloconida †

A number of extinct orders of corals have been classified as their calcium skeleton forms a prolific fossil record. These are generally thought to be close to the ancestors of modern Scleractinians and existed during the Paleozoic era 570–245 million years ago:[8][9]

Paleontology

Ceriantharia comprises the related tube-dwelling anemones. Tube-dwelling anemones or cerianthids look very similar to sea anemones, but belong to an entirely different subclass of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live and can withdraw into tubes, which are made of a fibrous material, which is made from secreted mucus and threads of nematocyst-like organelles, known as ptychocysts.

[5]

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