Anthozoa (redirected from Actinozoa)

Anthozoa [‚an·thō′zō·ə]

(invertebrate zoology)

A class of marine organisms in the phylum Cnidaria including the soft, horny, stony, and black corals, the sea pens, and the sea anemones.

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Anthozoa

A class of the phylum Coelenterata. These organisms are marine, solitary or colonial, and exclusively polypoid coelenterates with no traces of a medusoid stage. Most anthozoans live attached to some firm object of the shore or on the sea bottom; some embed in the soft sediment. Anthozoans have a cylindrical body with an oral disk, mouth, stomodeum, hollow tentacles, endodermal gonad, and cellular mesoglea. The gastrovascular cavity is partitioned longitudinally into radial compartments by endodermal mesenteries or septa whose free edges, particularly, thicken and differentiate into mesenteric or septal filaments. The nervous system is a diffuse network of scattered nerve cells over the ectoderm and the endoderm. No localized sense organs are present.

Both sexual and asexual reproduction occurs. The germ cells are derived from the endoderm, and fertilization occurs either in the female gastrovascular cavity or in the sea. The zygote develops into either a ciliated swimming larva, the planula, or a young polyp.

The class Anthozoa includes the soft, horny, stony, and black corals, the sea pens, and sea anemones. The horny corals include the sea fans, sea whips, and sea feathers. The Anthozoa may be classified as listed here.

• Class Anthozoa
• Subclass Alcyonaria (Octocorallia)
• Order: Stolonifera
• Telestacea
• Coenothecalia
• Alcyonacea
• Gorgonacea
• Pennatulacea
• Subclass Zoantharia (Hexacorallia)
• Order: Actiniaria
• Scleractinia (Madreporaria)
• Zoanthidea
• Antipatharia
• Ceriantharia
• Rugosa
• Tabulata

All anthozoans are marine and most are sedentary, except the free-swimming larval stages, while actinians, cerianthids, and pennatulans are somewhat movable. They are widely distributed over the world, extending from the Arctic to the Antarctic; however, they predominate in the tropic and subtropic areas of the Indo-Pacific Ocean. Actinians also inhabit colder water areas from which deep-sea species of gorgonians, pennatulans, and scleractinians have been collected.

Anthozoans seldom tolerate desiccation or heavy sedimentation. They are so sensitive to reduced salinity that they usually do not live near coastal areas where there is river drainage. Tropical corals are able to endure high temperatures and are adversely affected by low temperatures. Therefore, coral reefs are commonly located in tropic and subtropic regions. See Coelenterata, Hydrozoa