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What is the difference between Hexacorallia and Octocorallia?

The hexacorallia are distinguished from another class of Anthozoa, Octocorallia, in having six or fewer axes of symmetry in their body structure; the tentacles are simple and unbranched and normally number more than eight. Hexacorallia also include the significant extinct order of rugose corals.

Why are soft corals called Octocorallia?

This class is divided into two subgroups: the Octocorallia – so named because they have 8 tentacles around the mouth – include sea fans, sea pens and soft corals; the Hexacorallia – with multiples of 6 tentacles around the mouth – include stony corals, black corals, sea anemones, and others.

Does Octocorallia have internal skeletons?

Octocorallia (also known as Alcyonaria) is a subclass of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries. …

What phylum is octocorallia?

Octocorallia are a subclass of the class Anthozoa, phylum Cnidaria.

Are Octocorallia reef builders?

Alcyonacean octocorals in tropical reefs are usually not considered as reef builders. Some Sinularia species, however, are capable of consolidating sclerites at the colony base to form spiculite.

What is Siphonoglyph in zoology?

The siphonoglyph is a ciliated groove at one or both ends of the mouth of sea anemones and some corals. The siphonoglyph extends into a pharynx and is used to create currents of water into the pharynx. These water currents are important for respiration and maintenance of internal pressure.

Do all soft corals contain sclerites?

Reefs are ecosystems derived from biological organisms. They predominantly consist of cemented stony corals made of calcium carbonate. In contrast, the tissues of soft corals contain sclerites, which look like tiny pins or porcupine needles.

What is the soft part of the Great Barrier Reef?

Soft corals, sea fans and gorgonians are common names for a group with the scientific name Octocorallia or Alcyonacea. About 100 genera in 23 families are known to occur in shallow Indo-Pacific coral reefs.

Are fire corals Octocorals?

Hydrocorals are found in all the same habitat types that stony corals are found in. The most common kinds of hydrocorals are the fire corals. These types of corals are similar in appearance to octocorals and form a skeleton made of protein, however the skeletal structure of black corals is hard and inflexible.

Can coral be black?

Black corals are rarely black, but rather vary in color from white to red, green, yellow, or brown. They also range in shape from small bushes to bottle brushes to fans to single stalks. The black corals differ greatly from stony corals in terms of their skeletons.

What is the function of the siphonoglyph in Metridium?

It is called siphonoglyph which is a ciliated groove on one or both ends of the mouth. It extends in the pharynx and is used to create currents in the water which is important for respiration and maintenance of internal pressure.

What are the three orders of Octocorallia?

It includes the blue coral, soft corals, sea pens, and gorgonians (sea fans and sea whips) within three orders: Alcyonacea, Helioporacea, and Pennatulacea. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries.

How are Octocorallia different from the stony corals?

Full corallum of Tubipora musica. Octocorals resemble the stony corals in general appearance and in the size of their polyps, but lack the distinctive stony skeleton. Also unlike the stony corals, each polyp has only eight tentacles, each of which is feather-like in shape, with numerous side-branches, or pinnules .

What makes up the matrix of an octocoral?

Octocorals are colonial organisms, with numerous tiny polyps embedded in a soft matrix that forms the visible structure of the colony. The matrix is composed of mesogleal tissue, lined by a continuous epidermis and perforated by numerous tiny channels.

What do you mean by monophyletic in Octocorallia?

Octocorallia is considered to be monophyletic, meaning that all contained species are descended from a common ancestor, but the relationships between subdivisions are not well known.