Black Wire Coral

Appearance

Wire coral consists of a single, unbranched branch. It measures on average 80 cm in length, but specimens over 4 m can be encountered. The lower part of the rod is straight or curved, the upper part is wound in a spiral which recalls the shape of barbed wire.
It is strongly attached to the substrate * by an enlargement of the base.

The coenenchyma *, that is to say the fleshy part which covers the skeletal axis (dark), is variable in color, ranging from orange to brown-red.

The white polyps *, small in size (1.4 mm in diameter), are arranged in a single row, very tight. Rather oval in shape, they have 6 long, smooth, white, translucent tentacles * (4 lateral and 2 sagittal tentacles).

Microscope observations:
The branch is covered with conical spines measuring up to 340 µm in length. Covered with tubercles, these thorns are generally sloping, point directed towards the end of the branch. They are arranged in 13 rows or more, with 25-30 thorns per centimeter in each row.

Note: The arrangement of polyps in a single row is a controversial feature. Some settlements have a more irregular layout, giving the impression of a zig-zag arrangement (see photos). A review of the genus Stichopaths based on a molecular study is needed (personal communication, Dr. Dennis Opresko, National Museum of Natural History, Washington, Department of Invertebrate Zoology, 05/15/2016).


In Antipatharians, the dark-colored skeleton (from brown to black) is not calcified but keratinous. It is made up of a sulfur-based protein called antipathin.

This skeleton has elastic properties, while being very resistant, allowing these corals to develop in areas with strong currents.
Faced with strong currents, single branched Antipathaires, such as wire coral, are better suited than branched Antipathaires. Their smaller contact surface generates less resistance. In addition, the elasticity of the helical morphology increases the resistance of the colony to currents, while maximizing the filtration surface.

In closely related species, of the genus Cirrhipathes, it has been shown that the final size and shape of the colony are strongly related to the intensity of the current. In a weak current, the colonies grow larger and have a greater number of spirals.

Naming

Origin of the common name

The name wire coral comes from the shape of its single branch, which spirals in the manner of barbed wire.
Origin of scientific name

Stichopaths: from the Greek [sticho] = line, row (referring to the arrangement of polyps in a single row) and [pathes] = suffering, disease.
Since Milne-Edwards and Haime created the Antipatharia order in 1857, the suffix [pathes] has been used for all groups belonging to that order. Antipatharia comes from the Greek [antipathes] = anti suffering, anti disease in reference to the medicinal use of black coral in the Greco-Roman era.

lutkeni: species dedicated to Christian Frederik Lütken (1827-1901), Danish zoologist. The "type" copy is in the Museum of Zoology at the University of Copenhagen. It was first described as Cirrhipathes filiformis by Lütken. Brook, describing this specimen as a new species, would have finally paid homage to him.

Distribution

Originary from the Caribbean but also found in the Pacific.

Status

Wire coral is listed in Appendix II of the Washington Convention (CITES) which lists the species whose trade must be closely controlled.

Habitat

Species found at greater depths than 20 m.

Reproduction

The reproduction of wire coral is not known. It is probably gonochoric *, like most Antipatharia, that is, there are male and female colonies. However, a closely related species, Stichopathes saccula, has mixed colonies, with male and female polyps.
Reproduction takes place mainly by laying: the oocytes * and the sperm are released into the environment where fertilization takes place.

Asexual reproduction, by detachment of polyps, would possibly be a method of multiplication to escape environmental stress. This has been demonstrated for a species of Antipatharia, Antipathella fiordensis.

Finally, asexual reproduction, by colony fragmentation, could, under certain favorable conditions, be a mode of multiplication. Indeed, artificial transplantation experiments in a species of Stichopaths have shown very high survival rates. In addition, Stichopathic colonies often show signs of skeletal fracture. However, the probability of a fragment attaching to the bottom is low, so this mode of reproduction would be rare.

Unlike Branched Antipatharia, Wire Coral is relatively fast growing. Growth rates of several centimeters per month have been recorded.

Food

Stichopathes lutkeni is a passive filter * and a strong current is essential to bring it planktonic preys *. These are captured by the polyps and their crown of tentacles equipped with specialized stinging cells: cnidocytes *.
Unlike other Antipatharia, species of the genus Stichopathes are able to contract their polyps completely. They do this with the aim of reducing their energy expenditure. Thus, polyps only open at night when the zooplankton * is more abundant, and are contracted during the day, when it is less.

It is also possible that S. lutkeni will feed on nutrients dissolved in seawater.

Predators

This coral is very often parasitized by the copepod Calonastes imparipes Humes & Goenaga, 1978. Small in size (on average 0.68 mm in length), it lives between the coenenchyma and the keratinous skeleton *. It has never been reported on the surface of colonies, and moves freely under the coenenchyma. Despite a high density (1.2 copepods per centimeter of colony), no apparent damage was observed, even on highly parasitized colonies. 73% of Stichopathes lutkeni colonies can be parasitized by this copepod.

Other epibionts * have been observed, such as a shrimp of the Palaemonidae family, as well as a species of polychaete worm.