Black coral - WikiHQ

Antipatharians, also known as black corals or thorn corals, Black corals are also known as thorn corals due to the microscopic spines lining their skeletons. In Malay, the corals are called ("root of the sea"), likely named for their tendency to grow at low-light depths.

Taxonomy and classification

Black corals have historically been difficult to classify due to poor-quality specimens. They have few distinguishing morphological characteristics, and the few that there are vary across species, similar to other corals. When black corals were first documented by Henri Milne-Edwards and Jules Haime, two French zoologists in 1857, all species of Antipatharia were placed in the family Antipathidae.

Blacks corals are classified in the order Antipatharia with 7 families, 44 genera, and 280 distinct species. The families are Antipathidae, Aphanipathidae, Cladopathidae, Leiopathidae, Myriopathidae, Schizopathidae, and Stylopathidae. Black corals can be distinguished from other corals by their black, flexible skeletons and near-total lack of any kind of protection from sediment. All black corals have small or medium-sized polyps and a chitin skeleton, lined with small spines.

Genera

List of genera according to the World Register of Marine Species:

Family Ameripathidae Opresko & Horowitz, 2024
Ameripathes Opresko & Horowitz, 2024
Family Antipathidae Ehrenberg, 1834
Allopathes Opresko & , 1994
Antipathes Pallas, 1766
Cirrhipathes de Blainville, 1830
Hillopathes van Pesch, 1914
Pseudocirrhipathes Bo et al., 2009
Pteropathes , 1889
Stichopathes Brook, 1889
Family Aphanipathidae Opresko, 2004
subfamily Acanthopathinae Opresko, 2004
Acanthopathes Opresko, 2004
Distichopathes Opresko, 2004
Elatopathes Opresko, 2004
Rhipidipathes Milne-Edwards & Haime, 1857
subfamily Aphanipathinae Opresko, 2004
Aphanipathes Brook, 1889
Asteriopathes Opresko, 2004
Phanopathes Opresko, 2004
Pteridopathes Opresko, 2004
Tetrapathes Opresko, 2004
Family Cladopathidae Kinoshita, 1910
subfamily Cladopathinae Kinoshita, 1910
Chrysopathes Opresko, 2003
Cladopathes Brook, 1889
Trissopathes Opresko, 2003
subfamily Hexapathinae Opresko, 2003
Heteropathes Opresko, 2011
Hexapathes Kinoshita, 1910
subfamily Sibopathinae Opresko, 2003
Sibopathes Van Pesch, 1914
Family Leiopathidae Haeckel, 1896
Leiopathes Haime, 1849
Family Myriopathidae Opresko, 2001
Antipathella Brook, 1889
Cupressopathes Opresko, 2001
Myriopathes Opresko, 2001
Plumapathes Opresko, 2001
Tanacetipathes Opresko, 2001
Family Schizopathidae Brook, 1889
Abyssopathes Opresko, 2002
Alternatipathes Molodtsova & Opresko, 2017
Bathypathes Brook, 1889
Dendrobathypathes Opresko, 2002
Dendropathes Opresko, 2005
Lillipathes Opresko, 2002
Parantipathes Brook, 1889
Saropathes Opresko, 2002
Schizopathes Brook, 1889
Stauropathes Opresko, 2002
Taxipathes Brook, 1889
Telopathes MacIsaac & Best, 2013
Umbellapathes Opresko, 2005
Family Stylopathidae Opresko, 2006
Stylopathes Opresko, 2006
Triadopathes Opresko, 2006
Tylopathes Brook, 1889

Physical characteristics

right|thumb|A sample of coral next to its skeleton, showing the minuscule spines all along it

The skeletons of these corals grow in many patterns unique to this order, such as whips, trees, fans, or coils. These range in size from , though polyps can be as small as in size. Skeletons are also lined with tiny spikes. and are gelatinous and have six tentacles (the same as hard corals and unlike soft corals, which have eight). These polyps can be nearly any color.

Unlike the vast majority of other corals, black corals have no protection against abrasive materials such as sand and rocks and lack muscular development which can help the corals to hide. These factors can lead to sediment tearing the soft tissue, resulting in death. In response, corals live near crevices, which allows much of their body to be protected. Black corals are found on reefs, and may contribute to overall reef building, but are also often found as solitary colonies on isolated outcroppings. Most individuals require a hard surface for attachment. They will frequently grow where undersea currents flow, which allows them to feed on the meiofauna that is swept by. Since undersea currents benefit the corals, they will often grow on or by geographic structures that cause currents, such as continental slopes, cliffs, caves, or undersea plateaus.

Diet

Black corals are carnivorous, with the coral's polyps allowing it to feed mostly on meiofauna such as zooplankton.

Life cycle and reproduction

Due to the slow life cycle and deep-water habitats of black coral, little is known about their life cycle and reproduction. Asexual reproduction can also occur if a branch breaks off and a replacement is needed.

thumb|left|Antipathes dendrochristos growing several hundred meters down in the ocean

Sexual reproduction in these corals remains largely unstudied. It occurs after the coral colony is established; a colony will produce eggs and sperm, which meet in the water to create larvae that use currents to disperse and settle in new areas. A large tall coral tree is somewhere between 30 and 40 years old. Rarely, black corals will grow too large to support their own weight, and collapse. More recent harvesting has been for use as jewelry. Many Indo-Pacific peoples believed that black coral has curative and anti-evil powers and made them into necklace and bracelets; however, black corals are not ideal for jewelry-making due to it being soft as opposed to stony, causing jewelry made with it to dry out and break.

The best studied and regulated black coral fisheries are in Hawaii, where they have been harvested since the 1960s. In the Caribbean harvesting is typically done to produce jewelry for sale to tourists, and has followed a boom-and-bust cycle, where new coral populations are discovered and overexploited leading to rapid declines. leading to widespread black coral population declines. Despite improvements in management in Cozumel, including no harvesting permits issued since the mid-1990s, the black coral population had failed to recover when assessed in 2016. Though it is illegal to move black corals across international borders without authorization, as they are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), it is still possible to buy them.

Though various methods have been proposed for quicker and more efficient rejuvenation of black coral colonies, none have worked to the point where these corals could be commercially farmed.

Threats

thumb|left|A [[Bathypathes species growing in a brush shape]]

Though black corals are not listed on the IUCN Red List, a number of factors threaten them today. The largest single threat is poaching— though the majority of black coral fisheries are heavily regulated, there is still a black market for the corals. Particularly on tropical islands and Madagascar, the market for illegally-harvested black corals is large. Due to overfishing of mature corals, in some areas nearly 90% of corals are juveniles (less than tall.)

Global warming is the primary threat to black corals worldwide, as well as all other corals. Though black corals rarely builds reefs (the most threatened areas), threats caused by climate change such as coral bleaching, rising sea temperatures, changing underwater currents, and changing salinity and pH also affect deep-sea corals. Invasive species such as Carijoa riisei, which were introduced to Hawaiian waters by humans, may pose a significant threat to black corals.