Black corals  (Antipathella spp.)

The Antipathella corals belong to the group of black corals (those in the order Antipatharia), named after their dark brown or black skeletons (2). There are five species in the Antipathella group, all of which form branched structures (3) (4). Each polyp measures 0.5 to 1 millimetre across (5), and typically bears six simple tentacles arranged around a slit-like mouth (2). The skeleton is covered with a thin layer of pale, living tissue, which connects all the individual polyps (2), and the entire colony is covered with small protuberances (4) (5).

Antipathella aperta, A. strigosa and A. fiordensis occur off New Zealand, A. wollastoni occurs in the northeastern Atlantic Ocean, and A. subpinnata is found primarily in the Mediterranean Sea (4).

Antipathella corals are inhabitants of temperate marine waters, and are not thought to be able to survive in water exceeding 15 degrees Celsius (3).

Unlike reef-building corals, many black corals (species in the order Antipatharia), do not possess the symbiotic algae, zooxanthellae, within their tissues. They are therefore not restricted to shallow, sunlit waters where the zooxanthellae can photosynthesise, and instead are able to inhabit deep and dark waters (2).

Little information appears to be available on the biology and life history of Antipathella species, other than the New Zealand species, Antipathella fiordensisi (previously known as Antipathes fiordensis). A. fiordensis has separate male and female colonies (6), unlike the majority of corals which are hermaphrodite and thus possess both male and female reproductive organs. It is thought that this species reproduces primarily by spawning; eggs and sperm are released into the water column where fertilisation takes place. The fertilised egg develops into free-swimming larvae, which soon settles and attaches itself to the substrate, establishing a new colony. Spawning is thought to occur in mid- to late-summer (6). Genetic evidence has shown that A. fiordensis reproduces primarily by sexual means, but that some asexual reproduction also occurs. In a laboratory, they have been observed reproducing asexually via “polyp bail-out” (6), whereby polyps detach themselves from a colony, and form new colonies by normal budding (7). All black coral species are known to have a relatively slow growth rate and long lifespan (8).

Information regarding Antipathella corals specifically is lacking, but like all black corals, it is likely to be impacted by over-harvesting for the jewellery trade. Black coral is highly valued in the jewellery trade because its dark skeleton can be polished to a lustrous sheen (8). Identification of black corals in the trade down to the level of genus is difficult; therefore it is hard to determine the extent to which Antipathella species are affected by such exploitation (8). Black corals around the world are also known to be impacted by habitat degradation, and recently, a small trade in live specimens for aquariums has been reported (8).

Antipathella corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that trade in this species should be carefully regulated (1).

For further information on the trade in corals see:

• WWF:
  www.worldwildlife.org/what/globalmarkets/wildlifetrade/item5741.html

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk