page_title: Black coral
section_title: Physical characteristics
hierarchical_section_title: Black coral / Physical characteristics
caption_attribution_description: Figures 8–10; (8) Corallum morphology of Stylopathes adinocrada; (9) pinnulation pattern of S. adinocrada, showing the “worm run&#34;; (10) organization of spines in S. adinocrada. Scale bars: 8–9 = 10 mm, 10: 100 µm.
context_page_description: Antipatharians, also known as black corals or thorn corals, are an order of soft deep-water corals. These corals can be recognized by their jet-black or dark brown chitin skeletons, surrounded by the polyps. Antipatharians are a cosmopolitan order, existing at nearly every location and depth, with the sole exception of brackish waters. However, they are most frequently found on continental slopes under 50 m deep. A black coral reproduces both sexually and asexually throughout its lifetime. Many black corals provide housing, shelter, food, and protection for other animals.
  Black corals were originally classified in the subclass Ceriantipatharia along with ceriantharians, but were later reclassified under Hexacorallia. Though they have historically been used by Pacific Islanders for medical treatment and in rituals, its only modern use is making jewelry. Black corals have been declining in numbers and are expected to continue declining due to the effects of poaching, ocean acidification and climate change.
context_section_description: The skeleton grows of these corals grow in many patterns unique to black corals, such as whips, trees, fans, or coils. These range in size from 10 to 300 cm (3.94 to 118 in), though polyps can be as small as 1 mm (0.0394 in) in size. Skeletons are also lined with tiny spikes. These spikes are roughly 0.5 mm (0.0197 in) in size, and vary widely in terms of size, length, proportion, and sharpness. A layer of "bark" forms around the skeleton as the coral grows. The polyps that live inside this bark are less than 2 mm (0.0787 in)  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. Some corals also have "sweeper tentacles", which can grow up to 15 mm (0.591 in) long. Though individual polyps are either male or female, entire colonies are typically hermaphroditic.
  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.
caption: A sample of coral next to its skeleton, showing the miniscule spines all along it
exif: {}