Hidden cup coral (Phyllangia americana)

GenusPhyllangia (1)

Listed on Appendix II of CITES (1).

Unlike the reef-building corals, which are responsible for the networks of intricate coral reefs in tropical shallow waters, the hidden cup coral forms small, inconspicuous colonies of polyps (soft-bodied animals related to anemones). The flower-like polyps vary in colour from yellow-brown to red-brown, and often become overgrown by algae and sponges (3). The circular skeletal wall of each polyp has six septa, protruding inwards, while circular skeletal ridges may be visible around the outside (4). Two subspecies of the hidden cup coral have been described, with the nominate subspecies, Phyllangia americana americana, found in the western Atlantic, and Phyllangia americana mouchezii occurring in the eastern Atlantic (5).   

The hidden cup coral is one of the most common azooxanthellate corals in the western Atlantic, ranging from the Florida coastline, throughout the West Indian islands (3) (4). It is also found on the west coast of Africa, around the Ivory Coast and Gabon, and around the southern shores of the United Kingdom, and parts of the Mediterranean Sea (1).   

The hidden cup coral attaches to the underside of rocks, cave walls and ledges in tropical reefs, within a depth of two to over 80 metres. It is capable of tolerating a temperature range of 13 to 31 degrees Celsius, and a salinity range of 15 to 36.4 parts per thousand (3).

The hidden cup coral is an azooxanthellate coral, and thus lacks the symbiotic zooxanthellae that provide the reef-building corals, through photosynthesis, with the energy required to build their large, complex skeletons (2). As a result, nutrients are obtained by digesting free-floating microorganisms, which are trapped in protruding tentacles, or from dissolved organic matter. Most corals exhibiting this behaviour are restricted to depths where light does not penetrate; however, the hidden cup coral will grow in dark recesses, in depths of two to three metres (3). Colonies of the hidden cup coral grow through a form of asexual reproduction known as budding, in which the parent polyp divides to form new daughter polyps (2).

With an estimated 20 percent of the world’s coral reefs already destroyed, the hidden cup coral faces many threats that are affecting coral reefs globally (6) (7). Worldwide there is increasing pressure on coastal resources resulting from human population growth and technological development. Consequently, there has been a significant increase in domestic and agricultural waste in the oceans, poor land-use practices that result in an increase in sediment running on to the reefs, and over-fishing, which can have ‘knock-on’ effects on the reef (6). However, the major threat to corals is global climate change, with the expected rise in ocean temperatures increasing the risk of coral ‘bleaching’, in which the stressed coral expels its zooxanthellae, often resulting in the death of the coral. Although, the hidden cup coral is an azooxanthellate coral, and does not suffer from ‘bleaching’, subtle changes to the reef ecosystem are likely to impact on this species. Climate change may also lead to more frequent, severe storms, which can damage reefs, and rising carbon dioxide levels may make the ocean increasingly acidic. Such stresses can also make corals more susceptible to disease, parasites and predators, such as the crown of thorns sea star (Acanthaster planci) (6) (7) (8).

Like all other coral species, the hidden cup coral is 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). The hidden cup coral also forms part of the marine community in many Marine Protected Areas (MPAs), and in areas where management plans are in place to protect the coral community. However, legal enforcement is poor in many MPAs, and at present they only cover a small area of the world’s oceans. The coverage of protected areas therefore needs to be drastically increased to ensure the preservation of coral reef ecosystems (7) (8). 

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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:

  1. CITES (January, 2010)
  2. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
  3. Smithsonian Marine Station at Fort Pierce (January, 2010)
  4. Marine Species Identification Portal (January, 2010)
  5. Integrated Taxonomic Information System (IT IS) (January, 2010)
  6. Wilkinson, C. (2004) Status of Coral Reefs of the World: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Australia.
  7. Carpenter, K.E et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560 – 563
  8. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka. Available at: