African pillow coral (Siderastrea savignyana)

Description

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African pillow coral fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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African pillow coral description

The African pillow coral is a beautiful coral species with elaborately-shaped skeletal walls and neatly arranged septa that form a fan-like shape ^{(3) (4)}. Growing in an encrusting form or low mounds up to one metre in diameter, like other colony-forming corals, colonies of the African pillow coral are composed of numerous small polyps, soft-bodied animals related to anemones. Each polyp bears numerous tentacles that direct food into a central mouth, where it is digested in a sac-like body cavity. One of the most remarkable and ecologically important features of corals is that the polyps secrete a hard skeleton, which over successive generations contributes to the formation of a coral reef. The coral skeleton forms the bulk of the colony, with the living polyp tissue comprising only a thin veneer. Living colonies of the African pillow coral are pale tan, with dark centres and thick white walls ⁽³⁾. 

African pillow coral biology

Like many coral species, the tissue of the African pillow coral contains large numbers of single-celled algae called zooxanthellae. The coral and the algae have a symbiotic relationship in which the algae gain a safe, stable environment within the coral's tissues, while the coral receives nutrients produced by the algae through photosynthesis. By harnessing the sun's energy in this way, corals are able to grow rapidly and form vast reef structures, but are constrained to live near the water surface. While, on average, zooxanthellate coral can obtain around 70 percent of its nutrient requirements from zooxanthellae photosynthesis, the coral may also feed on zooplankton ⁽³⁾. 

African pillow coral range

The African pillow coral has a wide distribution, ranging from the Red Sea and the south-west Indian Ocean, through the eastern Indian Ocean and Southeast Asia to the west-central Pacific ⁽¹⁾.

African pillow coral habitat

The African pillow coral  is found in shallow reefs or sand lagoons, often with colonies embedded in sand, down to depths of around ten meres ^{(1) (3) (4)}. This species is one of the hardiest Scleractinia corals and, as a result, is often found in very high salinity and high temperature environments ⁽¹⁾.

African pillow coral status

Classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾ and listed on Appendix II of CITES ⁽²⁾.

African pillow coral threats

With an estimated 20 percent of the world’s coral reefs already destroyed, the African pillow coral faces many of the threats that are affecting coral reefs globally ^{(5) (6)}. Worldwide there is increasing pressure on coastal resources resulting from human population growth and development. 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. 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) ^{(5) (6) (7)}.

African pillow coral conservation

In addition to being listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which makes it an offence to trade this species without a permit, the African pillow coral also forms part of the reef community in numerous marine protected areas, including the Kiunga Marine National Reserve in Kenya ^{(1) (2) (8)}. To specifically conserve the African pillow coral, recommendations have been made for a raft of studies into various aspects of its biology, population status, habitat and threats to its survival ⁽¹⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Environment Agency - Abu Dhabi is a principal sponsor of ARKive. EAD is working to protect and conserve the environment as well as promoting sustainable development in the Emirate of Abu Dhabi.

Find out more

For further information on the conservation of coral reefs, see:

• Reef Check:
  http://www.reefcheck.org/
• Coral Reef Alliance:
  http://www.coral.org/

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Glossary

Algae

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Colony

Relating to corals: corals composed of numerous genetically identical individuals (also referred to as zooids or polyps), which are produced by budding and remain physiologically connected.

Photosynthesis

Metabolic process characteristic in which carbon dioxide is broken down, using energy from sunlight. Organic compounds are made and oxygen is given off as a by-product.

Polyp

Typically sedentary soft-bodied component of cnidaria, a group of simple aquatic animals including the sea anemones, corals and jellyfish. A polyp comprises a trunk that is fixed at the base, and a mouth that is placed at the opposite end of the trunk and is surrounded by tentacles.

Septa

In a coral, radial elements that project inwards from the corallite wall (the skeletal wall of an individual coral polyp).

Symbiotic relationship

Relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).

Zooplankton

Tiny aquatic animals that drift with currents or swim weakly in water.

Zooxanthellae

Single-celled dinoflagellates that form symbiotic relationships with hermatypic ‘reef-building’ corals.

References

1. IUCN Red List (October, 2010)
   http://www.iucnredlist.org/
2. CITES (October, 2010)
   http://www.cites.org/
3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia.
4. Dai, C. and Horng, S. (2009) Scleractinia Fauna of Taiwan: Complex Group. National Taiwan University, Taiwan.
5. Wilkinson, C. (2004) Status of Coral Reefs of the World: 2004. Volume 3. Australian Institute of Marine Science, Townsville, Australia.
6. 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.
7. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka.
8. Obura, D., Chuang, Y-Y., Olendo, M., Amiyo, N., Church, J. and Chen, C.C. (2007) Relict Siderastrea savignyana (Scleractinia: Siderastreidae) in the Kiunga Marine National Reserve, Kenya. Zoological Studies, 46: 427.