Crisp pillow coral (Anomastraea irregularis)

Crisp pillow coral massive colony
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Crisp pillow coral fact file

Crisp pillow coral description

GenusAnomastraea (1)

The only species in its genus, Anomastraea irregularis forms small, low, mound-like colonies that grow up to about 20 cm in height (3) (4). In common with other colony-forming corals, the colonies are comprised of a vast assemblage of tiny, soft polyps, each of which is equipped with numerous tentacles that direct food into a central mouth. The polyps secrete a hard skeleton known as a ‘corrallite’, which over time contributes to the formation of coral reefs (3). In Anomastraea irregularis the small corallites form an irregular honeycomb-like pattern, and the colonies have a bluish-grey or cream colour (3) (4).

Anomastrea irregularis.

Crisp pillow coral biology

Like all species in the Siderastreidae family, Anomastraea irregularis is zooxanthellate, living in symbiosis with unicellular algae known as zooxanthellae, which are essential to the coral’s growth and survival. Protected within the coral tissue, the algae provide the hosts with nutrients and energy, whilst also helping to remove metabolic wastes. The ‘cost’ of this symbiosis is that zooxanthellate corals are constrained to live in relatively shallow waters, where the algae are able to photosynthesise (3).

Although a zooxanthellate coral can obtain on average around 70 percent of its nutrient requirements through the photosynthesis of zooxanthellae, the coral may also feed on zooplankton, dissolved organic matter, and planktonic bacteria (5).


Crisp pillow coral range

A coral of the western Indian Ocean, Anomastraea irregularis is found along the east coast of Africa, in the southern Red Sea, the Gulf of Aden, the Arabian Sea and the Arabian Gulf, as well as around numerous oceanic islands (1) (3).


Crisp pillow coral habitat

Found in turbid water at the base of reefs and in intertidal pools from depths of 2 to 18 metres (1) (3) (4).


Crisp pillow coral status

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

IUCN Red List species status – Vulnerable


Crisp pillow coral threats

Around one third of the world’s reef building corals are threatened with extinction (6). The principal threat to corals is the rise in sea temperature associated with global climate change. This leads to coral bleaching, where the symbiotic algae are expelled, leaving the corals weak and vulnerable to an increasing variety of harmful diseases. Climate change is also expected to increase ocean acidification and result in a greater frequency of extreme weather events, such as destructive storms. The global impact of climate change on coral reefs is also compounded by localised threats to coral reefs from pollution, destructive fishing practices, invasive species, human development, and other activities (1) (6).

Anomastraea irregularis is also thought to be highly susceptible to the crown-of-thorns starfish (Acanthaster planci), a voracious predator of reef-building corals. Since the 1970s, outbreaks of crown-of-thorns starfish have become more and more frequent, and have resulted in the loss of large areas of coral habitat (1).

Although Anomastraea irregularis is still relatively widespread and common in parts of its range, evidence of an overall global decline in coral habitat is an indication that this species is almost certainly declining (1).


Crisp pillow coral conservation

In addition to being listed on Appendix II of CITES (2), which makes it an offence to trade Anomastraea irregularis without a permit, this coral falls within several Marine Protected Areas across its range. To specifically conserve Anomastraea irregularis, recommendations have been made for a raft of studies into various aspects of its taxonomy, biology and ecology, including an assessment of threats and potential recovery techniques (1).

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

Find out more

To learn about efforts to conserve Anomastraea irregularis see:

For further information on the conservation of coral reefs see:



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:



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.
Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.
Aquatic organisms that drift with water movements; may be either phytoplankton (plants), or zooplankton (animals).
Typically sedentary soft-bodied component of Cnidaria (corals, sea pens etc), which comprise of a trunk that is fixed at the base; the mouth is placed at the opposite end of the trunk, and is surrounded by tentacles.
Relationship in which two organisms form a close association, the term is now usually used only for associations that benefit both organisms (a mutualism).
Tiny aquatic animals that drift with currents or swim weakly in water.


  1. IUCN Red List (March, 2009)
  2. CITES (March, 2009)
  3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
  4. World Register of Marine Species (August, 2009)
  5. Barnes, R.S.K., Calow, P., Olive, P.J.W., Golding, D.W. and Spicer, J.I. (2001) The Invertebrates: A Synthesis, 3rd Edition. Blackwell Science, Oxford.
  6. Carpenter, KE et al. (2008) One-Third of Reef-Building Corals Face Elevated Extinction Risk from Climate Change and Local Impacts. Science, 321: 560 - 563.

Image credit

Crisp pillow coral massive colony  
Crisp pillow coral massive colony

© Steve Coles

Steve Coles, Ph. D


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