Starry cup coral
(Acanthastrea hillae)
Acanthastrea hillae is an encrusting coral that can grow up to 1.5m in diameter and its more prominent feature is the irregular shape of its corallites. Distributed in parts of the Gulf of Aden, Indian and Pacific Oceans this species is more commonly found in high latitude locations. Acanthastrea hillae diverged from a line of long evolutionary history and has a distinct molecular phylogeny. This coral obtains the majority of its energy requirement from a symbiotic relationship with zooxanthellae algae and it is a hermaphrodite which means each polyp produces both eggs and sperm. The threats to this species include coral bleaching, ocean acidification, over-fishing, sedimentation and pollution. Although there are no specific conservation measures in place for this species there are a number of marine protected areas (MPAs) and conservation initiatives in place throughout its distribution.
Urgent Conservation Actions
Conservation initiatives still need to be developed in some regions where this species is present and a species specific conservation action plan would be beneficial.
Gulf of Aden, Arabian and Iranian Gulf, Indian Ocean and Pacific Ocean.

Evolutionary Distinctiveness
Order: Scleractinia
Family: Mussidae
Acanthastrea hillae is diverged from a line of relatively long evolutionary history. There is record of it from the Miocene period or at least a species very similar to this. The molecular phylogeny of Acanthastrea hillae is very distinct and Fukami (2008) has placed it in a clade with just one other genus from the Mussidae family, Micromussa, and currently this clade contains just two species.

Up to and over 1.5m across
Colonies grow in irregular-shaped encrusting forms which can be red, cream or brown in colour. The corallites are irregular in shape and instead of being round they can be elongated or misshapen.
Acanthastrea hillae is a zooxanthellate coral which means that living in its tissue are single-celled algae called zooxanthellae. These zooxanthellae have a symbiotic relationship with the coral and provide it with the majority of its energy needs. Acanthastrea hillae also obtains additional nutrition by feeding on plankton that it catches using tentacles.

Acanthastrea hillae is a hermaphrodite coral which means each polyp is able to produce both sperm and eggs. The sperm and eggs are released by colonies simultaneously and are fertilised externally in the water. The fertilised eggs develop into larvae that travel in the water currents before settling onto substrate and developing into polyps. These polyps then grow into colonies through a process known as budding where the parent polyp divides into two daughter polyps. This budding process continues until the colony reaches its maximum size.

Acanthastrea hillae is found in sub-tidal, shallow reef environments. It is able to cope well with sediment or turbid (high sediment) water. This species can be found down to depths of 20m.

Gulf of Aden, Arabian and Iranian Gulf, northern Indian Ocean and Pacific Ocean.

Acanthastrea hillae is found in the Indian Ocean in countries such as Bahrain, Djibouti and Iran as well as in countries such as Mozambique, Mauritius and surrounding islands, the British Indian Ocean Territory (Chagos archipelago). This species is also extensively distributed throughout the Indo-Pacific and West Pacific including many islands such as the Solomon Islands and Vanuatu. The most northerly occurrence of this species is in Japan and the most southerly occurrence is in Australia. Acanthastrea hillae is thought to be more common in high latitude locations.
Population Estimate
There is no population estimate available for Acanthastrea hillae.
Population Trend
The population trend of Acanthastrea hillae is unknown. However, world wide 19% of corals have been damaged beyond recovery and a further 15% are under imminent risk of collapse within the next 10-20 years. From this it can be inferred that the population is in decline.
Near Threatened (NT) 2010.4 IUCN Red List of Threatened Species
The global threats to coral reefs include coral bleaching and ocean acidification. Ocean acidification is a result of the uptake of atmospheric carbon dioxide from the atmosphere and leads to a reduction in the pH of the ocean. This affects the corals calcification process by weakening skeletons and slowing growth. The effects of ocean acidification are not yet fully understood but are of significant concern to ocean ecosystems, particularly to calcifying organisms such as corals.

Thermal induced coral bleaching is caused by increasing sea temperatures that are a result of climate change. In response to the stress caused by higher than normal temperatures coral expels zooxanthellae from their tissue resulting in a white or bleached appearance. If high temperatures and the absence of zooxanthellae are prolonged, this bleaching can lead to  coral death.

Direct human threats to coral reefs include overfishing and destructive fishing techniques such as purse-seine nets, dynamite fishing and poison fishing which - although banned in many regions –still persist. Overfishing, regardless of techniques used, can lead to a reduction in the number of herbivorous fish which are needed to ensure coral reefs do not undergo a phase shift where algae out-competes coral and becomes the dominant species on the reef.

Human population growth in all regions where Acanthastrea hillae occurs is resulting in coastal development that increases levels of pollution and places greater pressure on coastal and marine resources. Coastal development can lead to increased amounts of sediment in the water which not only reduces the amount of light but it can also smother and kill corals. Pollution from both domestic and industrial sources reduces water quality and may carry pathogens which harm corals.

In addition to the direct consequences of overfishing and pollution these threats can weaken the health of corals and make them more susceptible to bleaching and disease, although it is not currently known to which diseases Acanthastrea hillae is susceptible.

Conservation Underway

Like all other EDGE Coral species, Acanthastrea hillae is listed on CITES Appendix II which regulates the international trade of threatened species of animals and plants.

There are no species specific conservation measures in place for Acanthastrea hillae but there are marine protected areas and regional conservation initiatives that may be benefiting this species.

There are a number of Marine Protected Areas (MPAs) and conservation initiatives throughout the range in which Acanthastrea hillae is found. The largest of the MPAs is the Chagos MPA declared in 2010 that encompasses the entire British Indian Ocean Territory to the 200nm limit. There are many other MPAs across the Indo-Pacific of varying size and effectiveness although the distribution of Acanthastrea hillae among these is unknown.

Conservation in Micronesia is being lead by The Micronesia Challenge which involves the Federated States of Micronesia, the Marshall Islands, Palau, Guam and the Northern Marianas Islands who have set out to conserve at least 30% of their near-shore marine resources by 2020.

Conservation Proposed
In regions such as the South-West Pacific (Solomon Islands etc) there is currently little conservation action despite high fishing pressure and continuing threats of sedimentation and coastal development.

Conservation in the Arabian and Iranian Gulf also needs to be developed.

Further research into the population of Acanthastrea hillae and its susceptibility to bleaching and disease would also benefit the development of conservation measures specific to this species.

Fukami, H., Chen, C.A., Budd, A.F., Collins, A. Wallace, C. Et al. 2008. Mitochondrial and Nuclear Genes Suggest that Stony Corals are Monophyletic but Most Families of Stony Corals Are Not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria). PLoS ONE 3(9):e3222. Doi:10.1371/journal.pone.0003222

Secretariat of the Convention on Biological Diversity (2009). Scientific Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. Montreal, Technical Series No. 46, 61 pages.

Toropova, C., Meliane, I., Laffoley, D., Matthews, E. and Spalding, M. (eds.) (2010). Global

Ocean Protection: Present Status and Future Possibilities. Brest, France: Agence des aires marines protégées, Gland, Switzerland, Washington, DC and New York, USA: IUCN WCPA, Cambridge, UK : UNEP-WCMC, Arlington, USA: TNC, Tokyo, Japan: UNU, New York, USA:WCS. 96pp.

Turak, E., Sheppard, C. & Wood, E. 2008. Acanthastrea hillae. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <>. Downloaded on 08 December 2010.

Veron J.E.N. 2000. Corals of the World. Volume 2. Townsville. Australian Institute of Marine Science

Veron, J.E.N. et al. 2009. The coral reef crises: The critical importance of <350 ppm CO2. Mar Pollut Bul 58:1428-1436

Wilkinson, C. 2008. Status of coral reefs of the world: 2008. Global Coral Reef Monitoring Network and Center, Townsville, Australia.


Distribution map based on data provided by the IUCN Spatial Data Collection.

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