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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.
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.
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.
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 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. <www.iucnredlist.org>. 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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