Starry cup coral (Acanthastrea hillae)

Description

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Starry cup coral fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Starry cup coral description

Usually forming colonies that are relatively small, but which can sometimes grow to over 1.5 metres across, Acanthastrea hillae is quite a conspicuous coral, with the thick, fleshy polyps typical of Acanthastrea species. As in all corals, each colony is formed from numerous tiny polyps, anemone-like animals which secrete the hard coral skeleton. The skeleton of each individual polyp is known as a ‘corallite’, and in this species these share common walls and can be quite irregular in shape. Each polyp bears numerous sturdy tentacles, which are usually extended only at night, and which surround a central ‘mouth’ ^{(3) (4)}.

The colonies of this species are usually red, cream or brown in colour, sometimes in mottled patterns, with the walls and centres of each polyp of contrasting colours ^{(3) (4)}. In some Acanthastrea hillae colonies, some of the polyps are very elongated ⁽⁴⁾.

Starry cup coral biology

Although able to feed on zooplankton, caught using stinging cells on the tentacles, Acanthastrea hillae, like other reef-building corals, obtains most of its nutrients from single-celled organisms, known as zooxanthellae, which live within its tissues. These produce energy-rich nutrients through photosynthesis, transferring most of what they produce to the coral, and in return receiving a protected, stable environment, waste nutrients from the coral, and access to sunlight. Although this limits the coral to living in relatively clear, shallow, warm waters where photosynthesis can take place, it does allow it to grow faster, forming large reef structures ^{(3) (4) (5)}.

Coral colonies can grow through a form of asexual reproduction known as budding, in which polyps divide to form new polyps. Corals also reproduce sexually, producing large numbers of sperm and eggs. Acanthastrea hillae is hermaphroditic, meaning that each polyp produces both eggs and sperm, which are released into the water for external fertilisation. The fertilised eggs develop into larvae, which travel in the water column before settling and developing into polyps ^{(3) (4)}.

Starry cup coral range

Acanthastrea hillae occurs in the Indian Ocean and western Pacific Ocean, including the Arabian Gulf, around Australia and South East Asia, and in the East China Sea. It is more commonly found at high latitudes rather than in the tropics ^{(1) (3) (4)}. Some claim that records of the species from the western Indian Ocean are doubtful ⁽³⁾.

Starry cup coral habitat

This coral occurs in a wide range of shallow reef environments, at depths of up to 20 metres, and does well in sedimented and turbid waters ^{(1) (3)}.

Starry cup coral status

Classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾ and listed on Appendix II of CITES ⁽²⁾.

Starry cup coral threats

An estimated 20 percent of the world’s coral reefs have already been destroyed ⁽⁶⁾, and around a third of all reef-building coral species are now threatened with extinction ⁽⁷⁾. 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, reducing the ability of coral to create its hard skeleton. Such stresses can also make corals more susceptible to disease, parasites and predators, such as the crown of thorns sea star (Acanthaster planci) ^{(1) (5) (6) (7)}.

These global threats are compounded by localised human impacts, such as coral harvesting, disturbance by fisheries, irresponsible tourism, invasive species, pollution and sedimentation ^{(1) (5) (6) (7)}. Although Acanthastrea hillae is still widespread and common throughout its range, it is thought to be moderately susceptible to a number of threats, including bleaching ⁽¹⁾. It also appears to be quite common in the live aquarium trade, although the extent of this and its potential impacts are unknown.

Starry cup coral conservation

Like all other coral species, Acanthastrea hillae is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that international trade in this species should be carefully monitored and controlled ⁽²⁾. Parts of this species’ range fall within Marine Protected Areas ⁽¹⁾, although enforcement in these areas is often poor ⁽⁵⁾, and overall less than one percent of all marine habitats currently receive protection ⁽⁸⁾. The species also occurs on the famous Great Barrier Reef, off the coast of Australia, the world’s largest coral reef ecosystem and a World Heritage Site. Extensive coral research programmes and various conservation actions are underway here ⁽⁹⁾.

Specific conservation measures recommended for Acanthastrea hillae include further research into its biology, ecology, habitats and populations, as well as into the threats facing it. The expansion and management of protected areas, together with better enforcement, will also be important, and techniques such as artificial propagation and the preservation of coral gametes (eggs and sperm) may become important tools for maintaining coral biodiversity in the long-term ⁽¹⁾.

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

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Find out more

To learn about efforts to conserve Acanthastrea hillae see:

• EDGE of Existence:
  http://www.edgeofexistence.org/coral_reef/species_info.php?id=1847

To find out more about corals and their conservation see:

• Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
• Reef Check:
  http://www.reefcheck.org
• The Coral Reef Alliance:
  http://www.coral.org

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Glossary

Budding

Type of asexual reproduction (reproduction that does not involve the formation of sex cells), in which new individuals develop from the parent organism, forming a swelling similar in appearance to a bud. The ‘bud’ slowly separates from the parent as it grows.

Colony

A group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or ‘individuals’), which are produced by budding and remain physiologically connected.

Hermaphroditic

Possessing both male and female sex organs.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Photosynthesis

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.

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.

Zooplankton

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

References

1. IUCN Red List (July, 2009)
   http://www.iucnredlist.org
2. CITES (July, 2009)
   http://www.cites.org
3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
4. Veron, J.E.N. (1993) Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu, Hawaii.
5. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka. Available at:
   http://data.iucn.org/dbtw-wpd/edocs/2008-012.pdf
6. Wilkinson, C. (2004) Status of Coral Reefs of the World: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Australia. Available at:
   http://www.crisponline.info/Portals/1/Skins/inside_fr/documents/0_statusofcoralreefs.pdf
7. 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.
8. UNEP: Fifty Key Facts about Seas and Oceans (July, 2009)
   http://www.unep.org/wed/2004/Downloads/PDFs/Key_Facts_E.pdf
9. UNEP-WCMC: Great Barrier Reef, Queensland, Australia (July, 2009)
   http://www.unep-wcmc.org/medialibrary/2011/06/23/c5f5632e/Great%20Barrier%20Reef.pdf