Mushroom coral (Ctenactis albitentaculata)

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Ctenactis albitentaculata
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Mushroom coral fact file

Mushroom coral description

KingdomAnimalia
PhylumCnidaria
ClassAnthozoa
OrderScleractinia
FamilyFungiidae
GenusCtenactis (1)

A member of the Fungiidae family of corals, also known as ‘mushroom corals’ due to their superficial resemblance to mushrooms, Ctenactis albitentaculata is a solitary, free-living coral. This means it is not attached to the substrate and does not form colonies. It is flat or dome-shaped and elongate in outline (3)

Like other mushroom corals, Ctenactis albitentaculata also has a wide, slit-like mouth in the centre that extends across most of the polyp’s length (3) (4). Ctenactis albitentaculata is usually pale brown, except for bright white (1), short, tapered, widely-spaced tentacles, which protrude from the coral mainly at night but also partly during the day. The septa are neatly spaced and have long, tapered, triangular teeth (3).

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Mushroom coral biology

Mushroom corals can reproduce sexually or asexually (5). During sexual reproduction, eggs and sperm are released into the water, where the egg is fertilised and develops into a larva (3). Within a fortnight, the larva will settle on to a hard substrate (5). Asexually reproduced young coral can develop from partly buried, damaged or dying parent tissue. Either way, the result is a vase-shaped polyp that gradually grows into a flattened disc, attached to the substrate via a stalk (4). The stalk of the ‘mushroom’ eventually dissolves, and the coral becomes mobile. The newly mobile coral rests on the bottom where it will mature and reproduce (4) (5)

The mobility of adult mushroom corals allows them to expand the reef by moving down-slope onto the soft substrate. This is an important process in reef ecosystems as it provides a hard substrate for other corals to establish, as well as shelter for other invertebrates (4) (5)

When mushroom corals are in immediate contact with other hard corals, they secrete a mucus that can damage coral tissues and prevents the over-growth of these neighbouring corals. This mucus also plays a role in removing sediment from the coral, and facilitates food capture (4). However, mushroom corals receive the majority of their nutrition from symbiotic algae, known as ‘zooxanthellae', which live within their tissues. The algae provide the corals with nutrients through photosynthesis, and in return receive a stable environment in which to live (3).

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Mushroom coral range

Ctenactis albitentaculata occurs in the eastern Indian and western Pacific Oceans, where it ranges from Southeast Asia, to New Caledonia, the Philippines and Papua New Guinea, and as far east as Palau and the South Marianas (1).

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Mushroom coral habitat

Ctenactis albitentaculata is found on shallow reef slopes at depths of 6 to 20 metres (1) (3).

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Mushroom coral status

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

IUCN Red List species status – Near Threatened

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Mushroom coral threats

With an estimated 20 percent of the world’s coral reefs already destroyed, Ctenactis albitentaculata faces many of the threats that are affecting coral reefs globally (6) (7). 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 (7). 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 starfish (Acanthaster planci) (6) (7) (8).

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Mushroom coral conservation

Parts of the range of Ctenactis albitentaculata fall within Marine Protected Areas (1), although enforcement within these can often be poor (8). It also occurs in the Great Barrier Reef, off the coast of Australia, where a range of conservation and research programmes are underway (9). International trade in the mushroom coral should be carefully regulated under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (2)

Recommended conservation measures for Ctenactis albitentaculata include research into its populations, abundance, ecology and resilience to threats, as well as monitoring and regulation of its harvest for the aquarium trade (1). It would also benefit from the expansion of Marine Protected Areas, together with further research into coral diseases and efforts to combat climate change (1) (7) (8).

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Find out more

Find out more about the conservation of coral reefs:

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Authentication

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:
arkive@wildscreen.org.uk

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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.
Asexual reproduction
Reproduction that does not involve the formation of sex cells (‘gametes’). In many species, asexual reproduction can occur by fission (or in plants ‘vegetative reproduction’); part of the organism breaks away and develops into a separate individual. Some animals, including vertebrates, can develop from unfertilised eggs; this process, known as parthenogenesis, gives rise to offspring that are genetically identical to the parent.
Colonies
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.
Fertilisation
The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
Hermaphroditic
Possessing both male and female sex organs.
Invertebrates
Animals with no backbone, such as insects, worms, spiders, corals and sea anemones.
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.
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.
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References

  1. IUCN Red List (May, 2011)
    http://www.iucnredlist.org/
  2. CITES (May, 2011)
    http://www.cites.org/
  3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia.
  4. Veron, J.E.N. (1986) Corals of Australia and the Indo-Pacific. Angus and Robertson Publishers, UK.
  5. Grant, N. and Manning, M. (2000) Distribution and Abundance of Five Subgenera of Fungia in Opunohu Bay, Moorea, French Polynesia. Report, unpublished.
  6. Wilkinson, C. (2008) Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. Available at:
    http://www.gcrmn.org/status2008.aspx
  7. 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.
  8. 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
  9. UNEP-WCMC: Great Barrier Reef, Queensland, Australia (May, 2011)
    http://www.unep-wcmc.org/
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Image credit

Ctenactis albitentaculata  
Ctenactis albitentaculata

© Ülar Tikk

Ülar Tikk
ylar@tikk.ee
http://www.flickr.com/photos/30583764@N05/

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