Closed brain coral (Leptoria phrygia)

GenusLeptoria (1)
SizeLength: colonies may be several metres wide (1)

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

Forming large, irregular-shaped mounds covered by a dense, maze-like network of sinuous ridges and valleys, Leptoria phrygia is a striking component of many Indo-West Pacific coral reefs. Each mound comprises a colony of polyps, which are anemone-like animals that secrete a hard skeleton. While some colony-forming corals are composed of polyps which are individually separated by hard walls, in Leptoria phrygia the polyps form rows that share a common wall and can only be distinguished by the separate polyp mouths. These mouths are situated in the valleys between the network of ridges formed by the shared walls, the sides of which bear tiny tentacles that trap food particles. Like many corals, Leptoria phrygia exhibits a variety of colours, appearing cream, brown or green, with the valleys and ridges usually displaying contrasting colours (3).

Widely distributed throughout the Indo-West Pacific, Leptoria phrygia colonies occur from the east coast of Africa, east through the Indian Ocean to the West Pacific, north as far as southern Japan and south as far as east-central Australia (1) (3).

Leptoria phrygia mainly occurs in shallow, tropical reef environments, particularly on the upper reef slope. It is usually found at depths of between 3 and 15 metres, but may occasionally be found at both shallower and deeper depths, but is unlikely to occur below 30 metres (1) (3).

Like many coral species, Leptoria phrygia is zooxanthellate, which means that its tissues contain large numbers of single-celled algae called zooxanthellae. The coral and the algae have a symbiotic relationship, in which the algae gain a stable environment within the coral's tissues, while the coral receives nutrients produced by the algae through photosynthesis. By harnessing the sun's energy in this way, corals are able to grow rapidly and form vast reef structures, but are constrained to live near the water surface (3).

Leptoria phrygia is capable of both asexual reproduction, whereby the polyps proliferate through the production of clones, and by sexual reproduction. As a hermaphroditic species, each colony of Leptoria phrygia produces both sperm and eggs, which are released simultaneously in a single, annual spawning event that takes place over the course of several days. The exact timing of the release is linked to the season and to the phase of the moon, for example, Leptoria phrygia colonies in Australia spawn in December during the last quarter of the lunar cycle (4). The fertilised eggs develop into planktonic larvae, which travel through the water column, before settling and metamorphosing into sessile polyps (5).

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, whereby the symbiotic algae are expelled, leaving the corals weak and vulnerable to an increasing variety of harmful diseases. Climate change is also expected to cause more extreme weather incidents and to increase ocean acidification, which impairs the coral's ability to form a skeleton. These global threats are compounded by localised threats from pollution, destructive fishing practices, invasive species and human development (1) (6).

In addition to these threats, Leptoria phrygia is targeted for the aquarium trade, with 582 pieces exported from Indonesia in 2005. While this species is currently abundant and widespread, loss of coral reef habitat indicates that it is declining, and with so many potential threats to its survival, could rapidly become threatened (1).

Like all coral species, Leptoria phrygia is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that all international trade is strictly controlled by the use of permits and annual quotas (2). In addition, Leptoria phrygia falls within several Marine Protected Areas across its range (1).

Specific conservation measures recommended for Leptoria phrygia include carrying out extensive studies of its population, biology, and ecology, along with more research into existing and potential threats. In addition, expansion of the protected area network is required, along with efforts to restore this species in regions where it has been lost or suffered severe declines. Finally, in response to the threat of climate change, artificial propagation and preservation of sperm and eggs may be necessary to safeguard this species against complete extinction (1).

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  1. IUCN Red List (October, 2008)
  2. CITES (October, 2008)
  3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
  4. Kojis, B.L. and Quinn, N.J. (1982) Ecology of two faviid corals (Coelenterata: Scleractinia). Marine Ecology Progress Series, 8: 251 - 255.
  5. Richmond, R.H. and Hunter, C.L. (1990) Reproduction and recruitment of corals: comparisons among the Caribbean, the Tropical Pacific, and the Red Sea. Marine Ecology Progress Series, 60: 185 - 203.
  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.