Typically forming large, dome-shaped or plate-like structures up to a metre or more in diameter (1)(3), the colonies of Platygyra lamellina are covered in a maze-like pattern of thick brown ridges, or walls, and grey or green depressions, known as valleys (3). However, as in many related coral species, there may be a wide variety in colony shape and form (3)(4). Coral colonies are composed of tiny, anemone-like animals, known as polyps, which secrete the hard coral skeleton. In Platygyra species, the polyps share common walls, with the polyp ‘mouths’ aligned in the valleys, and the polyps themselves not individually identifiable. The polyp tentacles are usually only extended at night (3).
Platygyra lamellina can be difficult to distinguish from the more common Platygyra daedalea, and the two species have sometimes been classed together in the past. However, Platygyra lamellina has thicker, more sloping walls, which lack a flat top, and has more rounded septa, the radial elements that project inwards from the skeletal walls of the polyps(3)(4)(5).
Like many corals, Platygyra lamellina is zooxanthellate, meaning it has microscopic algae living within its tissues. In return for offering the algae a protected, stable environment, the coral receives energy-rich nutrients that the algae produce through photosynthesis. Although this allows the coral to grow faster and form large reef structures, it restricts it to living in clear, shallow, warm waters where photosynthesis can take place. The coral may supplement its diet with minute zooplankton, caught using stinging cells in the tentacles (3)(6)(7).
Coral colonies can grow through a form of asexual reproduction known as budding, in which polyps divide to form new polyps. Corals can also reproduce sexually, producing large numbers of sperm and eggs. Platygyra lamellina is hermaphroditic, meaning that each polyp produces both eggs and sperm (3)(8). This species is reported to spawn once a year, between July and August, releasing sperm and eggs during the new moon (8). The fertilised eggs develop into larvae, which travel in the water column before settling and developing into polyps(3).
An estimated 20 percent of the world’s coral reefs have already been destroyed (9), and around a third of all reef-building corals are threatened with extinction (10). The main threat to corals is global climate change, with an expected rise in ocean temperatures increasing the risk of coral bleaching, in which the coral loses its zooxanthellae, often resulting in death. Climate change is also expected to lead to more severe, frequent storms, which can damage reefs, and rising carbon dioxide levels may lead to ocean acidification, which can reduce a coral’s ability to create its hard skeleton. Such stresses may also make corals more vulnerable to disease. These global threats are compounded by more localised human impacts, such as coral harvesting, disturbance by fisheries, development, irresponsible tourism, invasive species, and pollution (1)(6)(9)(10). In addition, Platygyra lamellina may be collected for export in some areas (1).
Like all coral species, Platygyra lamellina is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) (2), meaning international trade in the species should be carefully monitored and controlled. It is also present in some Marine Protected Areas (1), including the famous Great Barrier Reef off the coast of Australia (4), a World Heritage Site and the focus of many reef conservation and research efforts (11). However, overall less than one percent of all the world’s oceans are currently protected (12), and enforcement is often poor (6).
Conservation measures recommended for Platygyra lamellina include further research into its population, biology and ecology, the status of and threats to its habitat, and harvest levels, as well as reef conservation and restoration, and the establishment, expansion and management of new protected areas. The IUCN also recommend that the conservation status of corals be reassessed in ten years or sooner, in light of the predicted threats from climate change and ocean acidification (1).
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Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
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.
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.
Possessing both male and female sex organs.
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.
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.
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.
The production or depositing of large quantities of eggs in water.
Tiny aquatic animals that drift with currents or swim weakly in water.
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