Friday 03 July
Kingdom | Animalia |
Phylum | Cnidaria |
Class | Anthozoa |
Order | Scleractinia |
Family | Faviidae |
Genus | Platygyra (1) |
This coral gains its common name from the colony’s meandering, brain-like pattern of brown walls, separated by grey or green depressions known as ‘valleys’ (3) (4). Platygyra daedalea colonies are large, up to a metre or more in diameter (1) (4), and are typically mound-shaped or plate-like (encrusting) (3). However, there is wide variation in colony shape and form, which, intriguingly, appears unrelated to the species’ environment or genetic makeup (5) (6). Coral colonies are composed of polyps, tiny, anemone-like animals which secrete the coral skeleton. However, unlike in many other corals, the polyps of Platygyra daedalea colonies are not individually identifiable. Instead, all polyps within the colony share common walls, with the polyp ‘mouths’ aligned in valleys, which in this species typically measure up to 30 millimetres long and 6 millimetres wide (3) (4). The tentacles of the polyps are usually only extended at night (3).
Platygyra daedalea can be difficult to distinguish from the less common Platygyra lamellina, the two species sometimes being classed together in the past (6). However, it can be distinguished by its thinner, more flat-topped and straight-sided walls, and by having valleys that are wider than the separating walls. Platygyra daedalea also has characteristically ragged septa, the radial elements that project inwards from the skeletal wall of each polyp (3) (7) (8).
Platygyra daedalea is a hermatypic coral which has microscopic algae known as zooxanthellae living within its tissues. These produce energy-rich molecules through photosynthesis, transferring most of what is produced to the coral, and in return receiving protection from currents, access to sunlight, and some nutrients from the coral’s waste products. Since the zooxanthellae need sunlight for photosynthesis, corals such as Platygyra daedalea are restricted to clear, shallow, warm waters (3) (10).
Coral colonies grow through a form of asexual reproduction known as budding, in which polyps divide themselves to form new polyps (3). Corals can also reproduce sexually by spawning, which in Platygyra daedalea involves the release of gametes into the water, for external fertilisation. Platygyra daedalea is hermaphroditic, meaning that each polyp produces both eggs and sperm. Spawning in this species usually occurs once a year, sometimes twice, and in some areas may be timed to coincide with the monsoon, when sea surface temperatures are highest and wind conditions are slow and steady (11) (12).
Platygyra daedalea is thought to be a relatively ‘aggressive’ coral, producing elongated tentacles, known as ‘sweeper tentacles’, which can damage the tissues of neighbouring corals, helping Platygyra daedalea to compete for space on the reef (7).
Although widespread and common (1) (3), and believed to be relatively resilient to habitat loss and reef degradation (1), Platygyra daedalea faces a number of threats that are impacting coral reefs around the world, and so is assumed to be undergoing a population decline (1). An estimated 20 percent of the world’s coral reefs have already been destroyed (13), and a large percentage of those remaining are at risk of collapse as a result of human activities. These include overfishing, destructive fishing practices, coral mining, pollution, irresponsible tourism, and poor land management practices, which increase the amount of sediment, nutrients and pollutants entering the ocean (1) (10) (13).
In general, however, climate change may pose the greatest risk to corals, raising the risk of temperature extremes which can stress coral and cause it to lose its zooxanthellae. This process, known as ‘bleaching’, usually results in the death of the coral. Climate change may also lead to more severe, frequent storms, which can damage reefs, and rising carbon dioxide levels may lead to ocean acidification, which can reduce coral’s ability to create its hard skeleton (1) (10) (13). Such stresses may also make corals more susceptible to disease (1). In addition to these general threats, Platygyra daedalea is also the target of collection for the aquarium trade (1).
Platygyra daedalea 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 regulated (2). Parts of its range occurs within Marine Protected Areas (1), which are set aside from unrestricted human activities and may include, for example, ‘no-take’ zones, where removal of marine life is prohibited. However, less than one percent of all marine habitats currently receive protection (14), and enforcement in these protected areas is often poor (10).
Conservation measures recommended for Platygyra daedalea include the establishment and management of new protected areas, the expansion of existing protected areas, and the management of diseases and parasites. In particular, further research is needed into the species’ abundance and population trends, its ecology, its resilience to various threats, and the potential impacts of collection for the aquarium trade. Suitable management measures, such as quotas and size limits for harvesting, are also required. In the future, techniques for artificially growing corals and for preserving their gametes may become important in the conservation of coral biodiversity (1), and ongoing reef monitoring and increased awareness will also be important tools in efforts to protect these fragile marine ecosystems (10).
For further information on brain coral and other coral species, see:
To find out more about the conservation of coral reefs see:
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
Link to this photo
Embed this ARKive thumbnail link ("portlet") by copying and pasting the code below.
Terms of Use - The displayed portlet may be used as a link from your website to ARKive's online content for private, scientific, conservation or educational purposes only. It may NOT be used within Apps.
Read more about
MyARKive
MyARKive offers the scrapbook feature to signed-up members, allowing you to organize your favourite ARKive images and videos and share them with friends.