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BiologyPlatygyra 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).