Lesser Valley Coral

Platygyra daedalea, also known as the lesser valley coral (sometimes brain coral), is a species of stony coral in the family Merulinidae. It is commonly found in shallow waters on reefs in the Indo-Pacific region.

Typically, Platygyra daedalea forms large dome or boulder-shaped colonies, with diameters reaching over a meter. However, it can also take on flattened plate shapes or encrusting forms. The polyps of this coral are situated in meandering valleys with low walls, often perforated. The septa, or skeletal structures, are toothed and protrude, usually with uneven or pointed tips. A distinctive ridge, known as the columella, is present in the center of the valley. The coloration can vary, with contrasting valleys and ridges. One way to distinguish Platygyra daedalea from the similar Platygyra lamellina is by the wider valleys and the more vertical sides and flatter tops of the walls between them.

Platygyra daedalea is a widely distributed species throughout the Indo-Pacific region. Its range extends from 🇲🇬 Madagascar, the east coast of Africa, the 🌊 Red Sea and the 🌊 Gulf of Aden, to 🇦🇺 Australia, 🇮🇩 Indonesia, 🇯🇵 Japan, and the South China Sea. It can be found in various reef environments, particularly on back reef slopes, ranging from subtidal rocks to depths of approximately 30 meters (100 ft). It is particularly abundant in the Gulf of Thailand and South China Sea.

The polyps of Platygyra daedalea expand at night to capture planktonic particles, but the majority of its nourishment comes from its symbiotic relationship with zooxanthellae, a type of dinoflagellate housed within its tissues. These zooxanthellae provide organic carbon and nitrogen, products of photosynthesis, to the coral. To thrive in this symbiotic arrangement, Platygyra daedalea requires shallow, sunlit environments.

Platygyra daedalea is known for its aggressive behavior, as it tries to prevent competitors from outcompeting it. In an experiment conducted by researchers, small colonies of this coral were placed alongside similarly sized colonies of the less-aggressive Favites complanata. Sweeper tentacles, measuring up to 90 millimeters (3.5 in) in length and well-equipped with cnidocytes, developed on Platygyra daedalea and caused significant damage to the adjacent soft tissues of Favites complanata. This resulted in extensive soft tissue damage, with the skeleton exposed in some areas and other fouling organisms growing on it. Three out of the ten attacked corals eventually died.