Invertebrate · Stinging · Hard corals

Lesser Valley Coral

Platygyra daedalea (Ellis & Solander, 1786)

syn. Astroria astraeiformis, Astroria astreiformis, Astroria daedalea, Astroria esperi, Caeloria daedalea, Coeloria astraeiformis +19 more

<30 mCITES IILeast Concern

902

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.

Why it's threatened

Residential & commercial development

Housing & urban areas · Commercial & industrial areas · Tourism & recreation areas

Transportation & service corridors

Shipping lanes

Biological resource use

Intentional use: (subsistence/small scale) [harvest] · Unintentional effects: (subsistence/small scale) [harvest] · Motivation Unknown/Unrecorded

Human intrusions & disturbance

Recreational activities

Invasive species, genes & disease

Unspecified species

Pollution

Type Unknown/Unrecorded · Soil erosion, sedimentation · Ozone

Climate change & severe weather

Temperature extremes · Storms & flooding

This species has a relatively low susceptibility to coral bleaching (McClanahan et al. 2004). Most colonies of this species lost some tissue and few whole colonies died after the 1998 bleaching event on the Great Barrier Reef (Baird and Marshall 2002). The fecundity of this species was reduced in response to both bleaching and harsh environments off the Arabian Peninsula (Howells et al. 2016).

The collection of this species for the aquarium trade may lead to overharvest and localised reductions in abundance, especially for populations of naturally rare species (Bruckner and Borneman 2006). However, the wild collection of corals is highly selective and considered low impact in the long-term relative to other activities such as coral mining and dynamite fishing (Green and Shirley 1999, Pratchett et al. 2020).

In general, the major threat to corals is global climate change, in particular, temperature extremes leading to bleaching and increased susceptibility to disease, increased severity of ENSO events and storms, and ocean acidification.

Coral disease has emerged as a serious threat to coral reefs worldwide with increases in numbers of diseases, coral species affected, and geographic extent (Ward et al. 2004, Sutherland et al. 2004, Sokolow et al. 2009). Outbreaks of coral diseases have damaged coral reefs worldwide with the most widespread, virulent, and longest running coral disease outbreak currently occurring on the Florida Reef Tract and throughout the Caribbean. The disease, stony coral tissue loss disease, has been ongoing since 2014 (Precht et al. 2016) and has devastated affected reefs along Florida (Walton et al. 2018, Williams et al. 2021) and throughout the Caribbean (Alvarez-Filip et al. 2019, Kramer et al. 2019). Numerous disease outbreaks have also occurred in the Indo-Pacific (Willis et al. 2004, Aeby et al. 2011; 2016), Indian Ocean (Raj et al. 2016) and Persian Gulf (Howells et al. 2020). Escalating anthropogenic stressors combined with the threats associated with global climate change of increases in coral disease, frequency and duration of coral bleaching and ocean acidification place coral reefs in the Indo-Pacific at high risk of collapse.

Localized threats to corals include fisheries, human development (industry, settlement, tourism, and transportation), changes in native species dynamics (competitors, predators, pathogens and parasites), invasive species (competitors, predators, pathogens and parasites), dynamite fishing, chemical fishing, pollution from agriculture and industry, domestic pollution, sedimentation, and human recreation and tourism activities. The severity of these combined threats to the global population of each individual species is not known.

Threat classification from the IUCN Red List.