''Platygyra daedalea'', sometimes known as the lesser valley coral, is a colonial

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

stony coral Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Merulinidae Merulinidae is a family of reef-building stony corals. Characteristics All the genera in this family are colonial, reef-building corals. Skeletal structures are similar to those of Faviidae but are highly fused, without paliform lobes. The vall ...

. It occurs on reefs in shallow water in the Indo-Pacific region. It is a common species and the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed its conservation status as being of "

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

Description

''Platygyra daedalea'' usually forms massive dome or boulder-shaped colonies which may be a metre (yard) or more in diameter; however, sometimes it forms flattened plates or it may be encrusting. The polyps are situated in meandering valleys with low walls between them which are often perforated. The

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...

are toothed and protuberant, usually with uneven or pointed tips. There is an obvious ridge, the columella, in the centre of the valley. The colour varies and there may be contrasting valleys and ridges. This coral can be distinguished from the similar but less common '' Platygyra lamellina'' by the fact that the valleys are wider and the walls between them have more vertical sides and have flatter tops.

Distribution and habitat

''Platygyra daedalea'' is a common species with a widespread distribution in the Indo-Pacific region. Its range extends from Madagascar, the east coast of Africa, the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

and the

Gulf of Aden The Gulf of Aden ( ar, خليج عدن, so, Gacanka Cadmeed 𐒅𐒖𐒐𐒕𐒌 𐒋𐒖𐒆𐒗𐒒) is a deepwater gulf of the Indian Ocean between Yemen to the north, the Arabian Sea to the east, Djibouti to the west, and the Guardafui Channe ...

, to Australia, Indonesia, Japan and the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

. It is present in various reef environments, particularly on back reef slopes, from subtidal rocks down to about . It is particularly common in the

Gulf of Thailand The Gulf of Thailand, also known as the Gulf of Siam, is a shallow inlet in the southwestern South China Sea, bounded between the southwestern shores of the Indochinese Peninsula and the northern half of the Malay Peninsula. It is around in l ...

and South China Sea.

Ecology

The polyps of ''P. daedalea'' expand at night to catch

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic particles floating by. However, this coral obtains most of its nourishment from the

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s known as

zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Sy ...

it houses within its tissues. These provide organic carbon and nitrogen, the products of photosynthesis, to their

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

. To benefit from this

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

arrangement, ''P. daedalea'' needs to grow in shallow, sunlit environments. ''Platygyra daedalea'' is an aggressive coral and seeks to prevent competitors from overshadowing it. Researchers placed small colonies of this species alongside similar-sized colonies of the less-aggressive '' Favites complanata''. Some of the tentacles of ''P. daedalea'' developed into sweeper tentacles which then inflicted damage on the soft tissues of the adjoining ''F. complanata''. These sweeper tentacles were up to in length, about fifteen times as long as a normal tentacle, and well armed with

cnidocyte A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this ce ...

s. The soft tissue damage was extensive, the skeleton was laid bare in places and sponges, algae and other fouling organisms grew on it. Three of the ten corals that were attacked eventually died.

References

External links

* * * {{Taxonbar, from=Q3943742 Merulinidae Corals described in 1786