''Platygyra lamellina'', the hard brain coral, is a

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 ...

of colonial

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. 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 "

near threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify fo ...

Description

Colonies of ''P. lamellina'' usually form massive rounded mounds, sometimes with nodular swellings, but may also form flat plates. The

corallite A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...

s are long, narrow and meandering, with thick walls which are up to one and a half times the thickness of the valleys between them. 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 ...

protrude slightly and are rounded and even; they are very neatly arranged, and cross the valley walls. This coral is usually some shade of brown, with the valley bottoms sometimes being greenish or grey. It can be distinguished from the otherwise similar ''

Platygyra daedalea ''Platygyra daedalea'', sometimes known as the lesser valley coral, is a colonial species of stony coral in the family Merulinidae. It occurs on reefs in shallow water in the Indo-Pacific region. It is a common species and the International Union ...

'' by the thickness of the corallite walls and the more rounded septa.

Distribution and habitat

''P. lamellina'' has a widespread distribution in the Indo-Pacific region but is generally uncommon. Its range extends from Madagascar, the east coast of Africa and the Red Sea, to Australia, Indonesia, Japan and the East China Sea. It is present as part of the reef community in various habitats, particularly on back reef slopes, but also on fore reefs and in lagoons.

Biology

Spawning of ''P. lamellina'', a simultaneous

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

, occurs at night during the summer on a date determined by the

phase of the moon Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...

; in the Red Sea, this is the three- to five-day period around the

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

in July and the similar period in August. Clusters of eggs and sperm are released by the corals, and these are buoyant and rise to the surface. Fertilisation takes place here at least twenty minutes later, after the eggs and sperm have dispersed. Neither the eggs nor the

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

larvae, which develop about two days later, contains

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 ...

. The planula larvae settle on the seabed about two months later and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into polyps. The slow development of the larvae is believed to be due to the absence of zooxanthellae, and these

symbionts 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 ...

are acquired at the primary polyp stage in this species.

References

External links

* {{Taxonbar, from=Q3940167 Merulinidae Cnidarians of the Indian Ocean Cnidarians of the Pacific Ocean Corals described in 1834 Taxa named by Christian Gottfried Ehrenberg