75-397: See text Porites is a genus of stony coral ; they are small polyp stony (SPS) corals. (Also referred to as finger coral or hump coral) They are characterised by a finger-like morphology . Members of this genus have widely spaced calices , a well-developed wall reticulum and are bilaterally symmetrical . Porites , particularly Porites lutea , often form microatolls . Corals of
150-603: A monophyletic group. The earliest scleractinians were not reef builders, but were small, phaceloid or solitary individuals. Scleractinian corals were probably at their greatest diversity in the Jurassic and all but disappeared in the mass extinction event at the end of the Cretaceous, about 18 out of 67 genera surviving. Recently discovered Paleozoic corals with aragonitic skeletons and cyclic septal insertion – two features that characterize Scleractinia – have strengthened
225-556: A certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of evolutionary relatedness (the phylogenetic definition). Attempting to define a level of the Linnean hierarchy without referring to (evolutionary) relatedness is unsatisfactory, but a phenetic definition is useful when addressing questions of a morphological nature—such as how successful different body plans were. The most important objective measure in
300-407: A character unique to a sub-set of the crown group. Furthermore, organisms in the stem group of a phylum can possess the "body plan" of the phylum without all the characteristics necessary to fall within it. This weakens the idea that each of the phyla represents a distinct body plan. A classification using this definition may be strongly affected by the chance survival of rare groups, which can make
375-403: A cup surrounding this part of the polyp. The interior of the cup contains radially aligned plates, or septa , projecting upwards from the base. Each of these plates is flanked by a pair of mesenteries. The septa are secreted by the mesenteries, and are therefore added in the same order as the mesenteries are. As a result, septa of different ages are adjacent to one another, and the symmetry of
450-402: A group ("a self-contained unity"): "perhaps such a real and completely self-contained unity is the aggregate of all species which have gradually evolved from one and the same common original form, as, for example, all vertebrates. We name this aggregate [a] Stamm [i.e., stock] ( Phylon )." In plant taxonomy , August W. Eichler (1883) classified plants into five groups named divisions,
525-602: A group containing Viridiplantae and the algal Rhodophyta and Glaucophyta divisions. The definition and classification of plants at the division level also varies from source to source, and has changed progressively in recent years. Thus some sources place horsetails in division Arthrophyta and ferns in division Monilophyta, while others place them both in Monilophyta, as shown below. The division Pinophyta may be used for all gymnosperms (i.e. including cycads, ginkgos and gnetophytes), or for conifers alone as below. Since
600-400: A phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done a century earlier). The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by
675-471: A phylum much more diverse than it would be otherwise. Total numbers are estimates; figures from different authors vary wildly, not least because some are based on described species, some on extrapolations to numbers of undescribed species. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. The kingdom Plantae
750-706: A phylum, other phylum-level ranks appear, such as the case of Bacillariophyta (diatoms) within Ochrophyta . These differences became irrelevant after the adoption of a cladistic approach by the ISP, where taxonomic ranks are excluded from the classifications after being considered superfluous and unstable. Many authors prefer this usage, which lead to the Chromista-Protozoa scheme becoming obsolete. Currently there are 40 bacterial phyla (not including " Cyanobacteria ") that have been validly published according to
825-640: A rate up to three times faster than similar species without symbionts. These corals typically grow in shallow, well-lit, warm water with moderate to brisk turbulence and abundant oxygen, and prefer firm, non-muddy surfaces on which to settle. Most stony corals extend their tentacles to feed on zooplankton , but those with larger polyps take correspondingly larger prey, including various invertebrates and even small fish. In addition to capturing prey in this way, many stony corals also produce mucus films they can move over their bodies using cilia ; these trap small organic particles which are then pulled towards and into
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#1732776771369900-689: A result of teaming up with symbiotic algae . Nine of the sub-orders were in existence by the end of the Triassic and three more had appeared by the Jurassic (200 million years ago), with a further suborder appearing in the Middle Cretaceous (100 million years ago). Some may have developed from a common ancestor, either an anemone-like coral without a skeleton, or a rugose coral . A rugose coral seems an unlikely common ancestor because these corals had calcite rather than aragonite skeletons, and
975-408: A ring of tentacles . The base of the polyp secretes the stony material from which the coral skeleton is formed. The body wall of the polyp consists of mesoglea sandwiched between two layers of epidermis. The mouth is at the centre of the oral disc and leads into a tubular pharynx which descends for some distance into the body before opening into the gastrovascular cavity that fills the interior of
1050-401: A set of characters shared by all its living representatives. This approach brings some small problems—for instance, ancestral characters common to most members of a phylum may have been lost by some members. Also, this definition is based on an arbitrary point of time: the present. However, as it is character based, it is easy to apply to the fossil record. A greater problem is that it relies on
1125-401: A subjective decision about which groups of organisms should be considered as phyla. The approach is useful because it makes it easy to classify extinct organisms as " stem groups " to the phyla with which they bear the most resemblance, based only on the taxonomically important similarities. However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display
1200-424: A term that remains in use today for groups of plants, algae and fungi. The definitions of zoological phyla have changed from their origins in the six Linnaean classes and the four embranchements of Georges Cuvier . Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan . At its most basic, a phylum can be defined in two ways: as a group of organisms with
1275-474: Is a paraphyletic taxon, which is less acceptable to present-day biologists than in the past. Proposals have been made to divide it among several new kingdoms, such as Protozoa and Chromista in the Cavalier-Smith system . Protist taxonomy has long been unstable, with different approaches and definitions resulting in many competing classification schemes. Many of the phyla listed below are used by
1350-484: Is a level of classification or taxonomic rank below kingdom and above class . Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and
1425-405: Is defined in various ways by different biologists (see Current definitions of Plantae ). All definitions include the living embryophytes (land plants), to which may be added the two green algae divisions, Chlorophyta and Charophyta , to form the clade Viridiplantae . The table below follows the influential (though contentious) Cavalier-Smith system in equating "Plantae" with Archaeplastida ,
1500-481: Is generally included in kingdom Fungi, though its exact relations remain uncertain, and it is considered a protozoan by the International Society of Protistologists (see Protista , below). Molecular analysis of Zygomycota has found it to be polyphyletic (its members do not share an immediate ancestor), which is considered undesirable by many biologists. Accordingly, there is a proposal to abolish
1575-449: Is particularly challenging. Many species were described before the advent of scuba diving , with little realisation by the authors that coral species could have varying morphologies in different habitats. Collectors were mostly limited to observing corals on reef flats, and were unable to observe the changes in morphology that occurred in more turbid, deeper-water conditions. More than 2,000 nominal species were described in this era, and by
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#17327767713691650-770: Is summertime in their Caribbean habitat. Threats to corals in the genus Porites include predation, climate change, and anthropogenic pollution. When exposed to increased temperatures and copper, P. cylindrica slowed its rate of production. Additionally, the symbiotic zooxanthellae reduced their photosynthesis rate when exposed to both stressors. Done and Potts (1992) observed that when settled, larvae in Porites are vulnerable to competition from other corals and predation from sea urchins. Additionally, mortality likelihood increases following strong storms. Scleractinia About 35, see text . Scleractinia , also called stony corals or hard corals , are marine animals in
1725-565: The Catalogue of Life , and correspond to the Protozoa-Chromista scheme, with updates from the latest (2022) publication by Cavalier-Smith . Other phyla are used commonly by other authors, and are adapted from the system used by the International Society of Protistologists (ISP). Some of the descriptions are based on the 2019 revision of eukaryotes by the ISP. The number of protist phyla varies greatly from one classification to
1800-551: The Convention on International Trade in Endangered Species (CITES) meaning that their international trade (including in parts and derivatives) is regulated. The World Register of Marine Species lists the following families as being included in the order Scleractinia. Some species have not been placeable ( Incertae sedis ): Phylum In biology , a phylum ( / ˈ f aɪ l əm / ; pl. : phyla )
1875-732: The Indo-Pacific and Caribbean basins. Some species in this genus demonstrate high levels of halotolerance . In the Gulf of Thailand P. lutea tolerates daily tidal shifts of 10-30‰ salinity. Moberg et al. (1997) determined that when the salinity declines, the symbiotic zooxanthellae decrease their photosynthesis rate as the coral contracts its polyps to protect them. The corals maintain their metabolic rate by temporarily switching to heterotrophy, consuming prey such as brine shrimp and other zooplankton. Porites growth rates can be determined by examining annual rings in their skeleton. This method
1950-451: The effects of global warming and ocean acidification . Scleractinian corals may be solitary or colonial . Colonies can reach considerable size, consisting of a large number of individual polyps. Stony corals are members of the class Anthozoa and like other members of the group, do not have a medusa stage in their life cycle. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc surrounded by
2025-461: The endodermal cells are usually replete with symbiotic unicellular dinoflagellates known as zooxanthellae . There are sometimes as many as five million cells of these per 1 square centimetre (0.16 sq in) of coral tissue. Up to 50% of organic compounds produced by symbionts are used as food by polyps. The oxygen byproduct of photosynthesis and the additional energy derived from sugars produced by zooxanthellae enable these corals to grow at
2100-446: 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 mouth is fringed with tentacles. Although some species are solitary, most are colonial . The founding polyp settles and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as 25 cm (10 in) across but in colonial species
2175-488: The pyrgomatids , but a recent study recorded evidence of living pyrgomatids in stylasterids , casting doubt on this idea. Stony corals have a great range of reproductive strategies and can reproduce both sexually and asexually. Many species have separate sexes, the whole colony being either male or female, but others are hermaphroditic , with individual polyps having both male and female gonads. Some species brood their eggs but in most species, sexual reproduction results in
2250-478: The 19th and early 20th centuries. The two most advanced 19th century classifications both used complex skeletal characters; The 1857 classification of the French zoologists Henri Milne-Edwards and Jules Haime 's was based on macroscopic skeletal characters, while Francis Grant Ogilvie 's 1897 scheme was developed using observations of skeletal microstructures, with particular attention to the structure and pattern of
2325-746: The El-Nino Southern Oscillation, the Intertropical Convergence Zone, and the mean state of the climate system. Corals in the genus Porites are found in reefs throughout the world. It is a dominant taxon on the Pandora platform of the Great Barrier Reef . Potts et al. (1985) identified 7 dominant species: P. lobata , P. solida , P. lutea , P. australiensis , P. mayeri , P. murrayensis , and P. anae . The oldest of six colonies in this reef
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2400-497: The Zygomycota phylum. Its members would be divided between phylum Glomeromycota and four new subphyla incertae sedis (of uncertain placement): Entomophthoromycotina , Kickxellomycotina , Mucoromycotina , and Zoopagomycotina . Kingdom Protista (or Protoctista) is included in the traditional five- or six-kingdom model, where it can be defined as containing all eukaryotes that are not plants, animals, or fungi. Protista
2475-458: The above definitions is the "certain degree" that defines how different organisms need to be members of different phyla. The minimal requirement is that all organisms in a phylum should be clearly more closely related to one another than to any other group. Even this is problematic because the requirement depends on knowledge of organisms' relationships: as more data become available, particularly from molecular studies, we are better able to determine
2550-421: The adjacent colonies of the same species form a single colony by fusing. Most colonial species have very small polyps, ranging from 1 to 3 mm (0.04 to 0.12 in) in diameter, although some solitary species may be as large as 25 cm (10 in). The skeleton of an individual scleractinian polyp is known as a corallite. It is secreted by the epidermis of the lower part of the body, and initially forms
2625-525: The age of the coral. Solitary corals do not bud. They gradually increase in size as they deposit more calcium carbonate and produce new whorls of septa. A large Ctenactis echinata for example normally has a single mouth, may be about 25 cm (10 in) long and have more than a thousand septa. Stony corals occur in all the world's oceans. There are two main ecological groups. Hermatypic corals are mostly colonial corals which tend to live in clear, oligotrophic, shallow tropical waters; they are
2700-477: The amount of water movement and other factors. Many shallow-water corals contain symbiont unicellular organisms known as zooxanthellae within their tissues. These give their colour to the coral which thus may vary in hue depending on what species of symbiont it contains. Stony corals are closely related to sea anemones , and like them are armed with stinging cells known as cnidocytes . Corals reproduce both sexually and asexually. Most species release gametes into
2775-503: The assembling of species into the existing families , but not into the traditional suborders. For example, some genera affiliated with different suborders were now located on the same branch of a phylogenetic tree . In addition, there is no distinguishing morphological character that separates clades , only molecular differences. The Australian zoologist John Veron and his co-workers analyzed ribosomal RNA in 1996 to obtain similar results to Romano and Palumbi, again concluding that
2850-452: The body and tentacles. Unlike other cnidarians however, the cavity is subdivided by a number of radiating partitions, thin sheets of living tissue, known as mesenteries . The gonads are also located within the cavity walls. The polyp is retractable into the corallite , the stony cup in which it sits, being pulled back by sheet-like retractor muscles. The polyps are connected by horizontal sheets of tissue known as coenosarc extending over
2925-404: The budding of new polyps. There are two types of budding, intratentacular and extratentacular. In intratentacular budding, a new polyp develops on the oral disc, inside the ring of tentacles. This can form individual, separate polyps or a row of partially separated polyps sharing an elongate oral disc with a series of mouths. Tentacles grow around the margin of this elongated oral disc and not around
3000-414: The capture of plankton and suspended organic particles. The growth rates of most species of non-zooxanthellate corals are significantly slower than those of their counterparts, and the typical structure for these corals is less calcified and more susceptible to mechanical damage than that of zooxanthellate corals. Scleratinians were previously believed to be obligatory hosts of another group of barnacles,
3075-413: The coral, serving as additional aesthetic livestock. These particular Porites specimens are called "christmas tree worm rocks" or "christmas tree worm coral". Porites corals have been shown to be accurate and precise recorders of past marine surface conditions. Measurements of the oxygen isotopic composition of the aragonitic skeleton of coral specimens indicate the sea-surface temperature conditions and
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3150-589: The end of the 20th century prompted new evolutionary hypotheses that were different from ones founded on skeletal data. Results of molecular studies explained a variety of aspects of the evolutionary biology of the Scleractinia, including connections between and within extant taxa, and supplied support for hypotheses about extant corals that are founded on the fossil record. The 1996 analysis of mitochondrial RNA undertaken by American zoologists Sandra Romano and Stephen Palumbi found that molecular data supported
3225-507: The first publication of the APG system in 1998, which proposed a classification of angiosperms up to the level of orders , many sources have preferred to treat ranks higher than orders as informal clades. Where formal ranks have been provided, the traditional divisions listed below have been reduced to a very much lower level, e.g. subclasses . Wolf plants Hepatophyta Liver plants Coniferophyta Cone-bearing plant Phylum Microsporidia
3300-676: The form of "polyp bail-out", which may allow polyps to survive even though the parent colony dies. It involves the growth of the coenosarc to seal off the polyps, detachment of the polyps and their settlement on the seabed to initiate new colonies. In other species, small balls of tissue detach themselves from the coenosarc, differentiate into polyps and start secreting calcium carbonate to form new colonies, and in Pocillopora damicornis , unfertilised eggs can develop into viable larvae. The overwhelming majority of scleractinian taxa are hermaphroditic in their adult colonies. In temperate regions,
3375-444: The form of crystals of aragonite , however, a prehistoric scleractinian ( Coelosimilia ) had a non-aragonite skeletal structure which was composed of calcite . The structure of both simple and compound scleractinians is light and porous, rather than solid as is the case in the prehistoric order Rugosa . Scleractinians are also distinguished from rugosans by their pattern of septal insertion. In colonial corals, growth results from
3450-583: The fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta . The term phylum was coined in 1866 by Ernst Haeckel from the Greek phylon ( φῦλον , "race, stock"), related to phyle ( φυλή , "tribe, clan"). Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as
3525-415: The genus Porites also often serve as hosts for Christmas tree worms ( Spirobranchus giganteus ). Specimens of Porites are sometimes available for purchase in the aquarium trade. Due to the strict water quality, lighting and dietary requirements, keeping Porites in captivity is very difficult. Most Porites that are collected have Christmas tree worms ( Spirobranchus giganteus ) that bore into
3600-521: The hypothesis for an independent origin of the Scleractinia. Whether the early scleractinian corals were zooxanthellate is an open question. The phenomenon seems to have evolved independently on numerous occasions during the Tertiary, and the genera Astrangia , Madracis , Cladocora and Oculina , all in different families, each have both zooxanthellate and non-zooxanthellate members. The fact that zooxanthellate coral make up only about half of
3675-430: The individual mouths. This is surrounded by a single corallite wall, as is the case in the meandroid corallites of brain corals. Extratentacular budding always results in separate polyps, each with its own corallite wall. In the case of bushy corals such as Acropora , lateral budding from axial polyps form the basis of the trunk and branches. The rate at which a stony coral colony lays down calcium carbonate depends on
3750-705: The mouth. In a few stony corals, this is the primary method of feeding, and the tentacles are reduced or absent, an example being Acropora acuminata . Caribbean stony corals are generally nocturnal, with the polyps retracting into their skeletons during the day, thus maximising the exposure of the zooxanthellae to the light, but in the Indo-Pacific region, many species feed by day and night. Non-zooxanthellate corals are usually not reef-formers; they can be found most abundantly beneath about 500 m (1,600 ft) of water. They thrive at much colder temperatures and can live in total darkness, deriving their energy from
3825-411: The next. The Catalogue of Life includes Rhodophyta and Glaucophyta in kingdom Plantae, but other systems consider these phyla part of Protista. In addition, less popular classification schemes unite Ochrophyta and Pseudofungi under one phylum, Gyrista , and all alveolates except ciliates in one phylum Myzozoa , later lowered in rank and included in a paraphyletic phylum Miozoa . Even within
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#17327767713693900-645: The order is unusual, as symbiosis is almost always an all-or-nothing phenomenon. This symbiotic equilibrium suggests that there must be evolutionary processes simultaneously maintaining and limiting symbiotic relationships. This is likely because despite the energetic benefits it provides, photosymbiosis appears to be an evolutionary disadvantage during mass extinctions. Traits that generally enable corals to survive mass extinction include deep-water or large habitat range, non-symbiotic, solitary or small colonies, and bleaching resistance, all of which tend to characterize azooxanthellate (non-symbiotic) corals. Endosymbionts, on
3975-539: The other hand, the highly parasitic phylum Mesozoa was divided into two phyla ( Orthonectida and Rhombozoa ) when it was discovered the Orthonectida are probably deuterostomes and the Rhombozoa protostomes . This changeability of phyla has led some biologists to call for the concept of a phylum to be abandoned in favour of placing taxa in clades without any formal ranking of group size. A definition of
4050-523: The other hand, which rely on specialized conditions and access to light to survive, are especially vulnerable to prolonged darkness, temperature change, and eutrophication, all of which have been hallmarks of past mass extinctions. This makes zooxanthellate coral especially vulnerable to unstable conditions. Therefore, it is possible that coral and zooxanthellate coevolved loosely, with the relationship dissolving when advantages decreased, then reforming when conditions stabilized. The taxonomy of Scleractinia
4125-428: The outer surface of the skeleton and completely covering it. These sheets are continuous with the body wall of the polyps, and include extensions of the gastrovascular cavity, so that food and water can circulate between all the different members of the colony. In colonial species, the repeated asexual division of the polyps causes the corallites to be interconnected, thus forming the colonies. Also, cases exist in which
4200-480: The oxygen isotopic composition of the seawater at the time of growth. The oxygen isotopic composition of seawater can indicate the precipitation/evaporation balance because oxygen atoms of the more abundant mass 16 will preferentially evaporate before the more rare mass 18 oxygen. The relationship between temperature, precipitation, and the oxygen isotopic composition of Porites corals is important for reconstructing past climates, and associated large-scale patterns such as
4275-399: The polyps are usually only a few millimetres in diameter. These polyps reproduce asexually by budding , but remain attached to each other, forming a multi-polyp colony of clones with a common skeleton, which may be up to several metres in diameter or height according to species. The shape and appearance of each coral colony depends not only on the species, but also on its location, depth,
4350-463: The production of a free-swimming planula larva that eventually settles on the seabed to undergo metamorphosis into a polyp. In colonial species, this initial polyp then repeatedly divides asexually, to give rise to the entire colony. The most common means of asexual reproduction in colonial stony corals is by fragmentation. Pieces of branching corals may get detached during storms, by strong water movement or by mechanical means, and fragments fall to
4425-475: The relationships between groups. So phyla can be merged or split if it becomes apparent that they are related to one another or not. For example, the bearded worms were described as a new phylum (the Pogonophora) in the middle of the 20th century, but molecular work almost half a century later found them to be a group of annelids , so the phyla were merged (the bearded worms are now an annelid family ). On
4500-410: The risk of self-fertilization. Immediately after spawning, the eggs are delayed in their capability for fertilization until after the release of polar bodies. This delay, and possibly some degree of self-incompatibility, likely increases the chance of cross-fertilization. A study of four species of Scleractinia found that cross-fertilization was actually the dominant mating pattern, although three of
4575-642: The rules of nomenclature, the name given to the first described species has precedence over the rest, even when that description is poor, and the environment and even sometimes the country of the type specimen is unknown. Even the concept of "the species" is suspect, with regard to corals which have large geographical ranges with a number of sub-populations; their geographic boundaries merge with those of other species; their morphological boundaries merge with those of other species; and there are no definite distinctions between species and subspecies. The evolutionary relationships among stony corals were first examined in
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#17327767713694650-470: The scleractinian skeleton is radial or biradial . This pattern of septal insertion is termed "cyclic" by paleontologists. By contrast, in some fossil corals, adjacent septa lie in order of increasing age, a pattern termed serial and produces a bilateral symmetry . Scleractinians secrete a stony exoskeleton in which the septa are inserted between the mesenteries in multiples of six. All modern scleractinian skeletons are composed of calcium carbonate in
4725-469: The sea bed. In suitable conditions, these are capable of adhering to the substrate and starting new colonies. Even such massive corals as Montastraea annularis have been shown to be capable of forming new colonies after fragmentation. This process is used in the reef aquarium hobby to increase stock without the necessity to harvest corals from the wild. Under adverse conditions, certain species of coral resort to another type of asexual reproduction in
4800-481: The sea where fertilisation takes place, and the planula larvae drift as part of the plankton , but a few species brood their eggs. Asexual reproduction is mostly by fragmentation , when part of a colony becomes detached and reattaches elsewhere. Stony corals occur in all the world's oceans. Much of the framework of modern coral reefs is formed by scleractinians. Reef-building or hermatypic corals are mostly colonial; most of these are zooxanthellate and are found in
4875-507: The septa were arranged serially rather than cyclically. However, it may be that similarities of scleractinians to rugosans are due to a common non-skeletalized ancestor in the early Paleozoic. Alternatively, scleractinians may have developed from a Corallimorpharia -like ancestor. It seems that skeletogenesis may have been associated with the development of symbiosis and reef formation, and may have occurred on more than one occasion. DNA sequencing appears to indicate that scleractinian corals are
4950-486: The septal trabeculae . In 1943, the American zoologists Thomas Wayland Vaughan and John West Wells , and Wells again in 1956, used the patterns of the septal trabeculae to divide the group into five suborders . In addition, they considered polypoid features such as the growth of the tentacles. They also distinguished families by wall type and type of budding . The 1952 classification by French zoologist J. Alloiteau
5025-529: The shallow waters into which sunlight penetrates. Other corals that do not form reefs may be solitary or colonial; some of these occur at abyssal depths where no light reaches. Stony corals first appeared in the Middle Triassic , but their relationship to the tabulate and rugose corals of the Paleozoic is currently unresolved. In modern times stony corals numbers are expected to decline due to
5100-511: The species were also capable of self-fertilization to varying extents. There is little evidence on which to base a hypothesis about the origin of the scleractinians; plenty is known about modern species but very little about fossil specimens, which first appeared in the record in the Middle Triassic ( 240 million years ago ). It was not until 25 million years later that they became important reef builders, their success likely
5175-498: The species, but some of the branching species can increase in height or length by around 10 cm (4 in) a year (about the same rate as human hair grows). Other corals, like the dome and plate species, are more bulky and may only grow 0.3 to 2 cm (0.1 to 0.8 in) per year. The rate of aragonite deposition varies diurnally and seasonally. Examination of cross sections of coral can show bands of deposition indicating annual growth. Like tree rings, these can be used to estimate
5250-449: The traditional families were plausible but that the suborders were incorrect. They also established that stony corals are monophyletic, including all the descendants of a common ancestor , but that they are divided into two groups, the robust and complex clades. Veron suggested that both morphological and molecular systems be used in future classification schemes. All Scleractinian corals (excluding fossils) are listed under Appendix II of
5325-441: The usual pattern is synchronized release of eggs and sperm into the water during brief spawning events, often related to the phases of the moon. In tropical regions, reproduction may occur throughout the year. In many cases, as in the genus Acropora , the eggs and sperm are released in buoyant bundles which rise to the surface. This increases the concentration of sperm and eggs and thus the likelihood of fertilization , and reduces
5400-408: The world's primary reef -builders. Ahermatypic corals are either colonial or solitary and are found in all regions of the ocean and do not build reefs. Some live in tropical waters but some inhabit temperate seas, polar waters, or live at great depths, from the photic zone down to about 6,000 m (20,000 ft). Scleractinians fall into one of two main categories: In reef-forming corals,
5475-557: Was approximately 700 years old, and was estimated to be growing at 10.3 mm per year. Meyer and Schultz (1985) demonstrated that P. furcata has a mutualistic relationship with the schools of French and white grunts ( Haemulon flavolineatum and H. plumierii ) that rest in their heads during the day. The fish provide it with ammonium, nitrates, and phosphorus compounds. Coral heads with resting grunts experience significantly higher growth rates and nitrogen composition than those without. Representatives of this genus are found in both
5550-697: Was built on these earlier systems but included more microstructural observations and did not involve the anatomical characters of the polyp. Alloiteau recognized eight suborders. In 1942, W.H. Bryan and D. Hill stressed the importance of microstructural observations by proposing that stony corals begin skeletal growth by configuring calcification centers, which are genetically derived. Therefore, diverse patterns of calcification centers are vital to classification. Alloiteau later showed that established morphological classifications were unbalanced and that there were many examples of convergent evolution between fossils and recent taxa . The rise of molecular techniques at
5625-405: Was used to determine that P. astreoides grows its skeleton about the central axis by approximately 3.67mm/year, calcifies at approximately 0.55g/cm/year, and increases density in this region of the body at approximately 1.69g/cm/year. Additionally, Meyer and Schultz (1985) reported that coral growth varies seasonally. They observed that P. furcata's growth rate peaked between May and August, which
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