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Family Poritidae: (L. porous, pore; Gk. -ites, like).... relating to the porous nature of the corallum.
The Poritidae has been moved from its traditional position within the Fungiina to a suborder of its own because there is little significant correspondence between the microskeletal characters of the Poritidae and those of any other extant family. The five extant genera are morphologically very distinct. According to Veron (1986) this assemblage of only distantly related genera exhibiting a wide range of morphologies that range from massive to branching to laminar and ramose ( i.e. the monospecific Stylaraea, Porites, Goniopora, and the light-weighted Alveopora). In the western Indian Ocean a monospecific genus of Poritipora can be found.
Colonies have porous corallite walls and septa. Corallites are usually compacted, with little or no coenosteum.

The family is widely distributed, and tends to dominate in back-reef or lagoonal habitats. Massive colonies of genus Porites (e.g. P.lobata, P.lutea) are probably among the most important reef-builders of PNG. The genera Porites and Goniopora are characteristic groups of turbid coastal waters where they form large aggregations. Porites form massive structures called microatolls, and are the dominant reef-builders in back-reef environments. The corallites are closely packed with little coenenchyme. The coralla are generally very porous, and relatively fast-growing.

Some Poritids (120kB)

Both Porites and Goniopora are mainly gonochoric, i.e. each colony is of a different sex, with only a few species known to be hermaphroditic. There is some evidence that the large massive Porites spp. (like P.lobata) may be gonochoric spawners, while the smaller massive species, such as P.murrayensis, may be brooders. However, unlike the brooding Porites (with internal fertilization), Goniopora is a broadcast-spawner, where the gametes are shed into the water column and fertilization is external (Veron 1986). Of the Poritidae studied so far, 12 are spawners and nine are brooders.
In addition to sexual reproduction, colony fission and fragmentation in massive Porites spp. colonies, especially with branching morphology, is and important mode of asexual reproduction. For example, Porites furcata, and P.porites in the Atlantic as well as P.cylindrica, P.nigrescens, and P.compressa in the Indo-Pacific region can form extensive monospecific meadows hundreds of square meters in area, thus significantly contributing to reef development. Colony fission produces numerous genetic clones or ramets that are most obvious in P.lutea, P.australiensis, P.solida, P.mayeri, P.myrmidonensis, and P.lobata.

Key to the family Poritidae Corallites <2mm diameter Septa fused in non-cyclical pattern: Genus Porites
Septa not fused Columella present: Genus Stylaraea
Columella absent: Genus Poritipora
Corallites >2mm diameter Skeleton robust, not very porous: Genus Goniapora
Skeleton delicate, very porous: Genus Alveopora
Genera restricted to the Indo-Pacific region: -----------------------------------------------------------------------------

Stylaraea (Gk. stylos, pillar):

S.punctata as the only representative here, is a taxonomic and ecological isolate that, superficially, has as much in common with the primarily Mesozoic Actinacididae as the extant Poritidae. Like Oulastrea crispala, it is confined to shallow rocky - subtidal environments where other corals are seldomly found. This species resembles Porites except that septa are short, are in two cycles and do not fuse. Colonies are circular or encrusting, less than 15mm across with uniformly spaced corallites. Septa are in 2 cycles of 6 each. Columella is an irregular pinnule. Color is pale brown, with white septa and columella.
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean, Micronesia, GBR.
FOSSIL RECORD: Plio-Pleistocene of Guam.
NUMBER OF EXTANT SPECIES: 1 known species.
Poritipora (L. porus, pore; Gk. -ites, suffix denoting likeness; L. porus, pore): P.paliformis as the only member, forms dull brown, massive colonies, usually hemispherical, several meters across an occurs in shallow reef environments and lagoons. It resembles Porites densa, which has lightly smaller corallites, but this species is easily recognised under water. The undulating surface houses deeply excavated corallites that are 2-3mm in diameter (cellular appearance). The surface is smooth to undulating. Corallites are deeply excavated. Septa are arranged in 2 alternating cycles of 6 each, with the primary cycle forming decent paliform styli. Columella is absent. Corallite walls are very thin (coral skeleton is very light).
PRESENT DISTRIBUTION: western Indian Ocean, Sri Lanka.
NUMBER OF EXTANT SPECIES: 1 known species.
Goniopora (Gk. gonia, an angle; L. porus, pore): This genus has been a major reef-builder throughout much of the duration of the Cenozoic Tethys. The derivation of the poritid pattern of septal fusion from Goniopora is one of the few instances in scleractinian taxonomy where one taxon or taxonomic character can be said to be 'primitive' compared with another.
The genus Goniopora is not as problematic as Porites. Extant Goniopora frequently forms very extensive monospecific or multi-specific stands in inshore environments dominated by terrigenous sediments as well as offshore areas that are influenced by river runoff. Thus Goniopora can be found in turbid water and in areas generally protected from wave action; e.g. G.columna, G.lobata, G.tenuidens can form extensive stands that are tens of meters long and wide. Local dominance in certain habitats may be related to their sediments-rejecting ability, which may be facilitated by the fact t hat the large fleshy polyps of most Goniopora species are fully expanded most of the time.
Goniopora is also one of the most aggressive coral species, excluding other corals within its periphery. It has been observed that G.stokesi uses specialized elongated "sweeper polyps" to attack neighboring coral colonies. The sweeper polyps of G.lobata even contain a diverse battery of cnidocysts.
Species are easily recognized in situ by characters of soft tissues, but these may become unreliable over wide geographic ranges. Colonies are massive or rounded, few even encrusting to fine-branched colonies and far less massive than Porites. Polyps with 24 short tentacles are usually brown, gray, green, or blue and are always extended. The peristome, polyp, and the tentacles are of different color. Calices are rounded or hexagonal that extend 1-5mm in diameter. Septal margins are pitted or spiny and seem to come up from the floor of the corallite (contrary to Alveopora). Septa are usually 24 septa in 3 cycles. The larger first 2 cycles are very distinct (dorsal and ventral septa are isolated, while lateral septa merge), while the 3rd merges with the former at close proximity of the corallite wall.
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean to southern Pacific.
GENERAL ABUNDANCE: generally common, very conspicuous.
FOSSIL RECORD: Cretaceous, Eocene of the Caribbean and Tethys.
NUMBER OF EXTANT SPECIES: 24 known species.
Alveopora (L. alveolus, small, hollow; porus, pore): This genus is taxonomically isolated with unclear affinities. It is readily confused with Goniopora, although these genera are probably not closely related. Morphological differences between the two are demonstrated by all Goniopora having 24 tentacles per polyp, and all Alveopora having 12. It is rare to see many Alveopora species together in the same biotope, as habitats of individual species are very different, more so than for any other genus. These habitats include protected turbid biotopes (the majority of species), exposed upper reef slopes (e.g. A.marionensis) and high-latitude, non-reef biotopes (e.g. A.japonica).
Members form massive, plate-like, or branched colonies that are not as large as Porites colonies. Polyps are small with 12 tentacles and always extended. Corallum and tentacles are brownish or bluish. Calices are rounded or polygonal and about 1-2mm in diameter. They are crowded or closely united by their very brittle walls (entire skeleton is very light). There are 12-24 hardly distinguishable septa that seem to originate from the corallite wall (contrary in Goniopora); the shared wall is pierced by pores giving it a lace-like appearance.
PRESENT-DISTRIBUTION: Red Sea and western Indian Ocean to southern Pacific.
GENERAL ABUNDANCE: sometimes common, very conspicuous.
FOSSIL RECORD: Eocene of the Caribbean and Tethys.
NUMBER OF EXTANT SPECIES: 14 known species.
Circum-tropical genera (both Atlantic and Indio-Pacific): --------------------------------------------------------------

Porites (L. porus, pore; Gk. -ites, suffix denoting likeness):

According to Veron (1986) most species of Porites are not valid species. The number of true species is not known. Thus, more than any other major genus, Porites is in need of taxonomic revision, primarily because the majority of massive species do not have distinctive morphologies and are only identifiable in situ by minute corallite characteristics. Because of this, and because some species (P.lobata, P.lutea and P.australiensis) are extremely abundant throughout most of the lndo-Pacific, uncommon species or variants of common species may go undetected much more easily than the species of other genera.
There are further problems: corallite characters are very variable both within colonies and between colonies in different environments, and, as with most coral species, geographic variation goes beyond meaningful species distinctions. Morphometric taxonomic methods and the electrophoretic methods are mutually supportive for Caribbean Porites. Electrophoresis especially may provide an insight into the much greater complexity of Porites taxonomy and biogeography in the Indo-Pacific; questions of primary interest are the geographic ranges of morphologically meaningful species, the affinities of species in remote regions (the southern-eastern and far eastern Pacific), the structure of species complexes (like P.compressa in Hawaii) and the extent of speciation in areas of very high species diversity (especially Indonesia and the Philippines).
Despite the wide geographic range of the genus as a whole, and many of its species, latitudinal attenuation, especially between reef and non-reef environments, occurs more abruptly in Porites than in most major genera. This occurs not only in species diversity, but also in abundance and colony size: for example the number of species in the southern-most reefs of western Australia is about the same as in tropical reefs, but only one species (P.lutea) forms large colonies.
The taxonomy of the genus Porites is as, or even more, problematic than that of Acropora. The exceedingly small calices make it virtually impossible to identify some massive forms to species level in the field; thus, greatly complicating ecological studies; P.porites looks very similar to P.cylindrica, and is not found outside the Caribbean.
Colonies are massive, branching, encrusting, or nodular colony that are brown, yellow, blueish, light greenish, or pink in color that can measure several meters across. Corrallites are so tiny that the surface (peritheca) appears smooth or slightly granular. Calices are 1-1.5mm in diameter, rounded, polygonal or closely united by the walls. Septa may be visible in the calices. There are 3 septal cycles. The first 2 cycles are dominant and form 12 septa with a paliform lobe at the inner end (dorsal septum is isolated, while ventral and lateral septa merge), while the 3rd cycle merges with the former at close proximity of the corallite wall. Columella usually submerged. Tubercles are present on the corallite walls.
GENERAL ABUNDANCE: extremely common, conspicuous al generic level.
FOSSIL RECORD: Cretaceous (?), Eocene of the Caribbean and Tethys. The genus became overwhelmingly dominant in the Miocene Tethys.
NUMBER OF EXTANT SPECIES: 54 known species.