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Family Oculinidae: (L. oculus, eye; L. -ina, like).... presumably relating to the eye-like appearance of the calices.
This is a primarily Cenozoic family. It has a poor fossil record and doubtful affinities with the Rhipidogyridae, a Cretaceous family of doubtful validity.

The family is represented by only one extant zooxanthellate genera in the Indo-Pacific, while several genera are present in the Altlantic (i.e. Oculina, Simplastrea, and Schizoculina). Seven species grouped under the genus Galaxea are the only Indo-Pacific members (i.e. G.horrescens, G.astreata, G.paucisepta, G.cryptoramosa, G.acrhelia, G.longisepta, and G.fascicularis). All species of that genus, are found in PNG.
Because of their distinct corallite morphologies and most striking colorations, the four genera are easily recognizable on reefs. They are distantly related to Faviidae and are characterized by large upstanding claices. The generously spaced corallites with solid-walled but fragile tubes, have exsert septa (extend above the calice, thus giving the corallite a spiky appearance) and are linked by a smooth coenosteum (Veron 1986). The columella is weakly developed.


Some members of the family Oculinidae (61kB)

The Galaxea genus is quite distinct as its coenosteum is free of septa; species are a common, if not abundant, group in turbid coastal waters. In fact, they seem to be very tolerant of low light levels, caused by high turbidity. Galaxea astreata is capable of surviving on reefs that are heavily influenced by runoff and where coral communities do not extend below 3m depth. On inshore reefs, G.fascicularis was observed to form massive colonies extending 2-3m in diameter.
G.acrhelia (previously grouped seperately as Acrhelia horrescens) is an outer-reef coral, and found only on offshore and oceanic reefs. It seems to fit well into distribution patterns occurring out there, as it is a predominantly arborescent species, with wither bushy or open branches (Veron 1986). The corallites with very exsert septa are slender, and spiral around the branches.
G.fascicularis has a very unique mode of reproduction not found in other scleractininas, or in other metazoans. It is a pseudo-gynodioecious species, in which female colonies produce viable positively buoyant eggs, while the hermaphroditic colonies produce sperm bundles and non-viable eggs (Harrison, 1988). Functionally, G.fascicularis is a gonochoric broadcast-spawner, since the hermaphroditic colonies are female-sterile, and thus function as males only. G.fascicularis, together with G.astreata, have been observed to spawn during the GBR mass-spawning phenomenon. The non-viable eggs that are produced by the hermaphrodites in the population seem to function as "buoyancy compensators" that lift the sperm bundle to the surface where fertilization of eggs take place.

Key to the family Oculinidae Septa <2mm exsert Colony branching Budding intratentacular: Genus Oculina
Budding extratentacular: Genus Schizoculina
Colony not branching: Genus Simplastrea
Septa >2mm exsert: Genus Galaxea
Altlantic genera: --------------------------------------------------------------------------------------------------------------

Oculina (L. oculus, eye; -ina, suffix denoting likeness):

Like Astrangia, Cladocora and Madracis, the genus contains endosymbiotic (zooxanthellate) and azooxanthellate species. The two groups do not have morphologically distinctive characters.
Loosely branched colonies that are straggly and bushy (phaceloid) with usually pale yellowish in color. The main branches are less or about 1cm in diameter while the side branches are <1cm. Corallites are distinct, separate and widely spaced - sometimes crowded at the branch tips. Calices are 3-4mm in diameter. Septa are visible with 12 slightly exsert septa of the primary cycle and are more prominent than the intermediate ones. Septa are minutely dentate.
PRESENT DISTRIBUTION: Caribbean, Gulf of Mexico and Bermuda.
GENERAL ABUNDANCE: generally uncommon.
FOSSIL RECORD: Cretaceous (?), Oligocene of the Tethys, Miocene of the Tethys.
Schizoculina (Gk. schizos, split; L. oculus, eye): The distribution of S.fissipara, endemic to the east African coast, is unlike that of any other coral.
Encrusting to branching colonies that are sometimes over 1m across. Branching is upright and light brown or blue-gray. Corallites are circular and up to 4-5mm in diameter but are occasionally linked in a series.
PRESENT DISTRIBUTION: Eastern Atlantic only.
NUMBER OF EXTANT SPECIES: 2 known species.
Indo-Pacific genera: -----------------------------------------------------------------------------------------------------------

Simplastrea (L. simpel, simple; Gk. aster, star):

The genus is known only from the holotype of S.vesicularis, an eroded corallum which, nevertheless, cannot be placed in another genus.
Colonies are flat and encrusting. Corallites are circular, uniformly spaced and separated by a blistery coenosteum. Walls are thin with well developed septa that are thin and straight. The inner margins of septa form a columella tangle.
Galaxea (Gk. galaxaios, milky): G.fascicularis forms some of the largest of all coral colonies. However, the typical growth form of this genus forms massive, domed and rounded colonies that are relatively small. Tall columns, and flat plates may also be formed (G.paucisepta, G.longisepta). Color is green, brownish with purple tinges. Corallites are distinct and rise at least 2mm and sometimes even 15mm (stalked) above the peritheca (plocoid to phaceloid). Corallite diameters may range from 1.5 - 8mm and are 2-3mm apart. Septa are numerous and arranged in cycles, are strongly exsert, and protrude thin with sharp blades. Septal margins are smooth, granular, or minutely dentate, while the coenosteum is free of septal structures.
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean to southern Pacific.
GENERAL ABUNDANCE: very common, very conspicuous.
FOSSIL RECORD: Miocene (?) of the Pacific.
NUMBER OF EXTANT SPECIES: 7 known species.