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Related FAQs: The Fishes of the Red Sea

Related Articles: Reef Flats, Sandy Reef SlopeBiotopes, Fishwatcher's Guide to the Red Sea, Triggerfishes of the Red Sea, Butterflyfishes of the Red Sea, Angelfishes of the Red Sea,  

Marine Aquarium Biotopes: Pt.2

 Red Sea Reef Slope  2 of 5


By Bob Fenner


Back to: Red Sea Reef Slope 1 of 5, On to: Red Sea Reef Slope 3 of 5

Stinging-Celled Life, Phylum Cnidaria: Corals, Soft and Hard, Gorgonians (Sea Fans), Anemones, Clavulariid Polyps, Organ Pipe "Coral", even Black Coral and Tube-Anemones are found throughout the Red Sea. Here are the most hardy, readily available forms.

Soft Corals, Order Alcyonacea: Thirteen genera are listed from here. Some are hobby "standards", others you rarely see in the trade or the wild. Other species recorded from here include Parethropodium fulvum, Cladiella pachyclados, five species of Sinularia, Dendronephthyas (mentioned above), Stereonephthya cundabiluensis, Umbellifera oreni and Siphonogorgia spp. 

Litophyton arboreum Red Sea. Variable in color depending where growing, season. Red Sea image. 

Lobophytum spp. Common throughout its range in the Indo-Pacific. Feed via photosynthesis and plankton. Grow in folds or finger-like projections by folding coenenchyme. Pictured, an usually large "patch" of colonies on the reef lip (at the top of the slope), and two close-ups in the Red Sea.
Parerythropodium fulvum (Forsskal 1775), Sulfur Coral, Yellow Encrusting Leather Coral. So tough, it can be found creeping onto the reef flat in places. A typical creeping colony and close-up in the Red Sea. 

Sarcophyton trocheliophorum Marenzeller 1886, Elephant Ear Soft Coral. A large alcyoniid with symbiotic zooxanthellae. This and fine plankton, dissolved organics are nutritive. To two feet across. A popular aquarium species that loses easily to stinging anemones, large polyp stony corals. Likes bright light, moderate current. Red Sea images. S. ehrenbergi and S. glaucum also occur in the Red Sea.

Pulsing Corals, family Xeniidae occur here in good numbers, at times covering more than half the hard surface. Most often encountered are one of at least ten species of Xenia spp. Shown: a typical setting on a reef slope with pulsing corals, encrusting sponges and a skulking bass, Cephalopholis miniata in view. 

Stony Corals, Order Scleractinia, are more abundant and diverse than the reef flat above. Most of what you'll find are members of the following families, listed in order by preponderance by family, then genus within family, then species within genus.

Family Acroporidae: There are three genera of Staghorn Corals in the Red Sea; Acropora, Montipora and Astreopora. The first two are the predominant life forms on the reef flat. These genera and occasional colonies of Astreopora occur, though generally in less abundance down the reef slopes.

Acropora hyacinthus (Dana 1846). Colonies as wide, flat plates, possibly tiered. Branches fine in low wave action environments, fused in brisk ones. Branchlets are fine, upward facing. Axial corallites not exsert, but distinct; radial corallites are cup-shaped. Found on outer reef flats (shown) and reef slopes. Red Sea images. 

Acropora tenuis (formerly eurystoma) (Dana 1846). Colonies as  corymbose clumps. Often with their fine branches evenly spaced. Corallites: Axial ones are long, tubular. Radial ones in neat rosettes often with flaring colored lips. Common on Res Sea Rocky Reef Slopes.

Astreopora myriophthalma (Lamarck 1816). Smooth, hemispherical colonies. Corallites, conical, even-spaced. Coenosteum with rippled ridges. Most common species. Red Sea images. 

Montipora tuberculosa (Lamarck 1816). Colonies submassive or laminar. Small corallites occur as both exsert and embedded, separated by papillae, tuberculae of a corallite width. Found in most reef environments. Red Sea pix.

Family Pocilloporidae: All of the four genera of pocilloporids of the Red Sea are to be found here on the rocky reef slope; Stylophora, Seriatopora, Pocillopora and Madracis.

Seriatopora hystrix Dana 1846, the most common Bird's Nest Coral. Needle like endings on variably thick, twisted branches. Here is a Bird's Nest Coral colony in the Red Sea. This species is often encountered on the reef flat in other oceans; not here. Other members of the genus in the Red Sea are S. caliendrum and S. octoptera. They're less common by far.

Genus Stylophora. S. pistillata (shown on the reef flat) which occurs down the slope to about 25m. and is most common. S. danae (shown) prefers sheltered habitats, and S. subseriata, similar to S. pistillata are secondarily common. 

Family Poritidae: Porites, Goniopora (seven species) and Alveopora (five species) occur here, especially the first genus as a principal reef  builder. The other two genera are found more toward the middle to bottom of the rocky reef slope on down to the sandy reef slope. 

Porites lichen Dana 1846. Colonies as flat plates with fused nodules, columns. Corallites in irregular rows with slightly raised ridges between. Typically yellow in color. Common to dominant species on reef slopes. Red Sea image. 

Alveopora daedalea (Forsskal 1775). Colonies as thick plates or columns (up to a meter tall). Corallites with alternating short, long septa. Tentacles appear squared off, six each tall, short in number. Occur on protected upper reef slopes. Red Sea image.  

Family Fungiidae: Mushroom Corals. Do occur in the Red Sea in the genera Cycloseris (six species), Fungia (ten species), Ctenactis (two species, both common), Podabacia (one species) and Herpolitha (one species here), but sporadically as a rule. Some Fungia spp. are found on the reef flat, but most species occur lower on the reef slope out to the sandy reef slope.

Ctenactis crassa (Dana 1846). Axial furrow extends apparently to both ends of the polyp. Multiple mouths, all within the furrow. Juvenile and older polyp in the Red Sea.

Ctenactis echinata (Pallas 1776). Both septa and costal (top and bottom skeletal lines) bear teeth. One mouth. Close-up and adult in Fiji. Occurs in the Red Sea from the Reef Flat to 25 meters. 

Cycloseris sp. skeleton in the Red Sea, top view. This genus is distinguished from Fungia by its finely serrated costal edges (vs. denticular in Fungia), and lack of perforations of said walls.

Fungia fungites (Linnaeus 1758). Polyps irregularly circular to round in appearance. Regular, saw like, triangular septal teeth. Often with tentacular lobes showing. Aquarium and Pulau Redang, Malaysia photos.

Family Agariciidae: Cactus, Elephant Skin, Plate, Lettuce Corals; sporadically abundant in places. Four genera are found here: Pavona (seven species), Leptoseris (seven species), Gardineoseris (monotypic), Pachyseris (two species). Most are found in deeper water here, near the lower rocky reef slope, onto rocky bommies on the lower sandy slope. Most common species shown.

Pachyseris speciosa (Dana 1846). One sided colony faces, with regular ridging. Most common member of the genus. Red Sea image. 

Pavona varians Verrill 1864. Colonies encrusting to laminar, showing short, irregular valleys. Red Sea image.

Leptoseris explanata Yabe & Sugiyama 1941. Colonies made up of one-sided blades. Corallites expand as they grow toward end of blades. Red Sea colony and close-up.

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