Porites decasepta, Claereboudt, 2006

Claereboudt, Michel R., 2006, Porites decasepta: a new species of scleractinian coral (Scleractinia, Poritidae) from Oman, Zootaxa 1188 (1), pp. 55-62 : 56-59

Porites decasepta spec. nov. (figs. 2–4)

Material examined

Holotype: Sultan Qaboos University , SQU05080, Oman, Bar Al­Hikman, 4.0 m, 20º 20.301’ N, 58º 22.914’ E. Collector: Michel Claereboudt. Colony 6x 4 cm (figs. 2A, 3A, 3B).

Paratypes: 1— Florida Museum of Natural History , UF5672 , Oman, Bar Al­Hikman, 4.5 m, 20º 20.301’ N, 58º 22.914’ E. Collector: Victor Bonito.

2— Institut Royal des Sciences Naturelles de Belgique, IG30418 , Oman, Bar Al­ Hikman­, 5.0 m, 20º 20.301’ N, 58º 22.914’ E (). Collector: Michel Claereboudt (figs. 2B, 3B) .

Diagnosis

Corallites are about 1mm in diameter, almost circular. There are only 10 septa in six groups: one ventral, one dorsal and four pairs of lateral septa fused along their inner margins. A short columella is present and connects to the six groups of septa by well developed radii. Living colonies have small polyps, retracted during the day. All colonies were small and incrusting. They appeared and photographed bright blue­violet underwater. A very distinctive species in its environment.

Previous records

This species has been previously recorded and photographed but not identified (Blue Porites ) near Masirah Island ( Paulay & Meyer, 1999).

Description

Colonies are encrusting and small: rarely more than 7 cm across. Corallites are nearly circular in outline and small (slightly less than 1.0 mm in diameter on average). The wall is relatively thin and consists of complex anastomosing and irregular denticles. Calices are superficial. There are 10 septa in six groups: one dorsal, one ventral and two pairs of lateral septa on either side of the axis of symmetry. The two lateral septa of the ventral triplet characteristic of Porites are absent. The six groups of septa connect to a short pillarlike columella by six well developed radii slightly below the upper margin of the septa. A columella is present and there are no distinct pali but irregular, poorly defined granulated denticles are present on the margin of the septa. The coenosteum between corallites is coarse and porous.

Living colonies have small polyps normally retracted during the day. All observed colonies appeared bright blue­violet, contrasting with all specimens of other species of Porites present. The coral also photographed blue­violet under artificial light.

Etymology

The specific epithet decasepta “with 10 divisions” was chosen to illustrate the characteristic septal pattern of this species.

Habitat and distribution

All colonies were found attached to hard substrates: often fragments of dead folicaceous Montipora , between 3 and 7 m in depth in the “spur and groove” fore reef of the large reef complex extending south of the Bar Al­Hikman Peninsula (20º20.3’ N, 58º23.1’E) and Masirah Island (20º20.6’ N, 58º38.0 E). Despite extensive surveys this species was not observed in the Gulf of Oman and appears restricted to the Arabian Sea. Where present, Porites decasepta appeared quite common and easily identifiable underwater by its apparent bright blue color.