Litophyton arboreum Forskal , 1775

van Ofwegen, Leen P., 2016, The genus Litophyton Forskal, 1775 (Octocorallia, Alcyonacea, Nephtheidae) in the Red Sea and the western Indian Ocean, ZooKeys 567, pp. 1-128 : 6-8

Taxon classification Animalia Alcyonacea Nephtheidae

Litophyton arboreum Forskal, 1775 Figures 1B, 12, 13, 14, 15, 16

Litophyton arboreum Forskål, 1775: 139 (Red Sea); Roxas 1933: 384 (in key only; discussion about synonymy); Verseveldt 1965: 33 (Red Sea).

Ammothea virescens Lamarck, 1816: 411; Savigny 1817: pl. 2 fig. 6; Blainville 1830: 486; 1834: 522; Ehrenberg 1834: 283 (listed); Gray 1869: 129; Haeckel 1876: pl. 1 fig. 9; Kükenthal 1869: 129.

Nephthea cordierii Audouin, 1828: 48 (Savigny's, pl. 2 fig. 6).

Neptaea inominata Blainville, 1830: 487 (Savigny's, pl. 2 fig. 6); 1834: 523.

Ammothea arborea Klunzinger, 1877: 31, pl. 2 fig. 4 (Red Sea); May 1899: 133.

Litophytum arboreum ; Kükenthal 1903: 124 (Red Sea); 1913: 12 (Red Sea); Thomson and McQueen 1908: 55 (Sudanese Red Sea); Shann 1912: 511, pl. 61 fig. 1 (reproduction of Savigny's, pl. 2 fig. 6).

Litophyton viride ; Bayer et al. 1983: pl. 17 fig. 121.

Litophyton arboreum Not Litophyton arboreum ; Verseveldt 1966: 5, figs 1-2, pl. 1 (Sulawesi); Tixier-Durivault 1970a: 222 (Vietnam); 1972: 29 (Madagascar).

Material examined.

ZMTAU Co 26246, neotype, Red Sea, Gulf of Aqaba Eilat Marine lab, 12 m depth, 20 March 1978, coll. Y. Benayahu; RMNH Coel. 8917, Red Sea, Gulf of Suez, Abu Durba, coll. Hebrew Univ.-Smiths. Red Sea project; RMNH Coel. 8918, Red Sea, Gulf of Aqaba, 5 March 1972, coll. H. Schumacher; RMNH Coel. 8919, Red Sea, Gulf of Suez, Et Tur, depth 12 m, 1 January 1969, coll. Hebrew Univ.-Smiths. Red Sea project; RMNH Coel. 8949, Red Sea, Gulf of Suez, Et Tur, 20 September 1967, coll. Hebrew Univ.-Smiths. Red Sea project; ZMTAU Co 25847, two colonies, Red Sea, 1986-1987, coll. Y. Benayahu; ZMTAU Co 25858, Red Sea, Gulf of Suez, Shag Rock, depth 3-24 m, 14 July 1987, coll. Y. Benayahu; ZMTAU Co 26234, Red Sea, Gulf of Suez, El Bilaiyim lagoon, 24 August 1971, coll. D. Popper; RMNH Coel. 42083, Indian Ocean, Socotra, Ras Farun SW, sta. 207, sample 80, subtidal, 11 April 1999, coll. G. Reinicke, microscope slides only.

Reassigned to the species.

RMNH Coel. 8941, Red Sea, Gulf of Aqaba, Ophir Bay, 30 August 1967, coll. Hebrew Univ.- Smiths. Red Sea project (misidentified by Verseveldt as Nephthea laevis ).

Removed from the species.

RMNH Coel. 2218, Indonesia, Sulawesi, 18 April 1978; RMNH Coel. 17122, Australia, Lodestone reef, July 1972, coll. G.R. Pettit (see remarks).

Diagnosis.

Litophyton with many internal spindles of the base of the stalk with blunt ends. The polyp stalk with scales.

Description.

The neotype is 5 cm high and 7.5 cm wide; the colony stalk is 2-3 cm high (Figure 12).

The polyps (Figure 13) are up to about 0.5 mm wide and high. Supporting bundle not projecting, composed of clavate spindles with simple, tall tubercles, outer side and one end thorny (Figure 14A). Length of these spindles is up to 0.7 mm. Polyp body sclerites irregularly arranged, the smallest are present adaxially, they are sparsely tuberculated spindles (Figure 14B); abaxially they merge into the smaller spindles of the supporting bundle and likewise have a thorny outer side (Figure 14C). The tentacles have rodlets up to 0.05 mm long (Figure 14D). The polyp stalk has scales up to 0.05 mm long (Figure 14E).

Surface layer top of stalk. Spindles, radiates, and derivatives of these, merging into unilaterally spinose spindles; all sclerites with simple tubercles (Figures 14F, 15A). The spindles are up to 0.3 mm long.

Surface layer base of stalk. Sclerites similar to those of the top of the stalk but with longer and sharper spines (Figure 15 B–C).

Interior base of stalk. Spindles, up to 1.2 mm long, with simple sparse tubercles (Figure 16 A–B). A few spindles have one or more side branches, many have one or two blunt ends. The smaller spindles are more often branched than the larger ones.

Colour. The colony is white.

Distribution.

Red Sea, Socotra.

Remarks.

The microscope slide of the stalk of ZMTAU Co 26234 only has internal sclerites of the stalk because the specimen has the surface layer missing.

RMNH Coel. 8917, 8918, and 8919 agree with the above description, although of RMNH Coel. 8918 no interior stalk microscope slide exists.

Two of the 14 microscope slides of RMNH Coel. 2218, from Indonesia, are missing, notably those of the interior stalk sclerites. The unilaterally spinose sclerites of the surface layer of the stalk have much higher spines than those of the neotype of Litophyton arboreum , and the slide with polyp sclerites also shows different sclerites, no polyp stalk scales at all. I regard this a misidentification.

RMNH Coel. 17122, from Australia, is clearly a misidentification, it has pointed interior sclerites in the base of the stalk.

Litophyton arboreum is characterized by having large spindles with blunt ends in the interior of the stalk. Litophyton acuticonicum and Litophyton simulatum also have this type of sclerites. Litophyton acuticonicum differs in having branched, unilaterally spinose spindles in the surface layer of the stalk, which are also twice as long as the unbranched spinose spindles of Litophyton arboreum . Litophyton simulatum also differs in having twice as long unilaterally spinose spindles in the surface layer of the stalk. Moreover, Litophyton arboreum has small oval scales in the polyp stalk, a type of sclerite not present in Litophyton acuticonicum and Litophyton simulatum .