Phorbas tailliezi Vacelet & Perez, 2008, sp. nov.

Phorbas tailliezi sp. nov.

(Figs. 7, 8)

Holotype. MNHN DJV 117, National Park of Port-Cros (Bagaud island, Montrémian), 43°01’05.55”N, 6°21’46.66”E, 10 m under a small overhang, 29 May 1979.

Paratype. MNHN DJV 118, National Park of Port-Cros island (Bagaud island, Pointe du Bau), 43°01’06.20”N, 6°22’05.82”E, 12 m under a small overhang, 19 June 1980.

Other material examined. Specimen ECIMAR N° 080529 Gr4-13, sampled in Plakias (South of Crete, Greece), Calypso Rock at 35 m depth on alga Codium bursa.

Description. Thickly encrusting (Fig. 7), approximately 1–3 mm in thickness, covering areas from 25 to 80 cm ². Surface smooth, bearing numerous, non-adjacent pore-sieves 1.1 mm in diameter. Superficial canals very patent, in the living state, converging into a few oscules 2.8 mm in diameter. Consistency fleshy. Colour of ectosome and choanosome brownish red to dull red in live specimens, cream to clear brown in alcohol.

Skeleton. Dermal skeleton of tangential subtylotes poorly developed, without palisade around the poresieves. Choanosomal skeleton consisting in loose ascending fascicles of subtylotes and acanthostyles I, 30–40 µm in diameter, echinated by acanthostyles II. No microsclere.

Spicules (Fig. 8 A–E). Subtylotes, straight, with feebly inflated ends; 199.6 ± 28.5 (169–285) µm x 2.2 ± 0.4 (1.25–2.75) µm in holotype, 192 ± 15.7 (160–220) µm x 1.9 ± 0.3 (1.25–2.5) µm in paratype. Acanthostyles I, slightly curved, the thicker with an inflated head, wholly covered by small spines; 173.7 ± 10.1 (155– 195) µm x 4.25 ± 0.8 (3–5.25) µm in holotype, 162.8 ± 13.0 (140–190) µm x 3.7 ± 0.9 (2.5–5.25) µm in paratype. Acanthostyles II, straight, conical, entirely spinose; 91.6 ± 5.4 (80–100) µm x 3.3 ± 0.7 (2.5–4.5) µm in holotype, 87.8 ± 5.1 (78–95) µm x 3.5 ± 0.8 (2.5–5) µm in paratype.

The specimen from Crete has spicules in the same range of size (subtylotes 170–210 x 2.1–2.3 µm, acanthostyles I 120–160 x 3 –3.5 µm, acanthostyles II 80 – 92 x 3 µm).

Reproduction. The two type-specimens contain numerous embryos in early stages of development.

Ecology. The specimens, collected at 10–12 m depth in semi-shaded areas, were apparently not common.

Distribution. The typical form is known from Port-Cros islands and from Crete in the Eastern Mediterranean. A wider distribution should be considered if the species is conspecific with the various records of P. coriaceus in the Mediterranean (see Remarks).

Etymology. The species is dedicated to Cdt. Philippe Tailliez, who contributed so much in the establishment and protection of the National Park of Port-Cros.

Remarks. Phorbas coriaceus (Fristedt, 1887), which has been reported several times from the Mediterranean, is considered as a North-East Atlantic Hymedesmia by van Soest (1987), who however admitted that some specimens described from the Mediterranean could be an unnamed species of Phorbas or a lipochelous form of Phorbas tenacior. Several records of P. coriaceus from the Mediterranean clearly refer to another species of sponges of the genus Phorbas, for which the specific name coriaceus cannot be used. However, these sponges appear highly variable in color, shape and spicule characters, as shown in Table 3, suggesting that several different species may be present. The two specimens constituting the type material of P. tailliezi sp.nov. are well characterized by their field and skeletal features, and clearly differ from P. tenacior by their colour and megasclere spicules. This species has most likely a large distribution in the Mediterranean, as shown by the finding of a typical specimen in Crete. It is not sure, however, that all the Mediterranean records of P. coriaceus refer to the new species.