Ircinia lividus, Samaai & Pillay & Janson, 2019

Samaai, Toufiek, Pillay, Ruwen & Janson, Liesl, 2019, Shallow-water Demospongiae (Porifera) from Sodwana Bay, iSimangaliso Wetland Park, South Africa, Zootaxa 4587 (1), pp. 1-85 : 64

Ircinia lividus sp. nov.

( Fig. 28 A–F)

Material examined. Holotype. SAMC–A24782 (cross-reference TS 895 & Saf 03-Sod 15), Ramsay Reef , Sodwana Bay (27.4466°S, 32.7152°E), South Africa 0 3 November 2003, collected by T. Samaai, depth 18 m.

Paratype. SAMC–A24783 (cross-reference TS 945 & Saf 03-Sod 36), Five Mile reef, Sodwana Bay (27.5331°S, 32.6808°E), South Africa 0 3 November 2003, collected by T. Samaai; depth 20 m.

Type locality. Ramsay Reef, Sodwana Bay, east coast of South Africa.

Description. Amorphous tubular-digitate sponge, 100 × 70 × 270 mm diameter, with large central osculum, 5 mm in diameter, on tubular structure ( Fig. 28A, B ). Surface smooth but undulating with sand grains observed in the preserved specimen. No ectosomal armour visible. Texture soft and spongy, compressible, tears easily. Colour in life dark blue-black; in preservative brown.

Skeleton ( Fig. 28 C–F). Choanosomal skeleton consists of primary fibres, and abundant fine collagenous filaments. Primary fibres fully cored with foreign material viz. sand grains, and are fascicular. Fascicles complex, compact and tangled. Secondary fibres uncored and often fasciculate though some sand particles may also be found. Primary fibres, 260 (240–295) µm in diameter, secondary fibres 58 (36–87) µm in diameter. Interstitial filaments, 4 (3–5) µm in diameter.

Substratum, depth range and ecology. This species is restricted to sandy sediment. These sponges were found in sheltered areas of reefs at a depth range of 18– 20 m.

Etymology. Named for the blue-black colour of the species ( lividus meaning black and blue, L.).

Remarks. The genus Ircinia is large; the plastic nature of the species, in terms of overall morphology, creates difficulties in separating species ( Cook & Bergquist 2002) and as a result, few descriptions of Ircinia are definitive. Ircinia species are readily distinguished by the presence of fine filaments in the mesohyl, the fasciculation of primary fibres, foreign coring of primary, and an unarmored cortex ( Cook & Bergquist 1999). Ircinia arbuscula ’s original description by von Lendenfeld (1889) and the subsequent description by Samaai & Gibbons (2005) differ from I. lividus sp. nov. in having a massive, amorphous or thickly encrusting morphology, primary fibres 50–100 µm wide, filaments 2–3 µm wide, and a tough ectosome of foreign spicules. Three species of Ircinia are described from the WIO. These are I. conulosa ( Ridley, 1884) , I. cylindracea ( Vacelet, Vasseur & Lévi, 1976) and I. intertexta ( Hyatt, 1877) . Ircinia lividus sp. nov. is readily distinguished from these Ircinia species by its visibly short tubular form, large diameter of fibres, fasciculation of both primary and secondary fibres, and the prodigious coring of sand in the primary fibres.

Key diagnostic characters.

• Sponge tubular-digitate with dark blue-black colouration.

• Texture soft, spongy and compressible.

• Primary fibres thin, filaments very thin and cored with foreign material.

Figures

FIGURE 28. Ircinia lividus sp. nov. A & B. In situ; C–F. Skeletal architecture (C, x5; D, x10, E, 40; F, x65).