Ircinia colossa Calcinai, Bastari, Bertolino & Pansini

Calcinai, Barbara, Bastari, Azzurra, Bavestrello, Giorgio, Bertolino, Marco, Horcajadas, Santiago Bueno, Pansini, Maurizio, Makapedua, Daisy M. & Cerrano, Carlo, 2017, Demosponge diversity from North Sulawesi, with the description of six new species, ZooKeys 680, pp. 105-150 : 117-120

Ircinia colossa Calcinai, Bastari, Bertolino & Pansini sp. n. Figure 10

Material examined.

Holotype: MSNG 60141, PH-44, 15/01/2005, Timur (Bunaken Island), about 20 m depth. Paratype: MSNG 60142, BKA 25, 12/09/2014, Yellow coco (Bangka Island), about 20-25 m depth.

Other material.

BU-590, 27/07/2004, Timur (Bunaken Island), 25 m depth. INDO-431, 13/05/2005, Jetty (Siladen), depth not stated, N01°37'38.8"; E124°48'00.8".

Diagnosis.

Soft and elastic cup-shaped Ircinia with a large, central cavity; conulose surface; heavily fasciculated fibres with foreign material.

Description.

The sponge is columnar, reminding of a partially hollow cylinder, due to the presence of a wide central cavity (Fig. 10A). It may be as high as 80 cm, with a wall 1-2 cm thick. The holotype is a fragment approximately 4.5 × 2 cm. The external colour is light brown with greenish tinges on the conules and on the rim of the cavity (Fig. 10A). The freshly collected sponge is beige inside (Fig. 10B). Alcohol-preserved specimens remain almost the same in colour. The sponge surface is strongly conulose, with rounded or slightly flattened conules 2-4 mm high (Fig. 10A, B). The oscula (3-5 mm in diameter) are present in the inner part of the central cavity. Consistence is soft and elastic, but the sponge is difficult to tear off.

Skeleton. The choanosomal skeleton is formed by primary fibres cored by foreign spicules (Fig. 10C, D), 180-350 µm in diameter and heavily fasciculated (Fig. 10C). They are connected by secondary fibres 50-80 µm in diameter, sometimes cored by single spicules. The fibres form a reticulation of elongated meshes, 100-150 µm in size, and cribrose plates (Fig. 10C). Very abundant thin filaments are mainly organised in tracts (Fig. 10E), but also dispersed in the mesohyl. They are 3-5 µm thick and present an oval or rounded terminal knob (7.5-10 µm in diameter) (Fig. 10F).

Etymology.

The name refers to the sturdy and large size of the sponge.

Remarks.

The studied specimens are attributed, according to Cook and Bergquist 2002, to the genus Ircinia for the strong fasciculation of fibres, with foreign material inside and the presence of filaments. There are more than 40 species of massive, encrusting, digitate or branching Ircinia in the Indo-Pacific area ( van Soest et al. 2016), which differ from Ircinia colossa sp. n. in morphology, fibre thickness and quantity of external debris in the skeleton.

Only two species of Ircinia , living between 10 and 40 m depth in the temperate water of South-East Australia, show a central cavity: I. caliculata (Lendenfeld, 1888) and I. rubra (Lendenfeld, 1889). Ircinia caliculata differs from I. colossa sp. n. in the general morphology, colour, and organisation of the fibres. It has the rim of the cup bent outwards; the internal part of the cavity with small conules 2-3 mm high. The external part of the sponge presents digitate processes about 10 mm thick. The colour is dark-red brownish. It has fasciculated fibres full of sand grains. Ircinia rubra differs from I. colossa sp. n. in the general shape and fibre size. It is a small, conical, pedunculate sponge with a central cavity. All the fibres are full of debris and foreign spicules and the secondary fibres, 100 µm in diameter, are thicker than those of Ircinia colossa sp. n.

We also examined species belonging to the genus Sarcotragus ; none of them fits with the characters of the new species. Sarcotragus aliger (Burton, 1928) is clavate, cylindrical with an apical osculum and fibres 80 µm in diameter, while S. australis (Lendenfeld, 1888) is a massive red sponge. Sarcotragus coreanus (Sim & Lee, 2002) is massive to encrusting, beige in colour; S. gapaensis Sim & Lee, 2000 is subspherical, dark brown to black, with big primary fibres 280-530 µm in diameter. Sarcotragus maraensis Sim & Lee, 2000 is globular with sharp conules 2-8 mm high and an ivory and purple colour. Sarcotragus myrobalanus (Lamarck, 1814) is an ovoid sponge with a long peduncle, brown-reddish in colour; S. tuberculatus ( Poléjaeff, 1884) has fibres that often do not ramify and its surface, greyish in colour, is covered by rounded tubercles; filaments are roundish and 55 µm in diameter.

Ircinia colossa sp. n. is frequent in the Bunaken Park and the nearby Bangka Island (North Sulawesi); the paratype was found with other relatively large specimens (50 cm high or more) near a hot vent flowing from a sandy bottom ( Bertolino et al. 2017).

This species is probably present also throughout northern Australia and Papua New Guinea (J. Hooper, pers. comm.). Molecular analysis, compared against sequences made by Pöppe et al. (2011) for Ircinia and Psammocinia species from northern Australia, would be very useful to confirm if Ircinia colossa sp. n. and P. alba sp. n. are also present in Australia.