Tethytimea tylota (Hentschel, 1912)

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 : 106-108

Tethytimea tylota (Hentschel, 1912) Figure 3

Donatia tylota Hentschel, 1912: 317.

Material examined.

BU-98, 23/03/2000, Lekuan II (Bunaken Island), 5 m depth. BU-289, 17/05/2001, Raymond’s Point (Bunaken Island), unknown depth. BU-533, 21/06/2004, Bualo (Manado Tua Island), about 8 m depth. BU-545, 23/06/2004, Raymond’s Point (Bunaken Island), about 20 m depth. BU-562, 26/06/2004, Bualo (Manado Tua Island), unknown depth.

Description.

Encrusting sponge 3-6 mm thick; the largest examined specimen (BU-289) is approximately 10 cm in diameter. The consistence is firm; the body of the sponge lacunose. The surface is irregular, with extended verrucous areas covered by sand and largely colonised by epibiotic ascidians, algae and hydroids (Fig. 3A). In the microscopic observation, the surface appears micro-hispid. The colour of living specimens is orange; when preserved, the sponge becomes yellowish-green.

Skeleton. Tethytimea tylota does not have a distinguishable ectosomal skeleton or a proper cortex; the choanosomal skeleton is formed by bundles of big tylostyles of 100 -200 µm directed outwards (Fig. 3B). Close to the surface, these main bundles support fans of small tylostyles hispidating the sponge surface (Fig. 3B, C).

Spicules. Megascleres are straight tylostyles with a slightly developed head (Fig. 3D). They can be distinguished into two size classes (Fig. 3E, F); tylostyles I measure 930 - (1,104.8 ± 146.7) - 1,339 × 12.5 - (17.8 ± 3.4) - 25 µm; tylostyles II (Fig. 3D) measure 490 - (576.6 ± 72.5) - 660 × 5 - (6.6 ± 2.0) - 10 µm and form the superficial fans that protrude out of the surface; microscleres are two kinds of asters (Fig. 3 G–K). Oxyspherasters (Fig. 3 G–I) with thick ramified or rounded, often bifurcated rays, measuring 65 - (122.5 ± 39.6) - 200 µm. Tylasters with rays variable in length ending with apical groups of spines variable in number (Fig. 3J, K); they measure 7.5 - (11.1 ± 1.9) - 16.3 µm. Microscleres are abundant throughout the sponge, but more concentrated close to the surface (Fig. 3L), where the smallest tylasters form a thin, continuous layer (Fig. 4H, inlet).

Remarks.

This sponge was exclusively found as epizoic on Stelletta tethytimeata sp. n. (see below). It has been attributed to T. tylota for its skeletal organisation, made of bundles of main tylostyles supporting superficial fans of small tylostyles, the superficial layer of tylasters (present also in the holotype), the size and shape of megascleres and microscleres ( Sarà 2002). The genus Tethytimea is monospecific and T. tylota was found at Aru Island (Indonesia). This is the first record of this species since the original description ( Hentschel 1912). In the revision of the genus (based on the re-examination of the type material), Sarà (2002) confirmed the presence in the holotype of very rare spheres; these spicules were not detected in the present specimens as in the paratype ( Sarà 2002).

It is interesting to note that the holotype of T. tylota was encrusting on a stone and in association with another sponge ( Sarà 2002).

Remarks on the association.

See below.