Tentorium Vosmaer 1887

Genus Tentorium Vosmaer, 1887

Tentorium semisuberites (Schmidt, 1870) (Fig. 3 C)

Tentorium semisuberites (Schmidt, 1870): Vosmaer 1885: 18. Ridley and Dendy 1886: 489, 1887: 221–222. Brøndsted 1914: 522–523. Ferrer-Hernández 1914: 19. Stephens 1915: 29–30. Hentschel 1929: 868–869. Koltun 1966: 85–86, text-fig. 57, pl. 19 figs. 4–8, pl. 31 fig. 12. Boury-Esnault and van Beveren 1982: 37–38, pl. 5 fig. 19, figs. 8f, g. Boury-Esnault 2002: 215–216, fig. 12. Plotkin 2004: 544, figs. 1j, 2j. Plotkin & Janussen 2008: 119–122, figs. 12, 13, tab. 5.

Synonymy:

Thecophora elongata Marenzeller, 1877: 368 –369, pl. 2, fig. 4. Thecophora ibla Thomson, 1873: 147, fig. 24.

Thecophora semisuberites Schmidt 1870: 50, pl. 6 fig. 2. Hansen 1885: 8–9.

Material. 1 specimen from station 016-1 (SMF 11773), 488.7 m, 70° 35.35' S, 9° 2.31' W, 17.12.2007; 1 specimen from station 039-11 (SMF 11727), 2151.5 m, 64° 28.80' S, 2° 52.52' E, 03.01.2008; 11 specimens from station 039- 16 (SMF 11775), 2151.3 m, 64° 28.79' S, 2° 52.74' E, 04.01.2008; 3 specimens from station 039-17 (SMF 11776), 2153.1 m, 64° 28.66' S, 2° 53.14' E, 04.01.2008; 9 specimens from station 048-1 (SMF 11788–11790), 602.1 m, 70° 23.94' S, 8° 19.14' W, 12.01.2008.

Description. Small sponges of cylindrical shape with a globular or pointed top. Upper surface with one or few exhalant papillae. Skeleton consists of spicule tracts running straight toward the top of the sponge, made up of tylostyles about 1000 µm in length. Cortex on top of the sponge consists of a palisade of tylostyles about 450 µm long. Lateral surface skeleton formed of a very dense, irregular layer of tylostyles.

Remarks. Tentorium semisuberites specimens from ANDEEP expeditions were studied in detail by Plotkin and Janussen (2008). Our new specimens originate from a similar area and show similar characters. A remarkable feature of the species is its apparently bipolar distribution (Plotkin & Janussen 2008). However, such a distribution of two independent populations separated by such a distance seems very unlikely. Review of the apparent bipolar species Stylocordyla borealis (Lovén, 1868) by Uriz et al. (2011) has shown it to consist of two distinct species. Therefore, it seems very probable that these occurrences in fact represent at least two cryptic species which are not distinguishable by morphologic characters alone. Like P. invaginata, T. semisuberites was quite abundant at Maud Rise, where common elements of deep-sea sponge fauna like Cladorhizidae and hexactinellids were absent (see Brandt et al. 2011 for detailed discussion).