Tentorium semisuberites Schmidt 1870

Tentorium cf. semisuberites (Schmidt, 1870) (Figs. 12–13, Table 5)

Synonymy

Northern Hemisphere:

Thecophora semisuberites — Schmidt 1870: 50, Taf. VI (Fig. 2); Hansen 1885: 8 –9.

Tentorium semisuberites— Vosmaer 1885: 18; Brøndsted 1914: 522 –523; Ferrer­Hernández 1914: 19; Stephens 1915: 29 –30; Hentschel 1929: 868 –869; Koltun 1966: 85 –86, text­fig. 57, pl. XIX (figs. 4–8), pl. XXXI (fig. 12); Boury­ Esnault 2002: 215 –216, fig. 12; Plotkin 2004: 544, figs. 1j, 2j.

Southern Hemisphere:

Ridley and Dendy 1886: 489; 1887: 221–222; Boury­Esnault and van Beveren 1982: 37–38, pl. V (19), figs. 8f, g.

Material examined

SMF 10572 (1 specimen) and 10573 (2 specimens): PS61/132­3; SMF 10574 (1 specimen): PS67/074­7; SMF 10575 (8 specimens), 10576 (4 specimens) and 10577 (2 specimens): PS67/121­7; SMF 10578 (1 specimen): PS67/133­2.

Description

External morphology. Sponges are cylindrical or columnar, measuring 0.4–1.2 cm in diameter and 0.2–1.6 cm in height (figs. 12A, C, E). The upper surface is nearly hemispherical in shape, minutely rough in texture and brownish to greyish in colour. It is perforated by numerous ostia and bears one or few exhalant papillae which measure 0.6–2.6 mm in height and 0.6–1.6 mm in diameter with oscula of 0.2–1.5 mm in diameter. The cortex is restricted to the upper surface. It is hardly detachable, the consistency is firm, and the colour is nearly white. The lateral surface is smooth, firm, imperforate and always paler in colour in comparison with the upper surface. The choanosome is slightly darker than the cortex, its consistency may be resilient or firm and crumbly.

Skeleton. The choanosomal skeleton is constituted by the longitudinal tracts of principal spicules running from the base to the surface (figs. 12B, D). The internal tracts measuring 70–240 µm in thickness enter the cortex and diverge into bouquets. The peripheral tracts form a solid imperforate lateral sheath (fig. 12E). The cortex measuring 550–650 µm in thickness is reinforced by the bouquets of small spicules. In the sponge base, at the level of attachment to the substrate, small spicules form a pad where they lie tangentially to the substrate. Skeleton of papillae is constituted by the ascending longitudinal tracts (fig. 12D).

Spicules. Altogether 503 spicules from 7 specimens were measured. Two main size categories of tylostyles are well distinguished (fig. 13A). Summarizing results of spicule measurements are given in the main text below, indicating the total number of spicules measured for each category (n). Particular results of spicule measurements for each specimen are given in table 5.

Principal spicules are mainly tylostyles, rarely subtylostyles or styles (fig. 13B). They may be very fusiform or slender, often with blunt distal ends and measure: length 800­ 1064 ­1529 µm, proximal diameter 2­ 13.7­35 µm, central maximal diameter 3­21.4­51 µm (n =168). Their tyles, if present, are spherical and measure 9­17.8­41 µm in diameter (n =141).

Small spicules are tylostyles or subtylostyles (fig. 13C). They are usually stout, fusiform, with spherical tyles, sometimes with blunt distal ends. Their dimensions are: length 105­446­790 µm, tyle diameter 5­12.8­ 32 µm, proximal diameter 3­8.9­30 µm, central maximal diameter 5­15.1­32 µm (n =335).

Type locality: Arctic Ocean: Ubekendl, depth unknown.

Distribution: Northern Hemisphere: Arctic and North Atlantic (various localities, see Koltun 1966; Boury­Esnaul 2002). Depth: 26–2800 m (Koltun 1966); deeper in temperate waters, shallower in high latitudes (Boury­Esnault 2002).

Southern Hemisphere: Southern Indian Ocean: Kerguelen, 70–245 m (Boury­Esnault & van Beveren 1982). South Atlantic: Inaccessible Island, 109–164 m (Ridley & Dendy 1887), South Georgia (Sarà et al. 1992). Antarctic near­continent sectors (Sarà et al. 1992): NN 2–5 including the Western Ross Sea and N 9 including the Weddell Sea (present study as well). Depth: ca. 1050–2620 m in the Northern Weddell Sea (present study).

Remarks

This species is well known from the North Atlantic and Arctic, mainly from deep waters, except from high latitudes where it may be collected in the subtidal zone (Boury­Esnault 2002). The Southern Hemisphere specimens reported by Ridley and Dendy (1886, 1887) and Boury­Esnault and van Beveren (1982), as well as the specimens examined by us, do not considerably differ from the northern sponges. However, such a discontinuous distribution may testify for the existence of two sibling species within T. semisuberites.

TABLE 5. Tentorium cf. semisuberites: Results of spicule measurements. Measurements are given as in tables 2 and 4.

Specimen no. Principal spicules Small spicules

SMF 10572 860­ 1210 ­1482 280­532­760

10­12.7­16 / 6­9.7­13 9­10.4­14 / 3­6­10

14­18.9­26 (n= 23) 9­12.7­18 (n= 43)

SMF 10573 (specimen 1) 810­895­990 215­440­790

10­16.2­24 / 6­10­16 10 ­13.8­19 / 5­8.9­11

13­19.7­26 (n= 15) 11­17.7­26 (n= 48)

SMF 10574 814­ 1082 ­1500 400­618­729

15­32.4­41 / 11­26.5­35 14­23­32 / 11­18.9­30

16­36.9­51 (n= 21) 16­24.9­32 (n= 9)

SMF 10575 (specimen 1) 857­ 1146 ­1529 162­502­771

11­16.9­27 / 7­13.9­22 8­16.6­22 / 7­13.2­19

14­21.2­35 (n= 42) 8­21.1­28 (n= 22)

SMF 10576 (specimen 1) 800­836­920 105­421­790

10­16­21 / 6­12.3­16 5­12.2­19 / 4­8.8­16

10­21.4­29 (n= 14) 5­14.4­27 (n= 108)

SMF 10577 (specimen 1) 836­959­1178 190­395­700

9­15.4­19 / 2­10.3­ 14 10­14­19 / 5­9.6­13

3­18.8­27 (n= 21) 10­16­22 (n= 47)

SMF 10578 800­ 1085 ­1371 200­429­786

9­12.8­15 / 8­12.3­16 5­9.5­16 / 4­7.7­11

11­15.9­19 (n= 32) 5­11.6­19 (n= 58)