Thenea valdiviae

Thenea valdiviae von Lendenfeld, 1907

(Figures 18 G–H, 24, Table 5)

Synonymy (modified from Steenstrup & Tendal (1982)).

Thenea valdiviae von Lendenfeld, 1907: von Lendenfeld 1907, p. 190; Hentschel 1929, p. 863, p. 918; Steenstrup & Tendal 1982, p. 259; Klitgaard 1995; p. 1; Cárdenas et al. 2011, Table S1.

Thenea muricata: Vosmaer 1882, p. 5; Vosmaer 1885, p. 4; Levinsen 1886, p. 343; Lundbeck 1909, p. 427; Brøndsted 1933, p. 6; Burton 1934, p. 6.

Thenea muricata (in part): Stephens 1915, p. 11.

? Thenea muricata: Hansen 1885, p. 18; Koltun 1966, p. 36.

Material. ZMBN 85255, west of Marstein, western Norway, 60°8'18''N, 4°50'47''E, 300 m, Agassiz trawl; ZMBN 85256, Freifjorden, Møre, western Norway, 63°02.09'N, 7°51.82'E, 100 m, Møre 2006 cruise; NTNU-VM 55620, Sandøy, Risvaerfjorden, 65°0'15.00"N, 11°29'30.00"E, 100–130 m; ZMBN 85257, near Røst reef, northern Norway, 67°35.23'N, 9°28.92'E, Polarstern ARK-XXII/1a 2007 cruise, 598 m; NTNU-VM 55545, Vågsfjorden, Vesterålen, northern Norway, 69°0'30.99"N, 16°40'52.99"E, 250–300 m; NTNU-VM, 54950, Barents Sea, 70°43'N, 16°56'E, 740 m; NTNU-VM 54975, Barents Sea, 70°46'N, 17°00'E, 910 m; ZMBN 85233, Barents Sea, off Finmark, ‘Ecosystem Barents Sea 2007’ cruise, 71°48.32'N, 28°39.76'E, 297 m.

Comparative material.

Thenea valdiviae, ZMAPOR 2385, Willem Barents Sea Expedition 1878–84, off Finnmark, northern Norway (71°52'0.11"N, 19°46'59.88"E), 324 m, identified by G. C. J. Vosmaer as T. muricata, det. P. Cárdenas; ZMBN 85234, Schultz Massive Seamount, Greenland Sea, 73°50'N, 7°32.3'E, BIODEEP 2007 cruise, 578 m, ROV.

Outer morphology (Fig. 24 A–D). Massive sponge. Young specimens (ZMBN 85257) have cribriporal pores and a uniporal oscule on opposite sides (as in young T. muricata), with a flat top surface. A fringe surrounds the oscule. Budding was observed on the top surface of these young specimens (Fig. 24 D). Larger specimens are subcircular (ZMBN 85255, 85233) or slightly flattened (ZMBN 85256) with a triangular shape. They look very much like T. muricata but the oscule, separated from the poral area and situated on the top, always has a coarse sieve covering it. Surface is minutely to very hispid. Not compressible.

Skeleton (Fig. 24 E). Like T. abyssorum.

Spicules (ZMBN 85233) (Fig. 18 G–H). (a) oxeas, slightly bent, length: 4–10 mm; width: 20– 48.1 –70 µm (N=8). (b) dichotriaenes, rhabdome is with a single bend, more rarely flexuous, most rhabdomes have a swelling just below the cladome, rhabdome length: 620– 3933.7 –5075 µm (N=8); width: 23– 58.1 –90 µm; many irregular cladomes, protoclad length: 75– 236.8 –350 µm; deuteroclad length: 125– 600.2 –1175 µm. (c) anatriaenes, rare, rhabdome straight or bent, length: 4000–4125 µm (N=2); rhabdome width: 15–20 µm; bent clads (similar to T. muricata anatriaenes), clad length: 170–220 µm. (d) protriaenes, not observed in this specimen. (e) spirasters (and rare metasters) (Fig. 18 H), spined, length: 11– 18.2 –27.5 µm. (f) plesiasters (Fig. 18 G), few, 4–6 actines, faintly spined, actine length: 18.5– 41.4 –75 µm, actine width: 3– 7.4 –12.5 µm (N=23).

Reproduction. Oocytes in vitellogenetic phase were observed in the thick sections of ZMBN 85233, collected in mid– August 2007. Subglobular whitish buds were occasionally observed on specimens from the Røst reef (Fig. 24 D) and from the Schultz Massive Seamount (Greenland Sea).

Distribution. Greenland, Iceland, Faeroe Islands, Norway, Norwegian Sea, Greenland Sea, Barents Sea, Spitzbergen (Steenstrup & Tendal 1982); SW of Ireland (Stephens 1915).

Depth. 100–1900 m (Steenstrup & Tendal 1982; this study).

Discussion. The specimens from the Korsfjord have more anatriaenes and regular dichotriaenes than ZMBN 85233 from the Barents Sea. Protriaenes are very common in ZMBN 85234 from the Greenland Sea. Plesiasters are rare (ZMBN 85233) to moderately present (ZMBN 85255, 85257).

T. valdiviae is known to be at least dimorphic and our Norwegian specimens correspond to the ‘arctic form’ described by Steenstrup & Tendal (1982). Our new records show that T. valdiviae must be present all along the Norwegian coast whereas, to our knowledge, T. muricata has not been formally identified north of Trollsteinen (64°35’N), except for the type.

The easiest way to discriminate adult specimens is to look at the oscule morphology: large cribriporal irregular shaped oscules with a surrounding fringe in T. valdiviae, small uniporal round “naked” oscules in T. muricata. Young specimens are, without genetic markers, very difficult to differentiate since they both have opposite oscule/ pore areas on their sides. As for the spicules, they are fairly similar in both species (Table 5). There seems to be more metasters in T. muricata and T. schmidti than in T. valdiviae, but this need to be confirmed. Moreover, the rarity of plesiasters in T. valdiviae seems to be a general rule, observed by others (Vosmaer 1885; Steenstrup & Tendal 1982).

As sister-species, Norwegian T. valdiviae are genetically clearly separated from T. muricata (Fig. 25), but our specimen from the Greenland Sea seamount is somewhat different (ZMBN 85234): it has a COI sequence identical to T. muricata, and on the other hand a 28S sequence identical to T. valdiviae. This specimen, and others examined from the same seamount are all very hispid (hairy-like), with cribriporal oscule and pores on opposite sides, and rare plesiasters. So they are not morphologically different from the Norwegian T. valdiviae, except maybe for the larger spirasters (Table 5). This shared COI could be the result of ongoing hybridization with T. muricata and deserves to be further studied.