Stelodoryx siphofuscus Lehnert & Stone, 2015, n. sp.

Stelodoryx siphofuscus n. sp.

(Figs. 14 & 15, Table 5)

Material examined. Holotype: ZSM 20150391, collected by Ned Laman with a research survey bottom trawl (haul #2) from the FV Alaska Provider; 29 May 2013, 144 m depth, 2.3 km ESE of Concord Point, Chuginadak Island, Islands of Four Mountains, Samalga Pass, North Pacific Ocean (52°46.3500' N, 169°40.0200' W). Water temperature = 4.2°C. Complete specimen in ethanol.

Description. Habitus: The sponge is a stalked, dark brown tube, reaching a height of 23 cm and a maximum diameter of 3.4 cm (Fig. 14 A). The dark brown color persists in ethanol. There are small hydroids growing near the base on the stalk. The stalk is wiry, 0.8–1 cm in diameter and gradually widens into the softer, more elastic tube at a height of 2.5 cm. The base of the stalk is torn, without any remains of the substrate, so it might have been a little longer (Fig. 14 A). The outer walls of the tube are smooth (Fig. 14 B) and 2.4–4 mm in thickness. Small circular openings, presumably ostia, flush with the surface, are scattered over the surface and are 0.5–1 mm in diameter. The consistency is soft, very elastic. The inner walls of the tube bear numerous larger circular openings, presumably oscules, 1–2.5 mm in diameter (Fig. 14 C).

Skeletal structure: In the ectosome, nearly rectangular brushes of anisotornotes cause a microhispid surface (Fig. 14 D). In the choanosome pauci- to polyspicular tracts of thick styles are bound by spongin and connected by paucispicular tracts of the same styles (Fig. 14 E).

Spicules: Ectosomal anisotornotes often have a prominent tooth at the thicker end and measure 228–335 x 8– 10 µm (Figs. 15 A & B), choanosomal thicker styles measure 328–412 x 13–20 µm (Fig. 15 A). Microscleres are large polydentate isochelae, 72–91 µm (Figs. 15 C & D) and smaller polydentate isochelae, 28–45 µm (Figs. 15 E & F).

Discussion. As with the species described above we compare Stelodoryx siphofuscus n. sp. with the eight species of Stelodoryx already recorded from the North Pacific and the North Atlantic Oceans (Table 5) and with S. mucosa, described above. S. siphofuscus differs from these species in the following characters:

S. flabellata: North Atlantic and Arctic Oceans. A funnel-shaped sponge, 15 cm in height, with thinner ectosomal tornotes without apical tooth, with choanosomal acanthostyles, and one category of chelae only which is of intermediate size.

S. lissostyla: North Pacific Ocean (Sea of Japan and East Sea). A sponge with thinner ectosomal tornotes, thinner choanosomal styles, two categories of considerably smaller isochelae.

S. oxeata: North Pacific Ocean (Aleutian Islands). A stalked sponge with a ridged surface or massively encrusting with a smooth surface, greenish yellow in color, choanosomal oxeas with microspined ends, three categories of isochelae and one category of sigmas. Ectosomal tornotes are microspined and smaller.

S. pectinata: North Atlantic Ocean (Azores, Canaries, Madeira). A sponge with smooth ectosomal tornotes which are longer and thinner, with choanosomal acanthostyles, two categories of isochelae of different sizes.

S. pluridentata: North and South Atlantic Ocean. A stiff, yellowish orange to brown colored sponge with tornotes with microspined ends, larger choanosomal styles, one category of isochelae only.

S. procera: North Atlantic Ocean (Azores, Canaries, Madeira). A sponge with smooth ectosomal tylotes which are thinner, two categories of smooth choanosomal styles, and one category of isochelas only.

S. toporoki: North Pacific Ocean (Sea of Okhotsk and central Aleutian Islands) and Arctic Ocean. A stalked funnel-shaped sponge with much longer choanosomal styles, two categories of isochelae of very different size.

S. vitiazi: North Pacific Ocean (Sea of Okhotsk, western Bering Sea and central Aleutian Islands). A tubeshaped or irregularly cylindrical sponge with thinner ectosomal tornotes, with larger choanosomal acanthostyles, only one category of isochelae which does not fit into one size category of S. siphofuscus.

S. mucosa: is a massively encrusting light brown sponge, has microspined smaller tornotes, larger choanosomal spicules which are acanthostyles, only one category of isochelae which are of intermediate size and it has sigmas.

Etymology. From the Latin sipho—tube and the Latin fuscus—dark brown, meaning dark brown tube.