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

Stelodoryx mucosa n. sp.

(Figs. 12 & 13, Table 5)

Material examined. Holotype: ZSM 20150390, collected by Jim Stark with a research survey bottom trawl (haul #216) from the FV Ocean Explorer; 2 August 2012, 127 m depth, Stalemate Bank, western Aleutian Islands, North Pacific Ocean (52°59.0760' N, 170°55.5780' E). Water temperature = 3.7°C. Complete specimen in ethanol.

Description. Habitus: Massively encrusting or possibly standing upright, golden brown colored sponge, approximately 19.5 x 23 x 3.5–4.3 cm (Fig. 12 A). The sponge was probably attached to pebbles and was noted as incredibly mucous laden. In ethanol it is still thickly covered with mucus which comes off in long sticky strands. The consistency is firm and only slightly elastic but the sponge breaks into pieces under its own weight when handled. The surface is rugose and uneven and there are different surface patterns in different areas (Figs. 12 A & B).

Skeletal structure: The ectosome consists of a single row of tylote bundles, 300–550 µm in diameter, starting in the interior from a narrow base, fanning out towards the surface (Figs. 12 C & D). The choanosome is a reticulation of single acanthostyles with many thin sigmas and isochelae in between (Figs. 12 C & E).

Spicules: Ectosomal tylotes have unequal, microspined ends, 205–252 x 8–10 µm (Fig. 12 F, Figs. 13 A & B), choanosomal acanthostyles, 395–450 x 11–29 µm (Fig. 13 A), polydentate isochelae, 45–67 µm (Fig. 13 C), thin sigmas, 13–18 µm (Figs. 13 B & C).

Discussion. The WPD recognizes 14 valid species of Stelodoryx. Stelodoryx are stalked, lobate, massive, or encrusting sponges resembling Myxilla species in most respects, except they have a reticulate skeleton, a full complement of megascleres and polydentate anchorate isochelae (Van Soest, 2002). We compare Stelodoryx mucosa n. sp. with the eight species of Stelodoryx recorded from the North Pacific and the North Atlantic Oceans and with S. siphofuscus n.sp. described below (Table 5). S. mucosa differs from these species in the following characters:

S. flabellata: North Atlantic and Arctic Oceans. A funnel-shaped sponge, 15 cm in height, with longer but thinner ectosomal tylotes which are smooth, somewhat shorter and thinner choanosomal acanthostyles, and no sigmas.

S. lissostyla: North Pacific Ocean (Sea of Japan and East Sea). A sponge with smooth ectosomal tylotes which are longer but thinner, mostly smooth choanosomal styles which are shorter and thinner, two categories of isochelae, both shorter, and no sigmas.

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, and three categories of isochelae. This is the only other species of Stelodoryx in the comparison group that has sigmas as microscleres besides S. mucosa n. sp., but the sigmas are centrotylyte rather than fine and smaller.

S. pectinata: North Atlantic Ocean (Azores Canaries Madeira). A sponge with smooth ectosomal tylotes which are longer and thinner, two categories of isochelae, and no sigmas.

species ectosomal tornotes choanosomal styles isochelae other

flabellata Koltun, 1959 smooth, 250–312 x 4–6 microspined styles & strongyles, 322–425 x 12 – anchorate, polydentate, 56–72 none 20

lissostyla Koltun, 1959 smooth, 260–332 x 5–6 smooth, rarely slightly microspined, 332–421 x two categories: anchorate, 26–30 & anchorate, none 11–13 13–17

oxeata Lehnert et al., microspined ends, 230–270 x 9–11 oxeas with microspined ends, 517–558 x 20–30 three size categories: centrotylote sigmas, c 54–110, 23–32 & 9–13 8–12

pectinata Topsent, smooth, 415 x 5 acanthostyles, 465 x 16 two categories: 60 & 20 none +

Measurements from Topsent, 1892 (Topsent, 1890 provided no measurements). Measurements from Koltun, 1958.

S. pluridentata: North and South Atlantic Ocean. A stiff, yellowish orange to brown colored sponge with smooth choanosomal styles, larger isochelae, and no sigmas.

S. procera: North Atlantic Ocean (Azores, Canaries, Madeira). A sponge with smooth ectosomal tylotes which are thinner, two categories of smooth choanosomal styles, and no sigmas.

S. toporoki: North Pacific Ocean (Sea of Okhotsk and central Aleutian Islands) and Arctic Ocean. A stalked funnel-shaped sponge with mostly smooth and much longer choanosomal styles, two categories of isochelae of different size categories, and no sigmas.

S. vitiazi: North Pacific Ocean (Sea of Okhotsk, western Bering Sea and central Aleutian Islands). A tubeshaped or irregularly cylindrical sponge with thinner ectosomal tylotes, smaller isochelae, and no sigmas.

S. siphofuscus n. sp.: A dark brown, stalked, tube-shaped sponge, with longer ectosomal tornotes that are not microspined, smooth choanosomal styles, microscleres consisting of two categories of isochelae, none of which correspond in size to those of S. mucosa, and lacking sigmas.

Etymology. named after the excessive production of mucus observed in this species.