Artemisina clavata Lehnert & Stone, 2015, n. sp.

Artemisina clavata n. sp.

(Fig. 7, Table 3)

Material examined. Holotype: ZSM 20150385, collected by Jim Stark with a research survey bottom trawl (haul #162) from the FV Ocean Explorer; 16 July 2012, 262 m depth, 11.1 km southeast of Vega Point, south Kiska Island, western Aleutian Islands, North Pacific Ocean (51°46.3740' N, 177°27.4560' E). Water temperature = 4.1°C. Paratype: ZSM 20150386, collected by Jim Stark with a research bottom trawl (haul #193) from the FV Ocean Explorer on 27 July 2012, 228 m depth, 30.6 km SSE of Fox Beach Point, Shemya Island, Semichi Islands, western Aleutian Islands, North Pacific Ocean (52°26.5920' N, 174°18.1740' E). Water temperature = 3.7°C. Complete specimens in ethanol.

Description. Habitus: The holotype (ZSM 20150385, Fig. 7 A) was noted as extremely slimy and exuded a very thick mucous-like substance. It is light brown, starts from a narrow, short, almost circular, stiff stalk, 2.1 cm in diameter, 1.6 cm high. The sponge then becomes soft and elastic but, still resilient and widens at a height of 8.5 cm to 5 cm with a thickness of 1 cm. Several lobes grow independently from a central part, the largest lobe 9.5 x 4 x 1 cm. The paratype (ZSM 20150386, Fig. 7 B) is a golden-brown, club-shaped sponge, possibly a juvenile specimen, becoming stalked and branching later. Attached at the narrow end to a well-rounded pebble, gradually widening from 1.5 cm to a maximum diameter of 4.5 cm, reaching a height of 14.5 cm with a thickness of 1.3 cm. The surface of both specimens is corrugated with circular oscules, flush with the surface, 1.5–3 mm in diameter are scattered over the surface except for the stalk of the larger specimen.

Skeletal structure and spicules: The choanosome is a reticulation of styles, 560–620 x 30–35 µm (Fig. 7 C).The ectosome consists of a thin organic membrane with densely packed styles to subtylostyles with microspined heads, sometimes with one prominent tooth, 260–340 x 6–7 µm (Fig. 7 D). Microscleres are small, very thin, palmate isochelae, 5–9 µm (Fig. 7 E) and toxa with microspined ends, 280–540 µm (Fig. 7 F).

Discussion. The WPD recognizes 18 valid species of Artemisina. Artemisina are massive, cushion-shaped, bulbous, clavulate, tubular, digitate, or flabellate sponges of the family Microcionidae. They lack a distinctive choanosomal skeleton or definite spongin fibres and echinating spicules, and have a nearly radial ectosomal skeleton (Hooper, 2002c). We compare Artemisina clavata n. sp. with eight species occurring from the North Pacific and North Atlantic Oceans (Table 3) and with the second new Artemisina described below. The remaining ten species are not taken into consideration for zoogeographic reasons. Artemisina clavata n. sp. differs from these species in the following characters:

A. amlia: Northwest Pacific Ocean (central Aleutian Islands). A stalked, subhemispherical or conical sponge with longer and thicker ectosomal styles, shorter and thinner choanosmal styles, smooth toxa, and no microspined toxa.

A. apollinis: Southern Ocean, North Atlantic Ocean, and southern Indian Ocean. A massive to funnel-shaped sponge with longer ectosomal styles, thinner choanosomal styles, two categories of toxa, and larger isochelae.

A. archegona: Northeast Pacific Ocean (California to British Columbia). A thinly encrusting sponge, bright orange color in life, white in ethanol, with thinner ectosomal styles, shorter and thinner choanosomal styles, a special category of toxiform oxeas, smooth toxa only, and longer isochelae.

A. arcigera: Arctic Ocean, North Atlantic Ocean, and Northwest Pacific Ocean (central Aleutian Islands. A massive to spherical or stalked and tube-shaped (central Aleutian Islands) sponge, only 5.5 cm high, with longer and thicker ectosomal styles, much thinner choanosomal styles, shorter microspined toxa, and longer isochelae.

A. erecta: Northeast Atlantic Ocean (Azores, Canaries, Madeira). A small (11 mm x 5 mm x 3 mm), white colored sponge with longer ectosomal styles, longer but thinner choanosmal styles, shorter microspined toxa, and longer isochelae.

A. stipitata: Northwest Pacific Ocean (Sea of Okhotsk and central Aleutian Islands). A massive to spherical or flabellate (central Aleutian islands) sponge with thicker ectosomal styles, shorter and thinner choanosomal styles, no toxa, and longer isochelae.

A. transiens: Northeast Atlantic Ocean. A stalked, white-colored sponge with longer ectosomal styles with microspined ends, choanosomal styles not different from ectosomal styles, smooth toxa but no microspined toxa, and much longer isochelae.

A. flabellata n. sp.: Aleutian Islands. A fan-shaped sponge with longer and thicker ectosomal styles, longer choanosomal styles, smooth toxa but no microspined toxa, cleistochelae, and an additional category of acanthostyles.

Etymology. from the Latin clava—club, referring to the club-shaped growth.