Latrunculia (Uniannulata) oparinae Samaai & Krasokhin 2002, subgen. nov.

Latrunculia (Uniannulata) oparinae Samaai & Krasokhin, 2002 subgen. nov., comb. nov.

(Fig. 2 B, 8, 16AG; Tables 4, 8, 9)

Latrunculia oparinae Samaai & Krasokhin, 2002: 95 –101; Fig. 1 A–G, 2.

Latrunculia (Biannulata) oparinae, Samaai et al. 2006: 54; Fig. 1 S, 6N, 7, 8C, 9A; Table 2, 3. Latrunculia oparinae, Abbas et al. 2011: 2429 ‒2430, Fig. 8 A.

Not Latrunculia (Biannulata) oparinae, Stone et al. 2011: 113, Fig. 1–4; 141, 145. Latrunculia cf. tricincta, Austin et al. http://www.mareco.org/spongepage/ Latrunculia %20sp%20cf%20 tricincta.htm (not: Hentschel 1929).

Material Examined. Central Aleutian Islands: NHMUK 2011.2.11.1: south Amchitka Pass, 8.5 km WNW of Unalga Island, Delarof Islands, 51.594° N, 179.180° W, 223 m, 24 Jul 2010, NOAA Fisheries, FV Sea Storm, Station-haul 160, Cruise 201001, collected by J. Sims; RBCM 015-00488-001: 20.9 km S of SW Amlia Island, 51.859° N, 173.910° W, 195 m, 6 Jul 2004, NOAA Fisheries, RV Velero IV, Delta submersible Dive 6222, Station 2A, collected by H. Lehnert; RBCM 015-00489-001: 0.5 km N of SW Kasotochi Island, 52.174° N, 175.615° W, 112 m, 7 Jul 2004, NOAA Fisheries, RV Velero IV, Delta submersible Dive 6227, Station Kasotochi, collected by D. Carlile; RBCM 015-00484-002: 6.6 km SSW of Cape Tusik, Kanaga Island, Adak Strait, 51.622° N, 177.239° W, 155 m, 2 Jul 2004, NOAA Fisheries, RV Vel ero IV, Station 5E, collected by R. Stone with a 6 m shrimp trawl (4 specimens); NHMUK 2008.3.27.1: same locality data as above; RBCM 015-00490-003: 25.2 km WNW of Amtgnak Island, Delarof Islands, Amchitka Pass, 51.333° N, 179.503° W, 175 m, 3 Aug 2004, NOAA Fisheries, RV Roger Revelle, ROV Jason II Dive 102, Station 14, collected by R. Stone. Eastern Aleutian Islands: NHMUK 2006.8.24.3: 17 km NNE of Adugak Island, Samalga Pass, Aleutian Islands, 53.063° N, 169.087° W, 232 m, 12 Apr 2004, NOAA Fisheries, FV Gladiator, Station 279-48, Cruise 200401, Haul 25; RBCM 015-00487-001: 8.5 km SSW of Herbert Island, Islands of Four Mountains, 52.648° N, 170.052° W, 235 m, 18 Jun 2012, NOAA Fisheries, FV Ocean Explorer, Station-haul 41, Cruise 201201, collected by B. Knoth.

Type location. Kurile Islands, Sea of Okhotsk, Russia.

Distribution. Kurile Islands, Sea of Okhotsk, Russia to the Islands of Four Mountains, eastern Aleutian Islands, Alaska.

Description. Small globular to spherical or block-shaped sponge, width 47 (25–65) mm × height 34 (20–50) mm × thickness 39 (20–60) mm, n = 10; surface covered with distinctive trumpet-shaped areolate pore fields, and long, broad, cylindrical apical oscular tubes or long tapered oscular tubes on the periphery of the sponge (Fig. 8 A– E). Aquiferous structures on some specimens are short and squat. Texture firm, interior markedly fibrous and stringy, almost honeycombed, difficult to tear. Colour in life is khaki green to light greenish brown, darkening to oak brown in preservative. Often attached to pebbles or bivalve shells in life.

Skeleton. Ectosome, a palisade of anisodiscorhabds above a sub-ectosomal paratangential layer of megascleres, 475–550 µm thick (Fig. 8 F); this layer tends towards vertical near the pore fields. Choanosome, extremely cavernous and stringy with thick, compact tracts of megascleres 500–600 µm wide, but many are up to 800 µm wide. Gaps between tracts are well over several thousand µm wide. Microscleres are scattered between the megascleres in the ectosome and throughout the choanosome.

Spicules. Megascleres (Fig. 8 G; Table 4), anisostyles, centrally thickened and slightly sinuous, head acanthose with conical and retrovert spines, 507 (400–610) × 15 (11–19) µm.

Microscleres (Fig. 8 H–L; Table 4), anisodiscorhabds, manubrium composed of five chisel-shaped doublet projections, with a small number of scattered spines, emanating obliquely from the end of the shaft, basal whorl above the manubrium consists of another five sets of chisel-shaped, more distinctly doublet projections, ornamented with small spines (Fig. 8 L). The median whorl is composed of horizontal, micro-spined paddles with denticulate margins, 31 (28–38) µm. Subsidiary, apical whorl and apex are only partially differentiated (Fig. 8 K, right), forming a solid tuft of micro-spined spines with denticulate margins, 46 (35–53) µm long.

Substrate, depth range and ecology. Prior to this work L. (U.) oparinae was known only from the Kurile Islands, where it was found on a gravel and sand seafloor between 127–238 m (Samaai & Krasokhin 2002; Samaai et al. 2006). In the Aleutian Islands the species is quite common at depths between 79 and 288 m (Stone et al. 2011). The species is sympatric with L. (L.) hamanni sp. nov. (Stone et al. 2011), and grows directly on bedrock, pebbles, cobbles and boulders, in areas of relatively flat seafloor with moderate to high currents. Latrunculia (U.) oparinae is discrete and easily recognisable, having a globular shape with columnar aquiferous structures, and being a characteristic olive to khaki green in colour.

Remarks. Latrunculia (Uniannulata) oparinae and L. (L.) hamanni sp. nov. are sympatric species, separated in the field primarily on colouration, and morphology of the aquiferous structures; L. (U.) oparinae is khaki green with tall thin elevated pore fields and oscules, while L. (L.) hamanni sp. nov. is dark purplish brown and has short, sucker-shaped pore fields and oscules (see Fig. 8 B). Both species have a firm, fibrous, stringy texture. The key taxonomic point of difference, however, is the morphology of the anisodiscorhabds; in L. (U.) oparinae the subsidiary whorl does not appear independently above the median whorl as it does in L. (L.) hamanni sp. nov., and the whorls of the anisodiscorhabds in L. (U.) oparinae are composed of broad paddles, or petals with serrated edges, while those of L. (L.) hamanni sp. nov. are almost entirely composed of sculpted spines. Furthermore, the apical whorl and apex in the anisodiscorhabds of L. (U.) oparinae form crown-like rings of double serrated paddles that frequently occur in pairs (see Fig. 8 K, L), while the spines of the apex and apical whorl of L. (L.) hamanni sp. nov. form a solid undifferentiated tuft (Fig. 5 F). The megascleres of L. (U.) oparinae are about 20 µm longer than those of L. (L.) hamanni sp. nov. Latrunculia (U.) oparinae is also similar in colouration to L. (L.) austini but the latter species is very different morphologically and has not been found, to date, west of the eastern Gulf of Alaska.