Suberites luetkenii Schmidt, 1870

Morozov, Grigori, Ereskovsky, Alexander & Strelkova, Natalia, 2025, Deciphering Arctic sponge diversity: genetic and morphological evidence reveals cryptic lineages in Suberites, Zoological Journal of the Linnean Society 204 (2) : -

Suberites luetkenii Schmidt, 1870

• Suberites lütkenii Schmidt (1870) , von Marenzeller (1886), Topsent (1913), Hentschel (1929), Burton (1934), Alander (1942), de Laubenfels (1953), Morozov et al. (2023).

• Suberites montalbidus Carter (1880 , 1882), Fristedt (1885, 1887), Levinsen (1893), Lambe (1894, 1900), Swartschewsky (1906), Morozov et al. (2019).

• Suberites spec. Vosmaer (1882).

• Suberites domuncula var. ficus Koltun (1959) .

Material analysed: R / V Sevastopol 19 August 1960, Gulf of St. Lawrence, coll. Nesis K.N., st. 3147 (trawl 219), 46.67°N, 59.4°W, 318–320 m, one specimen , ZISP 13689 . Motorboat Clione in June 2023, White Sea, coll. Novikov A.A.: 66.3°N, 33.8°E, one specimen , KFUWS1 . R / V Vilnus in August 2023, Barents Sea, coll. Khacheturova K.S., st. 35, 69.34666667°N, 38.81°E, 147 m, 3.37°C, 34.522 psu, one specimen , KFULH48 . R / V Prof. Boiko in September 2023, Barents Sea, coll. Strelkova N.A.: st. 31, 68.20543333°N, 39.60551667°E, 95 m, 7.3°C, two specimens , KFULH49 , KFULH50 ; st. 46, 68.24341667°N, 39.73548333°E, 126 m, 7.63°C, one specimen, KFULH53 ; st. 52, 68.40363333°N, 40.37541667°E, 84 m, one specimen, KFULH57 ; st. 54, 68.42213333°N, 40.20763333°E, 71 m, one specimen, KFULH58 ; st. 64, 68.37958333°N, 39.56826667°E, 76 m, 6.5°C, two specimens, KFULH59 , KFULH60 ; st. 65, 68.36911667°N, 39.4627°E, 81 m, 6.8°C, one specimen, KFULH61 ; st. 67, 68.31066667°N, 39.3266°E, 117 m, 6.8°C, two specimens, KFULH62 , KFULH63 ; st. 68, 68.36021667°N, 39.362°E, 104 m, 6°C, one specimen, KFULH64 ; st. 77, 68.41466667°N, 39.05811667°E, 90 m, 6.8°C, three specimens, KFULH65 , KFULH66 , KFULH67 ; st. 79, 68.46776667°N, 39.08108333°E, 94 m, 6.8°C, one specimen, KFULH70 ; st. 80, 68.46533333°N, 38.92278333°E, 106 m, 5.4°C, one specimen, KFULH72 ; st. 81, 68.51375°N, 38.9243°E, 103 m, 5.4°C, four specimens, KFULH73 , KFULH74 , KFULH75 , KFULH76 ; st. 108, 68.35091667°N, 39.30106667°E, 106 m, 6.71°C, one specimen, KFULH84 . R / V Vilnyus in March 2024, Barents Sea, coll. Kudryashova A.S. and Strelkova N.A., st. 131, 71.99833333°N, 49.01°E, 128 m, −0,15°C, 34.714 psu, fourspecimens , KFULH85 , KFULH86 , KFULH87 , KFULH88 ; st. 158, 72.66166667°N, 50.335°E, 142 m, 2.2°C, two specimens, KFULH89 , KFULH90 . ZMMU SCUBA-diving and tidal collections, August 2024, White Sea, coll . WSBS diver team, site 1, 66.521017°N, 33.184518°E, 15 m, eight specimens, WS24241, WS24242, WS24243, WS24244 ; site 2, 66.543209°N, 33.185838°E, 1 m, two specimens, WS24162, WS24163; site 3, 66.5534167°N, 33.1046111°E, 0.1 m, three specimens, WS24164, WS24165.

Morphology: Barents and White Sea specimens of S. luetkenii analysed in this study grow atached to bivalve shells [e.g. Chlamys islandica (Müller, 1776) and Astarte borealis (Schumacher, 1817) ], on pebbles or rock surfaces ( Fig. 6 and Fig. 7). Te growth form typically is fig-shaped, with a welldefined peduncle; sometimes irregularly massive, cushionshaped, encrusting. In the later case, the base is tightly atached to the object on which the sponge grows. Te colour in life is pale orange or pale yellow. Preserved specimens are beige. Surface velvety, ofen slightly wrinkled. Sponge is firm, cork-like to touch in some cases, elastic and flexible in others. Usually, one to three oscula surrounded by a short spicular collar (not always) open at the top.

Some specimens grow out from the substratum, typically a bivalve shell, to become flat, lobate. Generally, these sponges appear to lie flat on the sea botom when in situ, rather than growing vertically. A few minute oscula scatered across the upper side. Sometimes there is a single wide osculum subdivided by septa. Lobate forms usually have an even outer surface in vivo; however, specimens with a more typical, wrinkled surface can also be found. Te consistency is elastic to touch.

Spicules: Megascleres are of two distinct types, choanosomal subtylostyles or ectosomal tylostyles, with overlapping size distributions ( Fig. 8). Choanosomal subtylostyles have only a slightly pronounced tyle near the basal end and are cylindrical in shape, straight or slightly curved, ofen long-pointed: 266–392.8–505 µm × 3.6–5.7–7.9 µm (N = 100). Small tylostyles have a distinctively pronounced head at the basal end and are cylindrical, short-pointed: 150–264–378 µm × 3.3–4.95–7.4 µm (N = 100). In some specimens, large centrotylote oxeas can be found.

Microscleres are minutely spined centrotylote microrhabds of three types. Tese spicules, except microtrongyles, can seem to be completely smooth, even under high magnification (×400). Microstrongyles, ~30 µm (N = 50); microxeas, ~50 µm (N = 50); microstyles, ofen rare, ~30 µm.

Skeleton: Te main skeleton consists of large subtylostyles, either as individual spicules or in bundles, which are scatered in a disorderly fashion or form a vague mesh. In the ectosome, small tylostyles are arranged into radial bundles, with the apical ends of the spicules slightly protruding beyond the surface. Microscleres are scatered throughout the interior but are especially abundant in the outermost layers.

Remarks: It was suggested earlier, by Morozov et al. (2023), that S. luetkenii might represent a species complex. In this study, we defined several distinct morphotypes in the Barents Sea population of S. luetkenii : a fig-shaped morph with a wrinkled surface as opposed to a lobose and flat morph with a smooth surface. However, the analysis of the 28S nuclear and COI mitochondrial loci from two morphotypes proved that they are conspecific; no differences were found in barcoding regions.