Suberites lutkenii, : Schmidt, 1870

Morozov, Grigori, Strelkova, Natalya Anisimova, Zimina, Olga & Sabirov, Rushan, 2023, A preliminary account of the Arctic / Subarctic Suberites (Porifera: Demospongiae) fauna, Zootaxa 5357 (1), pp. 50-70 : 53-55

Suberites lutkenii s. str. from the High Arctic Seas

( Fig. 1a–i 1 )

Material analyzed. Kara Sea, MMBI trawl survey 2016, st. C6-P35 (73.08N, 67.6E), depth 35 m (1 specimen; KFU-LH-2/003). Laptev Sea, MMBI trawl survey 2014, st. O-12 (75.3383N, 122.7867E), depth 45 m (1 specimen; KFU-LH-2/004); st. L-19 (75.1983N, 128.4633E), depth 45 m (2 specimens; KFU-LH-2/005) .

Description. Sponge subspherical, fig-shaped, slightly flattened ( Fig. 1h–i 1 ). Surface wrinkled, corrugated, velvety. Broad main body gradually narrows towards the short, weak pedicle, which closely embraces a substrate, usually the dead shell of a mollusc, polychaete tube or a stone. A single slit-like or roundish osculum on the sponge’s apex is surrounded by the short spicular collar. Colour (in alcohol) ash grey or pale pink.

Spicules. Megascleres (choanosomal vs. ectosomal) are clearly distinguishable into two distinct categories, viz. choanosomal subtylostyles and ectosomal tylostyles ( Fig. 1a–b 1 ). Large subtylostyles with only barely visible basal swelling, straight or slightly curved, rather short-pointed: 255.9–402±60–536 × 6.5–7.7±0.7–9 (n = 70) µm. Small tylostyles, slightly fusiform, short-pointed (rarely blunt): 173–296±54–421 × 6.5–7.6±0.6–8.5 (n = 50) µm. Microscleres are centrotylote microrhabds ranging in shape from microstrongyles to microstyles and microxeas ( Fig. 1c–f ). Sometimes tyle is slightly or completely shifted towards one end of spicule. In some individuals (e.g., from the Kara Sea) both smooth and microspined microscleres may occur. Dimensions: microstrongyles, 10–19±4.2–30.5 (n = 50) µm; microxeas, 30–43.5±7.2–67 (n = 40) µm; microstyles, often rare, 18.2–28±4.7–33.9 (n = 10) µm.

Skeleton. Choanosomal skeleton is a loose mesh of vague spicule tracts and a confused mass of single spicules ( Fig. 1 ch). In the ectosome tylostyles are organized into radial bundles ( Fig. 1 sb). Microrhabds are especially found near the surface, among the ends of ectosomal tylostyles ( Fig. 1 sm).

Remarks. Suberites lutkenii s. str. is quite common on the shelves of the High Arctic Seas. We have analyzed several specimens from the Kara and Laptev Seas. The description of this sponge from the Hudson Bay given by Lambe (1900) agrees well with our diagnosis. Other multiple species records known from the Arctic/Subarctic region (see S. lutkenii s. lat. section and references therein) are too ambiguous to be assigned to S. lutkenii s. str. without a hesitation. Re-examination of these specimens is required.

There are some morphological characters that would help in species identification: Suberites lutkenii s. str. is a pear-shaped sponge with weak pedicle and slightly wrinkled surface; a single apical osculum is surrounded by a short fringe.

Suberites lutkenii s. str. is apparently closely related to S. ficus ( Johnston 1842) from which it originated. In overall S. ficus s. lat. (see Ackers et al., 1992; Samaii et al., 2017) can be defined as follows: it’s a boreal species with no microrhabds other than centrotylote microstrongyles (both smooth and microspined), whose geographic distribution is presumably restricted by the North Sea to the north. A defining feature— centrotylote microxeas —sets the northern Suberites lutkenii s. str. apart from S. ficus and other boreal congeners.

Upon the examination of specimens collected in the Barents Sea, several more morphotypes of S. lutkenii have been recognized by the present authors. One of these new morphs was registered on several occasions. It’s description is given below.

Figures

FIGURE 1. S. lutkenii from the high Arctic, (a–f) scanning electron microscope (SEM) images of spicules; (g) cross section; (h–i1) habitus, scale 0.5 cm: (a) large subtylostyle and (a1) its basal end; (b) small tylostyle and (b1) its basal end; (c–d) microstrongyles; (e) microxea; (f) microstyle; (ch) choanosomal reticulation; (sb) radial bundles in the ectosome; (sm) surface microrhabds.