Weberella bursa Vosmaer 1885

Weberella bursa Vosmaer, 1885

Figs 2a–c, 3a–f

Weberella bursa Vosmaer, 1885: 16, pl. I figs 9, 12, 19, pl. III figs 6–8, 15– 20, 26–28; Topsent, 1928: 149; Uriz, 1975: 440; Boury-Esnault et al., 1994: 76, fig. 51; Van Soest, 2001: 89; Plotkin, 2004: 544, figs 1k, 2k; Plotkin et al. 2012: 25, fig. 1j.

Polymastia bursa (Müller, 1806); Koltun, 1964: 149; Koltun, 1966: 76, pl. IX fig. 2, pl. 23 figs 1–2, pl. 24: figs 1–2, text-fig. 49.

Weberella bursa (Müller, 1806): Boury-Esnault, 2002: 214, fig. 11; Plotkin et al. 2018: 1324, fig. 36; (not: Alcyonium bursa ? sensu Müller, 1806: 19, pl. 98 figs 1–2)

Material examined. Lectotype RMNH Por. 12422, Norway, Finnmark, Barents Sea, Willem Barents Expedition 1881, stat. 08, 72.6014°N 24.9514°E, depth 252–263 m, coll. M. Weber, 28 June 1881 (specimen of 8 x 6 x 5 cm (Fig. 2a) taken from a collective sample, RMNH Por. 706 (cf. Fig. 2c), indicated as ‘type’ by Vosmaer.

Paralectotypes, six remaining specimens in RMNH Por. 706 (Figs 2b–c) including the sectioned specimen shown in Fig. 2b, same data as the lectotype; ZMA Por. 02419, Norway, Finmark, Barents Sea, Willem Barents Expedition 1881, no station data, approximately 72°N 36°E, coll. M. Weber; ZMA Por. 02420, Norway, Finnmark, Barents Sea, Willem Barents Expedition 1881, stat. 06, 70.6667°N 31.1667°E, hard bottom, depth 238 m, coll. M. Weber, 24 June 1881; ZMA Por. 02691, Norway, Finnmark, Barents Sea, Willem Barents Expedition 1881, stat. 08, 72.6014°N 24.9514°E, depth 252–263 m, coll. M. Weber, 28 June 1881.

Additional non-type material: ZMA Por. 03256, Iceland, south coast, approximately 64°N 13°W, coll. L.C. Langenbroek, on board s.s.’ Anna’, June 1927; ZMA Por. 03257, same data; ZMA Por. 03297, North East Atlantic, no further data, coll. Oldmark, on board s.s.’ Alkmaar’, April 1938; ZMA Por. 03300, Iceland, 63.35°N 19.50°W, coll. Van der Duin, no further data.

Description. Colour in alcohol: yellowish to grey externally; dirty white inside.

Shape, size, surface and consistency (Figs 2a–c): Globular to massive, covered with papillae. Size up to 13 cm in diameter, but usually smaller, 2–10 cm (holotype 8 x 6 x 5 cm, cf. Fig. 2a). Consistency compact, solid, firm. Papillae conico-cylindrical, up to 5 mm high, 2 mm in diameter. Normally there are several dozens of papillae in a single specimen, but their number depends on size of the sponge. Most papillae bear a terminal osculum, those without visible opening are contracted. At first glance the papillae are more or less evenly distributed over the sponge, although they may be more numerous on the upper body part. Some papillae may occasionally be grouped in small clusters or even fused together. Just few, if any, ostia are visible on the walls of papillae. The sponge surface between the papillae is velvety, with regularly distributed ostia.

Skeleton (Figs 3a–d): Between the papillae, there is a distinct cortex of up to 1.5 mm in thickness (Figs 3a–b), strengthened by a 200–300 µm thick palisade of small tylostyles (Fig. 3b), underneath of which there are subdermal lacunae amid tissues lacking choanocytes, overlying a mass of intercrossing single large tylostyles, here and there united in bundles making an irregular subectosomal reticulation. In the choanosome the skeleton is made of large tylostyles arranged in an irregular reticulation of vague bundles with many loose single spicules. The skeleton of the papillae (Figs 3c–d) is more compressed, with subdermal reticulation largely absent, although the intercrossing spicule layer is clearly present (Fig. 3d).

Spicules (Figs 3e–f): (Tylo-)styles in two clear categories, small tylostyles of the ectosome (Fig. 3e), slightly curved, rounded heads, 133– 166.2 –232 x 2– 2.73 – 4.8 µm (overall measurements from various reliably identified specimens 125– 270 x 2–6.5 µm), and large subtylostyles (Fig. 3f) of the subdermal and choanosomal region, slightly fusiform, with ovoid, often mucronate, not very prominent heads, 402– 518.8 –652 x 9.8– 11.7 – 13 µm (overall measurements from various reliably identified specimens 330–700 x 5–16 µm).

Ecology: Attached on rocks and stones, from the upper sublittoral zone down to deep water in shelf and upper bathyal habitats, depth range 16–932 m (Plotkin et al. 2018; and pers. comm.).

Distribution: From the Arctic Ocean and Nordic Seas to the boreal North Atlantic: Russia (Franz Josef Land, Novaya Zemlya and Murman Coast), Norway (Svalbard, Bear Island, and along the mainland coast from Finnmark to Trøndelag), Iceland, South Greenland, Atlantic coast of France, west of Gibraltar, north of the Azores, Eastern Canada.

Etymology: bursa (Latin) = purse or bag, referring to the shape of the sponge. The genus name honours Dr Max Weber, director of the Zoological Museum of Amsterdam around the turn of the 20 th century, leading scientist of the Siboga Expedition (1899–1900) to Indonesian waters, and author of several papers on sponges.

Remarks. The combination of a globular shape, short surface papillae, solid consistency and an irregularly arranged choanosomal reticulation make this a very distinctive species. Apart from more northern localities, including a misidentification of Burton (1959) as Polymastia uberrima from Iceland, it has been reported convincingly from the mouth of the river Loire (Topsent, 1928, depth 150–932 m) and from the western inlet to the Strait of Gibraltar (Boury-Esnault et al. 1994, depth 133–137 m).

In the Western Mediterranean, a second species of Weberella is found, W. verrucosa Vacelet, 1960 (cf. also Vacelet, 1969), smaller in size, with only a few, if any, papillae and slightly smaller spicules. Uriz (1975) made an extensive comparison between Topsent’s (1928) record of W. bursa and a large number of W. verrucosa specimens. We can confirm that the spicules of W. bursa are larger than those of W. verrucosa, although there is an overlap in length and thickness. Boury-Esnault et al. (1994) found the two species occurring sympatrically west of the Strait of Gibraltar.

Samaai & Gibbons (2005) described Weberella namibiensis from southern Africa. It has less prominent papillae and its large subtylostyles exceed those of W. bursa in length, averaging 782 µm.

Austin et al. (2014) described Weberella perlucida from shallow waters (10 m) off British Columbia, Western Canada. It differs quite strongly in shape, with numerous semi-transparent papillae and a densely confused skeleton. The larger tylostyles differ from W. bursa in having distinct tyles and being considerably thicker averaging 20 µm.