Suberites topsenti Burton 1929

Suberites topsenti (Burton, 1929) (Figs. 16, 17)

Synonymy

Suberella topsenti — Burton 1929: 446, pl. IV (fig. 5). Laxosuberella topsenti— Burton 1930: 675.

Suberites montiniger — Topsent 1915: 39 –40; Koltun 1964: 25 –26; 1976: 169. Suberites topsenti —van Soest 2002: 242.

Material examined

SMF 10582 (1 specimen): PS67/078­11; SMF 10583–10584 (2 specimens): PS67/110­2.

Description

External morphology. Sponges are compact, massive, irregularly shaped (figs. 16A–C). The dimensions may reach 35x15 x 11 mm. Surface is minutely hispid or velvety, grey­coloured, with a single osculum of 0.4– 1 mm in diameter. Consistency is dense and compressible.

Skeleton. The choanosomal skeleton is dense, confusedly reticulate, constituted by long spicules (fig. 16D). The ectosomal skeleton is made of the smaller spicules arranged in bouquets (fig. 16E).

Spicules. Altogether 130 spicules from 2 specimens were measured. Two size categories are well distinguished (fig. 17A). The number of measured spicules of each category is given below, separately for each specimen (n1, n2).

Both long and small spicules vary from tylostyles to subtylostyles. They are straight, more or less slender, with terminal lobate tyles (figs. 17B–E). The long spicules measure: length 857­ 1092 ­1368 µm, tyle diameter 14­18.8­22 µm, diameter of the shaft underneath the tyle 8­13.0­18 µm, maximal diameter of the shaft 8­14.0­ 19 µm (n1=40, n2=30). The dimensions of the small spicules are: length 300­479­743 µm, tyle diameter 14­ 17.0­27 µm, diameter of the shaft underneath the tyle 8­12.4­19 µm, maximal diameter of the shaft 11­13.4­22 µm (n1=30, n2=30).

Type locality: Antarctic: Ross Sea: McMurdo Sound, depth unknown.

Distribution: Antarctic: Antarctic near­continent sectors (as S. montiniger: Koltun 1964; Sarà et al. 1992): NN 3 and 5 including the Western Ross Sea, as deep as 700 m. Northern Weddell Sea, ca. 2150–4700 m (present study).

SW Atlantic: Burdwood Bank, 102 m (as S. montiniger: Topsent 1915); Magellan area, Falkland Islands (as S. montiniger: Sarà et al., 1992).

Remarks

In 1929 Burton erected a genus Suberella for a new species, S. topsenti described by him from McMurdo Sound, Antarctica. He also allocated the Antarctic specimens, previously identified by Topsent (1915) as Suberites montiniger Carter, 1880, to Suberella topsenti. In fact, S. montiniger had been originally described from the Arctic (Carter 1880). Burton (1929) considered Suberella to be an evolutionary step between Suberites and Pseudosuberites. Belatedly, Burton (1930) discovered that Suberella had been preoccupied by Thiele (1905), and erected Laxosuberella with type species L. topsenti as a replacement of Suberella topsenti. Koltun (1964; 1976) disagreed with Burton and reverted S. montiniger again. Herein we follow van Soest (2002) who recently advocated the validity of topsenti as a species, but placed it in Suberites. The taxonomic history of S. topsenti is described in detail by the latter author. We should only emphasize the lobate tyles of the subtylostyles in our sponges which have not been previously mentioned by any author, and the larger size of the choanosomal spicules in comparison with those observed by Koltun (1964) who did not distinguish two spicule categories either.