Hemimycale topsenti ( Burton, 1929 ) Goodwin & Berman & Hendry, 2019

Goodwin, Claire E., Berman, Jade & Hendry, Katharine R., 2019, Demosponges from the sublittoral and shallow-circalittoral (<24 m depth) Antarctic Peninsula with a description of four new species and notes on in situ identification characteristics, Zootaxa 4658 (3), pp. 461-508 : 478-480

Hemimycale topsenti ( Burton, 1929) comb. nov.

( Figure 8 )

Synonomy: Laxosuberella topsenti ( Burton, 1929) ; Suberella topsenti Burton, 1929 ; Suberites topsenti ( Burton, 1929) .

Specimens. BELUM. Mc 2015.596 — Grotto Island , Verdansky Base (Site 1) (65°14.615’S, 64° 15.019’W), depth 14–24 m; collected by C. Goodwin and E. Priestley, 16/02/2015 . BELUM. Mc 2015.688 Rocks NW of Laktionov Island (65°45.536’S, 65° 47.319’W), depth 6–23 m; collected by C. Goodwin and E. Priestley, 22/02/2015 . BELUM. Mc 2015.709 Vieugue Island (65°38.758’S, 65° 12.540’W), depth 10–22 m; collected by C. Goodwin and E. Priestley, 23/02/2015 . BELUM. Mc 2015.767 and BELUM. Mc 2015.768 Paradise Bay Wall (64°53.841’S, 62° 52.391’W), depth 14–21 m; collected by C. Goodwin and E. Priestley, 24/02/2015 . BELUM. Mc 2015.834 Diomedea Island (62°12.185’S, 58° 56.760’W), depth 10–18 m; collected by C. Goodwin and E. Priestley, 01/03/2015 .

Comparative material examined. BMNH 26.10.26.186a Suberella topsenti Burton, 1929 Holotype. Station 14. Tissue section (label crossed out to say Suberella montiniger Carter but this is the specimen referred to in the type description, pp 446 Burton (1929)).

Suberites topsenti ( NIWA 28884). Specimen collected on TAN0402: A biodiversity survey of the western Ross Sea and Balleny Islands in 2004 undertaken by the National Institute of Water & Atmospheric Research ( NIWA) and financed by the former New Zealand Ministry of Fisheries.

External morphology. In situ appearance: Large globular or oval shaped sponges—our specimens ranged from 10–30 cm in diameter ( Figure 8A ). Beige or pale yellow in colour, the surface often has purplish-brown patches, presumably due to algae. Large pore sieve structures (around 0.5–1 cm in diameter) cover the surface of the sponge, in some specimens these have raised rims ( Figure 8B ). There are also occasionally large oscules up to 2 cm in diameter.

Preserved appearance. Pale brown soft sponge. Smooth surface with visible pore sieves. Alcohol coloured yellow.

Skeleton ( Figure 8C ): The choanosomal skeleton is a plumo-reticulation of columns of styles. The ectosomal skeleton is a dense palisade of styles with their points directed outwards.

Spicules ( Figure 8D ): Styles with a very slightly tylote head and an abrupt point. Measurements from BELUM. Mc2015.596 Thicker styles 380(420)443 by 7(9) 13 µm ( Figure 8E ), thinner styles 307(368)406 by 3(5) 7 µm ( Figure 22F ). These two categories of styles were not localised and presence of thin spicules was less common in other specimens.

Remarks. Specimens presumably of this species were reported by Topsent (1915) as Suberites montiniger Carter, 1880 . S. montiniger was described from the Barents Sea. Burton (1930) notes that S. montiniger differs in having a tangential layer of styles at the surface rather than a palisade and the distinction of the two species is maintained by Van Soest (2002b). However, some authors (e.g. Campos et al. 2007 for specimens from the Bransfield Strait) retain the use of S. montiniger for Antarctic specimens; a revision is required.

Suberites topsenti was originally described as Suberella topsenti Burton, 1929 . The genus Suberella ( Burton, 1929) is not valid as it is preceded by Suberella Thiele, 1905 . Burton subsequently proposed Laxosuberella ( Burton, 1930) as a replacement. Both genera are now regarded as synonyms of Suberites ( Van Soest 2002b) . Topsent (1915) reports style dimensions of 320–400 by 8 µm, his specimen from the Burdwood Bank was small with a diameter of 16 mm and had numerous surface papillae. Koltun (1964) reports styles 450 by 10 µm and describes specimens as spherical, up to 10 cm in height, with low papillae with crater-like openings. The spicule size (380– 440 by 10–12 µm) and form of the holotype corresponds well with our specimen. Brueggeman (1998) depicts in situ specimens very similar in appearance to ours.

The specimens reported by Plotkin & Janussen (2008) from the Weddell Sea have two categories of styles with lobate tyles (857–1368 and 300–743 µm) and a hairy surface with only a single osculum. They were also reported from 2150–4700 m where S. topsenti had previously only been reported up to 700 m deep. In our opinion these specimens represent a different species.

The presence of pore fields indicate that this species belongs in order Poecilosclerida Topsent, 1928 . Vargas et al. 2015 sequenced a specimen assigned to Suberites topsenti from the NIWA collections, collected from 244 m in the Ross Sea (NIWA28884). Their analysis, based on CO1, shows it clustering with other poecilosclerids in the family Hymedesmiidae Topsent, 1928 . Our specimens are the same species as NIWA28884. The preserved external appearance is very similar as our spicule dimensions and form (measurements of tylostyles in NIWA28884: 356(407)468 by 10(12) 15 µm). Given the absence of both microscleres and acanthostyles, the closest existing genus within the Hymedesmiidae is Hemimycale . This species corresponds to the current definition ( Huguenin et al 2018) ‘ Hymedesmiidae without acanthostyles and microscleres other than raphides. Megascleres strongyles, oxeas and styles. Styles and strongyles not divisible into ectosomal or choanosomal spicules. Oxeas when present are in the choanosome only’. Consequently, we tentatively re-assign this species to Hemimycale , despite closer similarity of the CO1 sequence to Phorbas species than existing Hemimycale . As noted by Uriz et al. (2017) both Hemimycale and Crella are polyphyletic. Further molecular and morphological work, using multiple markers, is required to resolve the taxonomy of these groups and this is beyond the scope of this paper.

Distribution. Antarctic Oates coast down to 700 m ( Koltun 1964); McMurdo Sound, Ross Sea ( Burton 1929; Brueggeman 1998), Weddell Sea ( Plotkin & Janussen 2008), although see notes above; Burdwood Bank, Falkland Islands ( Topsent 1915).

Figures

FIGURE 8. Hemimycale topsenti (Burton, 1929) comb. nov. BELUM.Mc2015.596. A. In situ appearance. B. Close up of surface in situ BELUM.Mc2015.688. C. Skeleton, scale bar 1000 µm. D. Styles, scale bar 100 µm. E. Thicker style, scale bar 10 µm. F. Thinner style, scale bar 10 µm.

FIGURE 22. Homaxinella balfourensis (Ridley & Dendy, 1886). A. In situ appearance BELUM.Mc2015.575. B. Skeleton BELUM.Mc2015.742, scale bar 1000 µm. C. Styles BELUM.Mc2015.742, scale bar 200 µm.