Clathria (Axosuberites) rosita, Goodwin & Brickle, 2012

Goodwin, Claire & Brickle, Paul, 2012, Sponge biodiversity of South Georgia island with descriptions of fifteen new species, Zootaxa 3542, pp. 1-48 : 13-15

Clathria (Axosuberites) rosita sp. nov.

( Figure 7)

Type material: Holotype: BELUM Mc 7611. Sample in 95% ethanol, tissue section and spicule preparation on slides; Rosita Harbour Site 2, South Georgia (54°00.649’S, 37° 25.618’W); depth 11.5m; collected by C. Goodwin, J. Brown, and S. Brown, 20 th November 2010.

Paratypes: Samples in 95% ethanol, tissue section and spicule preparation on slides . BELUM Mc 7619. Right Whale Bay, South Georgia (54°00.173’S, 37° 40.856’W); depth 18m; collected by C. Goodwin, J. Brown and S. Brown, 21 st November 2010 . BELUM Mc 7664. Husvik, South Georgia (54°10.285’S, 36° 40.412’W); depth 18m; collected by C. Goodwin, D. Poncet and P. Brewin, 26 th November 2010 . BELUM Mc 7679 and BELUM Mc 7683 Green Island , Stromness, Site 1, South Georgia (54°09.448’S, 36° 39.752’W); depth 17.4m; collected by C. Goodwin, P. Brickle and S. Cartwright, 27 th November 2010 . BELUM Mc 7688. Green Island , Stromness, Site 2, South Georgia (54°09.381’S, 36° 39.852’W); depth 17.4m; collected by C. Goodwin, J. Brown, and S. Brown, 28 th November 2010 .

Etymology: Named for the type locality Rosita Harbour, South Georgia

External morphology: In situ appearance: Massive yellow to pale orange cushion shaped or thickly encrusting sponge with small lobes over its surface which may develop into short branches in some specimens. Occasional large oscules visible ( Fig. 7a).

Chelae µm External appearance /Notes/Distribution

9–15 Subspherical massive sponge. New name for O. thielei

Burton,1932. Recorded from South Georgia.

n/a Stipitate, thin, flabelliform sponge. Type locality Antarctic, also Ross Sea ( Burton 1929), Wilkes Land, Oates coast, Victoria Land, Graham Coast, MacRobertson Coast ( Koltun 1964), South Georgia ( Burton 1932) South Shetland Islands ( Rios 2004)

20–22 Erect with ramifying branches. Three types of toxa. Type locality Argentina ( Cuartas 1992).

n/a Massive inverted pyramid shape. Koltun (1964) reports it is often stalked at base. Bold measurements from type description, remainder Koltun (1964). South Georgia, Antarctic shores (McMurdo Sound ( Burton 1929), Banzare Coast, Wilkes Land, Victoria Land, South Shetland Islands, MacRobertson Coast ( Koltun 1964)

n/a Digitiform, slightly branching. Type locality MacRobertson coast, Antarctic

20–24 Massive sponge with large oscules. Type locality New

Zealand

18–25 Erect branching sponge. Type locality New Zealand

8 Thin ramifying branches. Has rare acanthostyles. Type locality South Africa.

n/a Massive crust with ridged surface. Type locality South

Georgia.

Preserved appearance: Grey, firm with hispid surface composed of numerous small, finger-like, ridges.

Skeleton: The choanosomal skeleton is a confused mesh-like reticulation of bundles of 2–4 choanosomal styles, which fan out and become plumose in the ectosome. Well differentiated axial skeleton with a larger category of sub-ectosomal styles, of the same form as those in the choanosome, joining the plumose end of the choanosomal skeleton and protruding through the surface. The ectosomal skeleton consists of brushes of small styles, miscrospined on the head, each of which is supported by the tip of a protruding sub-ectosomal style of the choanosomal skeleton ( Fig. 7b).

Spicules: Measurements from Mc7611.

Choanosomal Styles: 272(311)385 by 11(15)19µm smooth styles, often slightly curved ( Fig. 7c).

Sub-ectosomal styles: 357(597)1012 by 15(20)31µm of the same form as the choanosomal styles but the majority are larger in size ( Fig. 7c).

Ectosomal styles: 197(243)334 by 4.9(6.9)9.6µm. Microspined on the head ( Fig. 7d,e).

Toxa: 51(149)327µm ( Fig. 7f), Small toxa: 15(22)34µm, fat oxhorn shaped toxa ( Fig. 7g).

Remarks: These specimens have been assigned to Clathria (Axosuberites) on the basis of their distinctive plumose extra axial skeleton which is well differentiated from the reticulate axial choanosomal skeleton (Hooper 2002). Several Clathria (Axosuberites) species have been reported from Antarctica and the Southern Ocean ( Table 3). Three of these have been recorded from South Georgia. The majority of species can be easily distinguished from our specimens as they possess chelae ( Table 3). The three species from the area without chelae, C. flabellata ( Topsent, 1916) and C. nidificata ( Kirkpatrick, 1907) , and C. ramea ( Koltun, 1964) , can be distinguished by their external form (fan shaped, pyramid shaped and ramifying respectively rather than encrusting) and the much larger size of their ectosomal and choanosomal styles ( Table 3). This new species also possesses a second category of small toxa (7–16µm) in addition to the larger category of toxa found all species. However, a wide size range of toxa is also reported from C. georgiaensis Hooper, 1996 and C. flabellata ( Topsent, 1916) and although not mentioned in the descriptions these could represent a separate category.