Clathria (Axosuberites) rosita Goodwin, Brewin & Brickle, 2012

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 : 488-489

Clathria (Axosuberites) rosita Goodwin, Brewin & Brickle, 2012

( Figure 15 )

Specimens. BELUM.Mc2015.724 and BELUM. Mc 2015.737 Port Charcot, Booth Island (65°03.853’S, 64° 01.868’W), depth 6–16 m; collected by C. Goodwin and E. Priestley, 23/02/2015 .

BELUM. Mc 2015.766 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.

Comparative material examined. Clathria (Axosuberites) rosita Goodwin, Brewin & Brickle, 2012 Holotype BELUM.Mc7611.

External morphology. In situ appearance ( Figure 15A ): Low, pale orange, small cushions (up to 10 cm in diameter) with rounded projections up to 1 cm long.

Preserved appearance. Brown mass composed of anastomosing columns 2–3 mm thick. Texture quite firm with a hispid surface. Alcohol coloured pale orange.

Skeleton ( Figure 15B ): Choanosomal reticulation of bundles of 2–4 styles, these fan out and become plumose towards the ectosome. Well differentiated axial skeleton with larger sub-ectosomal styles joining the plumose ends of the choanosomal skeleton and protruding through the surface. The ectosomal skeleton consists of brushes of small styles, each supported at the tip of a protruding sub-ectosomal style of the choanosomal skeleton.

Spicules: Measurements from BELUM.Mc2015.724.

Choanosomal styles ( Figure 15C ): 409(492)596 by 18(20) 25 µm. Smooth styles, often slightly curved.

Sub-ectosomal styles: 598 (793)1040 by 29(34) 50 µm. Smooth styles. Form similar to choanosomal style but size much larger.

Ectosomal styles ( Figure 15E ): 274(323)375 by 7(10) 14 µm, spined sparsely at their heads.

Toxas ( Figure 15F ): 87(202) 381 µm.Smooth (no spination of ends).

Small toxas ( Figure 15G ): 7(9) 15 µm. Smooth, fat, oxhorn type toxa.

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 2002b). Our specimens are a good match for the type species both in terms of external form and spicule dimen- sions: in the holotype choanosomal styles 272 (311) 385 by 11(15) 19 µm; sub-ectosomal styles (357(597)1012 by 15(20) 31 µm; ectosomal styles 197(243)334 by 4.9(6.9) 9.6 µm; Toxas 51(149) 327 µm, small oxhorn shaped toxas: 15(22) 34 µm). The small toxas in our Antarctic specimens do not seem to attain quite as large a size, and the choano- somal styles are slightly larger. Clathria flabellata ( Topsent, 1916) has similar spicule sizes and has been recently recorded from 22 m in the South Shetland Islands ( Rios et al. 2004). However, this species can be distinguished as it has three categories of toxas, the larger two of which have spined ends. Additionally, it is an erect and fan-shaped sponge.

Distribution. C. rosita was originally described from South Georgia in 11.5–18 m and these are the first other records, extending its range to the Antarctic Peninsula.

Figures

FIGURE 15. Clathria (Axosuberites) rosita Goodwin, Brewin & Brickle, 2012. BELUM.Mc2015.724. A. In situ appearance. B. Skeleton, scale bar 1000 µm. C. Style. D. Subectosomal style. E. Ectosomal style ends. F. Thin toxa. G. Oxhorn toxa. Spicule scale bars all 10 µm.