Hymedesmia (Hymedesmia) gaussiana Hentschel, 1914

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 : 482

Hymedesmia (Hymedesmia) gaussiana Hentschel, 1914

( Figure 10 )

Synonomy: Hymedesmia gaussiana Hentschel, 1914

Specimens. BELUM. Mc 2015.599 and BELUM. Mc 2015.609, Grotto Island , Verdansky Base (Site 1) (65°14.615’S, 64° 15.019’W), depth 14–24 m , BELUM. Mc 2015.637 and BELUM. Mc 2015.644 rocks near San Martin Island , BE- LUM. Mc 2015.657,— Detaille Island (Site 1) (66°52.373’S, 66° 46.967’W), depth 6–24 m; collected by C. Goodwin and E. Priestley, 18/02/2015 . BELUM. Mc 2015.684 Rocks NW of Laktionov Island (65°45.536’S, 65° 47.319’W), depth 6–23 m , BELUM. Mc 2015.699 and BELUM. Mc 2015.702 Vieugue Island (65°38.758’S, 65° 12.540’W), depth 10– 22 m. BELUM. Mc 2015.759 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. ZMB4795 slides of Holotype of Hymedesmia (Hymedesmia) gaussiana Hentschel, 1914 .

External morphology. In situ appearance ( Figure 10A ): Rusty orange thin crust which can form large patches on bedrock (up to 30 cm in diameter). Oval pore sieves ~ 5 mm in diameter densely packed on surface. In some specimens algae in the tissues gave them a brown colour which contrasted more strongly with the red pore sieves.

Preserved appearance. Thin crust (~ 1 mm thick). Firm with smooth surface. Preserving alcohol is coloured orange.

Skeleton ( Figure 10B ): Hymedesmioid with a densely packed basal layer of primary and secondary acanthostyles. Ascending columns of ~15 strongyles.

Spicules: Measurements from BELUM.Mc2015.599.

Primary acanthostyles ( Figure 10C ): 255(353)419 by 22(28) 35 µm. Entirely spined with small spines but spines sparser towards the tip.

Secondary acanthostyles ( Figure 10D ): 124(155)177 by 15(18(20 µm. Entirely spined with small spines.

Ectosomal aniso-strongyles ( Figure 10E, F ): 296(354)373 by 8(11) 14 µm often with one end slightly tylote.

Arcuate chelae ( Figure 10G ): 28(34) 37 µm with a strongly curved shaft.

Remarks. The spicules of our specimens were a good match in terms of size and form for the type specimen (our measurements from Holotype: Primary acanthostyles 243(282)323 by 28(30) 35 µm, secondary acanthostyles 125(148)170 by 17(22) 27 µm, strongyles 318(362)400 by 7(9) 10 µm, chelae 28(35) 41 µm. The large acanthostyles were slightly longer and more sparsely spined in some of our specimens than in the holotype. Our spicules also match those figured by Rios (2006), although she records longer primary acanthostyles (250–390 by 25–52 µm).

Distribution. Originally recorded from 350 m depth in the Antarctic, H. gaussiana has also recently been recorded from Marguerite Bay in 355 m ( Rios 2006). From our survey this species also seems to be fairly common on shallow rock along the Antarctic Peninsula.

Figures

FIGURE 10. Hymedesmia (Hymedesmia) gaussiana Hentschel, 1914. BELUM.Mc2015.599. A. In situ appearance. B. Skeleton, scale bar 500 µm. C. Primary acanthostyle. D. Secondary acanthostyle. E. Ectosomal aniso-strongyle. F. Ectosomal anisostrongyle ends. G. Chelae. Spicule scale bars all 10 µm.