Isodictya bentarti Rios, Cristobo & Urgorri, 2004

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 : 484-486

Isodictya bentarti Rios, Cristobo & Urgorri, 2004

( Figure 12 )

Specimens. BELUM.Mc2015.777. Under Spiggot Peak, Orne Harbour (64°37.755’S, 62° 33.018’W), depth 5–21 m ; collected by C. Goodwin and E. Priestley, 25/02/2015.

External morphology. In situ appearance ( Figure 12A ): Large sponge greater than 50 cm in height. Composed of several coalescing fingers, 4–8 cm in diameter, joined at a common base. Large oscules visible. Bright orange/ yellow in colour. Other specimens (not sampled) varied in form; some consisted of just one or two fingers and some were rounded lobes. Very large specimens (> 60 cm high) were seen.

Preserved appearance. Beige finger up to 2 cm in diameter. Firm texture. Surface with low conules. Oscules 3–4 mm across visible. Seems to be a clear ectosomal membrane but this is not detachable.

Skeleton ( Figure 12C ): Columns of 10–20 oxea which project through sponge surface. Reticulation of oxea in-between them. Chelae very abundant throughout tissue.

Spicules ( Figure 12B ): Oxeas ( Figure 12D ): 395(424)470 by 26(30) 35 µm.

Palmate chelae ( Figure 12E ): 63(69) 73 µm have knob on inside of alae.

Remarks. Our specimens are a good match for the external appearance and spicule form of the type specimen. This had a slightly wider size range of oxeas (185(407)535 by 2.5(19) 36 µm) and chelae (35–80 µm).

Distribution. The type locality is Livingston Island and South Shetland Islands 24– 56 m. This is the first record apart from the original description. This was the only site which we recorded this species at but it was very abundant here with very large specimens covering a vertical wall as far down as was visible (to depths of> 40 m). The species was only recorded from over 20m at this site and seemed more abundant lower down the wall so it may be that it is a deeper water species and not usually present in the shallow circalittoral areas that we were sampling.

Isodictya erinacea ( Topsent, 1916)

( Figure 13 )

Synonomy: Homoeodictya erinacea Topsent, 1916 ; Homoeodictya kirkpatricki Topsent, 1916

Specimens. BELUM.Mc2015.595and BELUM. Mc 2015.610— 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 2015.770 Paradise Bay Wall (Dive 1) (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. Homoeodictya erinacea Topsent 1916 . Holotype. MNHN DT680 , ‘Pourquoi-pas’ specimen no. 70, spicule preparation on microscope slide.

External morphology. In situ appearance ( Figure 13A, B ): Low cream cushion with hispid processes ~ 5 mm long and 1–2 mm wide. These have a spiky appearance sometimes fork at the end.

Preserved appearance. Untidy mass of clear, large branching fibres (~ 1 mm in diameter) with some brown tis- sue present in between them.

Skeleton ( Figure 13C ): Rather confused with bundles of 3–4 oxea crossing and anastomising. These bundles project from the surface, forming the hispid processes.

Spicules: Oxeas ( Figure 13D ): BELUM.Mc2015.610 (399(525)595 by 10(20) 26 µm) BELUM.Mc2015.595 (378(562)699 by 10(16) 28 µm).

Chelae ( Figure 13E ): BELUM.Mc2015.610 (45(52) 58 µm), BELUM.Mc2015.595 (53(61) 67 µm).

Remarks. The external form of our specimens is similar to that described by Topsent (1916) who states that his specimens are bristling with single or divided spines. Hajdu et al. (2016) note that their specimens were usu- ally cylindrical and light brown or yellowish in colour. The oxeas in our specimens are slightly shorter than those of the type (our measurements from the type specimen 710(769)837 by 24(31) 35 µm), but similar in size range to those reported by Rios et al. (2004) (400–712 by 7.5–30 µm). The chelae are of a very similar size to those of the type specimen (40–68 µm, 44(52) 58 µm from our measurements) and Rios et al. (2004) (40–50 µm). The form of the oxeas in our specimens is very similar to the type but the chelae do appear slightly more elongate. It seems that the presence of raphides may be variable in this species. Rios et al. (2004) note that they were not present in their specimens or those of Desqueyroux-Faúndez (1989) but they were abundant in the type specimen. We did not find them in our specimens.

Distribution. Widely distributed in the Antarctic (Wilhelm II Coast, Banzare Coast, Adelie Coast, George V Coast, Oates Coast, Balleny Islands, Victoria Land, Graham Coast, Palmer Archipelago, Elephant (Mordvinov) Is- land, Mac-Robertson Coast), Falkland Islands ( Koltun, 1964) and recently recorded from the South Shetland Islands ( Rios et al. 2004).

Figures

FIGURE 12. Isodictya bentarti Rios, Cristobo & Urgorri, 2004 BELUM.Mc2015.777.A. In situ appearance. B. Spicules, scale bar 500 µm. C. Skeleton, scale bar 1000 µm. D. Oxea, scale bar 10 µm. E. Chelae, scale bar 10 µm.

FIGURE 13. Isodictya erinacea (Topsent, 1916). A. In situ appearance BELUM.Mc2015.610. B. In situ appearance BELUM. Mc2015.770. C. Skeleton BELUM.Mc2015.770, scale bar 1000 µm. D. Oxea, scale bar 500 µm. E. Chelae, scale bar 10 µm.