Homaxinella balfourensis ( Ridley & Dendy, 1886 )

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 : 498-499

Homaxinella balfourensis ( Ridley & Dendy, 1886)

( Figure 22 )

Synonomy: Axinella balfourensis Ridley & Dendy, 1886 , Axinella supratumescens Topsent, 1907 , Homaxinella supratumescens ( Topsent, 1907) .

Specimens. BELUM. Mc 2015.541 and BELUM. Mc 2015.546 Gøuvernoren Wreck, Enterprise Island (64°32.407’S, 61°59.884’W),depth 8–18 m; collected by C. Goodwin and E. Priestley, 13/02/2015 . BELUM. Mc 2015.559 , BELUM. Mc 2015.565 , BELUM. Mc 2015.568 , BELUM. Mc 2015.569 , BELUM. Mc 2015.575 Port Lockroy (64°49.572’S, 63° 29.390’W), depth 12–17 m; collected by C. Goodwin and E. Priestley, 14/02/2015 . BELUM. Mc 2015.681— Jenny Island (67°43.325’S, 68° 20.590’W), depth 6–16 m; collected by C. Goodwin and E. Priestley, 21/02/2015 . BE- LUM. Mc 2015.742 Rocks on west side of Pleneau Island (65°06.407’S, 64° 04.417’W), depth 8–12 m; collected by C. Goodwin and E. Priestley, 24/02/2015 . BELUM. Mc 2015.827 Diomedea Island (62°12.185’S, 58° 56.760’W), depth 10–18 m; collected by C. Goodwin and E. Priestley, 01/03/2015 .

External morphology. In situ appearance ( Figure 22A ): Yellow branching sponge with branches ~ 0.5 cm in diameter. Specimens can be over 20 cm in height. Branches come abruptly to a sharp point. Some individuals have many branches, some only a few, and sometimes an individual may consist of a single branch. Branches may be undivided or divided. Dividing is sometimes dichotomous but can be very untidy and give the sponge a straggly appearance.

Preserved appearance. Fairly soft pale cream branch with smooth surface. Alcohol stained pale yellow.

Skeleton ( Figure 22B ): Choanosomal ascending columns of styles, up to 10 spicules thick, are joined by brush- es of ectosomal styles at the surface.

Spicules ( Figure 22C ): Measurements from BELUM.Mc2015.742.

Styles: 341(472)576 by 7.5(10.9) 14 µm. Thin styles, often slightly curved, heads not tylote.

Remarks. The type locality of Axinella balfourensis Ridley & Dendy, 1886 is Kerguelen Island in 37– 110 m. Axinella supratumescens Topsent, 1907 was described from Ile Wiencke in 2–30 m and Booth Island, dead specimen on shore. Both are now placed in Homaxinella ( Topsent 1916) and considered synonyms ( Van Soest 2002c). The species has been shown to be heavily impacted by anchor ice, with up to 87% being lost in a two year period ( Dayton 1989). Overwintering specimens may develop thinner branches and have a twiggy rather than bushy appearance (Jade Berman pers. obs.).

Distribution. This species is widely distributed in the Antarctic and sub-Antarctic, in depths of between 0 and 500 m ( Koltun 1964; Brueggeman 1998). Published records include the Ross Sea ( Burton 1929, 1934; Dayton 1989), South Georgia ( Burton 1932), Kerguelen ( Ridley & Dendy 1886), the Antarctic Peninsula ( Topsent 1907), and the South Shetland Islands ( Hajdu et al. 2016).

Figures

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.