Iophon unicorne Topsent, 1907

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 : 472-473

Iophon unicorne Topsent, 1907

( Figure 5 )

Synonymy: Iophon unicornis Topsent, 1907 , Iophon spatulatum Kirkpatrick, 1907 .

Specimens. BELUM. Mc 2015.646 Rocks near San Martin Islands (65°41.297’S, 65° 20.091’W), depth 6–21 m; collected by C. Goodwin and E. Priestley, 17/02/2015 . BELUM. Mc 2015.771 Paradise Bay Wall (64°53.841’S, 62° 52.391’W), depth 14–21m; collected by C. Goodwin and E. Priestley, 24/02/2015 . BELUM. Mc 2015.788 and BE- LUM. Mc 2015.789 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 . BELUM. Mc 2015.811 and BELUM. Mc 2015.819 Nelson Island, South Shetland Islands (62°59.607’S, 60° 33.601’W), depth 7–18 m; collected by C. Goodwin and E. Priestley, 27/02/2015 .

Comparative material examined. MNHN DT1665 Iophon unicornis Topsent, 1907 . Île Anvers, collected by ‘Le Francais’. Microscope preparations of tissue section and spicules.

External morphology. In situ appearance ( Figure 5A ): A yellow encrusting sponge.All but one of our specimens had thin branchlets arising from their surface, as the basal crust was often obscured by algae this gave the impression of a stalked branched sponge. The individual projections were thin (around 20 mm maximum diameter), translucent, up to 1.5 cm in length, and had rounded ends, although in some cases the branchlets rejoined the sponge surface.

Preserved appearance. Dark yellow branchlets or crust with smooth surface.

Skeleton ( Figure 5B ): Ascending bundles of up to 10 styles irregularly anastomising, joined by 1–2 spicules. Ectosomal fans of tylotes. Microscleres scattered throughout tissue.

Spicules: Measurements from BELUM.Mc2015.646:

Styles ( Figure 5C, D ): 389(418)446 by 13(16) 20 µm. Curved styles with an abrupt point and a large single spine on the basal end.

Tylotes ( Figure 5E ): 208(223)242 by 7(10) 11 µm Ends slightly swollen but not rounded and spined with several spines in a flattened crown ( Figure 5F ).

Chelae ( Figure 5G ): 17(20) 24 µm. Have a basal spine.

Remarks. The spicules of our specimen are a close match in terms of size and form to the type specimen (spicules measurements from type: styles 398(439)473 by 10(15)18μm, tylotes 212(234)248 by 8(11)14 μm, chelae 17(20)24 μm). Topsent (1907) does not record bipocilla as being present in the species description and we did not find them in our specimens or on re-examining slides of the type. However, Rios (2006) made new preparations from the type specimen and found them to be common. Goodwin et al. (2012) also noted bipocilla to be present in specimens they ascribed to this species which were collected from South Georgia. It is possible the species actually represents a species complex. However, Desqueyroux-Faúndez & Van Soest (1996) do not consider bipocilla to be a reliable character for species differentiation in Iophon as their presence can vary in different specimens from the same species.

Distribution. The type locality is Île Anvers (Anvers Island) on the Antarctic Peninsula. The species is widely distributed in the Antarctic and sub-Antarctic with records from Bransfield Strait, Bellinghausen Sea, Ross Sea, Kerguelen Island, South Orkney Islands, South Shetland Islands, South Georgia and Weddell Sea ( Kirkpatrick 1908; Topsent 1913, 1917; Hentschel 1914; Desqueyroux-Faúndez 1989; Pansini et al. 1994; Gutt and Koltun 1995; Rios 2006; Goodwin et al. 2012). Burton (1929) considered the majority of Antarctic species of Iophon to be synonyms so it is not clear if his specimens include this species.

Figures

FIGURE 5. Iophon unicorne Topsent, 1907 BELUM.Mc2015.771. A. In situ appearance. B. Skeleton, scale bar 1000 µm. C. Style. D. Style ends. E. Tylote. F. Tylote ends. G. Chelae. Spicule scale bars all 10 µm.