Mycale (Mycale) fibrosa Boury-Esnault & van Beveren, 1982

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 : 489-490

Mycale (Mycale) fibrosa Boury-Esnault & van Beveren, 1982

( Figure 16 )

Synonomy: Mycale fibrosa Boury-Esnault & van Beveren, 1982 . Specimens. BELUM.Mc2015.624 Grotto Island, Verdansky Base (Site 2) (65°14.529’S, 64° 15.451’W), depth 6–18 m; collected by C. Goodwin and E. Priestley, 16/02/2015; BELUM. Mc 2015.801 and BELUM. Mc 2015.802 Neptune’s Bellows, Deception Island (62°59.607’S, 60° 33.601’W), depth 7–18 m; collected by C. Goodwin and E. Priestley, 26/02/2015 .

External morphology. In situ appearance ( Figure 16A ): Low pale yellow mound with surface covered in conules. Ectosomal mesh visible through surface on close examination.

Preserved appearance. White mass of choanosomal fibres with detachable, thin, paper-like, ectosomal layer.

Skeleton: The choanosomal skeleton ( Figure 16B ) is an irregular reticulation of columns of mycalostyles. The majority of these are around 4 spicules thick but they are supported by much larger fibres up to 20 spicules thick. The ectosomal skeleton ( Figure 16C ) is formed of a felted mass of styles.

Spicules: Mycalostyles ( Figure 16D ): BELUM.Mc2015.624 524(549)578 by 15(20) 26 µm; BELUM. Mc2015.802 494(524)569 by 17(21) 31 µm.

Chelae 1 ( Figure 16E ): BELUM.Mc2015.624 43(48) 55 µm; BELUM.Mc2015.802 38(47) 56 µm. With gently curved lower alae.

Chelae 2 ( Figure 16F ): BELUM.Mc2015.624 77(84) 91 µm; BELUM.Mc2015.802 77(84) 91 µm. With gently curved lower alae.

Sigmas 1 ( Figure 16G ): BELUM.Mc2015.624 38(48) 61 µm, BELUM.Mc2015.802 41 µm (rare).

Sigmas 2 ( Figure 16H ): BELUM.Mc2015.624 254(273) 301µm BELUM.Mc2015.802 199(211) 226 µm.

Remarks. The spicule dimensions in the type specimen of Mycale fibrosa Boury-Esnault & van Beveren, 1982 , match those of our specimens closely (Styles 492(558)608 by 7(14) 18 µm; Chelae 54(80) 85 µm and 38(47) 54 µm; and sigmas 215(235) 249 µm and 31(37) 44 µm). The two specimens from which the species was originally described were in bad condition and it was not possible to see the ectosomal skeleton. Rios (2006) notes a disordered tangential layer of mycalostyles and therefore records the species as Mycale (Mycale) , we support this here. She reports styles 400(587)800 by 2.5–22.5 µm; anisochelae 45(70) 98 µm and 30(41) 53 µm and 28(31) 33 µm; sigmas 123(224) 295 µm and 33(41) 60 µm. Rios (2006) found the small category of isochelae in only one of her specimens and did not find them in the holotype.

Distribution. This species has been previously recorded from Livingstone Island 15–122 m ( Rios 2006); Ker- guelen Island ( Boury–Esnault & Van Beveren 1982), Paradise Bay, Leith Cove ( Desqueyroux-Faúndez 1989), and the Ross Sea ( Pansini et al. 1994).

Figures

FIGURE 16. Mycale (Mycale) fibrosa Boury-Esnault & van Beveren, 1982. BELUM.Mc2015.624. A. In situ appearance. B. Choanosomal Skeleton, scale bar 1000 µm. C. Ectosomal skeleton, scale bar 1000 µm. D. Mycalostyle. E. Small chelae. F. Large chelae. G. Small sigma. H. Large sigma. Spicule scale bars all 10 µm.