Scleritoderma tortuga, Schuster & Cárdenas & Pisera & Pomponi & Kelly & Wörheide & Erpenbeck, 2018

SCLERITODERMA TORTUGA View in CoL SP. NOV.

( FIGS 15, 16)

Diagnosis: Scleritoderma with tylostyles vertically protruding from the skeletons surface.

Synonymy: Scleritodermida sp. 1 and Scleritodermida sp. 2 ( Schuster et al., 2017, additional file 1, Fig. 4).

Type material: Holotype: HBOM 003 View Materials :02012, Coll. JSL-I dive 3923 [27 October 1995, Galápagos, SW Coast, Caleta Webb, 0.5 NM offshore of Tortuga Island, 1°04 ′ 59 ″ S, 90°51 ′ 56 ″ W, 242 m] GoogleMaps . Paratype: HBOM 003 View Materials :02009 (239 m), Galápagos , Isabela Island, 0°47 ′ 04 ″ S, 91°26 ′ 32 ″ W, Coll GoogleMaps . JSL-I dive 3919.

Comparative material: Scleritoderma camusi Lévi & Lévi, 1983 , Holotype MNHN DCL 2787, paratypes: MNHN DCL 2788, 355– 30 m, Norfolk Ridge. S. camusi (described in Schlacher-Hoenlinger, Pisera & Hooper, 2005), Norfolk Ridge 278–410 m, QMG318549, QMG318706. S. nodosum Thiele, 1900 , MNH DCL 3233, 90–110 m, Philippines (described in Lévi & Lévi, 1989). S. flabelliforme Sollas, 1888 (described in Schlacher-Hoenlinger et al., 2005), Norfolk Ridge, 458– 68 m, QMG318641, QMG318658, QMG318664.

Type locality: Tortuga Island, Galápagos Islands (242 m) ( Fig. 1) .

Distribution: Known from type locality and Isabela Island.

Habitat: Attached to hard substratum, depth range 239–242 m.

Description: Morphology, massive and flabelliform ( Fig. 15A, B). Dimension of the holotype is 8 cm in diameter and about 3–5 cm in height ( Fig. 15A, B). Texture, stony and hard. Surface, covered with small oscule openings 0.2–0.3 mm in diameter. Colour, beige in vivo ( Fig. 15A) and light brown in ethanol ( Fig. 15B). Ectosomal skeleton contains a thick layer of acanthorhabds ( Fig. 15D) on the surface. The heads of tylostyles project beyond the surface layer ( Fig. 15C, E). Very rare sigmaspires. Choanosomal skeleton composed of dense articulated slightly thorny rhizoclones ( Fig. 16). Large oscula openings on the surface of the choanosomal skeleton 300–400 µ m in diameter ( Fig.16A). Megascleres are rhizoclone desmas 225–350 µ m in diameter and tylostyles measuring 153– 256 –316 µ m (N15) ( Fig. 15E, H). Microscleres are C-shaped thick spinose sigmaspires 9–13 × 1–2 µ m (N3) ( Fig. 15F) and slightly curved acanthostrongyles 61– 84 –101 × 5–6 µ m (N30) ( Fig. 15D, G).

Etymology: Named after the type locality: Tortuga Island.

DNA barcodes: COI sequences as in Schuster et al. (2017), 28S (C1-D2) of the holotype and paratype as well as 18S (1770 bp) of the paratype (GenBank accession numbers: 28S KY652801, KY652802 ; 18S KY652839 View Materials , SBD record no. 1730, 1731). The 28S sequences were identical. The obtained COI sequence of HBOM 003:02012 was shorter (393 bp) compared to HBOM 003:02009 (630 bp). The 393 bp were identical (100%).

Remarks: Our new species Scleritoderma tortuga sp. nov. differs from the four other Scleritoderma species, S. camusi Lévi & Lévi, 1983 , S. cyaneum Van Soest & Stentoft, 1988 , S. flabelliforme Sollas, 1888 and S. nodosum Thiele, 1900 ( Van Soest et al., 2017), by the presence of tylostyles. Since tylostyles have never been observed in Scleritoderma species before, we first questioned if these could be due to a contamination from another sponge. However, we are convinced here that these are proper to the specimen, as we observed at least 15 tylostyles in both the holotype and paratype sections, all orientated in a vertical position protruding from the skeleton’s surface ( Fig. 15C, E). Additionally, in all of our preparations, no other spicule types were found, which may have indicated a possible contamination from another sponge. Furthermore, our concatenated molecular analyses including sequences of all known Scleritoderma species ( Fig. 5) indicate that Scleritoderma tortuga sp. nov. forms a sister-group relationship to S. nodosum from the Indo-Pacific (17–27 m). Additional supportive evidence of the new species is given by the presence of a 1109 bp long ‘intron 723’ located within the COI region ( Schuster et al., 2017) in both specimens. Our concatenated phylogenetic analysis supports the monophyly of the genus Scleritoderma which was first reported by Schuster et al. (2017) on single mitochondrial data. Based on the presence of tylostyles in S. tortuga sp. nov. the definition of Scleritoderma was amended. Tylostyles are actually not uncommon within Scleritodermidae , for example, they are known to occur in Aciculites and may have been overlooked in other species. We therefore recommend that future revisions of this family reassess the presence of tylostyles within this group.