Nodastrella asconemaoida, sp. nov.

Nodastrella asconemaoida sp. nov.

Synonymy: Asconema cf. foliata (van Soest and Lavaleye 2005: Fig. 2 A–B); Rossella nodastrella (van Soest et al. 2007: Figs. 1–3);? Rossella aff. nodastrella (Tabachnick and Collins 2008).

Material examined: One specimen, the holotype (HBOI 10-VIII-09-1 -001, USNM 1150045, SMF 11755) from deep-water Lophelia coral reefs off Cape Canaveral, Florida, lat. 28°19.426 N, long. 79°36.925 W, depth 723 m, collected August 10, 2009, and a second specimen (HBOI 5-VIII-05 -1-004) from Miami Terrace, Straits of Florida, lat. 25°42.0159 N, long. 79°52.0254 W, depth 337 m, collected August 05, 2005 using manned submersible Johnson-Sea-Link II. One specimen (ZMAPOR 19715, SMF 10363) from Rockall Bank, Ireland, lat. 55°29.619 N, long. 15°48.053 E.

Description: The holotype consists of the upper part of a large basiphytous specimen ca. 23 cm high and ca. 13 cm wide; size of the whole specimen is ca. 30 cm high and ca. 23 cm in diameter. The body is vase-shaped with the osculum having outward-flaring margins; colour white to grayish (Fig. 3). The second specimen, from which we had only a small piece of tissue, also had a similar bodyshape and was white when alive; it grew conjoined with another individual (Fig. 4).

Skeleton (Figs. 3 and 5, Table 2): the dermal surface shows a web of microspiny stauractins (occasionally with rudimentary tubercle of fifth ray), some tauactins with or without rudimentary fourth ray, and very rarely isolated pentactins and diactins; the web covers the paratangential rays of large, smooth (except for slightly rugose ray tips), orthotropal hypodermal pentactins. Atrialia are mainly hexactins with often somewhat shortened tangential rays, and pentactins combined with few stauractins. Choanosomalia are diactins of very variable size, up to several mm length, with rounded to pointed microspined or smooth tips, sometimes with one end swollen, with or without central swelling. Shorter diactins can protrude beyond the dermal surface as prostalia (Fig. 4). Further choanosomalia are rough hexactins, numerous regular oxy- and predominantly hemioxyhexasters with very short primary rays and 1–2, rarely 3 secondary rays, less common microhexactins, and very rare onychohexasters. Discasters with inflated centre and ~10–20 secondary rays, and calycocomes are situated mainly near the atrial surface, they are generally rare in the investigated specimens and were not found in SEM preparations. Calycocomes appear as two types, one with 7–8 secondary rays and well-developed calyces, and one with more numerous (up to 13) secondary rays and hardly developed calyces (therefore perhaps better termed "calycocome-like stellate discohexasters", as suggested by one reviewer). Spherical microdiscohexasters are rather common and situated mainly near the dermal surface, their primary rays are roughly of equal length as the ca. 35–40 secondary rays.

Remarks: N. asconemaoida differs from N. nodastrella by the lack of pappocome-like oxyhexasters, the abundance of hemioxyhexasters, the shape of microdiscohexasters (spherical in contrast to stellate in N. nodastrella [according to Topsent 1915]), and the presence of calycocome-like stellate discohexasters; also, the calycocomes/ calycocome-like stellate discohexasters are more abundant on the atrial side whereas calycocomes are more abundant on the dermal side in N. nodastrella. Furthermore, onychohexasters were not found in N. nodastrella, although they might have been overlooked as they appear to be very rare. Spicule composition and morphology of the Florida N. asconemaoida correspond well with the descriptions of the Irish specimens (van Soest et al. 2007: Fig. 3), an exception being the lack of "proper" calycocomes in the latter (only the calycocome-like stellate discohexasters were figured in van Soest et al. 2007). However, those were very rare in the Florida specimen, and might have been overlooked in the Irish material. Further differences concern the presence of some pentactins and stauractins among atrialia and a greater variation among the choanosomal diactins, which also include non-centrotylote spicules and more than two size classes, in the Florida material. However, we do not consider these differences sufficient evidence to distinguish separate species. After all, the Florida and the Ireland population seem to be genetically very close (see next section). For these reasons we synonymize the Irish species initially identified as Asconema cf. foliata (van Soest and Lavaleye 2005) and later assigned to Rossella nodastrella (Tabachnick and Menshenina 2007; van Soest et al. 2007) with our new species Nodastrella asconemaoida sp. nov. The specimens reported by Tabachnick and Collins (2008) from the N Atlantic Ridge probably also belong in this species, but due to their insufficient documentation this cannot currently be established with certainty.

Etymology: The species name refers to the adult body shape with outward-flaring oscular margin, which is typical for the genus Asconema, and was first reported for Nodastrella from the Irish population of this species (van Soest et al. 2007).