Asbestopluma (Asbestopluma) gracilior (Schmidt, 1870)

Figures 81 a–f

Cometella gracilior Schmidt, 1870: 49 .

Asbestopluma gracilior; Rützler et al. 2009: 299.

Material examined. RMNH Por. 9734, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 101, 8.0167°N 57.4°W, depth 500 m, Agassiz trawl, muddy bottom, 4 September 1970 .

Examined for comparison. BMNH Schmidt slide, 1870.5.3.97, labeled ‘ Cometella gracilior Schmidt n.g.n.sp., 66 (on backside of slide an unpublished genus name), Florida’.

Description. Stalked, thin-branched tree-like sponge (Fig. 81 a). Upper part a bilateral symmetrically branched ‘body’, with side branches curved upwards, ending in a thin ‘peak’, the lower half is a stalk that is thickest at the bottom. There is a color difference between the cream ‘body’ and the pale brown stalk. Total length 4.5 cm, stalk 2.5 cm, ‘body’ 2 cm. The ‘body’ is 3 mm in widest expansion, the stalk 1–1.5 mm.

Skeleton. The stalk and the ‘body’ axis are supported by a thick bundle of long styles, the skeleton of the side branches consists of long and shorter styles. The surface of the body axis and side branches is covered by acanthotylostrongyles/styles, echinating the axial bundles and forming a tangential ectosomal layer. Microscleres are densely covering the outsides of the ‘body’ parts.

Spicules. (Figs 81 b–f) Styles, acantho(tylo-)strongyles, sigmancistras, anisochelae.

Styles in two distinct shapes and sizes, (1) long, fusiform styles (Figs 81 b,b1), from the main axis, 777– 988 – 1140 x 22 – 24.3 –26 µm, and (2) shorter subtylostyles (Figs 81 c,c1), faintly polytylote, from the side branches, 576– 671 –729 x 12 – 14.4 –16.5 µm.

Strongyles (Fig. 81 d) or tylostrongyles, acanthose, thin, curved, 61– 99 –132 x 1.5– 1.9 –2.5 µm.

Sigmancistras (Fig. 81 e), largely resembling sigmas, but with slightly asymmetrical endings one of which is indistinctly bladed, 23– 25.4 –31 µm.

Palmate anisochelae (Figs 81 f), with characteristic Asbestopluma -shape, with upturned spur on the median lower ala, and the upper side alae leaving a slight stretch of the shaft clear, 9– 11.3 –13 µm.

Distribution and ecology. Guyana Shelf, Gulf of Mexico, 500–630 m depth.

Remarks. There is a problem with the original description and depiction of Schmidt’s (1870) Cometella gracilior: he pictures (pl. V fig. 9) a small sponge consisting of a long stalk and a small oval, seemingly smooth body (resembling Rhizaxinella clava Schmidt, 1870, see below, or perhaps Stylocordyla sp.), and with it there is a drawing of a thick style with a peculiar cut-off end. His description (p. 49) is somewhat more elaborate, as he mentions papilla-like outgrowths of the body (not visible in the drawing). The description lacks the mention of microscleres. The slide of Schmidt in the Natural History Museum (London) labeled ‘ Cometella gracilior n.g.n.sp.’ does not show a content conforming to Schmidt’s description and it is quite likely that the slide was not made from the specimen in Schmidt’s drawing (his pl. V fig. 9). As Hajdu & Vacelet (2002) (p. 637, at the bottom of the right hand column) stated, the contents of this slide are styles, subtylostrongyles, sigmancistras and anisochelae, as well as a few sections that make it clear that these conform closely to our Guyana specimen. In fact, the Guyana specimen resembles to a large extent the shape, structure and spiculation of the type of the genus Asbestopluma, A. (A.) pennatula (Schmidt, 1875) . A major difference is the presence of two size categories of anisochelae in A. (A.) pennatula, but otherwise the two species are similar. Since Hajdu & Vacelet (2002) assigned the status of lectotype to BMNH slide 1870.5.3.97, I am confident that the present Guyana specimen indeed belongs to A. (A.) gracilior, despite the discrepancy with Schmidt’s drawing, and to a lesser extent his unrecognizable description. However, there is an alleged type specimen in the BMNH collection, which was obtained in an exchange with the Museum of Comparative Zoology (cf. Desqueyroux-Faúndez & Stone 1992). This specimen has been recently found in the BMNH collection (Ms Emma Sherlock in litteris), labeled ‘Alligator Reef, BMNH 1939.2 . 10.45 (sp) MCZ Exchange (MCZ 8130)’. It has the shape of Schmidt’s pl. IV fig. 9, and in all probability is not an Asbestopluma, but possibly Rhizaxinella clava or Stylocordyla . Thus, it appears we have here a confusing case of either a mislabeled specimen or a mislabeled slide because the two do not match (the specimen likely to represent a Rhizaxinella or Stylocordyla, the slide an Asbestopluma). Since there is only a single specimen and a single slide, lectotype designation of BMNH 1870.5.3.97 might be contested. It is beyond the present study to settle this matter.