Discodermia dissoluta Schmidt, 1880

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 103-104

Discodermia dissoluta Schmidt, 1880

Figures 63 a–g

Restricted synonymy:

Discodermia dissoluta Schmidt, 1880: 87 ; Zea 1987: 220, pls 221, 265, text-fig. 80; Van Soest et al. 2014: table 2 (p. 436), fig. 21c; Pisera & Pomponi 2015: 1306, figs 2F, 10–11.

Material examined. RMNH Por. 9787, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 51, 7.6833°N 57.0333°W, depth 98 m, bottom calcareous sand, 30 August 1970 .

Description. Finger-shaped sponges ( Fig. 63 a), solitary or in a group of three, partially overgrown with hydroids, with dark-brown color in alcohol (possibly darkened by other sponges with aerophobic properties in the same sample haul), up to 4 cm high and 1.5 cm in diameter. Consistency firm to hard.

Skeleton. At the surface there is a closed cover of overlapping discotriaenes, carried by occasional perpendicular bundles of oxeas, and overlying a rather open desma network ( Fig. 63 b).

Spicules. ( Figs 63 b–g) Tetraclone desmas, oxeas, discotriaenes, acanthomicroxeas, acanthomicrorhabds.

Desmas ( Fig. 63 b) with smooth shaft and cladi, and strongly tuberculated zygomes, size difficult to measure, approximately 420– 508 –630 µm in overall diameter.

Oxeas ( Figs 63 c,c1), usually with bluntly rounded, sometimes even flattened apices, slightly curved, 372– 459 –552 x 5 – 7.8 –11 µm.

Discotriaenes ( Figs 63 d), with slightly concave, rounded or oval, occasionally polyangular discs, characteristically 210– 293 –330 µm in diameter, and conical rhabdomes, 48– 74.2 –120 x 10–20 µm.

Acanthomicroxeas ( Figs 63 e–g), in two categories, (1) larger ( Fig. 63 e) with sharply pointed ends, 99– 117 –129 x 4 – 4.3 –4.5 µm, (2) smaller ( Fig. 63 f), also sharply pointed, 38– 45 – 51 x 3 – 3.7 –4.5 µm.

Acanthomicrorhabds ( Figs 63 g,g1) with bluntly rounded ends, 13– 17 – 19 x 3 – 3.4 –4 µm.

Distribution and ecology. Guyana Shelf, Barbados, Colombia, Bonaire, Curaçao, Bahamas, offshore islands of NE Brazil, Florida, on reefs and sand bottoms, at 10–155 m depth ( Guyana Shelf 98 m).

Remarks. The present material conforms to previous descriptions of this species ( Schmidt, 1880; Zea, 1986; Kelly-Borges et al. 1994; Pomponi et al. 2001; Moraes, 2011; Van Soest et al. 2014; Pisera & Pomponi, 2015). The species shows a depth related variation in density of the desma skeleton, with few and thin desmas and discotriaenes in shallow-water specimens resulting in a remarkable compressibility, whereas deep-water species have proper stony lithistid skeletons with dense cover of discotriaenes overlying a strongly zygosed desma skeleton. It is as yet unverified if these skeletal variations are also reflected in the habit. Deep-water specimens appear to be more often finger-shaped, whereas shallow-water specimens tend to occur in dense, closely adhering clusters of lobes [compare shallow-water specimens depicted in Zea (1987) (p. 265) and Moraes (2011) (p. 115) with the deep-water specimens in Van Soest et al. (2014) (fig. 21c) and the present ( Fig. 63 a)].

The species is also widely known for its possession of rich bacterial populations (e.g. Brück et al. 2008) apparently responsible for the production of anticancer substances discodermolides and discodermide (Gunasakera et al. 1990, 1991).

Figures

FIGURE 63. Discodermia dissoluta Schmidt, 1880, a, habitus of RMNH 9787 (scale bar = 1 cm), b, SEM image of desma skeleton, c – g, SEM images of spicules, c, oxeote, c 1, details of c, d, discotriaenes, e, large acanthomicroxea, f, middle-sized acanthomicroxea, g, microrhabd, g 1, enlarged image of g.