Spheciospongia vagabunda ( Ridley, 1884 )

Sutcliffe, Patricia R., Hooper, John N. A. & Pitcher, Roland, 2010, The most common sponges on the Great Barrier Reef seabed, Australia, include species new to science (Phylum Porifera), Zootaxa 2616, pp. 1-30 : 19-22

Spheciospongia vagabunda ( Ridley, 1884)

( Figures 10 , 11 , Table 4 )

Spirastrella vagabunda Ridley, 1884: 468 ; Hooper & Wiedenmayer, 1994 (2005 web version): 375 Spheciospongia vagabunda ; Kelly-Borges, 1997: 108.

Spirastrella vagabunda trincomaliensis Ridley, 1884: 468 .

Spirastrella cylindrica Kieschnick, 1896: 534 .

Spirastrella vagabunda tubulodigitata Dendy, 1905: 123 .

Spirastrella vagabunda fungoides Dendy, 1905: 124 .

Spirastrella vagabunda gallensis Dendy, 1905: 124 .

Material examined. Syntypes BMNH 1882.2.23.307 2 specimens, wet, 7–13 m, Thursday and West Islands, Torres Strait, 10°35'S 142°13'E and 10°22'S 142°02'E; BMNH 1882.2.23.243 wet, 7–13 m, Thursday and West Islands, Torres Strait; BMNH 1882.2.23.243a–307a 4 slides 2/20, 7– 13 m, Thursday and West Islands, Torres Strait.

New material. QMG329980 (SBD527235), inner shelf, north of Townshend Island, Great Barrier Reef, 22° 10΄ 30ʺ S 150° 27΄ 54ʺ E, 35 m depth, epibenthic sled, 10 v. 2004, coll. RV Lady Basten. QMG329184 (SBD517192), seabed between South Ledge Reef and Albany Island, northern tip of Cape York, Great Barrier Reef, 10° 44΄ 0 5ʺ S 142° 42΄ 18ʺ E, 21 m depth, epibenthic sled, 2 ii. 2005, coll. RV Lady Basten. QMG329166 (SBD513801), inner shelf seabed between Pompey Reef and Mackay, Great Barrier Reef, 21° 0 2΄ 42ʺ S 149° 48΄ 53ʺ E, 21 m depth, epibenthic sled, 29 ix. 2004, coll. RV Lady Basten.

Other material: 95 specimens distributed between the seabed north of Wyborn Reef at the tip of Cape York to the seabed north of Fraser Island in the south ( Figure 10 ). Housed at the Queensland Museum, Brisbane, Australia.

Description. Shape. This species has a highly variable morphology ranging from large cushion shapes to masses buried within the sand, with thick, tapering fistules protruding from the substrate. Nearly all the specimens collected from the GBRSBD project are massive with a large base which is usually buried within the substrate, tapering to thick fistules with an apical oscule.

Colour. Grey/khaki colour when frozen and in ethanol. In situ coloration was not recorded.

Oscules. Protruding fistules are open, with a single, large oscule rimmed by a thick, firm layer of dense spongin, spicules and sand.

Texture and surface characteristics. This is an extremely dense sponge containing a large proportion of sand in the basal skeleton. It is easily cut or torn, and the internal texture is rough where the sand grains and other foreign material are exposed. The surface is smooth but not uniform, and firm to touch.

Skeletal structure. Small ectosomal tylostyles form distinct and dense brushes, with a crust of spirasters present at the base of these brushes. The choanosome is cavernous and consists of dense, seemingly random tracts of larger tylostyles. Elongated spirasters were rare in our material, seen mainly in the buried portion of the basal skeleton.

Megascleres ( Table 4 ). Two size classes of tylostlyles are present. Ectosomal tylostyles are small and fine (135–430 μm), commonly with a straight or slightly curved shaft, some more gently recurved. Choanosomal tylostyles are larger and more robust (350–750μm), with most but not all having at least slightly curved shafts. Swollen tyles range from flattened to evenly rounded, and some are simply styles with no subtylote swelling. Points range from sharp and evenly pointed, to heavily telescoped. There is a high amount of morphological variation in both size classes of megascleres.

Microscleres ( Table 4 ). Spirasters are present in two size classes. The shorter (Type I) spirasters have curved shafts showing thick, regular spination concentrated along the upper side of the shaft. Longer, thinner spirasters (Type II) are coiled with up to 4 rotations and exhibit evenly distributed spines concentrated in one line only which follows the coiling of the shaft.

Habitat and distribution. This species was collected from sites distributed along the entire GBR, in depths ranging from 14 to 92 m, mainly in habitats dominated by carbonate and sandy substrates. It was previously known from Torres Strait, Sri Lanka, Papua New Guinea, Indian Ocean, Philippines, the Central Pacific and tropical Australia (from the Great Barrier Reef to the Houtman Abrolhos, Western Australia).

Remarks. This current dataset confirms the commonality of this species within the Great Barrier Reef seabed as well as adjacent reefal areas. It often burrows within the substrate and can be easily missed when sampling. Published descriptions have also varied due to the large morphological variability across its broad geographic range. Spicule composition has also varied, with previous descriptions including only one size class of tylostyles, and microscleres including from one type – spirasters - ( Bergquist, 1965, Bergquist & Tizard, 1967) to two, including spinispires (Kelly Borges & Bergquist, 1988). Our current definition identified two size classes of tylostyles, spirasters and rarely more elongate spirasters, as described as spinispires in the description by Kelly Borges and Bergquist (1988).

We have left this species in the genus Spheciospongia for the time being, however, we recommend that the boundaries between Spheciospongia and Cervicornia Rützler & Hooper, 2000 need to be resolved and that a revision of Clionaidae and Spirastrellidae is needed.

Predicted distributions and biophysical preferences. Spheciospongia vagabunda is evenly distributed along the length of the GBR, with no latitudinal regionalisation evident. Specimens were collected from 68 sled (biomass 20.5 kg) and 17 trawl sites (biomass 10.9 kg) between 14 and 92 m depth. Most populations appear to be located closer to the mainland, with very few specimens occurring towards the outer barrier reef areas. There may be cross shelf variation between populations given that S. vagabunda displays a wide range of gross morphological variability, however, this apparent cross shelf variation may simply be an artefact of the division of this species at OTU level, reflecting the different morphotypes. This species has a distribution which is negatively correlated with slope ( Figure 10 ) and is found in sediments with a high carbonate content ( Figure 3 ). This is expected given that the main body of this sponge is buried within the sediment, which thus needs to be relatively friable.

Figures

FIGURE 3. Substrate composition plot, showing the relative composition of sand, carbonate, gravel and mud for four species (Dercitus xanthus sp. nov., Xenospongia patelliformis Gray, 1858, Coscinoderma nardorus (Lendenfeld, 1886) and Spheciospongia vagabunda (Ridley, 1884 )).

FIGURE 10. Model distribution map displaying predicted and actual distribution and biomass of Spheciospongia vagabunda (Ridley, 1884) from the Great Barrier Reef seabed, displaying: OTU code for this species (SCQMSB. BRS 192794), P-AUC: Area Under the Curve performance diagnostic for the Presence / Absence model; Dev. Ratio: Deviance Ratio (P-AUC) performance diagnostic for the Biomass model; Measuresled: a device factor accounting for the difference in sampling rates between devices; Measuretrawllog (AreaHa) and Measuresledlog (AreaHa): offsets accounting for the swept area sampled by the trawl and sled; and influential predictor variables including: CRS _ T _ SD: temperature (° C) standard deviation, GA _ CRBNT / GA _ CRBNT ^ 2: carbonate (%) and its quadratic term, TRWL _ EFF _ I: weighted average annual trawl effort, GBR _ SLOPE: slope.

FIGURE 11. Spheciospongia vagabunda (Ridley, 1884) (QMG 329980 (SBD 527235 )). A, Section through the choanosome (scale bar 250 μm). B, View of spicule arrangement at the ectosome (scale bar 250 μm). C, Specimen (scale bar 8 cm). D, Spiraster (Type II) (scale bar 5 μm). E, Spiraster (Type II) (scale bar 20 μm). F, Spiraster (Type I) (5 μm). G, Spiraster (Type I) (scale bar 8 μm). H, Style (Type II) (scale bar 50 μm). I, Style (Type I) (scale bar 120 μm).

Tables

TABLE 4. Measurement of spicules for Spheciospongia vagabunda (Ridley, 1884), as range (and mean) of length x width in μm, N = 30.

Specimen number	Tylostyles (Type I)	Tylostyles (Type II)	Spirasters (Type I)	Spirasters (Type II)
QMG329980 (SBD527235)	455–550 x 8–15 (500 x 10)	135–420 x 2.5–9.5 (255 x 7)	4–12 x 3–7 (9 x 5)	4–20 x 2 (11 x 2)
QMG329184 (SBD517192)	450–750 x 7–15 (550 x 10)	200–430 x 3–12 (300 x 7)	10–25 x 3–5 (13.8 x 4)	10–24 x 2–4 (14 x 2)
QMG329166 (SBD513801)	350–510 x 7–14 (400 x 9)	160–350 x 3–7 (250 x 5)	10–20 x 3–5 (11.3 x 5)	15–39 x 1–3 (17 x 2)