Strongylodesma aliwaliensis, Samaai, Toufiek, Keyzers, Robert & Davies-Coleman, Michael, 2004

Samaai, Toufiek, Keyzers, Robert & Davies-Coleman, Michael, 2004, A new species of Strongylodesma Lévi, 1969 (Porifera; Demospongiae; Poecilosclerida; Latrunculiidae) from Aliwal Shoal on the east coast of South Africa, Zootaxa 584, pp. 1-11 : 5-10

Strongylodesma aliwaliensis sp. nov.

( Fig. 2A , B, C; 3A, B, C, D)

Holotype Material. SAM H­ 5083 (cross ref. TS 970): Umkomaas, Aliwal Shoal, East coast of South Africa, 30° 26’202”S, 32° 02’558”E, collected by Toufiek Samaai and Vic Peddemors, 0 4 September 2003, at a depth of 18 m.

Paratype material. SAF 94–23: Umkomaas, Aliwal Shoal, East coast of South Africa, 30° 26’202”S, 32° 02’558”E, collected by Greg Hooper, 21 June 1994, at a depth of 18 m. TS VG 1: Umkomaas, Aliwal Shoal (Raggie Cave and Anvil Rock), East coast of South Africa, 30° 26’202”S, 32° 02’558”E, collected by Toufiek Samaai, 0 1 May 2004, at a depth of 15 m.

Description. Sponge is massive, semispherical, sometimes thickly encrusting, up to 8.5 x 7 x 4.5 cm in diameter ( Fig. 2A ). Ectosomal layer not readily separable from choanosomal tissue, but are distinguishable and approximately 1 mm thick. Texture soft, compressible but resilient. Surface smooth with numerous, randomly scattered cylindrical or volcano­shaped oscules, 1.5 cm high and 1–2 cm wide, with no internal canal divisions, and smooth mushroom­like areolate porefields 0.5 cm high and 0.5 cm wide ( Fig. 2 B). Sand particles and other epifauna (hydroids and Red algae) present on the surface and within the choanosomal tissue of the sponge. Exterior colour in life dark olive green; in preservative dark oily brown/black.

Spicules. Megascleres are smooth anisostrongyles, with one end narrower than the other, 428 (235–590) x 7 (4–9) m, n=20 ( Fig. 2 B) (Paratype SAF 94–23: 466 (245–549) x 6 (4–7) m, n=20 ( Fig. 2 C). Microscleres: absent

Skeleton. The choanosomal architecture is dense with convoluted tracts that may or may not form discrete chambers, these tracts range in width 100–294 m thick (paratype 200–490 m thick) ( Fig 2 , C, D). These convoluted tracts are a dense paratangential feltwork of anisostrongyles, similar to that found in the ectosome, suggesting that these convoluted tracts may represent an early ectosomal surface as in Tsitsikamma and Zyzzya and that the sponge grows in size and volume by putting on new chambers as in some species of Polymastiidae (from New Zealand), Zyzzya , Coelosphaera , Coelocarteria and Petrosia . Within and between the convoluted tracts the choanosome is much softer, containing the skeleton that consists of an ill­formed, irregular reticulation of anisostrongyles, these tracts range in width from 50–100 m, with no distinction between the primary and secondary tracts ( Fig. 2 B, C). Towards the centre of the choanosome the tracts are more confused and ill­defined, and towards the surface they become more robust and vertically arranged and radiate to form plumose tracts 200 m wide. Scattered throughout the choanosome, between the tracts, are a few interstitial megascleres in the same category as the main spicules. The ectosome is composed of a dense irregular interlocking paratangential feltwork of anisostrongyles approximately 200–350 m deep ( Fig. 2A , B). Below this interlocking paratangential layer a clear band of collagenous mesohyl is present (see Fig. 2 A ). Anisostrongyles do not protrude beyond the surface.

Chemistry. Preliminary chemical analysis of sponge extracts has confirmed the presence of several pyrroloiminoquinone products, for example makaluvamine I.

Substratum, depth range and ecology. Found on the shallow reef platform of Aliwal shoal, depth 18 m and on the vertical surfaces on the outside of a cave and boulder, depth 15 m. This species is very rare and is found in areas were there is current flow.

Geographic distribution. Aliwal Shoal on the east coast of South Africa (see Fig. 1 ).

Etymolog y. Named after the location Aliwal Shoal, Umkomaas.

Discussion. Strongylodesma aliwaliensis sp. nov. is easily distinguished from the genus holotype S. areolata Lévi on external and internal morphology and on colouration; S. areolata have elliptical areolate porefields with a reddish brown pigmentation, while S. aliwaliensis sp. nov. have fungiform areolate porefields and are darkly pigmented like the other South African Strongylodesma and other Latrunculiidae . Strongylodesma aliwaliensis sp. nov. also differs from the genus holotype S. areolata Lévi by the larger size of the megascleres ((299 (282–319) x 6 (5–7) um in the holotype MNHN VEM 131­DCL 1425), and in the possession of smooth anisostrongyles (as opposed to faintly terminally spined strongyles in the holotype). The subectosomal skeleton of the holotype is a clear band of collagenous mesohyl 227–270 m thick, the base of which is a thin band of paratangential strongyles (20 m deep) (see Samaai and Kelly, 2002; Samaai, 2002). This clear region is however, present in S. aliwaliensis sp. nov. but not at the base as in the holotype (MNHN VEM 131­DCL 1425) and occurs below the thick interlocking paratangential layer at the surface (see Fig. 3C ). This broad paratangential layer at the surface of the ectosome is also present in S. tsitsikammaensis and S. algoaensis (see Samaai et al., 2003).

The choanosome architecture of the new species is dense with convoluted tracts that may or may not form discrete chambers. These convoluted tracts within the choanosome are rather unusual for the genus Strongylodesma and it was first described in the type species of the genus Tsitsikamma (see Samaai and Kelly, 2002). This structure however, is not unique for Tsitsikamma (Family Latrunculiidae ), as evidence also shows that species of Zyzzya (Acarnidae) have a choanosomal structure reminiscent of that of Tsitsikamma (Samaai and Kelly, 2002) . The choanosomal architecture of S. aliwaliensis sp. nov however, differs considerably from Tsitsikamma favus Samaai and Kelly (2002) in that the choanosome lacks the discrete honey comb­like chambers as found in T. favus Samaai and Kelly (2002) . Thus, the “convoluted tract” morphological character as observe in Strongylodesma aliwaliensis sp. nov., Tsitsikamma and Zyzzya holds no phylogenetic weight; it is “cross taxon” — like the axial compression of Axinellidae , Raspailiidae , and the desmas of Lithistids and therefore cannot be used as a character for inclusion of this new species within either Tsitsikamma or Zyzzya . Tsitsikamma and Zyzzya also lacks the characteristic strongyle megascleres and fungiform areolate porefields as found in all species of Strongylodesma ( Tsitsikamma possesses large styles and cauliform areolate porefields; Zyzzya possesses tylotes, occasional stylotes, have isochelae microscleres and lacks areolate porefields). The suggestion that the new taxon is a Tsitsikamma without microscleres is likely to be incorrect because the phenomenon of reduction of microscleres in genera with known abundant microscleres is only observed in atoll locations where silicates are less available (Kelly­Borges & Vacelet 1997 on Diacarnus ).

The inclusion of the new taxon within Strongylodesma is strongly supported based on the presence of strongyles, the fungiform areolate porefields and structure of the ectosomal layer. These convoluted tracts are an artifact of growth, where new structures of the choanosome and ectosome overgrow the older ectosomal layers.

S. aliwaliensis sp. nov is found on the same habitat type as described for S. algoaensis (both are restricted to deeper waters on rocky platforms), but differs from it in that the former is found in subtropical waters on the east coast and the latter in the warm temperate waters on the south east coast of Algoa Bay ( South Africa). Strongylodesma tsitsikammaensis on the other hand is restricted to the intertidal rock pools and gullies in the Tsitsikamma National Park region. The new species also differ from the two known South African species in colouration, S. tsitsikammaensis is greenish brown while S. algoaensis is brown, whereas the new species is a dark olive green colour. Strongylodesma aliwaliensis sp. nov. also differs from S. tsitsikammaensis and S. algoaensis in having much larger megascleres (( S. tsitsikammaensis 348 (307–403) x 7.32 (7.2–9.6) m; S. algoaensis 328 (307–355) x 9 (7.2–9.6) m), and in that the strongyles tapper off or becomes narrow on one side, a character not previously recorded in the strongyles of Strongylodesma .

The ectosome also differ in the structure of the paratangential layer between the three South African species; in S. algoaensis the ectosome is composed of a loose feltwork of paratangential strongyles; in S. tsitsikammaensis and S. algoaensis the ectosome is dense and interlocking differing only in the presence of a clear subectosomal mesohyl layer in S. algoaensis (see above discussion). Strongylodesma aliwaliensis sp. nov. is very similar to species of Latrunculia in the field, with areolate porefields, a soft, inflated, compressible texture, and a typical dark pigmentation. It is only at the histological level that the genus and this species are distinguishable, by a lack of microscleres.

Apart from S. areolata Lévi (1969) and the two South African species of Strongylodesma at least four more undescribed species are known to exist worldwide (Samaai et al., in prep): there is one new species each known from New Caledonia ( Lévi, 1998), and the Kingdom of Tonga (Michelle Kelly, per. comm. 2002), and the genus is thought to be represented by two species in the west tropical Atlantic (see Samaai and Kelly, 2002; Samaai, 2002). These latter were previously considered to be species of Batzella (Van Soest, 1996) . The addition of further species will continue to refine the definition of the genus Strongylodesma and broaden our understanding of this important genus, both biologically and geographically.

Figures

FIGURE 1. Map of collection locality on the east coast of South Africa. Aliwal Shoal is situated about 5 km off the town of Umkomaas on the KwaZulu­Natal South Coast, about 45 minutes drive from Durban.

FIGURE 2. A. Gross morphology of Strongylodesma aliwaliensis sp. nov. (SAM H­ 5083); B. A close up frame of the fungiform areolate porefields and cylindrical oscules of Strongylodesma aliwaliensis sp. nov. (SAM H­ 5083); C. Smooth anisostrongyles with one end narrower within Strongylodesma aliwaliensis sp. nov. (Anisostrongyles) (1000 X).

FIGURE 3 A, C. Skeletal architecture of the holotype (SAM H­ 5083) (A, 100 X; C, 50 X); C. Skeletal architecture showing the clear mesohyl region below the paratangential layer of anisostrongyles (100 X); B. Skeletal architecture of the paratype (SAF 94 ­ 23) (50 X); D. Skeletal architecture showing the region of convoluted tracts of anisostrongyles (100 X).