Iotrochota sinki, Samaai & Pillay & Janson, 2019

Samaai, Toufiek, Pillay, Ruwen & Janson, Liesl, 2019, Shallow-water Demospongiae (Porifera) from Sodwana Bay, iSimangaliso Wetland Park, South Africa, Zootaxa 4587 (1), pp. 1-85 : 40-42

Iotrochota sinki sp. nov.

( Fig. 16 . A–G)

Material Examined. Holotype. SAMC–A24758 (cross-reference TS 889 & Saf 03-Sod 19), Ramsay reef, Sodwana Bay (27.4466°S; 32.7152°E), South Africa, 0 3 November 2003, collected by T Samaai, depth 18 m.

Paratypes. SAMC–A24759 (cross-reference TS 911 & Saf 03- Sod 72), Deep-sponge reef, Sodwana Bay (27.5167°S, 32.6835°E), South Africa, 0 6 November 2003, collected by T Samaai, depth 30 m ; SAMC–A24760 (cross-reference TS 924 & Saf 03- Sod 69), Two Mile reef, Sodwana Bay (27.5167°S, 32.6834°E), South Africa, 0 5 November 2003, collected by T Samaai, depth 12 m ; SAMC–A24761 (cross-reference TS 925 & Saf 03- Sod 109), Ribbon reef, Sodwana Bay (27.4880°S, 32.6977°E), South Africa, 0 7 November 2003, collected by T Samaai, depth 20 m ; SAMC–A24762 (cross-reference TS 950 & Saf 03- Sod 88), Seven Mile reef (27.4580°S, 32.7141°E), Sodwana Bay, South Africa, 0 7 November 2003, collected by T Samaai, depth 20 m.

Type locality. Ramsay reef, Sodwana Bay, east coast of South Africa.

Description. Thickly encrusting sponge, 110 × 70 × 5 mm diameter, with repent branches extending along the reef, or an amorphous bulky clathrous mass without any trace of individual branches. Branch lengths variable 5–30 mm diameter, depressed and wider where anatomizing. Branching phase, surface smooth but undulating; bulky phase surface lumpy or ridge like (conulose) ( Fig. 16A, B ). Conules 2 mm high on clathrous specimens. Oscules volcano-shaped, 2–3 mm in diameter, elevated, randomly scattered on surface apex. Ostia visible and randomly scattered over the surface. Texture firm, dense, resilient and rubbery to the touch, barely compressible, difficult to tear. Colour in life, light yellow-green typically mottled with light brown-green patches, interior yellow to brown; in preservative, black.

Skeleton ( Fig. 16C, D ). Choanosomal skeleton is a rectangular reticulation of multispicular spicule tracts, 56– 77 µm thick, with diameters varying between 130–320 µm and 150–417 µm in width. These tracts are composed of closely packed styles bound together by varying quantities of spongin. Interstitial megascleres consist of auxiliary styles and commonly occur in strands. Birotulate chelae are scattered throughout the choanosome. The ectosomal skeleton is an organic crust with scattered loose megascleres.

Spicules. Megascleres ( Fig. 16E, F ). Styles, smooth, relatively short and curved proximally or long, straight or curved, distally fusiform or hastate, in three size classes: I) 167 (152–177) × 7 (7) µm, n = 10; II) 258 (241–271) × 5 (5) µm, n = 10, occasionally strongyles (very rare), 227 (168–281) × 4 (4) µm; III) 148 (138–158) × 2 (2) µm, n = 10. Microscleres ( Fig. 16G ). Birotulate chelae, small and unmodified, 15 (14–16) µm, n = 10.

Substratum, depth range and ecology. Commonly found in and around sand and dead coral in shallow reefs. Depth range 18– 30 m.

Etymology. Named after marine ecologist Dr. Kerry Sink in recognition of the contribution she has made to our knowledge of South African marine biodiversity.

Remarks. Iotrochota baculifera ( Ridley, 1884) and I. purpurea (Bowerbank, 1875) have been previously reported from East Africa ( Thomas 1973, 1979c, 1981b; Pulitzer-Finali 1993; Richmond 1997). Pulitzer-Finali’s (1993) description of I. baculifera includes one class of styles (170–210 × 6–11 µm), strongyles (250–290 × 5–6 µm) and rare birotulate chelae (14.5 µm) with fibre tracts 120 µm in diameter.

Thomas (1979 c, 1981 b) description of I. baculifera includes only one class of styles (121-182 x 4-8 µm), tornotes (172–245 × 2–6 µm) instead of strongyles, rare birotulate chelae (9–16 µm) and fibre tracts 100 µm in diameter. Iotrochota purpurea , on the other hand, possesses two classes of styles, I (140–180 × 3–8 µm); II (210– 263 × 4–8 µm), no strongyles with rare birotulate chelae (14–16 µm), and fibre tracts 75–95 µm in diameter ( Thomas 1973; Pulitzer-Finali 1993). Iotrochota sinki sp. nov. differs from all three descriptions having three classes of styles, smaller strongyles, numerous birotulate chelae, and larger fibre tracts. Rützler et al (2007) differentiated four species of Iotrochota from Western Atlantic based on a combination of morphology and spicule content. Iotrochota sinki sp. nov. differs from I. nigra by its mottled light yellow-green to brown-green colour, undulating and conulose surface, thickly encrusting to clathrous morphology, and a spicule complement of two category of styles and strongyles, the latter being rarer in I. nigra . Like many species of Iotrochota , specimens of this new species are variable in form, and in details of spiculation.

Key diagnostic characters.

• Sponge light yellow-green.

• Three size categories of styles.

Figures

FIGURE 16. Iotrochota sinki sp. nov. A & B. In situ; C & D. Skeletal architecture (C, x5; D, x 10); E & F. Styles; G. Birotulate chelae.