Grantia aff. indica Dendy, 1913

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160 : 89-92

Grantia aff. indica Dendy, 1913

Figs. 52a–e , 53a–f

? Grantia indica Dendy, 1913: 20 , pl. 2 fig. 3, pl. 4 figs 4–5.

Material examined. ZMA Por. 10223b, Seychelles, Mahé, NE coast, Cap Maçons and Anse de Forbans, 4.7667°S 55.5167°E, depth 0–6 m, snorkeling, coll. R.W.M. van Soest, field nr. NIOP-E stat. 612, 12 December 1992; ZMA Por. 11566b, Seychelles, Amirantes, Île Desnoeufs platform, outer slope, 6.2167°S 53.0167°E, depth 12–15 m, scuba, coll. R.W.M. van Soest, field nr. NIOP-E stat. 738/22, 2 January 1993; ZMA Por. 11749, Seychelles, Amirantes, Île Desnoeufs platform, outer slope, 6.2167°S 53.0167°E, depth 12–15 m, scuba, coll. R.W.M. van Soest, field nr. NIOP-E stat. 738/24, 2 January 1993.

Description. Small white, very ‘hairy’, sycon-like individuals ( Fig. 52a ). Largest specimen squat, 5 mm high, 4 mm in diameter, but smaller specimens ( Figs. 52b–c ) may be more elongate. Fringe of long diactines ( Figs 52b, d ) about 1 mm long.

Aquiferous system. Syconoid.

Skeleton. ( Figs 52d–e ) Skeleton articulate, with long diactines protruding obliquely from the surface, cortical skeleton a layer of larger and smaller sagittal triactines, tubar skeleton consists of rows of triactines. Subatrial skeleton of sagittal tetractines, atrial skeleton of tetractines with long apical actines, protruding into the atrial lumen ( Fig. 52e ). Fringe consists of long diactines supported by sagittal tetractines ( Fig. 52d ).

Spicules. ( Figs. 53a–f ) Diactines, trichoxeas, sagittal triactines, and sagittal tetractines.

Diactines of the main body ( Fig. 53a ), inequiended, blunt at the proximal end, sharp at the distal end, quite variable in length both in the same specimen and among specimens, 276– 641 – 1022 x 10 – 19.4 –24 µm.

Trichoxeas ( Fig. 53b ) of the fringe, inequiended with one end slight swollen and the other sharply pointed, often broken, length of the larger fragments 420–970–2000 µm, thickness 1.5– 4.1 –8 µm.

Cortical triactines ( Fig. 53c ), sagittal with oxhorn-shaped paired actines; unpaired actines 33– 108 –165 x 4 – 6.7 –12 µm, paired actines 66– 80 – 99 x 4 – 5.9 –7 µm.

Tubar triactines ( Figs 53d ), sagittal, with straight or slightly curved paired actines, occasionally T-shaped; length of unpaired actines 45– 73 –120 x 6 – 9.4 –13 µm, paired actines 66– 102 –156 x 7 – 9.7 –12 µm; these also occur in a low number in the fringe.

Subatrial and fringe tetractines ( Figs 53e ), unpaired actine usually longer than paired actine, with short apical actine; unpaired actines 78– 114 –156 x 7 – 8.4 –11 µm, paired actines 48– 90.0 –104 x 7 – 7.7 –9 µm, apical actines 14– 23 – 39 x 3 – 4.7 –7 µm. They occur also in the fringe.

Atrial tetractines ( Figs 53f ), with straight unpaired actines, almost straight paired actines and long slightly curved apical actines; unpaired actines 105– 139 –174 x 8 – 8.3 –10 µm, paired actines 90– 132 –171 x 6 –7.2–8 µm, apical actines 54– 128 –210 x 5 –7.8–9 µm.

Distribution and ecology. Seychelles, shallow reef down to 15 m.

Remarks. The present material shares the shape and the composition of the spicule package with Dendy’s (1913) type, but almost all spicules are smaller and thinner. Dendy is known to frequently cite only the largest measurements for a spicule category. The type was larger (10 x 4.8 mm) than our specimens and that may be an additional cause of the spicule size differences, but it is also possible that our material belongs to a closely related separate species, hence our ‘aff.’ designation. For the time being we emphasize the shared characters.

Unfortunately, our attempt to obtain 28S rRNA sequences failed.

Sycon tabulatum ( Schuffner, 1877) (originally as Sycandra ) has similar shape, but the radial tubes are crowned by a conus of small diactines and there are no giant diactines. The original combination is preoccupied by Sycandra tabulata Hackel, 1872 . Below (section ‘Additional species..’), a new name for Schuffner’s species is proposed.

Figures

FIGURE 52. Grantia aff. indica Dendy, 1913, ZMA Por. 11556b, from the Seychelles, a, three individuals (scale bar = 1 cm), b, light microscopic image of small individual, c, detail of the same, d, light microscopic image of the fringe of trichoxeas supported by tetractines, e, cross section of body wall and atrium, showing syconoid structure and apical actines of atrial tetractines protruding in the atrial lumen.

FIGURE 53. Grantia aff. indica Dendy, 1913, ZMA Por. 11556b, SEM images of the spicules, a, diactines of the cortical skeleton, b, broken fragment of trichoxea from the fringe, c, cortical triactine, d, tubar triactines, e, subatrial tetractines, f, atrial tetractines.