Grantia kempfi Borojevic & Peixinho, 1976

Figures 130 a–d, 131a–h

Grantia kempfi Borojevic & Peixinho, 1976: 1019, figs 19–20.

Material examined. RMNH Por. 9941, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 63, 7.5833°N 57.0667°W, depth 71 m, sandy bottom, 31 August 1970 .

Description. (Fig. 130 a) Tubular sycon-like sponge, with coarsely spined surface and prominent apical fringe. Length 1.5 cm, diameter 0.5 cm at its widest thickness. Color in alcohol dirty white, fringe shiny white. Consistency firm.

Skeleton. (Figs 130 b–d) Syconoid structure (Fig. 130 b). Cortical ectosomal skeleton (Fig. 130 c) consists of a layer of ‘curly’ triactines with characteristically curved unpaired actine, among which giant diactines protrude far beyond the surface. The chamber layer is a regular system of tubar triactines and a minority of tetractines, aligning the choanocyte chambers with unpaired actine directed outwards. Subatrial triactines distinguished from the tubar triactines by their longer unpaired actines. Atrial skeleton (Fig. 130 d) a mixture of tri- and tetractines, the latter having their apical actines protruding in the atrial cavity. The skeleton of the fringe consists of long thin diactines, the region of attachment to the main body is supported by T-shaped triactines distinct from the tubar, cortical and atrial triactines.

Spicules. (Figs 131 a–h) Giant diactines, fringe diactines, at least four types of triactines, tetractines.

Giant diactines (Fig. 131 a) of the cortical region, asymmetrically fusiform, in a large size range, 168– 727 – 1320 x 15 – 32.6 –51 µm.

Cortical triactines (Figs 131 b), irregularly three-dimensional, with unpaired actines strongly curled, paired actines almost in one plane, rather uniform in size, unpaired actines 57– 106 –129 x 5.5– 6.6 –8 µm, paired actines 54– 73 – 89 x 5 – 6.3 –7.5 µm.

Tubar triactines (Fig. 131 c), with paired actines at a low angle, tending towards being T-shaped, unpaired actines 96– 112 –138 x 7 – 8.2 –9 µm, paired actines 63– 76 – 91 x 6 – 6.8 –8 µm.

Tubar tetractines (Fig. 131 d), with paired and apical actines at a low angle like those of the triactines, unpaired actines 87– 97 –130 x 5 – 5.8 –7, paired actines 57– 92 –105 x 5 – 5.5 –6.5, apical actines 15– 20 – 29 x 3 – 4.4 –6 µm.

Subatrial triactines (Fig. 131 e), sagittal, with curved paired actines, rather uniform in size, unpaired actines 151– 159 –168 x 6.5– 7.4 –8.5 µm, unpaired actines 88– 103 –126 x 5 – 5.4 –6 µm.

Atrial triactines (Fig. 131 f), sagittal, unpaired actines 61– 89 –135 x 6 – 6.3 –7 µm, paired actines 51– 77 –105 x 5 – 5.6 –6.5 µm.

Atrial tetractines (Fig. 131 g), sagittal, largely similar in size and shape to atrial triactines but slightly larger, unpaired actines 60– 123 –195 x 5 – 6.4 –8 µm, paired actines 78– 101 –117 x 4.5– 6.3 –8 µm, apical actines 15– 30 – 66 x 3 – 4.6 –6 µm.

Diactines of the fringe (Fig. 131 h,h1), long, straight, thin, slightly asymmetrical in thickness, 1495– 1748 – 2040 x 3 – 7.6 –12 µm.

Triactines of the oscular membrane (Fig. 131 i), paired actines longer than unpaired actines, with broader outline, T-shaped, unpaired actines 123– 164 –192 x 4.5– 5.7 –8 µm, paired actines 141– 179 –219 x 5 – 7.3 –10 µm.

Distribution and ecology. Guyana Shelf, NE Brazil, on sandy bottoms at 19–71 m depth.

Remarks. Shape and general skeletal characters match closely with the type material from Pernambuco, NE Brazil. Borojevic & Peixinho (1976) (p. 1021) interpreted the curiously curved triactines as ‘triactines des ostioles’. However, this is not my interpretation, as these spicules are numerous and form a distinct cortical layer over the triactines of the chamber region. The spicules with shorter actines indicated as cortical triactines by Borojevic & Peixinho are grading into those lining the choanocyte chambers. They are quite variable with respect to the length of the unpaired actines, and in my opinion belong to the subcortical upper layer of the chamber region. Furthermore there are slight differences in the size ranges of the various spicule types. Nevertheless, I am confident that the more northern and deeper occurrence of the species is well established by the present material.