Grantessa tenhoveni, Van Soest & De Voogd, 2015

Grantessa tenhoveni View in CoL sp. nov.

Figures 61a–d View FIGURE 61 , 62a–h View FIGURE 62

Material examined. Holotype ZMA Por. 15509a, Indonesia, Salayar , Guang, in cave, 6.35°N 120.45°E, depth 3–4 m, SCUBA, coll. H.A. Ten Hove, Indonesian-Dutch Snellius II Expedition stat. 152/A3, 28 September 1984. GoogleMaps

Description. A group of anastomosed thick-walled small tubes ( Fig. 61a View FIGURE 61 ), now fragmented. Color white in life and cream in alcohol. Largest tube fragment up to 2 cm high, 1 cm in diameter. No oscular fringe is apparent. Consistency soft, easily damaged.

Histology. Syconoid aquiferous system.

Skeleton. Articulate ( Fig. 61b View FIGURE 61 ). In cross section the skeleton shows a cortical layer of small sagittal triactines with the ends of radial tubes ornamented by a tuft of microxeas. Subcortical skeleton a layer of pseudosagittal triactines ( Fig. 61c View FIGURE 61 ). Choanosomal skeleton ( Fig. 61b View FIGURE 61 ) consists of a neatly organized tubar skeleton of predominantly sagittal tetractines, basal unpaired actines centripetally arranged, with a minority of similar-shaped triactines. Atrial skeleton ( Fig. 61d View FIGURE 61 ) multilayered, consisting of three morphologically distinct types of sagittal tri- and tetractines, (1) sagittal tetractines similar in shape to the tubar tetractines, wih unpaired actines protruding into the atrial lumen, (2) tangentially arranged tri- and tetractines with an elongated unpaired actine that is characteristically swollen in the distal part, lying tangentially in the atrial cortex, and (3) perpendicularly arranged tetractines with very long apical actines protruding far into the atrial lumen, with the basal triradiate system forming the atrial cortex along with (1 and 2). The atrial surface thus appears characteristically bristly.

Spicules. ( Figs 62a–h View FIGURE 62 ) Sagittal triactines, pseudosagittal triactines, sagittal tetractines, diactines.

Cortical diactines of the distal cones ( Fig. 62h View FIGURE 62 ), 63– 77.3 –91 x 3– 4.8 –6 µm.

Cortical triactines ( Fig. 62a View FIGURE 62 ), usual slightly sagittal, actines 51–67.8–100 x 5–6.2–9 µm, (unpaired actines 72– 100 x 6–7 µm, paired actines up to 51–65 x 5 µm).

Pseudosagittal triactines ( Fig. 62b View FIGURE 62 ), longest paired actines up to 90–155.6–239 x 8– 9.6 –14 µm, shortest paired actines 84– 100.8 –141 x 8– 9.3 –12 µm, unpaired actines 69–90.2–108 x 7– 8.9 –11 µm.

Sagittal triactines ( Fig. 62c View FIGURE 62 ) of the radial tubes, unpaired actines up to 66– 177.4 –288 x 6–9.7–14 µm, paired actines up to 39–88.0–123 x 5– 9.1 –12 µm.

Subatrial sagittal tetractines ( Fig. 62f View FIGURE 62 ), variable in shape, unpaired actines 156–220.1–301 x 7–11.6–13 µm, paired actines 96– 113.5 –123 µm, apical actines 18– 33.3 –48 x 7– 8.5 –10 µm.

Atrial sagittal triactines ( Fig. 62d View FIGURE 62 ) with distally swollen unpaired actines with sizes 165– 215.3 –270 x 5.5– 7.3 – 9 µm, paired actines 29– 88.5 –129 x 6– 9.6 –12 µm.

Atrial sagittal tetractines ( Fig. 62e View FIGURE 62 ) with distally swollen unpaired actines with sizes 174–230.2–291 x 7– 8.2 – 10 µm, paired actines 42– 55.2 –63 x 8– 9.8 –12 µm, apical actines 24– 39.6 –54 x 7– 8.1 –10 µm.

Atrial sagittal tetractines ( Fig. 62g View FIGURE 62 ) with very long apical actines up to 660– 840 –960 x 12 µm, actines of the basal triadiate system 60– 96.0 –135 x 5– 7.1 –10 µm.

Ecology. In shallow-water reef caves.

Distribution. Known only from the type locality, the island of Guang, W of Salayar, Indonesia.

Etymology. Named after our colleague, serpulid specialist Dr Harry A. Ten Hove, who collected the present material, and to acknowledge his friendship exhibited during many biodiscovery expeditions.

Remarks. The species differs from most Grantessa species in having tetractines supporting the walls of the choanosomal tubes, and the long apical actines of the atrial tetractines are also characteristic. Our new species is close to Grantessa intusarticulata ( Carter, 1886) , originally from SE Australia, but subsequently reported from several wideranging localities (Western Australia, New Zealand, Japan, see Burton, 1963). The habitus and general spiculation matches that species. The differences appear to be mostly in the sizes and shapes of the spicules, with the extreme length of the apical actines of the atrial sagittal tetractines as the most salient. Moreover, cortical diactines in our specimens are longer than those cited by Carter. South African Grantessa ramosa ( Haeckel, 1872) as described by Borojevic (1967a) is also closely similar but likewise differs in lacking the very long protruding apical actines of the atrial tetractines, and the cortical diactines are longer.

From Grantessa borojevici sp.nov. described above, the new species differs in shape, surface characteristics, size of diactines of the distal cones, presence of tubar tetractines, shape and size of the atrial tetractines, and the prolonged apical actines of many atrial tetractines. The present material originated from shallow caves, whereas G. borojevici sp.nov. is bathyal.

Genus Heteropi a Carter, 1886