Litophyton obtusum Van 2020, sp. nov.

Litophyton obtusum sp. nov.

(Figs. 31c, 32c, 36)

Material examined. Holotype NTM C4164, Queensland, Great Barrier Reef, Brewer reef, reef flat, 8 February 1981, coll. Z. Dinesen; paratypes: NTM C4035; Queensland, Great Barrier Reef, Davies reef, depth 5-10 m, 16 April 1981, coll. Z. Dinesen; NTM C4134, Queensland, Great Barrier Reef, Myrmidon reef, depth 10-15 m; 23 November 1980, coll. Z. Dinesen; NTM C4137, Queensland, Great Barrier Reef, Davies reef, depth 10-15 m, 16 April 1981, coll. Z. Dinesen; NTM C4138, Queensland, Great Barrier Reef, Dip reef, depth 15-20 m, 5 February 1981, coll. Z. Dinesen; NTM C4155, Queensland, Great Barrier Reef, Davies reef, depth 1-5 m, 16 April 1981, coll. Z. Dinesen; NTM C4237, Queensland, Great Barrier Reef, Flinders reef, depth 1-5 m, 20 November 1981, coll. Z. Dinesen; NTM C4327; Queensland, Great Barrier Reef, Rib reef, depth 10 m, 5 October 1980, coll. Z. Dinesen; NTM C4356, Queensland, Great Barrier Reef, Myrmidon reef, depth 10-15 m, 3 February 1981, coll. Z. Dinesen; NTM C4365; Queensland, Great Barrier Reef, John Brewer reef, depth 10-15 m; 7 February 1981, coll. Z. Dinesen; NTM C4373, Queensland, Great Barrier Reef, Myrmidon reef, depth 1-5 m, 3 February 1981, coll. Z. Dinesen; NTM C4375; Queensland, Great Barrier Reef, Dip reef, depth 10-15 m, 5 February 1981, coll. Z. Dinesen; NTM C4377, Queensland, Great Barrier Reef, Dip reef, depth 15-20 m, 5 February 1981, coll. Z. Dinesen; NTM C4394, Queensland, Great Barrier Reef, Dip reef, depth 5-10 m, 9 October 1981, coll. Z. Dinesen; NTM C5391, Queensland, Great Barrier Reef, Darley reef, 25 November 1982, coll. G. König.

Description. The NTM C4164 holotype is 10.5 cm high and 10 cm wide, the stalk is 1 cm long (Fig. 31c). The polyps are up to 0.7 mm wide and 0.9 mm high, mostly situated on long catkins.

Polyps. With a relatively regular arrangement of sclerites in points (Fig. 32c). Abaxial and lateral point sclerites are spindles with spines, the largest present abaxially, up to 0.50 mm long, laterally they are up to 0.25 mm long (Fig. 36a). Adaxially there are no sclerites, only the tentacles have sclerites in this part of the polyp, small, bent rods, up to 0.10 mm long (Fig. 36 b-c). Supporting bundle very weak and not projecting, composed of spindles, up to 1 mm long, with simple tubercles, more tuberculate at both ends (Fig. 36d).

Surface layer top stalk. Spindles and unilaterally spinose spindles, up to 0.80 mm long, with simple and complex tubercles (Fig. 36e).

Surface layer base stalk. Capstans and derivatives of capstans (Fig. 36 f-g), 0.05-0.20 mm long. Spindles and unilaterally spinose spindles are also present, up to 0.50 mm long, with simple and complex tubercles. The spines of the unilaterally spinose sclerites are very long.

Interior stalk. Spindles, up to 1 mm long (Fig. 36h), with pointed or blunt ends and quite tall complex tubercles (Fig. 36j). The smaller spindles are less tuberculate (Fig. 36i).

Variability. The length of the basal internal stalk spindles does vary, NTM C4377 has the longest, up to 1.80 mm long. Several specimens have rods in the polyp stalk, sometimes in larger numbers than present in L. acutum sp. nov.

Etymology. From the Latin obtusus, blunt, refers to the presence of interior stalk spindles with blunt ends.

Distribution. Great Barrier Reef: Brewer reef, Davies reef, Rib reef, Myrmidon reef, Dip reef.

Remarks. L. acutum sp. nov., L. obtusum sp. nov., and L. territoryensis sp. nov. all have unilaterally spinose sclerites with long spines. The differences are discussed with L. acutum.

The permanent microscope slide of NTM C4356 did not show the characteristic internal spindles of this species, an additional temporary slide did show them.

The species resembles L. capnelliformis (Thomson & Dean, 1931), from Timor, Indonesia, regarding the internal stalk spindles with blunt ends (Fig. 82g). However, L. capnelliformis lacks the unilaterally spinose sclerites in the polyps and in the surface of the stalk. Unfortunately, the polyp sclerite arrangement of L. capnelliformis is not clear due to a large amount of detritus present in the polyps. Therefore, the one polyp drawn (Fig. 82a) could have rods in the adaxial side of the polyp stalk, as others do, the rods are possibly just hidden by the detritus.