Xenia rubens Schenk, 1896

Halász, Anna, Mcfadden, Catherine S., Toonen, Robert & Benayahu, Yehuda, 2019, Re-description of type material of Xenia Lamarck, 1816 (Octocorallia: Xeniidae), Zootaxa 4652 (2), pp. 201-239 : 222

Xenia rubens Schenk, 1896

Fig. 13

Xenia rubens Schenk, 1896: 67–68

Xenia rubens ; Kükenthal 1902: 647–648

Material. Type: SMF 46 , Indonesia, Ternate Island, 1894, coll. W. Kükenthal.

Description. The type is 60 mm high; its stalk is 45 mm long and splits 30 mm above the base into two branches; one branch is 20 mm long, 12 mm wide at its base and 18 mm wide at its uppermost part. The other branch is 18 mm long, 22 mm wide at its base and 35 mm wide at the uppermost part. The polyp body is up to 4 mm long, and the tentacles are up to 3 mm long. Mostly four rows of pinnules are aligned along each of the tentacle margins, occasionally 3 and even 5 rows, with 12–19 pinnules in the outermost row. The pinnules are relatively short and stout, up to 0.3 mm long and 0.15 mm wide, with spacing of no gap to up to a half pinnule-width between adjacent pinnules.

Sclerites are mainly ellipsoid platelets that appear in all parts of the colony, 0.009 –0.013 X 0.011 –0.023 mm in diameter ( Fig. 13a, c, n =20). Some sclerites may feature a slightly rectangular outline and others are either round or elongated. Their surface appears uniformly granular with no fractures. Broken sclerites reveal the internal structure to consist of radial rods at the periphery and a centrally located void within their center (Fig. b). The ethanolpreserved type is light beige-yellow in color.

Remarks. In the original description Schenk (1896) indicates that X. rubens features 5–6 irregular rows of pinnules and 18–20 pinnules in the outermost row, which closely corresponds to the current findings.

Similar species and conclusions. Both X. rubens and X. fusca feature mostly four rows of pinnules and a similar number of pinnules in the outermost row (12–19 and 14–22, respectively). They share a similar type of granular sclerite surface but different internal microstructure ( Figs. 13 and 6 , respectively). Although the latter difference might be rather small, until further data based on freshly collected colonies become available the two species are considered as separate.

Distribution. Indonesia: Ternate Island.

Figures

FIGURE 6. Scanning electron micrographs of polyp sclerites of Xenia fusca Schenk, 1896 syntype (SMF 40). a. Ellipsoid platelets; b. Fractured sclerites composed of a latticework matrix of dendritic calcite rods and more or less radially arranged in the peripheral region; c. Overview of sclerites. Scale at a and c 0.010 mm, at b 0.002 mm.

FIGURE 13. Scanning electron micrographs of polyp sclerites of Xenia rubens Schenk, 1896 type (SMF 46). a. Ellipsoid platelets; b. Fractured sclerites revealing internal void; c. Overview of sclerites. Scale bar at a 0.010 mm, at b 0.002 mm, at c 0.020 mm.