Xenia viridis 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 : 224-227

Xenia viridis Schenk, 1896

Fig. 15

Xenia viridis Schenk, 1896: 62–63 , plate 2, Figs. 4–8

Xenia viridis ; Ashworth 1900: 516–518 fig. 14; Kükenthal 1902: 649–650; Kükenthal 1911: 309; Thomson & Dean 1931: 26; Roxas 1933: 84 fig. 6; Verseveldt 1960: 246–247 fig. 4c; Tixier-Durivault 1966: 363–5, fig 328; Verseveldt 1971: 63–64; Benayahu 1990: 118, table 1, listed only; Janes 2013; Janes et al. 2014; McFadden et al. 2014a.

Material. Holotype: SMF 42 , Indonesia, Ternate Island, 1894, coll. W. Kükenthal; additional material: SMF 77 , Indonesia, Klein-kei Nuhu , 3–4 m, 1908, coll. Wertau, determined by: W. Kükenthal.

The holotype is 40 mm high; its stalk is 25 mm long, 17 mm wide at its base and 42 mm wide at its uppermost part. The polyp body is up to 3 mm long, and the tentacles up to 3.5–4 mm long, featuring three rows of pinnules on each side. The pinnules are slender, up to 0.50 mm long and 0.25 mm wide, 15–22 in the outermost row with spacing of no gap up to half a pinnule-width between adjacent pinnules.

Sclerites are present in all parts of the colony, less dense in the stalk than in the polyps and lacking in the distal parts of the pinnules. They are ellipsoid platelets, measuring 0.008 –0.013 X 0.013 –0.020 mm in diameter ( Fig. 15 , n=26). Some of the sclerites possess a longitudinal or diagonal-transverse crest ( Fig. 15b ) and some a furrow on their narrow side (see arrow in Fig. 15a ). They are composed of calcite rods arranged radially, but assembled randomly at the sclerite center ( Fig. 15c ). The sclerite surface is granular. The ethanol-preserved holotype is light beige in color, polyps are lighter.

The dimensions of the additional colony examined are similar to the holotype; its polyp body is up to 8 mm long, and the tentacles are up to 6 mm long, featuring three rows of pinnules on each side, 15–20 in the outermost row with a space of up to half a pinnule-width between adjacent pinnules. Sclerites are present in all parts of the colony, measuring 0.010 –0.017 X 0.022 –0.026 mm in maximal diameter (n=24). They are ellipsoid platelets, composed of calcite rods, arranged radially, at least on the sclerite surface. The ethanol-preserved colony is light beige in color.

Remarks. In the original description of X. viridis, Schenk (1896) indicated three rows of pinnules, with 14–15 pinnules in a row and sclerites of 0.010 –0.015 mm in diameter. The number of rows corresponds to the current findings, but the range in number of pinnules was found to be slightly larger, 15–22 in the holotype and 15–20 in the other material. The sclerite dimensions were found to be larger than in the original observation. In his revision of Xeniidae, Kükenthal (1902) indicated the presence of the species in New Caledonia. Verseveldt (1960) reported it in Indonesia, with three rows and 15–17 pinnules, and sclerites 0.017 –0.020 X 0.015 mm in diameter, in full agreement with the type. Reinicke (1997) raised doubts concerning the presence of the species in the Red Sea, based on his examination of the material noted in Benayahu (1990), which he concluded should be assigned to X. crenata Reinicke, 1997 (= O. crenata in Halász et al. 2014 ). In McFadden et al. (2014) two specimens identified as X. viridis were described, bearing three rows and 14–18 pinnules in the outermost one, which partially overlaps with the current re-description of the type.

Similar species and conclusion. Xenia blumi and X. viridis feature three rows of pinnules and an overlapping number of pinnules in the outermost row. They also feature dendritic sclerite microstructures. Unlike X. blumi , X. viridis exhibits crests on the sclerite surface whose suggested taxonomic significance was noted above, and, therefore, it is concluded that these two species should be considered as separate.

Distribution. Indonesia: Ternate Island and Klein-kei Nuhu, Red Sea.

Figures

FIGURE 4. Scanning electron micrographs of polyp sclerites of Xenia plicata Schenk, 1896 holotype (SMF 45). a. Ellipsoid platelets, most fractured; b. Fractured sclerite; c. Fractured sclerite, enlarged, composed of calcite rods, often dendritic and sinuous, and more or less radially arranged in the peripheral region. Scale bar at a and b 0.010 mm, at c 0.001 mm.

FIGURE 5. Scanning electron micrographs of polyp sclerites of Xenia crassa Schenk, 1896 holotype (SMF 39). a. Sclerites with a surface crest, fractured; b. Ellipsoid platelet, mostly fractured; c. Fractured sclerite composed of a latticework matrix of dendritic calcite rods and more or less radially arranged in the peripheral region. Arrows at b, c indicate surface furrow. Scale bar 0.010 mm.

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 7. Scanning electron micrographs of polyp sclerites of Xenia garciae Bourne, 1894 type (BML 1921.11.18.1). a. Sclerite with a surface crest, fractured; b. Ellipsoid sclerites, fractured c. Fractured sclerite composed of a latticework matrix of calcite rods, dendritic and sinuous and radially arranged in the peripheral region; d. Overview of sclerites, fractured. Scale bar at a, b and d 0.010 mm, at c 0.002 mm.

FIGURE 8. Scanning electron micrographs of polyp sclerites of Xenia grasshoffi Verseveldt, 1974 holotype (SMF 2616). a. Ellipsoid platelets, fractured; b. Sclerites with surface crest; c. Fractured sclerites composed of a latticework matrix of dendritic calcite rods radially arranged, at least in peripheral region; d. Overview of variety of sclerites. Scale bar at a, b and c 0.010 mm, at d 0.020 mm.

FIGURE 15. Scanning electron micrographs of polyp sclerites of Xenia viridis Schenk, 1896 holotype (SMF 42). a. Ellipsoid platelets featuring rough granulated surface, arrow indicates surface furrow; b. Sclerites with surface crest, fractured; c. Fractured sclerites composed of a latticework matrix of calcite rods, dendritic and sinuous, and radially arranged in peripheral region. Scale bar at a and b 0.010 mm, at c 0.002 mm.