Xenia ternatana 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

Xenia ternatana Schenk, 1896

Fig. 14

Xenia ternatana Schenk, 1896: 64 , plate 3, Fig. 16

Xenia ternatana ; Kükenthal 1902: 649; Tixier-Durivault 1966: 359; Verseveldt & Cohen 1971: 62; Benayahu 1990: 118, table 1, listed only; Reinicke 1997: 35–36; Janes 2013; Janes et al. 2014; McFadden et al. 2014a.

Material. Holotype and paratype: SMF 43 , Indonesia, Ternate Island, 1894, coll. W. Kükenthal.

Description. The holotype is the larger colony under SMF 43, 25 mm high; its stalk is 18 mm long, 10 mm wide at its base and 15 mm at its uppermost part. The syntype is 23 mm high; its stalk is 12 mm long, 15 mm wide at its base, 22 mm wide at its uppermost part. The polyp body is up to 3.5–5 mm long, and the tentacles up to 3–3.5 mm long, featuring three rows of pinnules on each side. The pinnules are relatively slender, up to 0.5 mm long and 0.2 mm wide, 15–23 in the outermost row with no gap between adjacent ones.

Sclerites are present in all parts of the colony, more densely arranged on the aboral side of the tentacles and less so in the pinnules. They are ellipsoid platelets, measuring 0.008 –0.015 X 0.017 –0.021 mm in diameter ( Fig. 14 , n=20). Their surface is granular due to the dendritic rods that comprise the sclerite ( Fig. 14c ). Some sclerites feature a distinct longitudinal crest ( Fig. 14c ). The ethanol-preserved holotype is dark gray in color.

Remarks. The original description of X. ternatana by Schenk (1896) indicated two rows of pinnules and 18– 22 pinnules in each row compared to the three rows and 15–23 pinnules in the outermost row as revealed in the present study. The current examination demonstrated that some of the sclerites possess a central crest, resembling those of Yamazatum Benayahu, 2010 . As already indicated, it is suggested that the presence of a crest on the sclerite surface is diagnostic and important for xeniid species identification. Colonies of X. ternatana from various locations in the Red Sea (e.g., Kükenthal 1913; Verseveldt & Cohen 1971; Benayahu 1990) should be re-examined in order to verify the microstructure of their sclerites. Reinicke (1997) examined the type of X. ternatana and other material from the Red Sea, but repeated the original description and not his findings concerning the type; therefore, his material should also be re-examined. In McFadden et al. (2014a) a specimen collected from Indonesia bearing two rows of pinnules was identified as X. ternatana , which does not correspond to the current re-description of the type.

Similar species and conclusion. X. viridis , X. blumi , X. umbellata Lamarck, 1816 and X. ternatana share a similar pinnule arrangement, but differ in their sclerite microstructure ( Figs 15 , 3 , 16 and 14 , respectively), and therefore it is concluded that they should be considered as separate species.

Distribution. Indonesia: Ternate Island.

Figures

FIGURE 3. Scanning electron micrographs of polyp sclerites of Xenia blumi Schenk, 1896 holotype (SMF 44). a. Ellipsoid platelets, fractured; b. Fractured sclerite enlarged; c. Fractured sclerite composed of dendritic rods; d. Overview of sclerites. Scale bar at a, c and d 0.010 mm, at b 0.002 mm.

FIGURE 14. Scanning electron micrographs of polyp sclerites of Xenia ternatana Schenk, 1896 holotype (SMF 43). a. Ellipsoid platelets, most fractured; b. Fractured sclerite composed of dendritic calcite rods; c. Sclerites with surface crest. Scale bar 0.010 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.

FIGURE 16. Scanning electron micrographs of polyp sclerites of Xenia umbellata Lamarck, 1816, neotype (ZMTAU CO 36788). a. Ellipsoid platelets; b. Fractured sclerite enlarged, composed of a latticework matrix of calcite rods, in part aligned horizontally on surface; c. Fractured sclerite; d. Overview of sclerites. Scale bar at a, c and d 0.010 mm, at b 0.002 mm.