Xenia crassa 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 : 209-211

Xenia crassa Schenk, 1896

Fig. 5

Xenia crassa Schenk, 1896: 58

Xenia crassa ; Ashworth 1900: 510; Kükenthal 1902: 652; Hickson 1931a: 160; Thomson & Dean 1931: 28; Roxas 1933: 84; Tixier-Durivault 1966: 367; Utinomi 1977: 2–3; non Xenia crassa ; Benayahu 1990: 18, listed only (identified by Reinicke, 1997 as X. novaebritanniae Ashworth, 1900 ); Benayahu 1990: 18 listed only.

Material. Holotype: SMF 39 , Indonesia, Ternate Island, 1894, coll. W. Kükenthal.

Description. The holotype is 18 mm high; its stalk is 13 mm long, 11 mm wide at its base, and 14 mm wide at its uppermost part. The polyp body is 1.5–3 mm long, and the tentacles are up to 3–4 mm long, featuring three and sometimes four rows of pinnules on each side. The pinnules are up to 0.60 mm long and 0.20 mm wide, 13–18 in the outermost row with no gap between adjacent pinnules to a space of up to half a pinnule-width between adjacent pinnules.

Sclerites are present in all parts of the colony. They are ellipsoid platelets, and occasionally a crest is present on their surface ( Fig. 5a, b ). They occasionally feature a furrow on their apical narrow side. The sclerites measure 0.007 –0.014 X 0.012 –0.022 mm in diameter (n=26) and are composed of calcite rods which appear uniform in width ( Fig. 5c ). The sclerite surface is granular, including the crest, and often fractured. The ethanol-preserved holotype is gray and the tentacles are dark-gray in color.

Remarks. Schenk (1896) described Xenia crassa with three irregular rows of pinnules, 15–18 in the outermost one, thus corresponding to the current findings. The dimensions of the sclerites in that study differ from those in the current ones (0.02–0.030 mm vs. 0.007 –0.014 X 0.012 –0.022, respectively). Utinomi (1977: 3) described this species from Japan as featuring three rows of pinnules, 16–19 in the outermost row, and abundant “typical spicules”. That study reported the known distribution of Xenia crassa to include New Caledonia ( Ashworth, 1900), Great Barrier Reef, Australia (Hickson 1931), Malay Archipelago ( Schenk 1896; Thomson & Dean 1931), Philippines ( Roxas 1933) and Madagascar ( Tixier-Durivault 1966). Later, Reinicke (1997: 20) examined the type of X. crassa , compared it to Red Sea material identified by Benayahu (1990: 118), and concluded that the material identified as X. crassa by Benayahu belongs to X. novaebritanniae Ashworth, 1900 .

Similar species and conclusion. Xenia membranacea Schenk, 1896 and X. crassa feature mostly three rows of pinnules and occasionally four. They differ in the number of pinnules in the outermost row (20–25 vs. 13–18, respectively) and in sclerite microstructure, and therefore they should be considered as separate species.

Distribution. Indonesia: Ternate Island, New Caledonia, Great Barrier Reef ( Australia), Malay Archipelago, Philippines, Madagascar.

Figures

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.