Xenia blumi 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 : 207-209

Xenia blumi Schenk, 1896

Figs. 3 , 4

Xenia blumi Schenk, 1896: 65–66 ; May 1899: 81–82; Kükenthal 1902: 650; Roxas 1933: 83; Gohar 1940: 98–99; Verseveldt 1965: 45–46; Tixier-Durivault 1966: 365, fig 329; Utinomi 1977: 4; Benayahu 1990: 118, table 1, listed only.

Xenia plicata Schenk, 1896: 66–67 — new synonym; Kükenthal 1902: 647; Tixier-Durivault 1966: 363, fig 327; Utinomi 1977: 6–7; Benayahu 1990: 118, table 1, listed only

Material. Holotype: SMF 44 , Indonesia, Ternate Island, 1894, coll. W. Kükenthal; X. plicata Holotype: SMF 45 , Indonesia, Ternate Island, January 1894, coll. W. Kükenthal.

Description. The holotype of X. blumi is 30 mm high; its stalk is 22 mm long and 20 mm wide at its base, 25 mm wide at the uppermost part. The polyp body is up to 5.5 mm long, and the tentacles up to 3 mm long. Tentacles bear three rows of pinnules, 18–20 in the outer row. The pinnules are up to 0.40 mm long and 0.15–0.20 mm wide, with no gap between adjacent pinnules.

Sclerites are mostly ellipsoid platelets, 0.008 –0.012 X 0.014 –0.018 mm in diameter ( Fig. 3a, n =23). Under SEM they are mostly fractured thus enabling observation of the internal radially arranged calcite rods, occasionally branching towards the surface of the sclerite ( Fig. 3b, c ). Side view of the sclerites reveals their ellipsoidal platelet morphology ( Fig. 3d ). The ethanol-preserved holotype is gray in color. Unfortunately, the holotype is badly preserved and, therefore, the number of pinnule rows and the number of pinnules on the outermost row could not be clearly determined.

The holotype of X. plicata is 35 mm high; its stalk is 30 mm long, 12 mm wide at its base, and 15 mm wide at its uppermost part. The polyp body is up to 6 mm long, the tentacles up to 2–4 mm long, featuring three rows of pinnules on each side. The pinnules are relatively slender, 16–22 in the outermost row with no gap between adjacent pinnules. Sclerites are present in all parts of the colony; they are ellipsoid platelets, measuring 0.007 – 0.012 X 0.014 –0.017 mm in diameter, some of which are fractured ( Fig. 4a, n =22). They are composed of radially arranged calcite rods, uniform in width throughout their length and occasionally branched at their distal end ( Fig. 4b, c ). The surface of the sclerites is granular and often fractured. The ethanol-preserved holotype is gray in color.

Remarks. The original description of X. blumi indicated three rows of pinnules, 18–20 pinnules in the outermost row, and sclerites of 0.015 –0.020 mm in diameter. Later, May (1900) described colonies of this species without examining the type. May's material was examined by Reinicke (1997), who compared it to the type and concluded that it did not belong to that species. The four specimens identified as X. blumi in Benayahu’s study (1990) were re-examined during the present study and also found not to belong to that species, as suggested by Reinicke (1997). Gohar (1940: 98–99) described a colony of X. blumi from the Red Sea, indicating two to three rows of pinnules and 10–16 pinnules in pulsatile polyps. These morphological characters do not correspond to the original description of that species (three rows of pinnules, 18–20 in the outermost row). Utinomi (1977) described X. blumi and X. plicata from Japan, and similarly neither of them correspond to the current description of the type.

Similar species and conclusion. X. blumi and X. plicata feature three rows of pinnules, with 16–22 and 18–20 pinnules in the outermost row, respectively. The present study confirms that these species share similar sclerite microstructure and therefore should be synonymized, giving a chronological priority to X. blumi , as suggested by Reinicke (1997: 18–22). The types of X. viridis Schenk, 1896 and X. blumi feature overlapping numbers of rows of pinnules and numbers of pinnules, but differ in sclerite microstructure. The sclerites of X. viridis occasionally reveal surface crests, which are lacking in X. blumi , thus the two species should be considered as separate.

Distribution. Indonesia: Ternate Island, Philippines, Madagascar.

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 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.