Xenia garciae Bourne, 1894

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 : 213-214

Xenia garciae Bourne, 1894

Fig. 7

Xenia garciae Bourne, 1894: 475 , plate 12, Figs. 13–14 ; Xenia garciae ; Ashworth 1900: 520; Kükenthal 1902: 652–653; Gohar 1940: 100–101; Tixier-Durivault 1966: 363; Verseveldt 1970: 210, listed only; Benayahu 1990: 118, listed only; Reinicke 1997: 38–39.

Material. Type: BML 1921.11 .18.1, Indian Ocean, Chagos-Archipelago, Diego Garcia, 1886, coll. G. C. Bourne.

Description. The colony is very small, its stalk is up to 5 mm high and undivided, with polyps tightly packed on the capitulum. Three rows of pinnules are aligned along each of the tentacle margins, 16–22 in the outermost row, separated by less than a pinnule-wide space.

Sclerites are ellipsoid platelets 0.009 –0.016 X 0.016 –0.021 mm in diameter ( Fig. 7 a–d, n=20). A surface crest can occasionally be observed ( Fig. 7a ). The sclerites are composed of calcite rods arranged radially and assembled randomly within the sclerite interior ( Fig. 7c ). The rods are uniform in width throughout their length and provide a granular appearance to the sclerite's surface. Under SEM the sclerites are mostly fractured.

Remarks. The condition of the type of Xenia garciae is poor, probably due to inappropriate preservation; measurements of the colony and polyps could therefore not be made. According to Kükenthal (1902: 652–653), X. garciae features three rows of pinnules, 9–10 pinnules in the outermost row. Later, Gohar (1940) noted that X. garciae collected from the Red Sea, which was the first species to be reported from Hurgada, featured three rows of pinnules, 6–10 pinnules in the outermost row, and “spherical” sclerites, 0.018 –0.025 mm in diameter. That study also noted that the colonies are non-pulsating and that the species is known from Diego Garcia ( Bourne 1894: 475), Maldives ( Hickson 1903: 479), Malay Archipelago ( Thomson and Dean 1931), and at several Red Sea sites (Ghardaqa, Shadwan Island and Qoseir). The above two descriptions do not correspond to the current findings due to the much smaller number of pinnules described. Reinicke (1997) raised doubts concerning the species' presence in the Red Sea since Gohar's material could not be examined by him. Furthermore, colonies referred to by Reinicke (1995) as X. garciae were found in this study to belong to the genus Ovabunda : O vabunda gohari ( Reinicke, 1997) and O. arabica ( Reinicke, 1995) .

Similar species and conclusion. Both Xenia blumi and X. garciae feature three rows of pinnules, 18–20 pinnules in the outermost row and a similar sclerite microstructure. The current findings indicate that X. garciae occasionally features a small surface crest. Therefore, the two species should be considered as separate until further data on freshly collected colonies are available and the extent of these surface crests can be further investigated.

Distribution. Indian Ocean: Chagos-Archipelago.

Figures

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 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.

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.