Xenia flexibilis, Halász & Mcfadden & Toonen & Benayahu, 2019

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 : 205

Xenia flexibilis sp. n.

Fig. 1

Material. Type: ZMB 6105 , Puerto Galera, Mindoro, Philippines, 1931, coll. A. Roxas

Description. The holotype is 20 mm high; its stalk is 10–12 mm long, 22–24 mm wide throughout its length. The base of the stalk has a shallow longitudinal furrow at about the median region on both sides. The polyp body is up to 10 mm long, and the tentacles are up to 4–6 mm long, featuring four rows of pinnules on each side. The pinnules are relatively short and slender, up to 0.50 mm long and 0.15 mm wide, 14–32 in the outermost row with no gap or up to one pinnule-wide space between adjacent pinnules.

Sclerites are ellipsoid platelets, 0.014 –0.017 X 0.015 –0.021 mm in diameter ( Fig.1a, n =24), composed of calcite rods radially arranged at least at the sclerite periphery, thus providing a granular appearance to their fractured surface ( Fig.1a, b ). Under SEM the sclerites often appear in aggregates and the individual ones are cemented together in different orientations ( Fig 1c ). The ethanol-preserved type is white-beige in color.

Etymology. It was decided to retain the species name as it appears at the ZMB.

Remarks. ZMB 6105 was found labelled as Xenia flexibilis Tixier-Durivault, 1971 . A thorough literature survey indicated that it has not previously been referred to elsewhere (http://www.marinespecies.org/ aphia.php?p=taxdetails&id=204396). The current study carefully examined the type and concluded that it is a new Xenia species. The variation in the number of pinnules in the outermost row in the type is quite remarkable, 14–32 pinnules, greater than has been recorded in any other Xenia species. The variation in the number of pinnules is usually smaller, e.g. 26–33 in X. sansibariana May, 1899 , 15– 23 in X. ternatana Schenk, 1896 or as high as 16–27 in X. umbellata Lamarck, 1816 (see ahead).

Similar species and conclusion. Similar to X. flexibilis n. sp., both X. grasshoffi Verseveldt, 1974 and X. bauiana May, 1899 feature four rows of pinnules, and partly overlap in the number of pinnules in the outermost row, with X. flexibilis n. sp. featuring the largest range (15–24, 26–30 and 14–32, respectively). These species also share the same sclerite microstructures ( Figs. 1 , 2 and 8 , respectively), although X. grasshoffi possesses crests on the sclerite surface ( Fig. 8b ), absent in the other two species. It is suggested that the presence of a crest on the sclerite surface might be diagnostic and important for xeniid species identification. Moreover, the range of variation in number of pinnules in the outermost row in X. flexibilis n. sp. is larger than in the other two species, and therefore it is concluded that the three species should be considered as separate.

Distribution. Philippines.

Figures

FIGURE 1. Scanning electron micrographs of polyp sclerites of Xenia flexibilis n. sp. holotype (ZMB 6105). a. Ellipsoid platelets, some fractured; b. Fractured sclerite revealing matrix of calcite rods, more or less radially arranged, at peripheral region; c. Overview of group of sclerites. Scale bar 0.010 mm.

FIGURE 2. Scanning electron micrographs of polyp sclerites of Xenia bauiana May, 1899 syntype (ZMB 3673). a. Ellipsoid platelets, mostly fractured; b. Fractured sclerite composed of dendritic rods, more or less radially arranged in the peripheral region; Scale bar at a 0.010 mm, at b 0.005 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.