Sympodium arbusculum Benayahu & Ekins & Mcfadden 2021, sp. n.
Creators: name: Benayahu, Yehuda
name: Ekins, Merrick
name: Mcfadden, Catherine S.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Alcyonacea
Xeniidae
Sympodium
Sympodium arbusculum

description: Sympodium arbusculum sp. n.
Figs. 1, 2, 3A
Material. Madagascar. Holotype: SMNHTAU_ Co _36017, Ankaréa (12°50.054’S, 48°34.563.3’E), 6–9 m, 29 November 2012, coll. Y. Benayahu; Paratypes: SMNHTAU_ Co 38226, five colonies, same details as the holotype; SMNHTAU_ Co _36015, same details; Tanzania, SMNHTAU_ Co _32919, Shundo (4°52’53”S, 39°18’10”E), 0–25 m, 10 December 2004, coll. Y. Benayahu; Kenya. SMNHTAU_ Co _31143, off Mombasa, Turning Buoy, 10 m, 16 February 2001, coll. Y. Benayahu & S. Perkol-Finkel; SMNHTAU_ Co _31153, same details; SMNHTAU_ Co _31163, off Mombasa, Simon’s Corner, 20–26 m, 20 February 2001, coll. Y. Benayahu & S. Perkol-Finkel; Kenya, SMNHTAU_ Co _31173, off Mombasa, Shelly Beach, 10–12 m, 20 February 2001, coll. Y. Benayahu & S. Perkol-Finkel; SMNHTAU_ Co _31495, off Likoni, Shelly Reef (4°06.4’S, 39°41’S), 19 m, 9 March 2002, coll. Y. Benayahu; SMNHTAU_ Co _31512, off Likoni, Wall (4°06.4’S, 39°42’E), 15–27 m, 2 February 2002, coll. Y. Benayahu; SMNHTAU_ Co _31590, off Likoni, Shelly Reef (4°06.4’S, 39°41’E), 19 m, 9 March 2002, coll. Y. Benayahu.
Description. The holotype is an encrusting colony attached by a membrane to calcareous fragments, and measures 1.9 x 1.5 cm (Fig. 1A). Its soft basal membrane is thin, <1 mm thick. Clusters of non-retractile polyps bud off at different levels, occasionally dichotomously, to form small branched groups of polyps (Fig. 1A). Occasionally, individual polyps arise from the membrane between the clustered polyps. The polyps that are the most expanded are up to 4 mm long and the tentacles are up to 1 mm long. The poor preservation state of the sample prevents a precise pinnule count, but it is estimated to be a single row with up to 10 slender and pointed pinnules on either side of the tentacle.
The sclerites of the holotype are ellipsoid platelets, abundant throughout the colony, 0.010 –0.011 x 0.015 –0.017 mm in diameter (Fig. 2A). They are composed of tightly packed calcite rods whose tips provide a uniform granular appearance to the sclerite surface (Fig. 2B)
Color. The ethanol-preserved colony is light cream..
Etymology. The species’ name is derived from the Latin ‘arbuscula’, bush, referring to the clustered arrangement of polyps.
Variation. The paratype SMNHTAU_Co_38226 comprises four colonies that vary in size: the smallest colony measures 1.0 x 0.5 cm and the largest one 3.5 x 1.5 cm (Fig. 1B: one of the paratypes). Groups of polyps comprising these paratypes range in number of polyps from 4 to 18, and are up to 20 mm long from the basal membrane to the tip of the uppermost polyp. The paratype SMNHTAU_Co_36015 comprises eight colonies or fragments that resemble the holotype, except in size. The dichotomous arrangement of the polyps is visible (Fig. 1C, D). Both the dimensions of the paratypes’ sclerites (Fig. 2C) and their surface microstructure (Fig. 2D) correspond to those of the holotype (Fig. 2A, B).
Remarks. The morphology of the colonies, and in particular the arrangement of the non-retractile polyps in clusters, is considered to be diagnostic of the species. The holotype was sequenced and subsequently assigned to MOTU38 (McFadden et al. 2019).
Living features. The live brownish colonies feature clusters of expanded polyps (Fig. 3A).
Distribution. Kenya, Madagascar, Tanzania.
description: Published as part of Benayahu, Yehuda, Ekins, Merrick & Mcfadden, Catherine S., 2021, Overview of the genus Sympodium Ehrenberg, 1834 (Octocorallia, Alcyonacea, Xeniidae), with the description of new species, revealing regional endemism, pp. 324-350 in Zootaxa 5072 (4) on pages 328-331, DOI: 10.11646/zootaxa.5072.4.2, http://zenodo.org/record/5748862