Sympodium vegrandis, Benayahu & Ekins & Mcfadden, 2021

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, Zootaxa 5072 (4), pp. 324-350 : 340-341

Sympodium vegrandis sp. n.

Figs. 14B–C , 15 , 16

Material. Taiwan. Holotype: SMNHTAU_ Co _35751, Green Island, IronArtificial Reef (22°38’33”N, 121°28’31”E), 20–26 m, 9 September 2012, coll. Y. Benayahu ; Paratype: SMNHTAU_ Co _37888, Green Island, Lighthouse End (22°40’32.04”N, 121°27’44.58”E), 20–26 m, October 2019, coll. Y. Benayahu.

Description. The syntypes comprise 25–30 small encrusting colonies attached to a fluffy sponge fragment ( Fig. 15A ). Each features up to 15 polyps and measures approximately 2 x 4 mm. There are also a few individual polyps on the sponge surface ( Fig. 15 B ). Some colonies reveal a round outline ( Fig. 15B ) while in others their thin spreading membrane (<0.5 mm) forms an elongate, ribbon-like extension, bearing polyps. All of the colonies in the aggregation are designated as syntypes because it is not possible to separate a single colony as a holotype without compromising its integrity. The majority of the polyps are variously retracted. The few fully expanded polyps are up to 1.5 mm long and their tentacles are approximately 0.5 mm long. There is a single row of 3–4 pinnules on either side of the tentacles, which are almost fully retracted.

The sclerites of the syntypes are ellipsoid platelets, measuring 0.009 –0.010 x 0.012 –0.015 mm in diameter ( Fig. 16A ). They are composed of calcite rods whose tips provide a uniform granular appearance to the sclerite surface ( Fig. 16B ).

Color. The ethanol-preserved syntypes are light cream.

Etymology. The species’ name, vegrandis in Latin, meaning small, diminutive, refers to the size of the colonies.

Variation. The paratype resembles the syntypes.

Remarks. The colonies are characterized by their minute size and sclerites whose diameter is the smallest recorded to date among the congeners. The syntypes uniquely exhibit single (not clustered) polyps that are probably juvenile recruits. The ethanol-preserved syntypes and paratype were sequenced and subsequently assigned to MOTU54 ( McFadden et al. 2019).

Living features. The aggregated live colonies exhibit a distinct bluish/green color ( Fig. 14 B, C )

Distribution. Taiwan (Green Island).

Figures

FIGURE 14. Live colonies of Sympodium species on the reef. (A) Colonies of S. subtilis sp. n. with expanded polyps. (B, C) Colonies of S. vegrandis sp. n. (D, E) Colonies of S. yonaguniensis sp. n.

FIGURE 15. Sympodium vegrandis sp. n.: morphology of type material colonies. (A) Syntypes (SMNHTAU_Co_35751) are small colonies attached to a sponge, with several shown here. (B) Higher magnification of syntypes featuring mostly retracted polyps and a few expanded ones. The encrusting membrane also displays stolon-like extensions bearing polyps.

FIGURE 16. Scanning electron micrographs of sclerites of Sympodium vegrandis sp. n. syntypes (SMNHTAU_Co_35751): (A) Ellipsoid platelets. (B) Tips of calcite rods provide a uniform granular appearance to the sclerite surface.