Flagelligorgia gracilis, Cairns, Stephen D. & Cordeiro, Ralf T. S., 2017

Cairns, Stephen D. & Cordeiro, Ralf T. S., 2017, A new genus and species of golden coral (Anthozoa, Octocorallia, Chrysogorgiidae) from the Northwest Atlantic, ZooKeys 668, pp. 1-10 : 2-6

Flagelligorgia gracilis sp. n. Figs 1, 2, 3, 4

Material examined

(Types). Holotype: Alb-2666, 1 specimen now in two pieces, USNM 49503. Paratypes: Alb-2601, 34°39'15"N, 33°30'10"W, 196 m, 1 colony, USNM 16607, 18 October 1885; Alb-2602, 34°38'30"N, 75°33'30"W, 227 m, 1 colony, USNM 16821, 18 October 1885; Alb-2666, 30°47'30"N, 79°49'W, 494 m, 33 colonies, SEM stubs 2364-2367, USNM 14458, 5 May 1886; Alb-2667, 30°53'N, 79°42'30"W, 499 m, 40 colonies, USNM 14457, 5 May 1886; Gerda-179, 27°41'N, 79°11'W, 549-567 m, 9 colonies, USNM 57315, 1 July 1963; Megalopa, 11.2 km SSE of Carysfort Reef, Florida Keys, 205 m, 9 July 1950, 1 colony, USNM 51956, 9 July 1950; Pillsbury-105, 31°00'N, 79°42'W, 388-403 m, 2 colonies, USNM 57316, 27 July 1964; Pillsbury-197, 27°59'N, 79°20'W, 567-586 m, 2 colonies, USNM 52913, 11 August 1964.

Type locality.

30°47'30"N, 79°49'W (continental slope off Georgia), 494 m depth.

Description.

The colony is unbranched (flagelliform) and quite delicate, with an ascending clockwise spiral growth form (Fig. 1A, 2C). One of the largest specimens (the holotype) is 19 cm in length and only 1.1 mm in basal stem diameter. Colonies are attached to hard objects such as the deep-water coral Lophelia pertusa (Linnaeus, 1758), rocks, or echinoid tests, having a thin basal encrustation (holdfast) up to 7 mm in diameter; there are no root-like holdfasts. The axis is longitudinally grooved (Fig. 2D), resulting in four rounded longitudinal cords (1C, E), reflecting the underly ing undulated layers of scleroprotein (Fig. 1D), most easily seen in stem cross section. The axis is golden, the coenenchymal tissue usually pale brown to a dull yellow, in ethanol. Polyps are lacking from the proximal 45-50 mm of the stem, which is approximately 1/5-1/3 of the colony length, depending on its maturity (Fig. 1A). Polyps occur biserially, on opposite sides of the stem in alternating fashion (Figs 1B, 2A, C), and are relatively closely spaced such that 1.1-1.4 polyps occur per cm length. The polyps are 0.9-1.2 mm in length and are somewhat cigar-shaped (Fig. 2C), being slightly tapered distally; the greatest diameter (0.35-0.39 mm) is usually at mid-length. The body wall is covered with longitudinally oriented, elongate (L:W = 4.5-5.8), imbricating scales (Fig. 3B) that measure 0.17-0.24 mm in length. They are rounded distally, have smooth lateral edges, and are quite thin (e.g., 13-15 µm in thickness). Their outer and inner surfaces are smooth. Toward the end of the polyp are smaller scales associated with the tentacles (Figs 2B, 3D), similar in shape to the body wall scales but only 0.075-0.10 mm in length. Pinnular sclerites are virtually absent. Scales show concentric bands of interference colors in polarized light. There are no sclerites in the axial sheath of coenenchyme. The outer coenenchymal scales (Fig. 3A) are also longitudinally arranged on the stem, elongate (L:W = 4.8-7.9), and imbricate. They have pointed tips and their lateral edges are slightly serrate, each serration up to 5 µm in height; they are also quite thin, and their faces are also smooth. Coenenchymal scales on the first few centimeters of the stem are highly granular (Fig. 3C).

Remarks.

As in other unbranched octocorals, such as species of Radicipes , some specimens (e.g., from USNM 14458, USNM 51956 and USNM 14457) host commensal ophiuroids. Other octocoral species found at the same stations at which Flagelligorgia were collected include: Plumarella aurea (Deichmann, 1936), Plumarella pourtalesii (Verrill, 1883), Plumarella dichotoma Cairns & Bayer, 2004, Swiftia casta (Verrill, 1883) and Callogorgia americana Cairns & Bayer, 2002.

Distribution.

Southeastern coast of United States from off Outer Banks, North Carolina to off Carysfort Reef (near Key Largo, Florida) (Fig. 4), 196-567 m depths.

Etymology.

Named gracilis (Latin for slender, gracile), in allusion to the very slender aspect of the colony.