Chrysogorgia Duchassaing & Michelotti, 1864.

(after Cairns (2001) and Pante et al. (2012)). Calcaxonians having an unjointed, solid (non-spicular), concentrically layered scleroproteinous axis. The axial layers are usually smooth (not undulated) and thus not longitudinally grooved externally; the axis usually displays metallic or iridescent reflections. The colony may be branched or unbranched (flagelliform), arising from a root-like or discoidal, strongly calcified holdfast. Polyps are contractile but not retractile, arranged in rows (uniserial, biserial or multiserial), but never in whorls. Sclerites predominantly flat, smooth scales, in some species warty rods and spindles.

Fourteen genera have been assigned to the Chrysogorgiidae, but based on sequencing of three genes, Pante et al. (2012) have suggested that only six of these genera belong to Chrysogorgiidaesensu stricto, which they call the Monophyletic Chrysogorgiidae Clade, or MCC. They imply that the other genera may belong to as many as three other, as yet undescribed, families. The six genera of the MCC are keyed by Pante and France (2010) and their worldwide distributions plotted by Watling et al. (2011). They are further discussed by Pante et al. (2012) in the context of a phylogenetic analysis. Flagelligorgia is morphologically most similar to Radicipes, which is part of the MCC, but lacking material suitable for molecular analysis, the placement of Flagelligorgia in that family can only be a suggestion at this time. In fact, we did attempt to sequence four genes (COI, mtMutS, 28S and 18S) from specimens collected in 1964 with no results.

Worldwide, 31–4492 m depths (Pante and Watling 2011: 6).

Flagelligorgia gracilis, here designated. Gender: feminine.

Colonies unbranched (flagelliform), loosely coiled, attached by a holdfast; axis composed of undulating concentric layers (Figs 1C–E, 2D). Polyps arranged biserially. Body wall and coenenchymal scales elongate, smooth scales. Polyps lack an operculum.

Until 1956 (Bayer 1956) the Chrysogorgiidae had been divided into three subfamilies, one being the Lepidogorgiinae Versluys, 1902, consisting of genera with an unbranched colony and lacking polyp opercula. However, the subfamily classification has been ignored for decades and is not supported by molecular evidence. Nonetheless, it is incumbent to compare Flagelligorgia to the four other unbranched chrysogorgiid genera. Helicogorgia Bayer, 1981, known only from the east coast of Africa at 66–775 m depth range, is unbranched but has its polyps arranged in a multiserial fashion on one side of the stem, a naked track displayed on the opposite side. Furthermore, its body wall scales are irregular plates and its coenenchymal scales are spindles. For all of these reasons Helicogorgia is easily distinguished from Flagelligorgia. Based on sequencing of three genes, Pante et al. (2012) indicate that Helicogorgia might constitute a family on its own, as sister to the Chrysogorgiidae. Helicogorgia was revised by Williams (1992), recognizing four species in the African coast.

Chalcogorgia Bayer, 1949, known only from its type locality off northwestern Cuba at 708 m depth, is also unbranched and has biserially arranged polyps, like Flagelligorgia, but differs in having eight triangular opercular scales on each polyp, and body wall scales shaped as irregularly shaped platelets. According to Pante et al. (2012: 8), based on “very limited data,” Chalcogorgia was suggested to ally with Helicogorgia, and thus also outside of the MCC.

Distichogorgia Bayer, 1979, known only from the Blake Plateau off Florida at 814 m depth, is unbranched and has biserially arranged polyps, but differs in having unique body wall scales consisting of two fans of longitudinally arranged, blade-like scales, one on each side of the polyp, interspersed with tiny pointed sclerites, similar to its coenenchymals. Pante et al. (2012) did not report sequencing data for this genus, but based on its biserially polyps, they suggested an affinity with Helicogorgia and Chalcogorgia in a family separate from the Chrysogorgiidae.

Perhaps most similar to Flagelligorgia is the genus Radicipes Stearns, 1883, consisting of 9–10 species (see Cordeiro et al., in press), which occurs worldwide at depths of 241–3580 m. Radicipes is unbranched but differs from Flagelligorgia in having uniserially arranged polyps, and a body wall and coenenchymal sclerites that are rod-shaped to compressed rod-shaped. Furthermore, chrysogorgiids (MCC), including Radicipes, are characterized by having an axis formed by non-undulated (smooth) concentric layers (Bayer 1956), which is not the case for Flagelligorgia. Based on molecular evidence Pante et al. (2012) placed Radicipes firmly in the Chrysogorgiidae clade (MCC), as the sister genus to Chrysogorgia. Lacking molecular evidence for Flagelligorgia (all specimens are quite old), it is not possible at this time to determine if it is allied with Radicipes in the Chrysogorgiidae (based on similarity of body wall sclerites) or the other cluster of genera including Helicogorgia, Chalcogorgia and Distichogorgia (based on polyp arrangement), which may constitute an as yet undescribed family.

Off Southeastern United States from North Carolina to Florida, 196–567 m depths.

The name is a combination of flagellum (Latin for small whip) and gorgia (a common octocoral suffix and once the name of the order Gorgonacea, the name derived from the mythical female monster, the Gorgon), in reference to the flagelliform nature of the colony.

(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.

Figure 1. 

Diagnostic characters of Flagelligorgia gracilis sp. n. A general view of the holotype (USNM 49503) attached to a rocky substrate B detail of the holotype showing the biserial arrangement of polyps C,E cross-section of the stem of the holotype showing its four rounded longitudinal cords D detail of undulating concentric layers of the stem in cross-section. Scale bars: A: 10 mm, B: 5 mm, C, E: 0.1 mm, D: 0.01.

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

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 underlying 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).

Figure 2. 

Detailed view of polyps and axis in Flagelligorgia gracilis sp. n. (USNM 14458) through Scanning Electron Microscopy. A stereo view of polyps B oral view of a polyp C stereo view of a polyp’s abaxial side D stereo view of the axis. Scale bars: A, C: 0.2 mm, B: 0.04 mm, D: 0.01 mm.

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.

Figure 3. 

Sclerites of Flagelligorgia gracilis sp. n. (USNM 49503, holotype). A rods from coenenchyme B elongate rods from body wall C highly granular scales from first centimeters of the stem D tentacular scales. Scale bars: A–C: 0.05 mm, D: 0.02 mm.

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.

Figure 4. 

Distribution map of Flagelligorgia gracilis sp. n.

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