Corallium niobe Bayer 1964

Corallium niobe Bayer, 1964

(Figure 7 C, tables 1, 2)

Corallium johnsoni: Thomson 1927: 19 (partim).

Corallium niobe Bayer, 1964: 473, fig. 47.— Grasshoff 1982a: 738, 745 (tab. 1).— Grasshoff 1982b: 943, fig. 1, 2.— Carpine & Grasshoff 1985: 13.— Grasshoff 1986: 14.— Grasshoff 1989: 203, fig. 2.— Brito & Ocaña 2004: 287, pl. 49, fig. A- D.— Watling & Auster 2005: 292 (app. 1).—? Fuller et al. 2008: 9 (tab. 1.4.2.1).— Sampaio et al. 2009: 74, fig. 1df.—Simpson & Watling 2011: 370, 377, fig. 7–9.—Watling et al. 2011: 55 (tab. 2.1).— Britayev et al. 2014: 36, fig. 9E.

Material examined. INDEMARES 2010: Avilés Canyon System (Spain, Bay of Biscay), 0 5.08.2010, Stn. DR16, 44º01.509’N – 005º42.898’W, 928 m, some fragments with most of the soft tissues lacking.

Distribution. Corallium niobe is a bathyal species with an amphi-Atlantic distribution. First described from the Straits of Florida (Bayer 1964), it is known from western Atlantic seamounts (New England Seamount Chain, Corner Rise Seamount), Bahamas (Simpson & Watling 2011), Azores, Bay of Biscay, Portugal, Morocco, Strait of Gibraltar, the Canary Islands, and the Cape Verde Islands (Grasshoff 1986, 1989; Brito & Ocaña 2004; Sampaio et al. 2009). Records from northeastern Canada (Fuller et al. 2008; NAFO 2008, name in species lists) need verification. Northernmost records in the eastern Atlantic are from the Bay of Biscay at a 600–1534 m depth interval (Grasshoff 1982b, 1986). The present record agrees with the depth interval already known for the species in this geographic area. Despite its wide distribution, this species is rarely mentioned in the literature. It is probably the most common Corallium in the Atlantic Iberian bathyal, although records are few.

Remarks. Corallium niobe has been recently redescribed by Simpson & Watling (2011) from the northwestern Atlantic. Although it is fragmentary, the material collected in the INDEMARES 2010 expedition agrees morphologically with the colonies studied by these authors except for the size of the autozooids, which are smaller in the Spanish colonies, and by the absence of the pronounced longitudinal grooves on their wall, also depicted by Bayer (1964).

The material examined consists in a few fragments ramified in the same plane, some having second–order ramification, with the largest being 45.0 mm in length and having a few broken branches arising at acute angles (Fig. 7 C). Its cross-section is basally round and 4.0 mm in diameter, thinner and concave distally due to the action of commensal polychaetes (see also Britayev et al. 2014). In some fragments, branches anastomose. Most of the cortex is lacking in the samples, and only a few autozooids are present; these arise from one side of the colony. Contracted autozooids are small, almost as wide (0.98–1.08 mm) as tall (0.94–1.0 mm), cylindrical, not longitudinally grooved, but with 8 evident distal lobes that extend toward base.

The most relevant characteristic of the sclerome is a lack of true double clubs. Only a single, ill-defined double club form was observed in a microslide (0.048 wide and 0.033 mm high). Most of the sclerome consists of 6- radiates (0.050–0.052 mm long and 0.028–0.036 mm wide), 7-radiates (0.048–0.060 mm long and 0.036–0.039 mm wide), 8-radiates (0.055–0.085 mm long and 0.030–0.042 mm wide), a few crosses (0.055–0.060 mm long and 0.052–0.056 mm wide), and other irregular and asymmetrical sclerites with uneven projections. The 8-radiates are the most abundant radiates, with some rather elongated. Cortex and autozooids are white in ethanol.

All the fragments that we have examined have modifications on the front side of the axis resulting from the presence of commensal polychaetes. One worm, identified as Gorgoniapolynoe caeciliae (Fauvel, 1913), was present within its gallery on the axis of a fragment (see Britayev et al. 2014, fig. 9E). This worm has been also noted on C. niobe from the Bay of Biscay by Hartmann-Schröder (1985).

The material at our disposal is scarce. However, its identification as C. niobe is certain. In having cylindrical polyps, and a lack of double-clubs, it is soon distinguished from other Corallium species that occur in the north- Iberian bathyal.

Carpine & Grasshoff (1985) noticed that the material described by Thomson (1927) as C. johnsoni included, in fact, three species, one of them being C. niobe.