Narella horrida ( Versluys, 1906 )

Cairns, Stephen D., 2018, Primnoidae (Cnidaria: Octocorallia: Calcaxonia) of the Okeanos Explorer expeditions (CAPSTONE) to the central Pacific, Zootaxa 4532 (1), pp. 1-43 : 31

Narella horrida ( Versluys, 1906)

Figs. 1N, 15 A –L

Stachyodes horrida Versluys, 1906: 101 –103, pl. 8, fig. 24, figs. 129–133.—K̹kenthal, 1919: 465; 1924: 315.

Narella irregularis Kinoshita, 1907: 233 ; 1908: 49–51, pl. 3, figs. 23–24, pl. 6, fig. 52.

Narella horrida: Cairns & Bayer, 2007: 86 ; 2009: 30.

Types and Type Locality. The holotype of S. horrida consists of a small colony and several branch fragments, deposited at Naturalis (ex ZMA Coel. 3423), and a fragment is also deposited at NMNH (USNM 1097264). Type Locality: Siboga 252, 5˚28.4’S, 132˚0.2’E (off Kei Island, Banda Sea, Indonesia), 204 m.

The type of S. irregularis is untraced. Type Locality: west of Satsuma, Japan, depth unknown.

Material Examined. Holotype: a single colony now in six pieces, and SEM stubs 2487-2492, 2530-2531, EX 1703-2-03, 7.1926˚S, 173.6361˚W (off Pao Pao , Tokelau Islands), 327 m, USNM 1453686 .

Description. The figured specimens ( Fig. 1N) consist of about a dozen (entire colony not collected) unbranched branches, all but one of which originate from a common basal calcareous encrustation about 3 mm in thickness; one bifurcates a branch 1 cm above the encrustation. The longest of the individual branches are about 10 cm in length, altogether producing a small bushy colony. The polyps are evenly spaced at about 3 per cm, each whorl having five or six polyps, space on one side of each branch occupied by a rather large (up to 2.5 mm in diameter) polychaete worm tube produced by the lateral extensions of contiguous basal scales. The whorl diameter is 7–9 mm. The horizontal length of a contracted polyp is 3.0– 3.4 mm.

The basal body wall scales are quite tall (up to 4.3 mm in height) and thick (massive), the distal third to half of the scale constituting a flattened spine ( Fig. 15 B–D, E). The dorsolateral edge of the basal scales are rounded (not ridged) and it, as well as all other body wall and coenenchymal scales, is uniformly granulated. The basal scales are closed in the adaxial position, but the medial and buccals are open. The medial body wall scales are narrower ( Fig. 15F), also massive, but rarely more than 2 mm in length, and also bear one or two elongate distal spines, these spines circular in cross section. The buccal scales are not massive ( Fig. 15G), 1.5–1.7 mm in length, and have a rounded distal edge that forms a cowl ( Fig. 15J) around the opercular crown. The ratio of the length of the body wall scales is thus approximately: 1:0.54: 0.46. The adaxial side of the polyp is mostly covered with three or four pairs of thin, flat, elliptical scales, the greater axes ranging from 0.24–0.41 mm.

The abaxial opercular scales are symmetrical, measuring up to 1.3 mm in length (L:W = about 1.9). The asymmetrical laterals are 0.85–1.1 mm in length (L:W = 1.8–2.2). The small adaxial operculars are about 0.9 mm in length and have an L:W of about 2.6.

The coenenchymal scales ( Figs. 15 K–L) are irregular to elongate in shape, massive (thick, up to 0.08 mm), and non-imbricate. Most are about 0.6–0.7 mm in greater length, but some are as long as 1.1 mm.

Comparisons. Narella horrida is easily distinguished from the other 26 species of Narella having rounded dorsolateral edge of the basal scales, by having prominently spinose basal and medial body wall scales. It belongs to a group of species having massive basal body wall scales and mosaic, non-imbricate coenenchymal scales.

Remarks. The Okeanos specimen differs from the type in having slightly larger polyps (3.0– 3.4 mm vs 2.0 mm) and thus a larger whorl diameter, and in having a primarily unbranched colony, that of the type of N. horrida being sparsely branched. Since all other characters are similar and at least one of the branches of the Okeanos specimen is branched, it is likely that they are conspecific. This would appear to be the first report of this species subsequent to its description in 1906.

Distribution. Banda Sea, Indonesia; Tokelau Islands; off Japan, 204– 327 m.