Narella calamus, Cairns, 2018

Cairns, Stephen D., 2018, Primnoidae (Cnidaria: Octocorallia: Calcaxonia) of the Okeanos Explorer expeditions (CAPSTONE) to the central Pacific, Zootaxa 4532 (1), pp. 1-43 : 29

Narella calamus , n. sp.

Figs. 1P , 14 A–H

Etymology. Named calamus (Greek for a fishing rod), in that the unbranched colony of this species resembles a small fishing rod and is used for the purpose of catching prey.

Types and Type Locality. Holotype, and SEM stubs 2419-2422,2479-2481, USNM 1424208 . Paratypes: EX 1706-10-04, 15.04˚N, 170.87˚W ( Wetmore Seamount , off Johnston Atoll), 1994 m, one colony, USNM 1457388 , 25 July 2017 ; Pisces 4-2672, 21˚30’51”N, 167˚56’22” W ( Necker Ridge ), 1793 m, 15 October 2011 , 1 colony, USNM 1170790 ; Pisces 4-2638, 21˚37’52”N, 167˚49’02”W ( Necker Ridge ), 1746 m, 14 October 2011 , 1 branch, USNM 1171059 . Type Locality: EX 1606-6-03 : 19.4447˚N, 165.79899˚E ( Unnamed Seamount , northwest of Wake Island), 2073 m, 6 August 2016 .

Material Examined. Types.

Description. Only the distal 14.5 cm (27 whorls) of the holotype colony was collected, but in situ photographs of the type show it to be an unbranched colony approximately 77 cm in length ( Fig. 1P ). The color of the colony is white. The whorls are arranged in relatively closely spaced (1.8–2.0 polyps/cm) whorls of four polyps each; the whorl diameter is about 5 mm. The horizontal length of contracted polyps is 4.4–5.0 mm. Polychaete commensalism was not noted.

The basal body wall scales are 1.8–1.9 mm in height, the distal margin serrate (but with rounded apices) and extend only slightly past the proximal portion of the medial scales ( Figs. 14A, C ). The dorsolateral edge of the basal scales are rounded; none of the body wall scales are ridged, all having a smooth to slightly granular outer face. The adaxial edges of the basal scales do not meet (open position, Fig. 14B ). The medial body wall scales ( Fig. 14D ) are much smaller, only 1.1–1.3 mm in length. The buccal scales ( Fig. 14E ) are the largest of the body wall scales, up to 2.4 mm in length and also having a slightly wavy distal edge. The ratio of major body wall scales is: 1: 0.65: 1.2, the buccal scales being larger than the basals. There is one pair of square adaxial body wall scales ( Fig. 14F ), each measuring about 0.5 mm to a side, below which the polyp is naked. All body wall scales are quite thin and thus fragile and often were often broken in collection.

The abaxial opercular scales are symmetrical, up to 2.0 mm in length, with an L:W of about 1.4, often having a bifid tip. The lateral opercular scales are asymmetrical, 1.5–2.3 mm in length, having an L:W of 2.1–2.3; some of the lateral operculars also have a bifid tip. The adaxial operculars are the smallest and most slender, being symmetrical, only 1.5–1.8 mm in length, and having an L:W of 2.5–3.5. All opercular scales ( Fig. 14G ) have a highly concave outer surface.

The coenenchymal scales ( Fig. 14H ) are elongate (up to 1.5 mm in length, with an L:W ranging from 3.5–6.0), thin and imbricate. Most coenenchymals bear one tall longitudinal ridge on their outer surface.

Comparisons. Only two of the 27 known species of Narella that lack a dorsolateral ridge have unbranched colonies, the other species being N. versluysi (Hickson, 1909) (Amphi-Atlantic, 550–3100 m). Narella calamus differs from N. versluysi in having a serrate edge to their basal scales and much longer polyps. Narella calamus and N. macrocalyx have the longest polyps in the genus.

Remarks. The fragility of the corallum may be associated with the depth of capture, deep-living primnoid taxa often having thin scales and thus brittle polyps, which are prone to damage when collected.

Distribution. Off Wake Island, Johnston Atoll, and Necker Ridge, 1746-2073 m.

Figures

FIGURE 1. In situ images of various species: A, Callogorgia cracentis, holotype. B, Calyptrophora lyra, holotype (not in situ). C, C. diaphana, EX1606-9-1. D, C. carinata, holotype. E, C. clarki, EX1605-L3-6. F, C. pourtalesi, holotype. G, C. distolos, holotype. H, Candidella gigantea, EX1606-6. I, Macroprimnoa ornata, holotype. J, Narella virgosa, holotype. K-L, N. aurantiaca, holotype. M, N. merga, holotype. N, N. horrida, EX1703-2-3. O, N. fordi, holotype. P, N. calamus, holotype. Q, N. virgosa, paratype, EX1504-L4-9-4. R, N. macrocalyx, EX1606-7. S, N. hawaiiensis, EX1504-9-2. T, Paracalyotrophora hawaiiensis, EX1703-2-1. U, P. echinata, EX1703-10-1. V, P. spiralis, holotype. W, Plumarella circumoperculum, EX1603-2-3. X, Thouarella hilgendorfi, EX1605-L1-17.

FIGURE 14. Narella calamus, holotype: A–B, stereo views of lateral and adaxial sides of polyp. C, basal scales. D, medial scale. E, buccal scales. F, adaxial buccal scales, in situ. G, opercular scales. H, coenenchymal scales. Scale bars in mm.