Plumarella (Faxiella) abietina (Studer, 1894)

Cairns, Stephen D., 2018, Deep-Water Octocorals (Cnidaria, Anthozoa) from the Galapagos and Cocos Islands. Part 1: Suborder Calcaxonia, ZooKeys 729, pp. 1-46 : 16-18

Plumarella (Faxiella) abietina (Studer, 1894) Figures 3b, 11

Amphilaphis abietina Studer 1894: 65; Menneking 1905: 255-260, pl. 8, figs 7-8, pl. 9, figs 17-20; Versluys 1906: 22; Cairns 2007b: 512 (listed); Cairns and Bayer 2009: 28 (listed): Cairns 2016: 58.

Thouarella (Amphilaphis) abietina Kükenthal 1919: 410-411; 1924: 290.

Not Thouarella abietina Pasternak 1981: 49-50 (= T. vityazi Zapata-Guardiola and López-González 2012).

Plumarella (Faxiella) abietina Zapata-Guardiola and López-González 2012: 372-375, figs 20-22.

Material examined.

Alb-2818, 1 colony in very poor condition (most of its polyps detached) and SEM stubs 2343-2346, USNM 49605; JSL-I-1929, 1 branch, USNM 1406397; holotype.

Types.

Holotype: Alb-3399, MCZ 4802.

Type locality.

1°07'N, 81°04'W (lower continental slope off northwestern Ecuador, at same latitude as Galápagos Islands but about 860 km to the east), 3181 m depth.

Distribution.

Galápagos: east of Santa Cruz and off Roca Redonda, 717-808 m deep. Elsewhere: off Ecuador, 3181 m depth.

Description.

The colony is uniplanar to slightly bushy, the Galápagos specimen (Alb-2818, Figure 3b) measuring 12 cm in height, but it is part of a badly damaged colony that was probably larger. Branching is equal and dichotomous. The upward-directed polyps are usually arranged in pairs but may also occur in whorls of three as well as individually. Polyps are about 2.6 mm in length, about two pairs occurring per cm branch length.

The body wall scales (Figure 11e) are arranged in eight somewhat irregular longitudinal rows, the sclerite formula being: 5 –6:4–5:4– 5: variable. All marginal scales, except for the abaxial marginals, are roughly rectangular, 0.35-0.64 mm in width, and have a straight distal margin that covers only a small proximal part of the opercular scales. The distal edges of the two marginal scales project as small teeth. All body wall scales except for the adaxials become progressively larger and transform to triangular toward the base of the polyp. The adaxial body wall scales (Figure 11a, g) are small (0.25-0.35 mm in diameter) and random (variable) in arrangement, but cover the entire adaxial side of the polyp. The body wall scales are relatively thick, convex, and covered with low ridges; their distal edges are finely serrate. The opercular scales (Figure 11f) are triangular in shape (0.75-1.2 mm in length, L:W = 2.2-2.9), each with an elongate distal process, the length and L:W progressively decreasing from ab- to adaxial side; the operculum is quite prominent (Figure 11 a–c). The outer opercular face is covered with granules basally and short serrate ridges distally; the inner face is also covered with serrate ridges raised into a keel-like structure distally, but having tubercles proximally. The coenenchymal scales (Figure 11h) are elongate (L:W about 4), with a granular outer surface and a tuberculate inner surface.

Comparisons.

This is the deepest of the 37 known species in the genus. Only one other species occurs in this subgenus, P. (F.) delicatula (Thompson and Rennet, 1931), known only from the New Zealand region at 650-2743 m depth ( Cairns 2016). These species are compared by Cairns (2016).

Remarks.

The specimens reported herein are only the second report of the species. It fits the re-description of the holotype given by Zapata-Guardiola and López-González (2012), except that the Galápagos specimen sometimes has polyps arranged in whorls of three.