Plumarella recta ( Nutting, 1912 ), 2013

TAYLOR, M. L., CAIRNS, S. D., AGNEW, D. J. & ROGERS, A. D., 2013, <strong> A revision of the genus <em> Thouarella </ em> Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on <em> Plumarella </ em> Gray, 1870 and <em> Dasystenella </ em>, Versluys, 1906 </ strong>, Zootaxa 3602 (1), pp. 1-105 : 94-97

Plumarella recta ( Nutting, 1912)

Figs 37c,d , 38

Thouarella recta Nutting, 1912: 67–68 , pl. 7, figs 1, 1a, pl. 19, fig. 2; Kükenthal 1919: 440–1; 1924: 302; Aurivillius 1931: 255–256

Thouarella (Thouarella) recta Cairns & Bayer 2009: 28 (listed)

Plumarella recta Cairns 2011:8

Material examined: Holotype, USNM 30040, R/ V Albatross, sta. 5079, south of Omae Zaki , Honshu Island, Japan, 34˚15’N, 138˚E, 475–505 m, 19 Oct 1906, 5 cm fragment.

Description

The colony appears uniplanar, however, branchlets depart the main stem in 3 directions (2 rows at 160˚ creating an almost flat surface, with a third row placed sporadically along the dorsal spine at 260˚), thus it is technically bottlebrush ( Fig. 37c ). The ventral branchlets (in 2 rows) depart alternately from the stem. The branchlets are usually simple, sometimes forked, upwardly inclined at 60˚, and the longest branchlet is 24 mm.

The polyps stand at 90˚ to the branchlets ( Fig. 37d ), 1.2–1.4 mm high, generally isolated in one plane along the branchlet, with a density of 7–9 polyps per cm, and are modestly distally flared ( Fig. 38m ).

The operculum is a raised cone of 8 acute triangle-shaped operculars ( Fig. 38n,c–e ), 260–320 µm high (average 290 µm), 120–230 µm wide (average 165 µm), with a H:W of 1.4–2.3 (average 1.8). The distal and lateral scale edges are serrate although the lateral edges of some are pectinate whilst the proximal edges are roughly lobate. The inner surface is smooth (unkeeled) with a small patch of tubercles in the centre proximally. The outer surface is smooth with several small granules in the central proximal area.

Between 2 and 4 accessory operculars are found underneath the operculars ( Fig. 38a,b ), which are identical to those of P. alternata . They are generally less than 200 µm high and 100 µm wide, round-tipped, tongue-shaped with a small patch of tubercles at the base of the inner surface and a smooth outer surface.

The marginal scales have a circular base with an elongated smooth distal spine. The circular base has a pectinate edge which can continue up the edges of the spine ( Fig. 38f–h ). These scales, 320–840 µm high (average 530 µm), 165–350 µm wide (average 220 µm), with a H:W of 1.4–3.3 (average 2.5), are too long to fold over the operculars. The adaxial marginals are smaller than those found abaxially. The inner surface is smooth with a sparsely tuberculate central circle at the base. The outer surface is smooth with few small granules towards the proximal area of the basal circle.

The body-wall scales are mostly elliptical to fan-shaped ( Fig. 38i–k ), although the shape is obscured by the large pectinate lateral and distal edges. Some are smaller and placed irregularly, disrupting row placement. The body-wall scales are 190–290 µm high (average 230 µm), 255–365 µm wide (average 290 µm) with a H:W of 0.7–1 (average 0.8). The outer surface is smooth with few granules whilst the inner surface has sparse tubercules and a tuberculate proximal edge.

The coenenchymal scales are numerous, small, and circular to elliptical in shape with finely serrate edges ( Fig. 38l ), 100–120 µm high (average 110 µm), 80–160 µm wide (average 125 µm), with a H:W of 0.7–1.4 (average 0.9). The inner surface has only several sparse tubercles whilst the outer surface is smooth with just a few granules.

Distribution

This species is only known from the south coast of Honshu Island, Japan, at depths of 475–505 m.

Remarks

All species of Thouarella have polyps with keeled marginals, however T. recta does not, and was thus transferred to Plumarella ( Cairns 2011) . The mostly smooth, unkeeled inner surface of the operculars and the marginals, the elongated marginals unable to fold over the operculum, and the smooth outer surface of the body-wall scales are characters found in P. recta and common to Plumarella . Unlike Cairns (2011), we keep P. recta and P. alternata as separate species.

The holotype is mostly denuded of polyps making the estimation of the density of polyps per cm tentative.

The longitudinal rows of scales along the polyp body are disrupted with smaller, circular body-wall scales (see Fig. 38m ), which makes counting the number of scales in the two abaxial rows difficult. Nutting (1912) counted 8–9 scales in a longitudinal row. Within this study we count 4–6 large scales in the abaxial rows, discounting smaller proximal circular scales.

Comparisons

Plumarella recta is most similar to P. alternata (see below) except that its polyps stand at 90˚ to the branchlet whereas those of the latter are at 45˚, and roughly alternating. Without being certain of the importance of this morphological feature, and despite the identical appearance of these polyps, these species are kept distinct.

Figures

FIGURE 37. Plumarella alternata, holotype, USNM 30097: a) colony, approx. 16 cm long; b) close up of polyps. Plumarella recta, holotype, USNM 30040: c) colony 5.5 cm long; d) close up of polyps. Photos by RZG.

FIGURE 38. Plumarella recta, holotype, USNM 30040, identical sclerites to those of P. alternata: a) inner and b) outer surface of accessory operculars; c,d) inner and e) outer surface of opercular scales; f,g) inner and h) outer surface of marginal scales; i) outer and j,k) inner surface of body-wall scales; l) coenenchymal scales—first column of scales show the inner surface, remainder are the outer surface; m) lateral view of polyp; n) stereo opercular view of polyp. SEM taken by ZGR.