Thouarella viridis Zapata-Guardiola and López-González, 2010a

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 : 69-70

14. Thouarella viridis Zapata-Guardiola and López-González, 2010a

Thouarella viridis Zapata-Guardiola & López-González, 2010a: 169–180 , figs 7–10.

Holotype (not examined): ZMH C11744, ANT XIX/5, sta. PS61/164–01, west of South Georgia, Antarctica, 53˚23.8’S, 42˚42.03’W, 312.5–321.6 m, 9 Apr 2002.

Material examined: Paratype, USNM 1128949, Antarktis XIX/5, R/ V Polarstern, sta. PS61/167–01, west of South Georgia Island, sub-Antarctic, 53˚23.68’S, 42˚42.23’W, 306–342.7 m, 9 Apr 2002, 1 colony, 1 fragment .

Other material: USNM 1130303 and USNM 98027 (same location), R/ V Eltanin, cruise 22, sta. 1536, west tip of South Georgia Island, sub-Antarctic, 54˚30’S, 39˚20’W, 659–686 m, 8 Feb 1966 ; USNM 78401, R/ V Eltanin, cruise 5, sta. 217, Le Maire Strait, Tierra del Fuego, Argentina, 54˚22’S, 64˚42’W, 106–110 m, 23 Sep 1962; ZMH , R/ V W. Herwig, sta. 328, Patagonian Shelf, SW Atlantic, 42˚52’S, 58˚38’W, 1200 m, 22 Feb 1971; ZMH , R/ V W. Herwig, sta. 285, Patagonian Shelf, SW Atlantic, 42˚19’S, 58˚01’W, 825 m, 21 Jun 1966; ZMH , R/ V W. Herwig, sta. 311, Patagonian Shelf, SW Atlantic, 46˚54’S, 60˚28’W, 480 m, 18 Feb 1971; ZMH , R/ V W. Herwig, sta. 243, Burdwood Bank, SW Atlantic, 54˚57’S, 56˚54’W, 500 m, 04 Feb 1971; ZMH , R/V W. Herwig, sta. 271, south Falkland Islands, sub-Antarctic, 52˚40’S, 60˚39’W, 405 m, 09 Feb 1971 .

Description

Description modified from Zapata-Guardiola and López-González (2010a).

The holotype consists of a fragment of one colony. Branching is in at least 3 directions, and thus bottlebrush, however branches can be curved, giving the colony a bilateral appearance. The branchlets are up to 30 mm long, at a density of 7–8 per cm, and usually simple with occasional secondary branching. Fresh specimens are a shade of green, fading to white after preservation. The axis is ochre coloured, stiff and thick, with a basal axis diameter of 4 mm.

The polyps are clavate with a conical operculum, 1.5–2.5 mm high, isolated (occasionally opposite) but emanating from branchlets in irregular spirals. The polyps are more clustered towards the branchlet tip and sparser at the base, with an average density of 14–15 per cm. The polyps have 8 longitudinal rows of body-wall scales, 6–7 scales in each abaxial row.

The operculars are lanceolate to arrow-head shaped, some with a wide bilobate base, and are 620–780 µm high and 470–640 µm wide. The inner surface bears a prominent simple keel that often has lateral projections and adjacent longitudinal ridges; tubercles densely cover the proximal third of the scale. The outer surface is deeply longitudinally concave, corresponding to the keel on the inner surface whilst the proximal region has radial striations extending from a proximal centre, and granules distally.

The marginal scales are pentagonal to widely trianglular in shape, 450–630 µm high and 470–640 µm wide. The inner surface has a wide, multiple keel with ridges adjacent and tubercles cover the proximal two-thirds to three-quarters of the inner surface. The outer marginal surface is covered with low relief granules that are more concentrated proximally.

The body-wall scales and submarginals cannot be differentiated. Both are fan-shaped with a rounded distal edge, wider than they are high, 270–510 µm high, 340–740 µm wide, decreasing in size towards the polyp base. The inner surface is tuberculate, with a smooth distal band broken by several ridges perpendicular to the distal scale edge with the occurrence of ridging decreasing from polyp tip to its base. The outer scale surface is similar to that of the marginals. All polyp sclerites of this species have a coarsely lobate proximal edge.

The coenenchymal scales are round to elliptical in shape and up to 130–360 µm high. The inner surface is tuberculate and the outer surface has closely spaced granules that stretch into striations. The scale edges are irregular with warts proximally whilst the distal edge is finely serrate.

For images see the original description ( Zapata-Guardiola and López-González 2010a).

Distribution

Our specimens extend the range of this species from the Falkland Islands and South Georgia Island, west to the Patagonian Shelf at depths from 106–825 m.

Remarks

The green shading makes this species easily recognisable.

Comparisons

The opercular scales of the polyps of Thouarella viridis have a deep longitudinal groove on the outer surface, and a complex keel, with many longitudinal adjacent ridges, on the inner surface. Conversely, those of T. antarctica has a relatively shallow groove on the outer surface and the keel is more simple, with multiple projections extending from a central point. The polyps of T. antarctica are also more flared than those of T. viridis , the latter having clavate polyps.

The polyps of Thouarella koellikeri have more scales in the abaxial rows than T. viridis (7–10 in the former, 6–7 the latter), so although the polyps are of a comparable size, the scales of T. koellikeri are generally smaller. The keels on the marginal scales of the former are simple whereas those of the latter have adjacent ridges. The abaxial body-wall scales of the polyps of T. koellikeri also lack the distinctive teeth/ridges found on those of T. viridis .

The polyps of Thouarella parachilensis are densely clustered at a branchlet tip. This clustering is absent on the branchlets of T. viridis , and the flat operculum of the former differs markedly from the tall, rounded operculum of the latter.

The polyps of Thouarella affinis have a similar number of scales in the abaxial rows as the polyps of T. viridis however the marginals of the former have simpler keels. The submarginal scales of T. viridis also have multiple ridges on their inner distal edge and on some of the body-wall scales, which are absent in the former.

The polyps of Thouarella crenelata are clavate, similar to those of T. viridis however, the latter has a tall operculum whereas the former has an operculum not visible in lateral view. The polyps of T. crenelata also tend to have more scales in the abaxial rows than is found on the polyps of T. viridis .