Thouarella minuta 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 : 70-71

15. Thouarella minuta Zapata-Guardiola and López-González, 2010a

Thouarella minuta Zapata-Guardiola & López-González, 2010a: 169–180 , figs 11–13.

Material unavailable: Holotype, ZIZMH C11742, ANT XXI–2, sta. PS65–166–01, Austasen , Antarctica, 70˚56.83’S, 10˚32.61’W, 253.2–338 m, 15 Dec 2003.

Material examined: Paratype, USNM 1128948, ANT XXI/2, sta. PS65/166–01, Austanen , Cape Norvegia, Antarctica, 70˚56.83’S, 10˚32.61’W, 253.2–338 m, 15 Dec 2003 .

Other material: USNM 82873, Deep Freeze II, sta. 17, Staten Island , Tierra del Fuego, Argentina, 71˚18’S, 13˚32’W, 238 m, 27 Dec 1956; SMF, EPOS 3 , sta. 257, AT19, Weddell Sea , Cape Norvegia, Antarctica, 71°39.5’S, 12°34.7’W, 301–330 m, 15 Feb 1989 .

Description

Description modified from the original ( Zapata-Guardiola and López-González 2010a):

The holotype is a single branch which is 66 cm long, 5.5 cm wide, with branchlets emerging from all sides in a bottlebrush arrangement although the basal 9 cm of the main branch lacks branchlets. The branchlets are up to 45 mm long, simple at the base, then dividing into 2, sometimes 3, branchlets with the terminal branchlets being up to 35 mm long. The axis is woody, light brown in colour, with a diameter of 3 mm. The holotype is fixed to a rock by a greyish discoidal holdfast, which is 13 mm in diameter.

The polyps are isolated, arranged alternately or in loose spirals, 11–18 per cm, and are very small, 0.71–0.96 mm high, 0.3–0.44 mm wide, cone-shaped, and appressed against both the branchlets and the main stem. There is a quick reduction from 8 marginals at the polyp tip as the polyp scales are arranged in 5 longitudinal rows. The polyps have 3–4 scales in the abaxial rows.

The tall, conical operculum gives the polyp a tapered distal shape. The operculum is composed of isosceles triangle or spoon-shaped operculars 250–450 µm high, 70–160 µm wide, which are reduced in size on the adaxial side of the polyp. The inner opercular surface has a simple, sometimes flat surfaced keel, with tubercules across the keel base and a smooth band along the lateral edges of the scale. The outer opercular surface is smooth with a few, small granules towards the proximal edge.

The marginals are round to diamond-shaped, 210–280 µm high, 160–230 µm wide, and reduced in size on the adaxial side of the polyp. The proximal two-thirds of the inner surface is tuberculate with a smooth band along the distal edge broken by a small, simple keel whilst the outer surface is smooth.

The submarginals are indistinguishable from body-wall scales; both are roughly circular, 220–280 µm diameter, with adaxial scales being reduced in size. The inner scale surface is tuberculate and the outer surface is smooth. All polyp sclerites have a finely serrate distal edge and coarsely lobate proximal edge.

The coenenchymal scales are round to elliptical, 120–220 µm maximum diameter/width. The inner surface is sparsely tuberculate whilst the outer surface is smooth to slightly sculpted with sparse ridges and granules sometimes arranged radially.

The images of the colony and sclerites are in the original description by Zapata-Guardiola and López-González (2010a).

Distribution

Our specimens extend the range of T. minuta from Austasen, eastern Weddell Sea, Antarctica, to circum-Antarctic, at depths of 226–610 m.

Remarks

Thouarella minuta has the smallest polyps of any described Thouarella species.

Comparisons

With only three or four scales in the longitudinal abaxial rows, Thouarella minuta is comparable to T. variabilis , T. striata , T. pendulina , T. hicksoni and T. andeep ( Table 3). However, all these species generally have polyps of 1 mm or greater length. The smallest polyps are found on colonies of T. pendulina and T. hicksoni , which sometimes have polyps of 1 mm (polyps of T. minuta are 0.71–0.96 mm high). The operculars of the polyps of T. hicksoni are blunttipped and those of T. pendulina are more triangular than the spoon-shaped operculars of T. minuta .