Thouarella koellikeri Wright and Studer, 1889

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 : 37-41

5. Thouarella koellikeri Wright and Studer, 1889

Figs 12 , 13

Thouarella Köllikeri Wright & Studer, 1889: 64–65 , pl. 11 fig. 5; Thomson & Henderson 1906: 38 (list); Versluys 1906: 35 Thouarella (Parathouarella) köllikeri Kükenthal 1915: 150 (key); 1919: 435; 1924: 299

Thouarella (Thouarella) koellikeri Cairns & Bayer 2009: 27 (list)

Material examined: Holotype, NHM 1889.5 .27.41 and USNM 1002247, which is a fragment of the holotype, H.M.S. Challenger, sta. 308, 50˚08’30”S, 74˚41’W, 320 m, 5 Jan 1876, 1 colony.

Other material: USNM 1112997, sample 5, Puyuhapi , Chile, South Pacific Ocean, 30 m, 10 Jan 2000 , 2 colonies, no location information; USNM 1002247, sample 174, Chile, South Pacific Ocean , no location information, 25 m, 12 Mar 2006 , 2 colonies; NHM (no catalogue number), H.M.S. Challenger, 51˚27’30”S, 74˚3’W, 730 m, 10 Jan 1856, fragment; SMF, R/ V W. Herwig, sta. 245, SW Atlantic, 36˚49’S, 54˚02’W, 550 m, 14 Jun 1966; SMF, R/ V W. Herwig, sta. 376, SW Atlantic, 43˚23’S, 60˚19’W, 100 m, 16 Jul 1966; SMF, R/ V W. Herwig, sta. 311, Patagonian Shelf, SW Atlantic, 46˚54’S, 60˚28’W, 480 m, 18 Feb 1971; SMF, R/ V W. Herwig, sta. 293, North Falkland Islands, 49˚36’S, 59˚25’W, 350 m, 13 Feb 1971; USNM 97997, R/V Eltanin, cruise 7, sta. 499, south of Coronation Island, South Orkney Islands, sub-Antarctic, 62˚06’S 45˚08’W to 62˚06’S 45˚10’W, 485 m, 20 Feb 1963, 7 colonies; USNM 98169, R/V Eltanin, cruise 6, sta. 339, west of Beauchene Island, Falkland Islands, sub-Antarctic, 53˚06’S, 59˚27’W, 512–586 m, 3 Dec 1962; USNM 98019, R/V Eltanin, cruise 12, sta. 1089, NE of Clarence Island, South Shetland Islands, Antarctic Ocean, 60˚47’S, 53˚30’W, 641 m, 14 Apr 1964; USNM 79475, R/V Eltanin, cruise 9, sta. 740, east of Cape Horn, Drake Passage, South Atlantic Ocean, 56˚06’S, 66˚19’W, 384–494 m, 18 Sep 1963; USNM 1130298, R/V Hero , cruise 721, sta. 1075, 64˚47’24”S, 64˚07’36”W, south of Anverse Island , Palmer Basin, Antarctica, 91–110 m, 23 Feb 1972 .

Description

The holotype has one main branch off the stem ( Fig. 12a ). The branchlets are mostly undivided, leaving the main stem primarily in 4 directions. Two of the 4 directions are consistently around 120˚ apart, roughly alternately pinnate, and between these 2 rows of branchlets there is often another row of branchlets. These 3 planes/rows of branchlets depart on one side and there are occasional branchlets directly opposite, which tend to be short or broken, especially towards the colony base (possibly because of the reduced protection these branchlets receive). The arrangement of branching can appear pinnate, however, the branchlets are on all sides of the main stem in 4 directions, and thus the colony is bottlebrush.

The polyps are isolated and clavate with a rounded opercular cone ( Fig. 12c,e ). They emanate from branches and branchlets in a roughly alternating arrangement ( Fig. 12b ), 12–15 per cm (more clustered towards branchlet tip), upwardly inclined at 45–60˚ and are 1.6–2.5 mm high (average 2.2). The sclerites are in 8 longitudinal rows with 7–10 scales in abaxial rows ( Fig. 12d ) but reduced in number adaxially to only 5–7.

The scales on each polyp fit into 4 categories: 8 operculars, 8 marginals, 8 submarginals and many body-wall scales.

The operculars are isosceles triangle- ( Fig. 13a,d ) to arrowhead-shaped ( Fig. 13b ), 360–560 µm high (average 480), 180–350 µm wide (average 250), with an average H:W of 1.95. They have a large, single keel on their inner surface (side view of keel, Fig. 13c ), with a corresponding deeply concave longitudinal outer surface ( Fig. 13b ). The proximal half of the inner surface is covered with small densely placed tubercles. The outer surface has granules that are often aligned to form striations arranged radially from the proximal third.

As the distal circumference of a polyp is not wide enough to accommodate 8 marginal scales they are arranged in 2 alternating circles of 4 with their lateral edges overlapping ( Fig. 12e ). The marginals fold over the operculars, fitting into their concave outer surface. The marginals are mostly triangular distally ( Fig. 13e–g ), and rounded laterally with a flat proximal edge. They are 420–580 µm high (average 480 µm), wider than operculars (340–520 µm, average 430), with an average H:W of 1.1. Abaxial marginals are more pointed than the adaxial. The inner surface bears a large keel usually with a single channel running its length and lateral projections ( Fig. 13e ). Tubercles are more widely spaced than on operculars but still cover the basal portion of the inner surface. The outer surface has granules in radial rows from the central proximal area that fade towards scale edges ( Fig. 13g ).

The submarginals are shorter than the marginals ( Fig. 13h–k ), 320–590 µm high (average 430 µm), 230–490 µm wide (average 430 µm), with an average H:W of 1. Generally the submarginals have a more rounded distal edge than the marginals. The submarginals are more pointed on the abaxial side of the polyp ( Fig. 13h,j ) than the adaxial ( Fig. 13k ). The scales proximal to the submarginals also sometimes have a modest distal point and a small keel on their inner surface. The submarginals differ from the marginals as tubercles cover a larger proportion of inner surface.

The body-wall scales arch slightly away from the polyp body and are of various shapes. They are often pentagonal with a rounded distal edge, or circular to elliptical ( Fig. 13l–p ), 280–520 µm high (average 390 µm), 220–600 µm wide (average 380 µm), with an average H:W of 1. The inner surface is tuberculate with a narrow smooth band distally that can bear a few small ridges ( Fig. 13l,o ) whilst the outer surface is covered in granules.

The coenenchymal scales are small, circular ( Fig. 13q ), 120–180 µm diameter (average 150 um), with an average H:W of 1. The outer surface has radial striations from centre to the scale edge whilst the inner surface is tuberculate. The distal edge of all sclerites are finely serrate and the proximal edge irregularly lobate.

Distribution

This species has been found along the southern coast of Chile, Argentina, and off the Antarctic Peninsula from 91–1920 m.

Remarks

Contrary to Wright and Studer (1889), who described dorsal branchlets as simple and short (10–25 mm), some colonies have dorsal branchlets up to 51 mm long with similar polyp orientation and stem flexibility as the ventral and lateral branchlets.

Comparisons

Thouarella koellikeri most closely resembles T. viridis , as both have clavate polyps and a bushy, bottlebrush to bilateral appearance. However, the marginal scales of the polyps of T. koellikeri are high with a single-channelled keel, whereas those of T. viridis are shorter and have 2–4, and sometimes five, longitudinal ridges instead of a keel. Distal inner surface ridges are found on submarginal scales of the polyps of T. viridis whereas the polyps of T. koellikeri specimens tend to have a small, single keel on the submarginals of the first row. The polyps of T. koellikeri also have more scales in the abaxial row than those of T. viridis .

Versluys (1906) described the ramification of T. koellikeri as similar to that of T. moseleyi and the two species do have long, fine, flexible branchlets that could appear similar. However, the latter has pinnate, uniplanar colonies and the former has colonies that are bottlebrush to bilateral. Also, the polyps of T. koellikeri specimens are isolated while those of T. moseleyi occur in pairs.

Although most are modestly flared, some polyps of T. antarctica have a similar clavate shape to those of T. koellikeri , but the polyps of the latter tend to have more scales in the abaxial row (7–10, rather than 5–7). Also the marginals of T. antarctica are larger and bear a more complex keel than those found on the polyps of T. koellikeri . Lastly, T. antarctica has a true bottlebrush colony form whereas the branchlets of T. koellikeri colonies leave the main stem in two or three directions giving it a bushy to bilateral appearance.

The bushy appearance of colonies of T. koellikeri is similar to that of T. bipinnata however the former has polyps with a wider head and, when dried, the body-wall scales reflect away from the polyp body, something that is not seen in polyps of T. bipinnata . The polyps of T. koellikeri are also longer and narrower, with taller operculars, and marginals with a higher H:W ratio than those of T. bipinnata .

Thouarella koellikeri has similar sclerite shapes to both T. brevispinosa and T. brucei , however, colonies of T. brucei have distally flared polyps, fewer scales in the abaxial row, longer marginals bearing a more acute distal point, and flatter keels than T. koellikeri . Thouarella brevispinosa , although having a similar number of abaxial scales as T. koellikeri , has taller marginals and more flared, open polyps (see Table 3).

Figures

FIGURE 12. Thouarella koellikeri, holotype, NHM 1889.5.27.41: a) 19 cm long colony; b) close up of branchlet; c) lateral polyp view; d) abaxial polyp view; e) stereo opercular view.

FIGURE 13. Thouarella koellikeri, holotype, NHM 1889.5.27.41: a,d) inner and b) outer surface of opercular scales; c) side view of opercular keel; e) inner and f,g) outer surface of marginal scales; h–j) inner and k) outer surface of submarginal scales; l,o) inner, and m,n,p) outer surface of body-wall scales; q) top left, fourth and fifth from left on top row and fifth on bottom row are of the inner surface of coenenchymal scales, the remainder are outer surface images. Some SEM by ZGR.