Thouarella clavata Kükenthal, 1908

TAYLOR, M. L., CAIRNS, S. D., AGNEW, D. J. & ROGERS, A. D., 2013, A revision of the genus Thouarella Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on Plumarella Gray, 1870 and Dasystenella , Versluys, 1906 , Zootaxa 3602 (1), pp. 1-105 : 52-53

publication ID	https://doi.org/ 10.11646/zootaxa.3602.1.1
publication LSID	lsid:zoobank.org:pub:10304FBF-3969-4EFA-83F1-BB8A5E2B37F3
persistent identifier	https://treatment.plazi.org/id/EE36E867-FFB6-FFDF-FF0A-AF63FD9E0997
treatment provided by	Felipe
scientific name	Thouarella clavata Kükenthal, 1908
status

Treatment

9. Thouarella clavata Kükenthal, 1908 View in CoL

Figs 20 View FIGURE 20 , 21 View FIGURE 21

Thouarella aff. antarctica Kükenthal 1907: 203–4 View in CoL

Thouarella clavata Kükenthal, 1908: 11 View in CoL

Thouarella (Parathouarella) clavata Kükenthal 1919: 430–433 View in CoL , text figs 209–212, pl.43, fig. 69

Thouarella (Thouarella) clavata Cairns & Bayer 2009: 27 View in CoL (listed)

Material examined: Holotype, ZMB Cni 6080, D.T.E Agulhasstrom, sta. 103, SW of Port Elizabeth , South Africa, 35˚10.5’S, 23˚2.0’E, 500 m ; Syntype, MNHWU, 2 cm dried fragment; USNM 1140264, University of Cape Town Ecological Surveys , LBT 75 G, 32”03.3' S 16”02' E, 680–800 m, 25 Sep 1971 .

As so little material was available for study the colony description is based on Kükenthal’s 1908 study and his more detailed 1919 record of this species. There is some confusion surrounding this species as the specimen from ZMB has clavate polyps, very unlike those seen in Kükenthal (1919) and they in fact look similar to T. crenelata .

As the MNHWU syntype more closely resembles images within Kükenthal (1919) we have based descriptions on this specimen. Unfortunately, it was not possible to take adequate SEM images of sclerites and polyps of the syntype as the specimen is in a very poor condition and disintegrated in SEM preparations. Using microscopy it was possible to identify a second T. clavata specimen: USNM 1140264. We thus illustrate specimen USNM 1140264, whose polyps and sclerites are identical to the few poor SEM images obtained from the syntype.

Description

The holotype stem base is slightly curved, the main stem is straighter (no holdfast), and branching is dense and in all directions ( Fig. 20a View FIGURE 20 ), although the branchlets curve to create ventral and dorsal colony planes. The branchlets are mostly 30 mm long (some 35 mm), often forked at the branchlet base, and orientated at almost 90° to the main stem or branch. The dorsal plane branchlets of USNM 1140264 are greatly shortened and the proximal branchlets are also reduced in length ( Fig. 20d View FIGURE 20 ).

We believe that USNM 1140264 is conspecific to the MNHWU syntype. The following descriptions are of USNM 1140264 (unless stated) as this is the only known whole colony of T. clavata from which it was possible to take clear SEM images. Isolated polyps are sparsely placed on branchlets ( Fig. 20d View FIGURE 20 ), 7–8 per cm. They are distally flared ( Fig. 20e View FIGURE 20 , 21c View FIGURE 21 ) with a low a conical operculum, 1.4–1.7 mm high (average 1.5), and mostly in a single plane. Each polyp has 6–7 scales in one abaxial row ( Fig. 21a View FIGURE 21 ) and 4 scales in each adaxial row.

The operculars are arranged in 2 rings, an inner ring made up of smaller operculars and an outer ring of large operculars. The inner operculars are a tall–triangular shape ( Fig. 21d,h View FIGURE 21 ), 350–390 µm high (average 370 µm), 150–230 µm wide (average 180 µm), with a H:W of 1.6–2.5 (average 2.1). Most of the outer operculars are larger with a wider lanceolate shape ( Fig. 21e–g View FIGURE 21 ), 590–770 µm high (average 680), 340–420 µm wide (average 390), with a H:W of 1.5–1.9 (average 1.7). The operculars have a simple keel on the inner surface ( Fig. 21e View FIGURE 21 ), are tuberculate proximally, and the outer surface is deeply concave and smooth ( Fig. 21g View FIGURE 21 ). The proximal edge is coarsely lobate whilst the distal edge is serrate.

The distal edge of the marginals are triangular with an angular proximal edge and are tuberculate across most of the inner surface, 790–900 µm high (average 860 µm), 480–650 µm wide (average 600 µm), with a H:W of 1.4–1.6 (average 1.5). The keel is simple and flat faced ( Fig. 21j View FIGURE 21 ) and the outer surface is covered in granules with a smooth distal border ( Fig. 21i View FIGURE 21 ).

The submarginals are diamond-shaped, 690–750 µm high (average 720 µm), 650–730 µm wide (690 average µm), with a H:W of 1. There is a small keel on the inner surface corresponding to the peak on the distal edge ( Fig. 21k View FIGURE 21 ). The remainder of the inner surface is tuberculate whilst the outer surface is covered in granules ( Fig. 21l View FIGURE 21 ).

The body-wall scales have a circular distal edge, are often irregular in shape ( Fig. 21m, n View FIGURE 21 ), 220–340 µm high (average 260 µm), 250–490 µm wide (average 330 µm), with a H:W of 0.4–1.5 (average 0.9). The proximal edge is coarsely lobate. The inner surface is tuberculate, with a narrow smooth band along the distal margin whilst the outer surface is relatively smooth but has sparsely distributed granules.

The coenenchymal scales are smaller than the body-wall scales, 120–220 µm high (average 160 µm), 140–250 µm wide (average 190 µm), with a H:W of 0.5–1.2 (average 0.9). They are circular to widely elliptical in shape ( Fig. 21o–s View FIGURE 21 ) with a very smooth outer surface that bears a few small granules and a tuberculate inner surface.

Distribution

This species is only known from the type locality, southwest of Port Elizabeth , South Africa, at 500 m depth .

Remarks

The hand-drawn images in Kükenthal’s 1919 publication (text figs 209, 210) show modestly flared polyps like those on his plate XLIII. However, he described these polyps as clavate. We use the word ‘clavate’ to describe a polyp with a rounded distal head region, and Kükenthal appears to use the word to describe any polyp with a wider head than base. The syntype from MHWU is in bad condition, the sclerites are brittle and they partially disintegrated when they were cleaned in an attempt to carry out SEM observations—however, the polyps are distally flared, as in Kükenthal’s (1919) illustrations. The ZMB sample afforded clearer SEM images but the polyps are clavate and not like those illustrated by Kükenthal (1919), and also the opercular keel is strong, whereas it was described by Kükenthal (1907) as weak. The illustration of T. clavata ( Kükenthal 1919: text figs 209, 210) shows a distally flared polyp with pointed marginals and the holotype description mentions clustered polyps. The MHWU sample most closely resembles this description and we are thus inclined to believe this is the true T. clavata , although this makes the name T. clavata a contradiction to our current use of this descriptive term.

More samples of this species are required from the type locality to complete a full description and improve comparisons (below).

Two polyp morphs were illustrated by Kükenthal (1919, Fig. 210), one of which may have been brooding.

Comparisons

The number of polyps per cm, number of pairs of abaxial scales (5–6), and flared polyp shape makes this species comparable to T. antarctica , T. brucei , and T. andeep ( Table 3). Thouarella antarctica has a bottlebrush colony shape and shorter, more rigid branchlets than colonies of T. clavata . The remaining species have a bottlebrush to bilateral appearance similar to T. clavata , although colonies of T. andeep have shorter more rigid branchlets and marginals that are more acutely pointed than those of T. clavata . The polyps of T. clavata and T. brucei look almost identical, but branchlets of colonies of T. brucei are more sparsely placed than those of T. clavata ( Fig. 20a View FIGURE 20 ). However, these differences in growth form are very minor. Thouarella brucei was originally described from Burdwood Bank and is found around Antarctica whereas T. clavata has been found only off the south coast of South Africa so there could be a separation in geographical distribution. More material of T. clavata is required to confirm that these two species are distinct.