“Dendrobrachia paucispina sp. nov.
FIGS 3-8, 12-13; Table I
Material Examined: Off the southern coast of Western Australia: 125 nautical miles East of Cape Arid, 34°03'S, 125°31'E, 1011-1020 m, F/V "Adelaide Pearl", 31 July 1988, Coll. K. GowlettHolmes, K. Olsson, M. Cameron, syntypes: South Australian Museum SAM H715, 1 spec.; USNM 87769, I spec.; about 80 nautical miles SW of Pearson Island, 35°04'S, 133°35'E, 900-960 m, F/V "Comet", 13 April 1989, coll. K. Gowlett Holmes, syntype: SAM H716, 1 spec.; about 100 nautical miles due west of Whidbey Point, 34°49'S, 133°07'E, 884-859 m, F/V "Longva III", coll. K. Gowlett-Holmes, 11 November 1989, syntypes: SAM 14728, 1 spec.; USNM 87768, 1 spec.
Description: Colony planar, loosely branched, with some overlapping of adjacent branches; branchlets bilateral and very irregularly alternate; highest order branches usually not more than 3 cm long, 0.4-0.8 mm in diameter, on average about 1 cm apart on same side of lower order branches. Six, occasionally seven, rarely eight longitudinal axial ridges on branchlets, increasing in number on thicker branches. Spines sparse, often absent, arranged in one row per axial ridge where present. Spines not uniform in size and shape, but increasing in length on larger branches; about 0.1 mm long on branches 1 mm in diameter. Polyps bilateral, in alternate or subopposite pairs, 3-6 per cm.
Discussion: The type series consists of six specimens, all of which are to some degree bent over and twisted in the upper part of the corallum, a condition which may have resulted in part from preservation and storage in small containers. When unfolded into what was probably its natural shape, the largest colony is about 45 cm tall and 15 cm wide, with a basal stem diameter of 7.5 mm. The smallest colony is 15 cm tall and about 7 cm wide, with a basal stem diameter of about 2 mm.
A colony of medium size (SAM H715) is described in detail. This specimen is about 28 cm tall and 6 cm wide, and has a basal stem diameter of 4 x 4.3 mm (Fig. 3). The branching pattern of the corallum is generally planar with some overlapping of adjacent branches. The branching is irregular to about the 9th order. The highest order branching consists of small, relatively thin branchlets arranged in a very loose bilateral and alternating pattern. The smallest unbranched branchlets range in length from 0.4-3.0 cm (7 = 1.47 cm, n = 23), and they are 0.4-0.6 mm in diameter. The average distance between the bases of adjacent branchlets and/or branches on the same side of a lower order branch is 9.0 mm (range 4-19 mm, n = 30). The average distance between adjacent branchlets and/or branches on opposite sides is 4.8 mm (range 3-8 mm, n = 9). The branch angles (delineated by the distal side of a branch and the lower order branch from which it arises) are generally greater than 45°.
At the tips of the smallest branchlets, the axial skeleton consists of six, occasionally seven, and rarely eight narrow longitudinal ridges separated by deep, u-shaped grooves (Fig. 4, top). The ridges increase in number on the thicker, older parts of the corallum (Fig. 4, bottom), are present on the stem and also faintly visible on the upper part of the holdfast. On branches 2-3 mm in diameter, 12 or more ridges can be seen in one lateral view.
Over most of the corallum, and particularly on branches less than 1 mm in diameter, the skeletal ridges are smooth (Fig. 5, top); however, in some places scattered spines occur in a single row along several of the ridges. On the smaller branchlets they take the form of small rounded elevations (Fig. 5, bottom); on the older branches they are more spine-like (Fig. 6). Where present, the spines occur on only one or a few of the ridges and never on all the ridges around the circumference of the axis. Although quite variable, the height of the spines is generally about 0.07 mm on a branchlet 0.6-0.8 mm in diameter, 0.07-0.12 mm on branches about 0.8-1.0 mm in diameter, and 0.12 to 0.18 mm on branches 1.0-2.0 mm in diameter. There are usually 3-5 spines per millimeter in each row. Spines are also found at the base of several of the small branchlets which arise directly from the stem or thicker branches. In these cases the spines can be 0.25 mm or more in height.
Polyps are present throughout the corallum. They are not arranged in a strictly regular order but are more abundant on the lateral and front sides of the branches (relative to the plane of the corallum). On many of the larger branches a narrow band of coenenchyme without polyps extends down the middle of the posterior side. On the branches the polyps are spaced irregularly (Fig. 7), sometimes unilaterally, and sometimes bilaterally with alternating or opposite pairs. Most polyps are about 5 mm apart, and there can be 3-6 polyps per centimeter depending on whether they are placed singly or in pairs. They are usually inclined distally, often with their adaxial side lying against the axis. The largest polyps are about 2.2 mm tall (including tentacles); the body column is about 1 mm in length (Fig. 8). On several polyps in which the tentacles were adequately expanded, 8-10 pairs of pinnules could be seen on each tentacle.
The remaining specimens in the type series are similar in most morphological features to the one described above. All the colonies have a typical planar branching pattern, with the highest order unbranched branchlets being not more than 3 cm long and spaced about 1 cm apart in a very loose bilateral and alternating fashion. In the larger colonies, there are infrequent fusions of some of the lower-order branches and the larger branches and stem have a distinctive golden, somewhat iridescent sheen.
From specimen to specimen, and even within a single colony — from branch to branch —differences can be seen in the occurrence, size, and density of the axial spines. In the two largest specimens (SAM H728 and USNM 87768), the spines are overall slightly smaller and sparser than those in the described colony. Furthermore, spines are only rarely present on branches of about 2 mm in diameter or more; however, the axial ridges remain distinct and can be seen on both the branches and the stem.
In another specimen (SAM H728, height 30 cm, basal stem diameter about 4 mm) spines are present on all parts of the corallum including the stem and basal plate; however, they are not uniformly distributed, are absent in some places, but present on all the axial ridges in other places. This variability in the occurrence of the axial spines is a characteristic feature of this species.
Remarks: Although the general form of the corallum of D. paucispina sp. nov. is very similar to that of D. fallax, this species can be differentiated on the basis of the very sparse number and relatively smaller size of the axial spines (Table 1). The complete absence of spines on many parts of the axis is quite distinctive. Where present, and for branches of similar thickness, the spines in this species are only about one-half as large as those in D. fallax. Although in both species the smallest branchlets most commonly have six primary axial ridges, in D. paucispina sp.nov. there are occasionally seven and sometimes even eight ridges present. In contrast, in D. fallax there are occasionally five or seven ridges on the smallest branchlets. The polyps in D. paucispina sp. nov. and D. fallax appear to be similar in size and number; however, there is some evidence suggesting that the number of pairs of pinnules on the tentacles may be different in the two species. In this species there are eight-ten pairs of pinnules per tentacle. According to Thomson (1910), there are only six-seven pairs per tentacle in D. fallax.
Distribution: Known only from the Great Australian Bight, 884-1020 m, on the continental slope.”
(Opresko & Bayer, 1991)
