Diplopathes multipinnata, Opresko & Stewart & Voza & Tracey & Brugler, 2022

Opresko, Dennis M., Stewart, Rob, Voza, Tatiana, Tracey, Di & Brugler, Mercer R., 2022, New genus and species of black coral from the SW Pacific and Antarctica (Cnidaria: Anthozoa: Antipatharia: Schizopathidae), Zootaxa 5169 (1), pp. 31-48 : 39-40

Diplopathes multipinnata sp. nov. Opresko & Stewart

( Fig. 1 , 4 )

Material examined. Holotype: NIWA 88617 , Stn TRIP3883 /55, 34.2 S, 162.7 E, Lord Howe Rise, South West Pacific, 478‒685 m, 10 October 2013 ( USNM 1491425 , SEM stub 457, Genbank ON572256 ) . Other material: NIWA 95270 , Stn TRIP4543 /5, 64.5 S, 177.6 E, Ross Sea, Pacific Antarctic Ridge, 1048.0–1477.0 m, 3 December 2015 ; NIWA 95271 , Stn TRIP4543 /8, 64.2 S, 177.6 E, Ross Sea, Pacific Antarctic Ridge, 1677.0–1636.0 m, 4 December 2015 ; NIWA 95273 , Stn TRIP4543 /8, 64.2ºS, 177.6 E, Ross Sea, Pacific Antarctic Ridge, 1677.0–1636.0 m, 4 December 2015 .

Type locality. Lord Howe Rise, 478‒685 m.

Distribution. Lord Howe Rise in the SW Pacific, and the Ross Sea, Pacific Antarctic Ridge ( Fig. 1 ); 478–1636 m.

Diagnosis. Corallum planar and densely branched to second and third order; pinnules bilateral and alternating, usually less than 1 cm long (maximum 3 cm); pinnular density 11–16 per 3 cm (total for both rows); polypar spines up to 0.1 mm tall; abpolypar spines up to 0.09 mm tall; 4–5 spines per mm in each row; polyps up to 4 mm in transverse diameter; polyp density 2.5 per cm.

Description. The holotype (NIWA 88617) is a complete colony approximately 28 cm tall and 17 cm wide, with a basal stem diameter of about 2 mm ( Fig. 4A ). It is branched mostly to the second order. The stem and branches are pinnulate; the pinnules are placed in two lateral rows and also arranged in an alternating pattern; there are no signs of more than two rows of pinnules on any part of the corallum. The unpinnulated basal part of the stem is 2.4 cm long, and the stem extends to the top of the corallum. Most of the pinnules originating on the stem are developed into pinnulated branches which can be 10 cm or more in length. On the lower part of the stem the pinnules are 3.6–4.4 mm apart on each side of the axis, resulting in a total of 15–16 pinnules per 3 cm. A similar pinnular density occurs on the upper part of the stem and on most of the branches; although in a few locations the pinnules are much further apart resulting in as few as 11 pinnules per 3 cm. The pinnules are mostly 1 cm or less in length; however, some are up to 1.5 cm long. Fusions occur among the pinnules, especially on the outer parts of the corallum. The pinnules on the lower part of the stem do not become pinnulated for a distance of up to 2.5 cm from the stem, thus giving that part of the corallum a more open appearance along the stem. In most other places on stem and branches the distance to the first pinnules is 0.5 to 1.0 cm.

The spines ( Fig. 4B ) on the pinnules are conical, smooth, with a rounded apex. The polypar and abpolypar spines are nearly equal in size. The spines are about as wide at the base (in an axial direction) as they are tall. On pinnules 0.29–0.35 mm in diameter, the polypar spines are 0.078‒0.1 mm tall, the abpolypar spines 0.05‒0.09 mm. The spines are arranged in axial rows, with 3‒6 rows visible in lateral view. Within the rows, the spines are spaced 0.24‒0.37 mm apart, resulting in 4–5 spines per mm. The size and density of the polyps could not be determined.

Three additional specimens are assigned to this species. All are similar to the holotype in having fusions among neighboring pinnules and in having relatively small spines that are equally wide as tall. In NIWA 95270 , the pinnules reach a maximum length of 2.5 cm; there are 14‒15 pinnules per 3 cm; and the polypar spines are 0.08 mm tall. In NIWA 95271 , the pinnules are up to 3 cm long; there are 16–17 pinnules per 3 cm, and the spines are up to 0.08 mm tall. In NIWA 95273 , the pinnules are up to 3 cm long; there are 14‒15 pinnules per 3 cm and the spines are 0.08 mm tall. In this last colony the polyps were found to be 3.5–4 mm in transverse diameter, with a density of ~2.5 per cm .

Comparisons. Diplopathes multipinnata differs from both D. antarctica and D. tuatoruensis (see below) in having a much more densely branched corallum. In D. multipinnata almost every pinnule originating on the stem becomes pinnulated, whereas in the other two species only a few of the stem pinnules develop into branches. In addition, the length of the pinnules (1.5 to 3 cm) is less than that of the other two species ( Table 3 ). The size of the polypar spines (0.08–0.1 mm) is similar to that of D. antarctica (0.09–0.1 mm), but greater than that in D. tuatoruensis (0.035 –0.046 mm). Diplopathes multipinnata is also more similar to D. antarctica in having slightly larger polyps than D. tuatoruensis .

In general appearance Diplopathes multipinnata is similar to Lillipathes ritamariae Opresko & Breedy, 2010 . The latter species forms large densely branched flabellate colonies with pinnules that are alternately arranged in two lateral rows over much of the corallum, but in four rows on some branches, especially near the distal ends of the branches. In both species many branches and pinnules become fused together. In L. ritamariae the pinnules are up to 1.5 cm long, the density of the pinnules is 10–14 per cm when four rows are present, and 14–16 per 3 cm when only two rows are present; the polypar spines are up to 0.12 mm tall, and the polyps are mostly 2.4–2.6 mm in transverse diameter (3–3.5 per cm). The major differences between the two species are in the size of the polyps and in the presence of four rows of pinnules in L. ritamariae .

Genetic Distances. A K2P-based genetic distance analysis based on cox3-cox1 indicated a 0.61% separation between D. multipinnata (NIWA 88617) and D. antarctica (NIWA 38070), and a 1.29% separation between D. multipinnata (NIWA 88617) and D. tuatoruensis (NIWA 16055).

Etymology. The species name is derived from the Latin multus, much, and penna, feather, in reference to many pinnulated branches on the colony.

Figures

FIGURE 1. Distribution of the three described species.

FIGURE 4. Diplopathes gen. nov. multipinnata sp. nov., holotype, NIWA 88617: A. corallum; B. sections of pinnules showing spines (B from schizoholotype, USNM 1491425, SEM stub 457). The larger projections on the right side of the pinnules are the polypar spines.