Antipathes falkorae Horowitz, 2022

Horowitz, Jeremy, Opresko, Dennis, Molodtsova, Tina N., Beaman, Robin J., Cowman, Peter F. & Bridge, Tom C. L., 2022, Five new species of black coral (Anthozoa; Antipatharia) from the Great Barrier Reef and Coral Sea, Australia, Zootaxa 5213 (1), pp. 1-35 : 8-10

Antipathes falkorae Horowitz sp. nov.

( Figs. 1–2 and 4 ; Supplementary Table 1 )

Material examined. Holotype, MTQ G80067, Australia, Great Barrier Reef , Ribbon Reef Canyons , Schmidt Ocean Institute R / V Falkor , Seamounts , Canyons , and Reefs of the Coral Sea expedition FK200802, ROV SuBastian dive S0385, collected on August 18, 2020, - 15.3968° S, 145.7934° E, 111 m depth, collector Jeremy Horowitz.

Diagnosis. Colony fan-like, with unilateral and sparse branching mostly to the second and third order; terminal branchlets 3 to 5 cm long and curved proximally forming 45° distal branch angles. Spines conical, mostly smooth with distinct apical knobs, secondary knobs, and some papillae on the apical section of spines 0.15 to 0.17 mm tall. Four to five axial rows of spines counted in one view. Polyps 0.8 to 1 cm in transverse diameter and eight polyps per cm.

Description of holotype. Specimen is fan-like and 21 cm in height (lowermost 5 cm or more of the stem and the holdfast not collected); branched mostly to the second and rarely to the third or fourth order, with stiff and straight or slightly curved vertically directed branches ( Figs. 4A–B ). Distal branch angles are mostly 45°. Branching is sparse and in one plane, with mostly one and sometimes two or three branches occurring on a given lower order branch. Branching is unilateral with successive orders of branches often arising on the same side as the lower order branches. The five most basal branches are disposed on one side of the stem with subsequent branches disposed on the same side as lower order branches, while the four most apical branches occur on the opposite side of the stem and have higher order branches disposed on the same side as their direct lower order branches ( Fig. 4B ). The one branch between the five most basal and four most apical branches is disposed on the same side as the basal branches but has secondary branches occurring on both sides of the branch. Terminal branchlets are 3 to 5 cm in length and 0.19 to 0.2 mm in diameter near the base ( Fig. 4B ). The lowest portion of the stem is 0.9 mm in diameter.

Spines on a branch 0.2 mm thick or greater have polypar spines 0.15 to 0.17 mm tall and abpolypar spines 0.1 to 0.15 mm tall ( Fig. 4C ). On branches 0.20 mm in diameter, spines are about 0.14 mm tall ( Fig. 4D ), and on terminal branchlets 0.2 mm or less in diameter, spines are at most 0.13 mm tall ( Fig. 4E ). Spines on large (about 0.2 mm or thicker) branches have extensive apical knobbing with knobs reaching maximum heights of 0.04 mm ( Fig. 4F ). Where knobbing is most pronounced, spine tips flare outward (at right angles to the direction of the branch axis) and become vertically compressed with small secondary knobs occurring on primary knobs ( Fig. 4G ). Faint papillae can be seen on and in between well-developed knobs ( Fig. 4G ). Spines on terminal branchlets less than 0.2 mm in diameter have few or no apical knobs, and are smooth, triangular, slightly distally directed, laterally compressed. Four to five axial rows of spines can be counted in one view; 3.5 to 4 spines can be counted in one mm; and distances between axial rows range from ~0.3 to 0.4 mm.

Polyps are yellow to white in color, 0.8 to 1 mm in the transverse diameter with about 0.5 mm space between polyps resulting in about eight polyps in one cm ( Fig. 4H ).

Comparative diagnosis. A. falkorae sp. nov. is most like Antipathes coronata Opresko, 2019 by having straight and vertically directed branches, unilateral branching, slightly larger polypar than abpolypar spines, and apical knobs on the spines. However, the new species has more extensive apical knobbing where on a spine ~ 0.14 mm tall, the new species has five to six primary knobs compared to A. coronata , which has three knobs. The new species also has small protrusions that could be considered secondary knobs on top of primary knobs that are absent on A. coronata . The new species has on average a smaller terminal branchlet diameter than A. coronata (0.2 vs 0.3 mm); however, both species have ~5 axial spine rows visible in a lateral view. The new species also has slightly wider distal branch angles that create more of a fan shape compared to A. coronata . Lastly, the new species has very faint papillae on and in between primary and secondary knobs, which differs from A. coronata that has smooth knobs. Antipathes elegans Thomson & Simpson 1905 and A. gallensis Thomson & Simpson 1905 are also morphologically like A. falkorae sp. nov. where both have apical knobbing on the spines and faint papillae on the surface of the spines; however, the new species is different from both species by having more extensive knobbing (about six knobs per spine vs three to four in A. elegans and A. gallensis ) and a presence of secondary knobs that are lacking in these other species.

This new species is phylogenetically similar to Ar. ericoides and A. aculeata (Supplementary Table 3); however, the new species does not possess fused branches while Ar. ericoides and A. aculeata have high levels of fused branches. Additionally, the specimens representing A. aculeata are not holotype or topotype specimens, which explains why they do not form a monophyletic relationship. The new species also has a low phylogenetic distance with A. morrisi sp. nov. and a feature that unites the two new species is a presence of apical knobs on the spines. However, A. morrisi sp. nov. has fused branches, unlike A. falkorae sp. nov.

Etymology. In recognition of the Schmidt Ocean Institute R/V Falkor, onboard which this and many other black coral species were collected from the Great Barrier Reef and Coral Sea.

Distribution. Known only from the Great Barrier Reef at 111 m depth.

Figures

FIGURE 1. Locations where specimens were collected shown on a bathymetric surface map of the Great Barrier Reef and Coral Sea. Blue boxes represent specimens hand collected while on SCUBA, and red circles represent specimens collected via a remotely operated vehicle.

FIGURE 2. Maximum likelihood phylogeny of the Antipatharia based on a 50% complete matrix containing 1,047 loci. Taxa in blue and imaged represent species described in this study.

FIGURE 4. Antipathes falkorae sp. nov. Holotype, MTQ G80067: A, in-situ image of colony; B, image of colony showing branching pattern; C–E, sections of terminal branchlets showing spines (scale in C applicable for three subfigures); F–G, closeup of skeletal spines with knobs, secondary knobs, and papillae; H, image of polyp row on terminal branch.