Adelogorgia hannibalis, Breedy, 2018

Breedy, Odalisca, 2018, Revision of the genus Adelogorgia Bayer, 1958 (Cnidaria: Anthozoa: Octocorallia) with the description of three new species, Zootaxa 4369 (3), pp. 327-348 : 341-344

Adelogorgia hannibalis sp. nov.

( Figs. 10–11 , 7B )

Material examined.

Holotype: STRI 1206 A, ethanol preserved, Hannibal Bank , Panamá, 184 m deep, Dive 1552, submersible DeepSee, M / V SeaHunter, 9 March 2012.

Paratypes: STRI 1205, 1206B, 1207-1212, data as the holotype. STRI 1243 , ethanol preserved, Hannibal Bank , Panamá, 200 m deep, Dive 1552, submersible DeepSee, M / V SeaHunter, 9 March 2012 . STRI-HH 1047 , ethanol preserved, Hannibal Bank , 181 m deep, Dive 288, submersible Nadir, M / V Alucia, 2 April 2015. HH 1088, ethanol preserved, Hannibal Bank, 182 m deep, Dive 290, submersible Nadir, M / V Alucia, 5 April 2015 . STRI-HH 1090 , ethanol preserved, Hannibal Bank , 203 m deep, Dive 290, submersible Nadir, M / V Alucia, 5 April 2015 . STRI-HH 1142 , ethanol preserved, Hannibal Bank , 188 m deep, DR 310, submersible Nadir, M / V Alucia, 5 April 2015.

GenBank accession numbers MF579539 and MF579542 .

Diagnosis. Colonies flexible with few branches, branching dichotomous, without anastomoses. Branches thin, of uniform thickness 1.5–2 mm in diameter. Branching up to 12 times, mostly 3–6 times. End branches up to 70 mm long. Polyps distributed all around branches. Polyp mounds prominent, sparsely placed, closer at branch tips. Anthocodiae with about 8 slightly curved spinous rods in points up to 0.2 mm long. Coenenchyme with tuberculate spindles, up to 0.15 mm long, double discs with serrate edges up to 0.11 mm long and 0.09 mm wide; and leaf clubs up to 0.19 mm long. Outermost coenenchyme with predominance of double discs. Axial sheath with less complex spindles and smaller radiates. Colony orange. Sclerites orange, red, whitish to transparent.

Description. The holotype is a sparse, flexible colony, 18 cm long and 16 cm wide colony. The branching is mostly dichotomous ( Fig. 10A ). The stem, 2 mm diameter and 3 mm long, rises from a 1 cm diameter holdfast. The stem subdivides producing branches of uniform thickness, 1.5–2 mm diameter. They bifurcate mostly 0.5–2.5 cm apart at angles of 30–90°. Some branches extend and curl inwards in larger angles (180°). The colony branches up to 12 times. Unbranched terminal ends are 3–7 cm long ( Fig. 10 A-B). The polyps are distributed all around the branches, up to 2 mm apart, closer at the tips ( Fig. 10B ). The axes are composed of longitudinal gorgonin layers with a loculated central cord filled with organic fibres without mineralization ( Fig. 7B ). The polyps are fully retractile into raised polyp mounds, 0.5-0.75 mm height, with circular apertures ( Fig. 10B ). The polyp mounds do not have a special type of sclerites but they mostly contain leaf clubs and spindles. The anthocodiae are composed of eight points consisting of a few vertically arranged spiny rods each one, without a collaret. The anthocodial rods are 0.148–0.2 mm long and 0.029–0.06 mm wide ( Fig. 11A ). The coenenchyme is thin. The superficial layer with a dominance of double discs. Beneath this layer, warty spindles, radiates, and immature forms. The leaf clubs are 0.11–0.196 mm long and 0.04–0.08 mm wide (at the head) with warty handlers and from elongated warts to foliate heads ( Fig. 11B ). The spindles are 0.11–0.17 mm long and 0.06–0.078 mm wide ( Fig. 11C ), immature forms 0.09– 0.10 mm long and 0.05–0.08 mm wide; radiates are 0.05–0.09 mm long and 0.02–0.05 mm wide ( Fig. 11D ). The double discs are 0.06–0.088 mm long and 0.08–0.11 mm wide (along the disc’s crests) ( Fig. 11E ). Coenenchymal sclerites are orange, red and whitish to transparent ( Fig. 10C ). Colour of the colony is orange, with reddish polyp mounds ( Fig. 10 A-B).

The colony has some nude branches colonised by polychaete tubes and cirripedia.

Variability. The colony colour varies to lighter hues of orange in some paratypes (STRI 1209, 1212) and the branch thickness reaches up to 3 mm in the paratype STRI 1212. The polyp mounds extend up to 1 mm in STRI 1212. The paratype series are 7-16.5 cm long. All of them with scant branching, less than the holotype, which is the most copious colony. The paratype sclerites are consistent with the holotype.

Habitat and Distribution. The species was found on the Hannibal Bank, a coastal guyot-type seamount that rises from approximately 500 m to 45 m, located 50 km from the mainland ( Cunningham et al. 2013). The seamount is relatively protected as part of the Coiba National Park and World Heritage. The species was found on rocky substrate with strong currents. It is only known from the type locality, Hannibal Bank, from 180 to 200 m deep.

Etymology. Named after the Hannibal Bank and the surveyor USS Hannibal that discovered and charted the bank for the first time, presumably in 1934. The name Hannibal evokes the Carthaginian general, considered one of the greatest military commanders in ancient history. In genitive: hannibalis (L) meaning ¨of Hannibal¨.

Remarks. This species is the only one that has colonies with elongated branches and free branches up to 7 cm long. Furthermore, it has a characteristic orange colony. The closest species is A. osculabunda (as discussed above). However, the flabellate branching pattern in A. osculabunda , the prominent polyp-mounds and the coenenchymal sclerites, make clear distinction among these two species. The comparative characteristics are in Tables 1 and 2.

Figures

FIGURE 10. Adelogorgia hannibalis sp. nov., STRI 1206 (holotype) (A) colony; (B) detail of the branches; (C) sclerites.

FIGURE 11. Adelogorgia hannibalis sp. nov., STRI 1206 (holotype) SEM micrographs. (A) anthocodial rods; (B) leaf clubs; (C) spindles; (D) spindles from inner coenenchyme; (E) double discs.

FIGURE7. Structure of non-mineralised axes:Longitudinal sectionof axial core showing chamberswith fibres (left); detail of fibres (right).(A) Adelogorgia osculabunda; (B) Adelogorgia hannibalis; (C) Adelogorgia adusta.