Bathypathes tiburonae, Opresko & Molodtsova, 2021

Opresko, Dennis M. & Molodtsova, Tina N., 2021, New species of deep-sea Antipatharians from the North Pacific (Cnidaria: Anthozoa: Antipatharia), Part 2, Zootaxa 4999 (5), pp. 401-422 : 410-412

Bathypathes tiburonae n. sp.

( Fig. 4 )

urn:lsid:zoobank.org:act:8901BBD9-21F8-4C8A-B266-2207CBF942C0

Material examined. Holotype: USNM 1116837 ( SEM stub 251), North Pacific, off California, Gorda Transform, 41.6688ºN, 127.3090ºW, R/ V Western Flyer , ROV Tiburon, Dive 193, Sample No. W-193-A1, 3121.2 m, MBARI, 1 Mar 2006 . Paratype: USNM 1234549, North Pacific, Gorda Ridge, off Oregon, 42.6690ºN, 126.7850ºW, R/ V Western Flyer , ROV Tiburon, Dive 886, Sample No. T 886 A7, 3150.2 m, MBARI, 25 Aug 2005 . Other material: USNM 1459868, North Pacific , Gulf of Alaska, 53.2911°N, 164.0460°W, ROV Jason II, Dive 87 (Field Identification Number: JD-087), 3356 m, coll. A. Baco-Taylor, July 2004 .

Diagnosis. Colony monopodial and pinnulate; pinnules simple, arranged along the stem in two anterolateral rows and in subopposite pairs. Stem up to 55 cm in length. Pinnules spaced 10–18 mm apart (density 4–6 per 3 cm). Spines simple, smooth, triangular; polypar spines up to 0.09 mm tall on the pinnules. Polyps uniserially arranged on one side of corallum, up to 12 mm in transverse diameter on the pinnules, with about three polyps per 4 centimeters.

Description of holotype. The holotype (USNM 1116837) is about 55 cm tall and has a maximum width of 30 cm about 3 cm above the start of the pinnulated section. The basal stem diameter is 3 mm at a distance about 3 mm above the holdfast which is intact ( Fig. 4A ). The unpinnulated portion of the stem is about 37 cm long; the pinnulated portion covers the remaining 18 cm. A striatum is present on the stem; it starts 16 cm above the base and extends for 6 cm. The pinnules are arranged in subopposite pairs (11 pairs in all), the left pinnule of each pair (viewing the polyp side of the corallum) is inserted on the axis about 3 mm lower than the subopposite member (as measured from the middle of the pinnules; 1–2 mm as measured from the nearest edges of the subopposite pinnules) for all but one of the pairs where the arrangement is reversed. Most of the pinnules are broken off at the distal end; the longest pinnule on the corallum is 17 cm in length and 0.9 mm in basal diameter; it is in the third pair distal from the most basal ones. The pinnules appear swollen near their proximal end, and the diameter of the central axial canal is more than three-quarters of the width of the pinnule. In each row, the pinnules are spaced about 13–18 mm apart on the lower section of the corallum and about 13 mm apart on the upper section. There are two pairs of pinnules per 3 cm on the lower part of the stem and up to three pairs per 3 cm on the upper part. The pinnules are inclined slightly, such that the distal angle with the stem is about 80°. The interior angle formed by the two rows of pinnules near their point of origin on the stem is 120° or more. The spines are simple, smooth, triangular, compressed, with a rounded apex ( Fig. 4C ). On pinnules about 0.5 mm in axial diameter, the polypar spines are 0.06–0.09 mm tall and the abpolypar spines are 0.05–0.08 mm. The spines are arranged in rows, usually five of which (rarely six) are visible in one lateral view. Within the rows the spines are spaced irregularly, 0.12–0.52 mm apart; the spine density is usually around three per millimeter (range 2–4 per mm). In places the spines undergo splitting; eventually forming double spines. Spines occur along low ridges on the proximal, thicker part of the pinnules. The polyps ( Fig. 4B ) are uniserially arranged on one side of the stem and on the same side of the pinnules. The polyps on the pinnules are mostly 9–12 mm in transverse diameter as measured from the distal edge of the distal lateral tentacles to the proximal edge of the proximal lateral tentacles; the interpolypar space is 2–3 mm, and there are three polyps per 4 cm or four to five polyps in 5 cm. The polyps on the stem are up to 1.7 cm in transverse diameter, with two polyps per 4 cm.

Description of paratype and other material. The paratype (USNM 1234549) is similar to the holotype in having subopposite pinnules, large polyps, relatively long pinnules, and moderately large polypar spines. It consists only of the upper 7 cm of a colony (with the growing tip intact) with the equivalent of five pairs of pinnules (several pinnules are missing on one side of the stem). The length and thickness of the pinnules (18–24 cm and 0.8 mm in basal diameter) are similar to those of the holotype. Based on the length of pinnules of the fragment collected, the length of the unpinnulated stalk can be estimated to be 25-30 cm; however, in contrast to the holotype, the complete colony, as could be seen in an in situ photo, had a longer pinnulated section with at least 17 pairs of pinnules. The axial canal is about two-thirds the width of the pinnule near the distal end, but is not visible at the lower basal part of the pinnule. The subopposite pinnules are offset by about 1.5 mm. The spacing of the pinnules in each lateral row of the collected fragment is quite variable, 1–1.7 cm apart, and there is the equivalent of six pinnules total per 3 cm. On sections of pinnules 0.5–0.7 mm in diameter, the polypar spines are 0.07–0.09 mm tall, and five to seven rows are visible in lateral view. Within each row the mutual distance is very variable (0.12–0.45 mm), but, on average, there are 3–4 per mm. The polyps are 10–11 mm in transverse diameter in the middle of the pinnules, with four polyps occurring along a 4.5 cm length of pinnule.

USNM 1459868 consists only of a few pinnules; however, the polyps (9–10 mm in transverse diameter with 2.5 per 3 cm) and spines (0.066–0.08 mm) are very similar in size to those in the holotype.

Genetic data. In DNA sequencing studies ( Chery et al. 2018) using the mt gene region nad5-nad1, two of the specimens assigned to this species, the paratype of P. tiburonae (USNM 1234549) and USNM 1459868 had identical haplotypes, and this haplotype was different from the haplotype of the holotype of Bathypathes ptiloides (USNM 1070974). The holotype of Bathypathes tiburonae (USNM 1116837), however, was not included in the DNA analysis.

Comparisons. Bathypathes tiburonae n. sp. differs from B. platycaulus by its subopposite pinnules, and from B. bifida by having more than one pair of pinnules. By its moderately tall pinnular spines (up to 0.09 mm) B. tiburonae differs from B. erotema , B. patula , B. plenispina , B. ptiloides n. sp. and B. tenuis (all normally have spines <0.06 mm); and also B. bayeri (0.1–0.32 mm) and B. galathea (0.08–0.2 mm). It differs from B. conferta and the herein described B. alaskensis n. sp. by less densely set pinnules (4–6 vs. 8–12 per 3 cm) and larger polyps on the pinnules (9–12 mm vs. 4–5 mm in transverse diameter).

Etymology. Species name “ tiburonae ” is derived from the name of MBARI’s ROV Tiburon which was used to collect the holotype.

Distribution. Northeast Pacific, off California, Oregon and Alaska at depths of 3132–3356 m.

Figures

FIGURE 4. Bathypathes tiburonae n. sp., holotype, USNM 1116837: A. corallum; B. polyps; C. three sections of pinnules and one section of stem (far right) showing spines; scale bars 0.2 mm except as indicated. (C from SEM stub 251).