Bathypathes ptiloides, 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 : 407-409

Bathypathes ptiloides n. sp.

( Fig. 3 )

urn:lsid:zoobank.org:act:5CDAF402-E496-429F-91CA-A444396A4AB2

Bathypathes sp. Brugler et al. 2013: 327, 330, fig. 2, fig. 3, fig. 5; Horowitz et al., 2020: 559, fig.3a.

Material examined. Holotype: USNM 1070974 ( SEM Stubs 205 and 410), N. Pacific, Derickson Seamount, 53.1175°N, 161.3000°W, ROV Jason II, Dive 94 (Field Identification Number: JD-094, spec. #4), 4664 m, coll. A. Baco-Taylor, 23 July 2004 . Other Material: USNM 1071408, N. Pacific, Derickson Seamount, 53.1117°N, 161.2990°W, ROV Jason II, Dive 94 (Field Identification Number: JD-094, spec. #8), 4477 m, coll. A. Baco-Taylor, 23 July 2004 .

Diagnosis. Colony monopodial and pinnulate; pinnules simple, arranged along the stem in two lateral or anterolateral rows and in subopposite pairs. Pinnular density 6–8 per 3 cm. Unpinnulated stalk up to 66 cm long; pinnulated section about 10 cm long. Spines simple, smooth, triangular, up to 0.04 mm tall on the polyp side of the axis; with five to six rows visible in lateral view. Polyps arranged uniserially; mostly 6–7 mm (up to 8 mm) in transverse diameter on pinnules, with 3 to 3.5 polyps per 3 cm.

Description of the holotype. The corallum of the holotype (USNM 1070974) consists of a very long unpinnulated stalk topped by a short pinnulated section ( Fig. 3A ). An in situ photo ( Fig. 3B ) indicates that the lower section of the stem was tilted forward towards the polyp side of the colony and at the about half the distance to the pinnulated section it was more strongly curved in the same direction after which it curved back such that the upper part of the pinnulated section is almost vertical. As measured on the preserved specimen, which is now in three sections and broken off at the top, the length of the entire stem is about 76 cm. The unpinnulated portion of the stem is 66 cm long and the pinnulated portion covers the remaining 10 cm, including the broken off tip. The maximum width of the corallum across the pinnulated section is approximately 15 cm, and the basal diameter of the stem is 1.6 by 2 mm (the holdfast was not collected). There is no visible striatum on the stem. The pinnules are arranged in subopposite pairs. Viewing the polyp side of the corallum, the left pinnule of each pair (except for one) is inserted on the axis about 3 mm lower than the opposite member for the lower pairs and about 2 mm apart for the more distal pairs. Most of the pinnules are broken off at the distal end; the longest remaining pinnule is about 12 cm in length and 0.6 mm in basal diameter. Photos taken in situ suggest that the longest pinnules were those in the third distal pair from the bottom after which the pinnules gradually decrease in length towards the top of the corallum. The pinnules are spaced 6–13 mm apart in each lateral row, and, on average, there are three pairs per 3 cm on the lower pinnulated portion of the stem and four pairs per 3 cm higher up. The pinnules are inclined distally such that the distal angle they form with the stem is 70–80°. The interior angle formed by the two rows of pinnules is 120° or more. The spines ( Fig. 3D–E ) are simple, smooth, triangular, compressed, with a rounded apex and a base that extends out in a very shallow slope in both the distal and basal directions. On sections of pinnules 0.5–0.7 mm in axial diameter, the polypar spines are 0.04 mm tall and the abpolypar spines 0.035 mm. The spines are arranged in axial rows, five or six of which are usually visible in one lateral view. Within the rows the spines are spaced irregularly, 0.3–0.6 mm apart, but on average there are 3 or 4 spines per mm. The polyps ( Fig. 3C ) are uniserially arranged on one side of the stem and on the same side of the pinnules. The polyps on most parts of the pinnules are 6–7 mm in transverse diameter (measured from the distal edge of the distal lateral tentacles to the proximal edge of the proximal lateral tentacles), although the range varies from about 5 to 8 mm depending on the state of contraction. The density of the polyps in the middle of the pinnules is mostly 3 to 3.5 per 3 centimeters. On the stem the polyps are 7 mm in transverse diameter.

Description of other material. The other specimen assigned to this species is USNM 1071408. Field notes indicate that the unpinnulated section of the stem and the holdfast were not collected, but most of the upper pinnulated part of the colony was collected; however, only a small vial containing several pinnules was found in the NMNH collection. One of the pinnules is about 15 cm long and 1.8 mm in diameter. In situ photos ( Fig. 3F ) indicate that the intact colony was quite large, the stem somewhat S-shaped in lateral view, with a basal unpinnulated stalk estimated to be 50–60 cm long, and with an upper pinnulated section at least 25 cm in length. It was also estimated from the in situ photo that on the lower part of the pinnulated section there were about eight pinnules total per 5 cm and perhaps up to 15 pinnules total per 10 cm, and that the longest pinnules were 25–30 cm in length. On one of the pinnules retained, the spines are 0.03 mm tall, and the polyps are up to 8 mm in transverse diameter, with about three polyps per 3 cm. These measurements fall within the ranges of those for the holotype.

Genetic data. GenBank Acc. Nos.: USNM 1070974 [ KF054479 (igrW); KF054612 (igrN); and KF054371 (cox3-cox1)] ( Brugler et al. 2013) .

Brugler et al. (2013, Suppl. Table S1) sequenced the mt gene regions trnW -nad2, nad5-nad1, and cox1 of the holotype of B. ptiloides n. sp. (USNM 1070974) and found that all three haplotypes were different from the corresponding haplotypes of six specimens of Bathypathes alaskensis n. sp. Furthermore, two of the haplotypes were unique when compared to those of four other Bathypathes morphotypes. [Note: a phylogenetic tree for the nad5- nad1 (= igrN) results in Brugler et al. (2013), is presented in Horowitz et al. (2020)]. The holotype of B. ptiloides was also one of thirteen Bathypathes specimens that Chery et al. (2018) analyzed using the mt gene regions cox3- cox1 and nad5-nad1. For the gene region cox3-cox1 the holotype was found to have a unique haplotype that did not match that of any of the other specimens analyzed, including the holotype of B. tiburonae n. sp. For the gene region nad5-nad1, the B. ptiloides holotype was genetically distinct from all the other Bathypathes species analyzed (including the holotype of B. tiburonae as well as a specimen identified in Chery et al. (2018) as Bathypathes . sp. (USNM 1453622) which we have identified as B. patula .)

Comparisons. Bathypathes ptiloides n. sp. differs from B. platycaulus by having subopposite pinnules, and from B. bifida by having more than one pair of pinnules. By its relatively short pinnular spines (up to 0.04 mm) B. ptiloides differs from B. bayeri , B. conferta , B. galathea and herein described B. alaskensis n. sp. and B. tiburonae n. sp., all of which have pinnular spines> 0.08 mm. Bathypathes ptiloides n. sp. resembles B. erotema , B. patula ( Fig. 2A–B ), B. plenispina ( Fig. 2C–D ) and B. tenuis ( Fig. 2E–H ) in having a simple monopodial colony with subopposite pinnules, short triangular and smooth pinnular spines and moderate size polyps (5–7 mm), but differs from all these species in that the stalk is much longer (66 cm in the holotype vs. about 10 cm in the types of B. patula , B. erotema and B. tenuis ), and there are more rows of spines visible in lateral view (5–6 vs. 3–5). The differences in the length of the stalk are also reflected in differences in the ratio of the length of the stalk to that of pinnulated section for colonies having pinnulated sections of similar length. For example, in both the type of B. patula and B. ptiloides the upper pinnulated section is about 10 cm; therefore, the ratio is 6:1 for B. ptiloides , but only 1:1 for B. patula . Other differences between the types of these two species are in the relative length of the pinnules; the longest pinnules are slightly longer in B. ptiloides (more than 12.5 vs. 7.5 cm) even though the pinnulated sections are similar in length, and in the size of the pinnular spines which are slightly smaller in B. ptiloides (up to 0.04 mm vs. up to 0.07 mm in B. patula ).

Etymology. Species name “ ptiloides ” is derived from the Greek ptilon (feather) and the suffix oides (like), an illusion to the general shape of the corallum.

Distribution. North Pacific, Derickson Seamount, at depths of 4477–4664 m.

Figures

FIGURE 2. Bathypathes spp.: A. probable holotype of B. patula Brook (NHMUK 1890.4.9.19-20); B. sections of pinnules of specimen shown in A; C. holotype of B. plenispina Brook (NHMUK 1890.4.9.18); D. section of pinnule of the specimen shown in C; E. digital scan of original figure of B. tenuis Brook; F. two sections of pinnules from type material of B. tenuis; G. section of stem of type material of B. tenuis; H. current condition of type material of B. tenuis Brook (NHMUK 1890.4.9.24). Scale bars 0.5 mm in B, D, F, and G.

FIGURE 3. Bathypathes ptiloides n. sp.: A‒E, holotype, USNM 1070974: A. corallum (lower section of stem not shown); B. in situ photo; C. polyps; D. sections of pinnules showing spines, from SEM stub 410; E. close-up view of spines, from SEM stub 410; F. in situ photo of USNM 1071408.