Bathypathes Brook, 1889

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 : 405-407

Bathypathes Brook, 1889 (emended)

partim Bathypathes Brook, 1889: 151 ; Thomson 1905: 76–79; van Pesch 1914: 27; Pasternak 1958: 180–181; 1977: 157; Opresko 2002: 415; Brugler et al., 2013: 317; MacIsaac et al., 2013: 241–243; Molodtsova 2006: 141; Molodtsova 2014: 5. Bathypathes, Horowitz et al., 2018: 312 .

partim Schizopathes Brook, 1889: 146–147 , 150.

Diagnosis. Corallum attached to substrate; monopodial, unbranched or rarely with a branch forming where the corallum has been broken and is regenerating. Pinnules simple, arranged alternately or suboppositely in two anterolateral or lateral rows. Length of pinnules on stem and branches usually longest near the middle of the pinnulated section of the corallum. Striatum present or absent. Spines conical, smooth, simple, forked or multiply knobbed at apex, with acute to slightly rounded apex. Spines often larger on polypar side of axis than on abpolypar side. Polyps from 2 mm to as much as 17 mm in transverse diameter.

Type species. Bathypathes patula Brook, 1889 (see Fig. 2A–B ).

Remarks. The genus Bathypathes is very close morphologically to Stauropathes in that most species have bilateral, subopposite pinnules, a characteristic which is typical for all species of Stauropathes . In general, the members of the pairs of pinnules are more offset in Bathypathes and in some species they are even alternately arranged. Species of Bathypathes are monopodial without branches or subpinnules and with simple pinnules originating from the stem, whereas in Stauropathes the pinnules on the stem are usually pinnulated themselves, thus forming branches. In recent DNA sequencing studies using the mt gene region nad5-nad1 ( Chery et al. 2018) the two genera were not clearly separable; however, in an analysis with cox3-cox1 all four specimens of Stauropathes fell into a single subclade, along with one typical Bathypathes species , whereas all six other Bathypathes specimens analyzed fell into a separate subclade.

The diagnosis of the genus is herein emended as a result of the transfer of the species Bathypathes alternata Brook to the genus Alternatipathes Molodtsova & Opresko, 2017 . In contrast to the genera Alternatipathes and Schizopathes , that have a triangular-shaped pinnulated section with the basal pinnules being the longest and the pinnules gradually decreasing in length toward the top of corallum, all hitherto known species of the genus Bathypathes usually have the longest pinnules near the middle of the pinnulated section of the corallum and the pinnules have approximately the same length for some distance.

Species assigned to the genus. Bathypathes bayeri Opresko, 2001 ; B. bifida Thompson, 1905 ; Schizopathes conferta Brook, 1889 ; B. erotema Schultze, 1903 ; B. galathea Pasternak, 1977 ; B. patula Brook, 1889 ; Stichopathes robusta Gravier, 1918 (see Molodtsova 2014); B. platycaulus Totton, 1923 ; B. patula var. plenispina Brook, 1889 (see Fig. 2C–D ); B. ptiloides n. sp.; B. tenuis Brook, 1889 (see Fig. 2E–H ); B. tiburonae n. sp.; and B. alaskensis n. sp. Note: B. patula var. plenispina is here recognized as a distinct species, B. plenispina , based on more densely set pinnules (6-7 mm apart vs. 10 mm apart in B. patula ), upright conical spines with little difference in the size of the polypar and abpolypar spines (compare Fig. 2B and 2D ), and a greater density of the spines on the pinnules (4‒5 per mm vs. 3 per mm).

Except for B. platycaulus , all nominal species have subopposite pinnules. Bathypathes seculata is now considered a junior synonym of B. patula (see Horowitz et al. 2018), and Bathypathes erotema may be a junior synonym of B. plenispina (or B. tenuis ) but with more densely arranged pinnules and larger spines. Bathypathes tenuis was previously thought to belong in the genus Umbellapathes based on the fact that in the original description ( Brook 1889, p.155) and original illustration (see Fig. 2E ) it was reported to have secondary pinnules ( Opresko 2005). Museum records indicate that over the years the type material (NHMUK 90.4.9.24) dried out and was subsequently rehydrated in 1987. When later re-examined, the remaining type material consisted only of five pieces ( Fig. 2H ), none of which possessed secondary pinnules. Examination of sections of the stem revealed the presence of a structural modification ( Fig. 2G ), resembling a striatum, which is typical of the genus Bathypathes . Unfortunately, this species is only known from the now incomplete and damaged type material of what were most likely juvenile specimens; therefore, further evaluation of the affinities of the species is not possible at this time, and the species for now must be considered incertae sedis. Future genetic evaluation of any remaining soft tissue on the type material might resolve the issue.

Distribution. The genus occurs in the Pacific, Indian, Atlantic and Southern Oceans at depths of 102–5393 m. The shallowest distribution record for the genus ( Bathypathes patula var. plenispina from Burdwood Bank, Scotia Sta. 346, 56 fathoms) was reported by Thomson (1905); however, there are serious concerns as to whether this species really occurred at such a shallow depth considering that the type was originally reported from a depth of 1070 fathoms (1956.8 m). It is possible that the lot was mislabeled.

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.