New species of deep-sea Antipatharians from the North Pacific (Cnidaria: Anthozoa: Antipatharia), Part 2

Unveiling the early evolution of black corals

Black corals, primarily deep-sea cnidarians (Anthozoa: Antipatharia), are inferred to have originated either in the Ediacaran or Cambrian based on molecular clock estimates. However, only the fossil family Sinopathidae, comprising Sinopathes and Sterictopathes, from the Early Ordovician of Hubei, China, has been recorded in the fossil record. The affinity of this family has been questioned because of morphological inconsistencies between fossil and extant species. Here we describe two transitional species of Sterictopathes from the Middle Ordovician of Shaanxi, China, bridging the fossil gaps and thereby elevating the genus Sterictopathes to a new family, Sterictopathidae fam. nov. The hypothesized evolutionary trend toward regularity in the axial skeleton from the Ordovician to modern Antipatharia is highlighted by reduced ridges and longitudinal fusion of networks. This discovery and confirmation of Ordovician black corals paves the way for future fossil findings and offers new insights into the early evolution of Hexacorallia.

Alternatipathes longispina sp. nov. and Bathypathes longicaulis sp. nov., two black corals (Antipatharia, Schizopathidae) from seamounts in the Western Pacific

Members of the order Antipatharia Milne-Edwards & Haime, 1857 are important structural components of hard bottom communities in the shallow and deep seas. However, their diversity in the Western Pacific is poorly known. Here we describe two new species of black corals within the family Schizopathidae Brook, 1889 from the tropical Western Pacific seamounts: Alternatipathes longispina sp. nov. and Bathypathes longicaulis sp. nov. The new species Alternatipathes longispina is characterized by a monopodial and unbranched corallum with the maximum width nearly two times as long as the height, the lower unpinnulated section of stem slightly shorter than the upper pinnulated one, the pinnules decreasing in length from the lowermost ones to the uppermost, and the prominent polypar spines ranging from 0.29 mm to 0.58 mm high, such a feature make the species differ from all congeners. Bathypathes longicaulis sp. nov. is characterized by a monopodial and unbranched corallum with a much longer unpinnulated stem and alternately arranged pinnules along the upper part of stem. It can be distinguished from congeners by its much longer unpinnulated stem, the alternately arranged pinnules, and the number of pinnules. Phylogenetic analyses based on the nuclear internal transcribed spacer region (ITS1-5.8S-ITS2) and three mitochondrial fragments cox3-IGR-cox1, trnW-IGR-nad2 and nad5-IGR-nad1 shows that A. longispina sp. nov. clusters with the type species A. bipinnata, and the genus Alternatipathes is closely related to Umbellapathes. The present phylogenetic trees confirm the polyphyly of Bathypathes and show that B. longicaulis sp. nov. is sister to Telopathes cf. magna MacIsaac & Best, 2013.

Complete mitochondrial genomes of the black corals Alternatipathesmirabilis Opresko & Molodtsova, 2021 and Parantipatheslarix (Esper, 1788) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae)

We describe the complete mitogenomes of the black corals Alternatipathesmirabilis Opresko & Molodtsova, 2021 and Parantipatheslarix (Esper, 1790) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae). The analysed specimens include the holotype of Alternatipathesmirabilis, collected from Derickson Seamount (North Pacific Ocean; Gulf of Alaska) at 4,685 m depth and a potential topotype of Parantipatheslarix, collected from Secca dei Candelieri (Mediterranean Sea; Tyrrhenian Sea; Salerno Gulf; Italy) at 131 m depth. We also assemble, annotate and make available nine additional black coral mitogenomes that were included in a recent phylogeny (Quattrini et al. 2023b), but not made easily accessible on GenBank. This is the first study to present and compare two mitogenomes from the same species of black coral (Stauropathesarctica (Lütken, 1871)) and, thus, place minimum boundaries on the expected level of intraspecific variation at the mitogenome level. We also compare interspecific variation at the mitogenome-level across five different specimens of Parantipathes Brook, 1889 (representing at least two different species) from the NE Atlantic and Mediterranean Sea.

One of the Deepest Genera of Antipatharia: Taxonomic Position Revealed and Revised

The genus Abyssopathes Opresko, 2002, comprises deep-sea black corals known almost exclusively from lower bathyal and abyssal depths, mainly from seamounts covered by cobalt-rich crusts and areas of polymetallic nodules. The taxonomical position of the genus and its placement in the family Schizopathidae has been repeatedly questioned, but fruitlessly. Known only in extremely deep habitats, these corals have rarely been collected in a state suitable for morphological or molecular studies that could help to clarify their status. Recently, increasing attention has been paid to the study of fauna associated with deep-sea minerals. Using material of Abyssopathes lyra (Brook, 1889) sampled during these studies, we transfer the genus Abyssopathes from the family Schizopathidae to the family Cladopathidae based on morphological and molecular data. Morphological data includes six mesenteries in the polyps, a unique pinnulation pattern found only in genera within the Cladopathidae, and relatively short polyp tentacles, a feature typical of some cladopathids. Sequencing data, consisting of 626 bp from the mitochondrial cox1 gene, showed that Abyssopathes is 99% identical to Chrysopathes Opresko, 2003, Cladopathes Brook, 1889, Heteropathes Opresko, 2011, and Trissopathes Opresko, 2003 (all Cladopathidae), in this gene region.

A new species of Bathypathes (Cnidaria, Anthozoa, Antipatharia, Schizopathidae) from the Red Sea and its phylogenetic position

A black coral, Bathypathesthermophila Chimienti, sp. nov. is described from the Saudi Arabian coasts of the Gulf of Aqaba and north Red Sea (Neom area) using an integrated taxonomic approach. The morphological distinctiveness of the new species is confirmed by molecular analyses. The species thrives in warm and high salinity waters typical of the Red Sea at bathyal depths. It can form colony aggregations on muddy bottoms with scattered, small hard substrates. Colonies are monopodial, feather-like, and attached to a hard substrate through a thorny basal plate. Pinnules are simple, arranged biserially and alternately, and all the same length (up to approximately 20 cm) except for few, proximal ones. Spines are triangular, laterally compressed, subequal, smooth, and simple or rarely bifurcated. Polyps are elongated transversely, 1.5-2.0 mm in transverse diameter. Large colonies can have one or few branches, whose origin is discussed. The phylogenetic position of B.thermophila sp. nov. within the order Antipatharia, recovered using three mitochondrial markers, shows that it is nested within the family Schizopathidae. It is close to species in the genera Parantipathes, Lillipathes, Alternatipathes, and Umbellapathes rather than to the other available representatives of the genus Bathypathes, as currently defined based on morphology. In agreement with previous findings, our results question the evolutionary significance of morphological characters traditionally used to discriminate Antipatharia at higher taxonomic level.

Description of a new and widely distributed species of Bathypathes (Cnidaria: Anthozoa: Antipatharia: Schizopathidae) previously misidentified as Bathypathes alternata Brook, 1889

For many years an undescribed species of the genus Bathypathes has been misidentified as Bathypathes alternata Brook, 1889 (a species currently re-assigned to the genus Alternatipathes). This new species is rather common at mid- and lower bathyal depths of the Pacific, Atlantic and Indian oceans, often in areas with high concentrations of commercially valuable cobalt-rich ferromanganese crusts, where it was observed in underwater photo and video transects to occur in high densities. Under the name B. alternata this species is recorded in several inventories and databases. There is an urgent need for a formal description of this misidentified and widely distributed species to avoid further confusion. The new species is superficially similar to A. alternata in having a monopodial corallum and simple, bilateral and alternately arranged pinnules. However, it differs from the former in that it has an upright corallum with a straight pinnulated part (vs. a horizontally bent pinnulated part), pinnules of uniform length and density (vs. decreasing regularly distally), and a constant distal angle formed by the pinnules and the stem along different parts of the corallum (vs. a decreasing distal angle near the top). The new species can therefore be easily distinguished from A. alternata in underwater imagery. We formally describe this new species in the genus Bathypathes and assign it the new name B. pseudoalternata. An extensive synonymy list with previous misidentified records is provided. To evaluate the distributional patterns of the new species we review the geographic distribution of antipatharians reported below 800 m. The majority of the hitherto described lower bathyal and abyssal species have been recorded from one biogeographic province; however, 20 species are known from more than two provinces, and only three species are widely distributed (>5 provinces), including the newly described Bathypathes pseudoalternata. Members of the family Schizopathidae, to which the new species belongs, represent the majority of the lower bathyal (50.54%) and abyssal (82.35%) species.