Research Article |
Corresponding author: Haibin Zhang ( hzhang@idsse.ac.cn ) Academic editor: Alexander Martynov
© 2022 Hasitha Nethupul, Sabine Stöhr, Haibin Zhang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Nethupul H, Stöhr S, Zhang H (2022) Review of Ophioplinthaca Verrill, 1899 (Echinodermata, Ophiuroidea, Ophiacanthidae), description of new species in Ophioplinthaca and Ophiophthalmus, and new records from the Northwest Pacific and the South China Sea. ZooKeys 1099: 155-202. https://doi.org/10.3897/zookeys.1099.76479
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The ophiuroid genus Ophioplinthaca is well characterized by the deep incisions in the disc. Prior to this study, it contained 32 accepted species, but species limits and geographic distributions were not well understood. The manned submersible vehicle ‘Shenhaiyongshi’ was used to collect ophiuroid specimens from the deep-sea seamounts and cold seeps in the South China Sea and Northwest Pacific at 602–3600 m depth, during 2018 to 2020. The genus Ophioplinthaca was reviewed using both morphological data and a phylogenetic analysis, based on COI sequences. The taxonomic status of the genus Ophiophthalmus Matsumoto, 1917, a junior homonym of Ophiophthalmus Fitzinger, 1843 (a reptile) was clarified by proving prevailing usage of the ophiuroid name. A total of eight species were identified, including two new species, described as Ophioplinthaca brachispina sp. nov. and Ophiophthalmus serratus sp. nov., and two new records. The new species are characterized by unique features of the arm skeletons. Tabular keys to all Ophioplinthaca and Ophiophthalmus species are provided. Interspecific and intraspecific genetic distance of Ophioplinthaca species ranged from 2.32% to 19.72%, and from 0.26% to 0.90%, respectively. The data suggest that species of the genus Ophioplinthaca are more widely spread around the Northwest Pacific region deep-sea seamounts than previously known.
COI, cold seep, molecular phylogeny, morphology, seamounts, SEM, taxonomy
The ophiuroid family Ophiacanthidae Ljungman, 1867 is one of the largest and diverse families in the order Ophiacanthida, containing 239 accepted species within 15 genera to date (
The genus Ophiophthalmus was created by
This study covers deep waters around the Northwest Pacific region near southwest Guam Island, and in the South China Sea (Xisha Islands and Haima cold seep). Here, we present an account of the ophiuroid species collected. Our goal is to present a diagnosis of the morphological features of these species, combined with molecular details, to complement the limited original descriptions and the lack of figures in the literature. We present comprehensive tabular keys for all species within the genera Ophioplinthaca and Ophiophthalmus. Two new species, one in Ophioplinthaca and one in Ophiophthalmus, are described, and six species of Ophioplinthaca are redescribed, including two new records from the Northwest Pacific region, all richly illustrated. These species live on seamounts and cold seeps, and this study adds to the known diversity in these unique habitats to better understand ophiuroid distribution and biogeography.
The manned submersible vehicle ‘Shenhaiyongshi’ was used to collect samples for this study on a seamount near Xisha Islands and on the Haima cold seep in the South China Sea, as well as on a seamount southwest of Guam Island (Fig.
Specimens were photographed through a dissecting stereo microscope (OLYMPUS SZX7) to identify external morphological characters. Arm skeletons were photographed by a scanning electron microscope (SEM) Phenom ProX. Arm skeletal elements were prepared by dissolving the soft tissue in undiluted NaOCl. The excess NaOCl in skeletal elements (ossicles) was removed by repeated flushing with distilled water. After drying, the ossicles were mounted on a stub, using ethanol dissolvable carbon tapes. Holotypes, paratypes and all other newly recorded specimens were deposited at the Institute of Deep-sea Science and Engineering (CAS), Sanya, China. The terms used to describe ophiuroids follow previous authors (
Type material and one other specimen of Ophioplinthaca lithosora (H. L. Clark, 1911) were examined from digital photographs.
DNA of identified specimens was extracted by using the TIANamp Marine Animals DNA kit (TianGen, Beijing) following the manufacturer’s protocol. We sequenced cytochrome c oxidase I (COI) partial genes for phylogenetic analysis by amplifying COIceF (5´- ACTGCCCACGCCCTAGTAATGATATTTTTTATGGTNATGCC-3´) and COIceR(5´-TCGTGTGTCTACGTCCATTCCTACTGTRAACATRTG-3´) COI primer set, with an initial denaturation at 95 °C for 3 min, followed by 40 cycles of denaturation at 94 °C for 45 s, annealing temperature at 51 °C to 55 °C for 70 s, and extension at 72 °C for 80 s; and a final extension at 72 °C for 5 min as a suitable PCR cycle (
We constructed a maximum likelihood (ML) phylogenetic tree to represent the family Ophiacanthidae by adding ten species from our collection and an additional 11 sequences from NCBI GenBank (Table
Localities, voucher information, and GenBank accession numbers for all specimens used in this study.
Species | Locality | Voucher number | COI |
---|---|---|---|
Ophioplinthaca sp. | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0108 | OK043831 |
Ophioplinthaca defensor | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0112 | OK043836 |
Ophioplinthaca defensor | Northwest Pacific Ocean: Caiwei Guyot | RSIO410611 | MT025778 |
Ophioplinthaca athena | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0110 | OK043833 |
Ophioplinthaca sp. | Northwest Pacific Ocean: St. RC-ROV08 | RSIO56058 | MW284981 |
Ophioplinthaca cf. lithosora | South China Sea: Xisha islands | IDSSE-EEB-SW0111 | OK043834 |
Ophioplinthaca globata | Papua New Guinea | MNHN BP32 | KU895134 |
Ophioplinthaca semele | Northwest Pacific Ocean: St. RC-ROV08 | RSIO56057 | MW284980 |
Ophioplinthaca semele | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0113 | OK043835 |
Ophioplinthaca plicata | Australia: Tasman Sea | MV F144758 | EU869989 |
Ophioplinthaca plicata | New Zealand | MV F188868 | KU895133 |
Ophioplinthaca grandisquama | Northwest Pacific Ocean: St. RC-ROV05 | RSIO56060 | MW284982 |
Ophioplinthaca amezianeae | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0109 | OK043832 |
Ophioplinthaca brachispina sp. nov. | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0106 | OK043829 |
Ophioplinthaca brachispina sp. nov. | Mariana Trench: Southwest of Guam island | IDSSE-EEB-SW0107 | OK043830 |
Ophiophthalmus cataleimmoidus | Canada: British Columbia, Kyoquot Sound | RBCM EC00208 | HM542946 |
Ophiophthalmus normani | Canada: British Columbia, Kyoquot Sound | RBCM EC00186 | HM542947 |
Ophiophthalmus serratus sp. nov. | South China Sea: Haima cold seep | IDSSE-EEB-SW0136 | OK043837 |
Ophiophthalmus serratus sp. nov. | South China Sea: Haima cold seep | IDSSE-EEB-SW0137 | OK043838 |
Ophiomyxa brevirima | New Zealand | MVF95868 | KU895170 |
Ophiomyxa anisacantha | Japan: Sagami Sea | NSMT E-6269 | AB758822 |
The following abbreviations are used in the text, tables, and figures:
ars arm spine;
as adoral shield;
ASE arm segment;
ass adoral shield spine;
COI Cytochrome C oxidase subunit 1;
D dorsal;
DAP/dap dorsal arm plate;
DAS/das dorsal arm spines;
de depression;
dist distal;
dl dorsal lobe;
ds disc spine;
dsc disc scale;
gra granules;
gs genital slit;
IDSSE Institute of Deep-sea Science and Engineering;
j jaw;
lac lateral ambulacral canal;
lap lateral arm plate;
LOP lateral oral papillae;
m madreporite;
ML Maximum Likelihood;
mo muscle opening;
msv manned submersible vehicle;
no nerve opening;
os oral shield;
pb podial basin;
prox proximal;
ri ridge;
RS/rs radial shield;
th thorns;
TS/ts tentacle scale;
v ventral;
VAP/vap ventral arm plate;
VAS/vas ventral arm spines;
vl ventral lobe;
VMT ventralmost tooth;
vs volute-shape;
Seven species of Ophioplinthaca were identified, among them one new to science, and all are described below. One specimen was identified as belonging to Ophiophthalmus and is described as a new species. One unidentified specimen of Ophioplinthaca is described, but not assigned to a name pending further investigations of variability within the genus. A tabular key to all species of Ophioplinthaca is provided in Table
A total of 21 COI sequences trimmed to 581 bp were obtained after removing ambiguous aligned sites and successfully reconstructing a genera Ophioplinthaca and Ophiophthalmus ML tree (Fig.
Two main clades were detected within the ML Tree (clade 01: genus Ophiophthalmus); clade 02: genus Ophioplinthaca). Average mean genetic distance of Ophiacanthidae was 21.74 ± 2.79% SE (19 specimens), and maximum value between two genera was 46.09 ± 4.81% SE. Overall average mean genetic distance of COI within Ophioplinthaca was 11.85 ± 1.70% SE (15 specimens). Interspecies and intraspecies genetic distance range among Ophioplinthaca species were 2.32–19.72% and 0.26–0.9% respectively. Overall average mean genetic distance of COI among Ophiophthalmus was 12.99 ± 1.76% SE (4 specimens), and interspecies genetic distance ranged between 7.06–21.20% (Table
Ophioplinthaca and Ophiophthalmus, pairwise distance values based on 581 bp mitochondrial COI sequences, calculated using the Kimura 2-parameter method with 1,000 bootstrap replicates (values in blue color represent Standard Error).
No. | Species | P-distance (%) | ||||||||||||||||||||
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1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | ||
1 | Ophioplinthaca sp. | 0.90% | 1.15% | 1.16% | 2.13% | 1.64% | 1.86% | 1.92% | 1.59% | 1.91% | 1.60% | 2.01% | 2.01% | 1.97% | 2.02% | 3.60% | 3.80% | 3.12% | 3.11% | 3.47% | 3.54% | |
2 | Ophioplinthaca defensor_1 | 4.27% | 0.26% | 1.17% | 2.11% | 1.63% | 1.81% | 1.97% | 1.60% | 1.89% | 1.60% | 1.68% | 1.94% | 1.85% | 1.89% | 3.70% | 3.97% | 3.24% | 3.23% | 3.37% | 3.52% | |
3 | Ophioplinthaca defensor_2 | 4.34% | 0.26% | 1.45% | 2.26% | 2.04% | 2.39% | 1.95% | 1.95% | 1.97% | 2.01% | 1.81% | 2.41% | 2.36% | 2.43% | 4.25% | 4.70% | 4.68% | 4.64% | 4.76% | 4.75% | |
4 | Ophioplinthaca athena | 6.73% | 7.09% | 7.20% | 1.94% | 1.54% | 1.76% | 1.71% | 1.50% | 1.70% | 1.55% | 1.84% | 1.78% | 1.81% | 1.86% | 3.69% | 3.85% | 3.28% | 3.27% | 3.40% | 3.51% | |
5 | Ophioplinthaca sp. RSIO56058 | 15.13% | 15.34% | 15.59% | 12.50% | 1.01% | 1.41% | 1.29% | 1.22% | 1.39% | 1.36% | 1.98% | 2.23% | 2.16% | 2.21% | 3.90% | 4.33% | 4.70% | 4.68% | 4.54% | 4.32% | |
6 | Ophioplinthaca cf. lithosora | 13.34% | 13.29% | 13.89% | 11.47% | 4.17% | 0.73% | 1.03% | 0.85% | 1.04% | 0.95% | 1.84% | 1.92% | 1.84% | 1.88% | 3.86% | 4.33% | 3.64% | 3.66% | 3.60% | 3.66% | |
7 | Ophioplinthaca globata | 13.06% | 12.20% | 11.77% | 11.16% | 5.21% | 2.32% | 1.31% | 0.96% | 1.33% | 1.20% | 2.04% | 2.15% | 2.02% | 2.07% | 4.28% | 4.69% | 3.63% | 3.62% | 3.95% | 4.04% | |
8 | Ophioplinthaca semele_1 | 12.97% | 13.81% | 13.24% | 10.28% | 5.81% | 4.15% | 4.43% | 0.43% | 1.01% | 1.11% | 1.80% | 2.48% | 2.34% | 2.40% | 4.25% | 4.56% | 4.80% | 4.81% | 4.74% | 4.52% | |
9 | Ophioplinthaca semele_2 | 13.15% | 13.32% | 13.26% | 11.26% | 5.48% | 3.92% | 4.00% | 0.76% | 0.88% | 0.80% | 1.74% | 1.98% | 1.82% | 1.86% | 3.97% | 4.29% | 3.47% | 3.47% | 3.47% | 3.58% | |
10 | Ophioplinthaca plicata_1 | 13.88% | 13.80% | 13.57% | 11.40% | 6.76% | 4.39% | 5.08% | 3.87% | 3.20% | 0.45% | 1.72% | 2.44% | 2.25% | 2.28% | 4.12% | 4.38% | 4.74% | 4.77% | 4.15% | 4.06% | |
11 | Ophioplinthaca plicata _2 | 13.34% | 13.51% | 14.18% | 12.05% | 6.74% | 5.01% | 5.95% | 4.67% | 3.54% | 0.90% | 1.79% | 2.04% | 1.91% | 1.94% | 4.12% | 4.48% | 3.68% | 3.69% | 3.31% | 3.48% | |
12 | Ophioplinthaca grandisquama | 13.96% | 10.46% | 10.79% | 11.62% | 13.89% | 12.14% | 10.26% | 11.43% | 11.27% | 11.25% | 12.08% | 2.50% | 2.31% | 2.36% | 4.22% | 4.33% | 4.47% | 4.44% | 4.35% | 4.48% | |
13 | Ophioplinthaca amezianeae | 16.84% | 15.90% | 15.96% | 14.17% | 16.99% | 16.45% | 16.04% | 18.62% | 17.81% | 19.72% | 18.21% | 19.37% | 1.70% | 1.68% | 3.59% | 3.78% | 3.16% | 3.14% | 3.59% | 3.58% | |
14 | Ophioplinthaca brachispina sp. nov. holotype | 17.35% | 15.96% | 17.44% | 14.76% | 15.80% | 15.35% | 15.43% | 16.97% | 15.37% | 17.66% | 16.40% | 18.83% | 12.66% | 0.25% | 3.96% | 4.15% | 3.38% | 3.35% | 3.80% | 3.98% | |
15 | Ophioplinthaca brachispina sp. nov. paratype | 17.68% | 16.25% | 17.80% | 15.03% | 16.13% | 15.42% | 15.53% | 17.32% | 15.45% | 17.68% | 16.27% | 19.17% | 12.46% | 0.35% | 3.91% | 4.10% | 3.36% | 3.33% | 3.86% | 4.03% | |
16 | Ophiophthalmus cataleimmoidus | 35.83% | 36.53% | 39.34% | 35.96% | 38.04% | 39.02% | 34.92% | 41.28% | 39.91% | 41.56% | 41.75% | 41.45% | 35.60% | 39.28% | 39.24% | 2.52% | 2.54% | 2.56% | 3.96% | 3.56% | |
17 | Ophiophthalmus normani | 37.88% | 40.61% | 44.94% | 37.99% | 41.88% | 43.15% | 37.96% | 43.18% | 42.77% | 43.61% | 45.13% | 43.34% | 37.52% | 40.43% | 40.38% | 21.20% | 1.37% | 1.34% | 3.62% | 3.51% | |
18 | Ophiophthalmus serratus sp. nov. holotype | 35.29% | 36.45% | 44.60% | 35.71% | 45.98% | 41.04% | 34.51% | 45.59% | 39.18% | 47.62% | 41.61% | 45.15% | 34.14% | 36.18% | 36.04% | 20.86% | 7.31% | 0.24% | 2.99% | 3.13% | |
19 | Ophiophthalmus serratus sp. nov. paratype | 34.99% | 36.15% | 44.08% | 35.41% | 45.50% | 41.04% | 34.51% | 46.09% | 39.18% | 48.09% | 41.61% | 44.68% | 33.56% | 35.58% | 35.43% | 21.17% | 7.06% | 0.35% | 3.00% | 3.15% | |
20 | Ophiomyxa brevirima | 41.60% | 40.93% | 47.22% | 41.42% | 45.76% | 41.96% | 39.47% | 47.33% | 40.93% | 43.09% | 38.75% | 44.10% | 41.77% | 45.04% | 45.07% | 39.60% | 38.90% | 35.26% | 35.54% | 2.05% | |
21 | Ophiomyxa anisacantha | 41.81% | 41.07% | 46.86% | 40.25% | 43.58% | 40.99% | 38.67% | 44.39% | 40.64% | 41.50% | 39.95% | 44.05% | 41.43% | 45.62% | 46.31% | 35.76% | 35.91% | 35.47% | 35.77% | 17.85% |
The new species, described morphologically below, were confirmed by the molecular analysis as separate from all other sequenced species (Fig.
Superorder Ophintegrida O’Hara, Hugall, Thuy, Stöhr and Martynov, 2017
Order Ophiacanthida O’Hara, Hugall, Thuy, Stöhr and Martynov, 2017
Suborder Ophiacanthina O’Hara, Hugall, Thuy, Stöhr and Martynov, 2017
Family Ophiacanthidae Ljungman, 1867
Holotype. Northwest Pacific • 1 specimen; near Mariana Trench, Southwest of Guam Island, seamount; 11°49.09'N, 140°6.93'E; depth 2713 m; 23 October 2019; Collecting event: stn. SC039; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043829; IDSSE-EEB-SW0106. Paratype. Northwest Pacific • 1 specimen; same data as for holotype; GenBank: OK043830; IDSSE-EEB-SW0107.
Disc sub-circular and deeply incised interradially to nearly 1/4 disc radius (Fig.
Ophioplinthaca brachispina sp. nov., holotype (IDSSE-EEB-SW0106) A dorsal disc B ventral disc C center of the disc D–F disc spines G radial shield H оral frame I ventral side of the arm base J dorsal side of the arm base K dorsal arm L ventral arm M lateral arm. Abbreviations: ars arm spine, as adoral shield, ass adoral shield spine, dap dorsal arm plate, das dorsal arm spine, dp disc plate, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (A, B); 1 mm (C, G–M); 200 µm (D–F).
Disc diameter 12 mm, arm base width 3 mm (Fig.
Disc. Disc sub-circular and deeply incised interradially to more than 1/3 disc diameter, creating five wedge-shaped lobes over each arm base in contrast to sunken center and interradii of disc (Fig.
Arms. Five moniliform arms with rough plates. Dorsal arm plates longer than wide, slightly separated, straight to slightly convex distal end, triangular proximal end, with curved lateral margins on first few proximal arm segments, but as long as wide, fan-shaped, and widely separated on middle to distal half of arm (Fig.
Color. In live specimen, orange-brown disc, and arm spines, but arms pale brown (Fig.
Arm spine articulations well developed and placed at slight angle to distal edge of lateral arm plate (Fig.
Ophioplinthaca brachispina sp. nov., paratype (IDSSE-EEB-SW0107) A, B lateral arm plate C dorsal arm spine D ventral arm spine E disc spine F dorsal arm plate G–K vertebrae G proximal view H distal view I ventral view, J dorsal view, K lateral view. Abbreviations: d dorsal, de depression, dist distal, dl dorsal lobe, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, ri ridge, th thorns, v ventral, vl ventral lobe. Scale bars: 800 µm (A, C, F–G, I–K); 500 µm (B, E, H); 100 µm (D).
One specimen from same location as holotype, but badly damaged due to rough handling. Therefore, only small disc part with arms present. Possibly smaller than holotype according to size of arms (arm base width 1.5–2 mm). Arm characters similar to holotype, but spines slightly thinner, and denser compared to holotype (Fig.
Ophioplinthaca brachispina sp. nov., paratype (IDSSE-EEB-SW0107) A dorsal arm B ventral arm C lateral arm D lateral arm plate (small thorns on the lateral arm plate surface shown in the orange rectangle). Abbreviations: dap dorsal arm plate, das dorsal arm spine, lap lateral arm plate, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 1 mm (A–C); 200 µm (D).
2713 m depth, Northwest Pacific, near Mariana trench, Southwest of Guam Island.
Species name derived from a combination of two Latin words, brachium (arm), spina (spine) referring to the unique rough arm surface with spines.
Deep interradial incisions into the disc, which are lined distally by enlarged disc scales are the main delimiting character of the genus Ophioplinthaca from other genera within the family Ophiacanthidae. Ophioplinthaca brachispina sp. nov. showed similar morphological characters to many other Ophioplinthaca species. However, O. brachispina sp. nov. can easily be distinguished from congeners by the rough thorny surface on the arm plates and additionally by the number of arm spines, disc spines, and tentacle scale (Table
Tabular key to all species of the genus Ophioplinthaca. Abbreviations: ASE arm segment, ASS Adoral shield spine, DAP dorsal arm plate, DAS dorsal arm spines, L length, LOP lateral oral papillae, VAP ventral arm plate, VAS ventral arm spines, VMT ventralmost tooth, W width.
Species | No. of arm spines | Radial shields | Oral frame | Tentacle scale | Dorsal arm plate (DAP), and ventral arm plate (VAP) | Arm spine shape and length | Disc spines | References |
---|---|---|---|---|---|---|---|---|
Ophioplinthaca abyssalis Cherbonnier & Sibuet, 1972 | up to 7 | separated proximally but connected at distal ends | 4–5 LOP, spiniform, 1 VMT | 1st pore 2, then 1, elongated, blunt | VAP-separated, DAP 1–3 have few spines and contiguous then separated | thorny surface | long, conical |
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Ophioplinthaca amezianeae O’Hara & Stöhr, 2006 | up to 10 | separated, L = 2W | up to 4–5 LOP, spiniform, 1 VMT | 1st pore 2–3, 2nd pore 1–2, then 1, spiniform with rounded base, tapering sharply or tip covered in irregular thorns | separated | covered with conspicuous thorns | long, rounded base, with spinelets on lateral surface |
|
Ophioplinthaca athena A.H. Clark, 1949 | up to 5 | separated proximally, connected at distal ends, L = 4W | 4 LOP, pointed, flattened, larger, equal in size, 1 VMT | 1st pore 2, then 1, oval, pointed, beyond 3rd pore slender spiniform | VAP on 1st ASE contiguous with next, then separated, DAP contiguous (terminal portion slightly separated) | 1st DAS smooth, 2 × ASE length; 2nd DAS, 4 × ASE length; shorter thorny VAS | elongated with thorny tip, at periphery with smooth tip | A. H. |
Ophioplinthaca brachispina sp. nov. | up to 5 | separated by large single disc scale or connect at distal ends | 4 LOP, pointed, distal one with wider flat edge, 1 VMT, ASS covered by cluster of granules | 1st pore 2, half as long as VAP, terminally spiniferous, oval on base of arm, then slightly pointed along arm | DAP and VAP separated, thorny surface | DAS with distal lateral thorns; VAS ≈ 1–2 × ASE length, pointed, thorny, rugose | bifid or thorny pointed tip, cylindrical | this study |
Ophioplinthaca bythiaspis (H. L. Clark, 1911) | up to 6 | separated, L = 4W | 4–5 LOP, equal in height, distally slightly wider, 1 VMT | oval to bottle-shaped, as long as VAP | VAP separated beyond 3 ASE | DAS smooth, VAS with thorny surface | conical or more rounded with thorns at tip | H. L. |
Ophioplinthaca carduus (Lyman, 1878) | up to 6 | separated | 4–5 LOP, first 3–4 conical, blunt tip, distalwards flat, spearhead-shaped, small, pointed, 1 VMT, curved adoral shield | strongly thorny, after 1st pore, with 1 or 2 lateral thorns | VAP separated, DAP on 1–3 × ASE contiguous, then separated | stout, cylindrical, glassy, blunt, very thorny | short, stout stump with thorny tip |
|
Ophioplinthaca chelys (C. W. Thomson, 1877) | up to 6 | separated, deeply sunken | 5 LOP, first 3–4 conical, blunt tip, 1 VMT | large and flat | VAP and DAP separated | cylindrical, glassy, blunt, very thorny | cylindrical, thorny or smooth, thorny tip, spines dense in disc center. | C. W. |
Ophioplinthaca citata Koehler, 1904 | up to 9 | separated L = 3–4W | 3–4 LOP, blunt, distal one has wider flat edge, 1 VMT | oval to elliptical | DAP contiguous, except first few ASE, VAP contiguous | DAS ≈ 4 × ASE length, VAS short, thorny, hollow | cylindrical, terminal crown of thorns |
|
Ophioplinthaca clothilde A.H. Clark, 1949 | up to 7 at arm base then 5 | contiguous, ovoid, about half as long as broad | 4 LOP, pointed, flattened, large, 1 VMT of equal size | 1st pore 2, then 1, leaf-like to narrow, sharply pointed with numerous spinelets at tip | VAP separated after 2 ASE, DAP separated | DAS ≈ 4 × ASE length, DAS and VAS with thorny surface, DAS longest | in disc center cylindrical base ending in 2–3 sub-crowns, at periphery short, stout with irregular crown of a dozen or more thorns | A. H. |
Ophioplinthaca codonomorpha (H. L. Clark, 1911) | up to 8 | widely separated, small, convex proximally, as wide as long | 3 LOP, 1 VMT | 1st pore 2, oval, conspicuously large, then oval with pointed tip | VAP at 1st to 2nd ASE contiguous then separated, DAP barely contiguous | 1–3 DAS smooth or thorny; VAS also smooth | minute rough granules | H. L. |
Ophioplinthaca crassa H. L. Clark, 1939 | basally 4 then up to 5 or 7 | distally connected, small, as wide as long, convex proximally | 3 LOP, narrow, elongated, pointed, distalwards short and wide, 1 large VMT | 1st pore 2–3, blunt, 1mm long and wide, very thick, somewhat triangular, then less stout, slender pointed | VAP, DAP in first 1–2 ASE contiguous, then separated | short, stout, but fragile, thorny spines, DAS ≈ 2 × ASE length | low cylindrical tube | H. L. |
Ophioplinthaca defensor Koehler, 1930 | up to 7 at arm base | separated proximally, connected distally | 4 LOP, 1 VMT | 1st pore 1, long, and leaf-like then narrower with pointed tip | DAP and VAP contiguous | thorny surface, conspicuous thorns on DAS; DAS ≈ 3 × ASE, VAS ≈ 1 × ASE length | cylindrical with thorn at tip |
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Ophioplinthaca dipsacos (Lyman, 1878) | up to 6 | separated proximally, connected distally | 4–5 LOP, pointed, flattened, ill-defined distalwards, 1 VMT | large, pointed with 1 or 2 microscopic thorns | VAP and DAP separated | long, slender, DAS 5–7 × ASE length, with conspicuous thorns, VAS 1½–2 × ASE length with thorny surface | short, stout, with thorny tip, at periphery smooth |
|
Ophioplinthaca globata Koehler, 1922 | up to 6 | separated proximally, connected distally | 3–4 LOP, bunt, distal one has wider flat edge, 1 VMT, ASS covered by small granules | 1st pore 2–3, as long as VAP, terminally spiniferous in larger specimen | DAP and VAP separated | thorny surface | cylindrical, bifid or tip mostly with 3 thorns |
|
Ophioplinthaca grandisquama Chen, Na, & Zhang, 2021a | up to 7 | contiguous, L = 1.5W | up to 3–4 LOP, spiniform, 1 or 2 VMT | 1st pore 1–2, only 1 in following ASE, long, thorny with thick base, tapering into blunt point | DAP contiguous, VAP separated | DAS thin with distal lateral thorns, up to 3 × ASE length; VAS short, blunt, and finely rugose | stout, tall, bearing numerous distinct thorns laterally or at tip, some bifurcated into two prongs with thorny tips |
|
Ophioplinthaca grenadensis John and A. M. Clark, 1954 | up to 5 | separated oval proximally | up to 5 LOP, spiniform, 1 VMT | leaf-like, then slightly elongated with pointed tip along arm | DAP in first 1–2 ASE contiguous, then separated, VAP separated | flattened, covered by glassy spines | long, thick spinelets with rough thorny lateral surface in disc center, at periphery shorter | John and A. M. Clark (1954) |
Ophioplinthaca hastata Koehler, 1922 | up to 7 | contiguous, L = 1.5W | 4–5 LOP, spiniform to club-shaped, distal ones largest, sometimes small granules present on distal edge of jaw, 1 VMT, 1 or 2 ASS | 1st pore 2, then 1, clavate, terminally spiniferous, longer than VAP | separated | smooth, DAS ≈ 3 × ASE length | numerous thorns at cylindrical tip |
|
Ophioplinthaca incisa (Lyman, 1883) | up to 5 | small, separated proximally, connected distally | 4–5 LOP, spiniform., distal ones wide, flat, 1 VMT, 1 or 2 ASS | 1st pore 3, then 1 | VAP separated | smooth, DAS ≈ 3 × ASE, VAS ≈ 1 × ASE length | cylindrical with thorny tip or thorny surface laterally, at disc periphery smooth |
|
Ophioplinthaca laudator Koehler, 1930 | up to 7 | small, separated proximally, connected distally | 4 LOP, sometimes irregularly arranged, elongated, pointed but distalmost one flat and wide, 1 VMT | – | VAP separated beyond 2nd ASE, DAP separated | DAS thorny, VAS smooth, DAS ≈ 2 × ASE, VAS ≈ 1½ –2 × ASE length | cylindrical with 2–3 thorns at tip or lateral thorns, at disc periphery smooth, conical |
|
Ophioplinthaca lithosora (H. L. Clark, 1911) | up to 6 or 7 | long, narrow, separated | 10–15 LOP including small granules at distal edge of jaw | 1st pore 3, 2nd pore 2, then one, large, pointed tip | VAP separated, tetragonal | first 1–2 DAS, smooth, 3 × ASE length, with thorny tip, 3 thorny VAS | cylindrical, bifid or mostly with 3 thorns at tip or with lateral thorns | H. L. |
Ophioplinthaca manillae Guille, 1981 | up to 6 | as wide as long, contiguous | 3 LOP, 1 VMT, rough edges, large, pointed, small granules at distal edge of jaw | oval, large, rough edges | DAP on first 1–2 ASE contiguous, then separated, VAP separated | DAS ≈ 3 × ASE, VAS ≈ 1 × ASE length, thorny | bifid or mostly with 3 divided thorns at tip, central spines longer than peripheral ones |
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Ophioplinthaca miranda Koehler, 1904 | up to 5 or 6 | separated proximally, connected distally | 3 LOP, 1 large VMT | triangular | DAP and VAP contiguous | both DAS and VAS small, thorny, rugose and same length | cylindrical with thorny circular tip |
|
Ophioplinthaca monitor Koehler, 1930 | up to 7 or 8 | separated | 4 LOP, 1 VMT, distalmost one smaller | 1st pore 2, then 1, oval to rounded proximally and pointed distally | DAP on first 2 ASE contiguous, then separated, fan-shaped | DAS with conspicuously sparse thorny surface, VAS thorny | granules with thorny tip |
|
Ophioplinthaca papillosa H. L. Clark, 1939 | up to 7 | separated, narrow | 3–4 LOP, narrow, subequal, long, pointed, 1 VMT | flat, moderately, large, pointed | separated | rough surface, DAS ≈ 3 × ASE, VAS ≈ 1 × ASE length | in disc center with long tip dividing into 2–3 thorns, at periphery with spinous tip | H. L. |
Ophioplinthaca plicata (Lyman, 1878) | up to 8 | contiguous, L = 2–2.5W | 3–5 LOP, 1–3 VMT, spiniform | 1st pore 2–3, curved inward, pointed round tip | DAP contiguous, VAP separated | thorny surface | conical, cylindrical, finely rugose or rarely with few longer thorns |
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Ophioplinthaca pulchra Koehler, 1904 | up to 7 | separated proximally, connected distally | 4 LOP, 1 VMT | leaf-like | first two VAP contiguous, then separated, DAP contiguous | thorny, rugose surface, uppermost DAS longest | cylindrical with thorny tip in center, at periphery smaller and conical |
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Ophioplinthaca rudis (Koehler, 1897) | up to 5 | completely separated or distally connected | 5–6 LOP, spiniform, 1 VMT | leaf-like | DAP contiguous or separated, VAP widely separated | finely thorny | long spines with smooth surface |
|
Ophioplinthaca sarsii (Lyman, 1878) | up to 8 | separated | 3 LOP small, pointed, 1 VMT | flat, tapering, jagged | DAP, VAP separated | stout, cylindrical, glassy, blunt, very thorny | smooth cylindrical |
|
Ophioplinthaca semele (A.H. Clark, 1949) | up to 7 | separated proximally, connected in distally, L ≈ 2½–3W | 5 LOP, pointed, flatted, ill-defined, 1 VMT | 1st pore 3 or rarely 5, 2nd pore 2–3, 3rd pore 2, then one, large, pointed tip | VAP in first 1–2 ASE contiguous, then separated, DAP separated | long, slender, DAS with conspicuous thorns, VAS thorny surface | short, stout, with thorny tip, or 3 thorns, at periphery smooth spines without thorns | A. H. |
Ophioplinthaca sexradia Mortensen, 1933 | up to 4 | separated proximally, connected distally | 3 LOP, 1 VMT | small, leaf-like | separated, small | small, thick base | irregular scales with conical tubercles |
|
Ophioplinthaca spinissima H. L. Clark, 1900 | up to 9 | separated proximally, connected in distally, longer than wide | up to 5–7 LOP, spiniform, 1VMT | 1st pore one or divided into two, then more pointed distalwards along arm | DAP widely separated | thorny surface | spine with thorny tip, or 3 thorns, at periphery smooth spines without thorns, tip relatively flat with thorns | H. L. |
Ophioplinthaca sp. | up to 6 | contiguous, distally convex, proximally triangular L = 2W | 4–5 LOP, pointed, elongated, slightly flattened distal end, 1 VMT large, slightly longer than LOP | 1st pore 1–2, then 1, leaf-like, but along arm narrower, thorny, pointed; as long as VAP | both VAP and DAP widely separated | DAS has conspicuous lateral thorns; VAS with thorny surface | disc center: conical or short cylindrical spines, when cylindrical with two sub-thorns; at periphery smooth, conical or short, cylindrical, finely rugose to smooth | this study |
Ophioplinthaca tylota H. L. Clark, 1939 | up to 6 | separated proximally, connected distally | 4 LOP, narrow, equal, long, pointed, 1 VMT | very thick, heavy, smooth but increasingly flatter along arm, smaller, very thorny | first and second DAP contiguous, then separated, VAP separated | thorny spine, DAS with conspicuous thorns, DAS ≈ 3 × ASE, VAS ≈ 1 × ASE length | smooth, rounded spine | H. L. |
Ophioplinthaca webri (Koehler, 1904) | up to 7 | separated proximally, connected distally | 4 LOP, narrow, equal, long, pointed, 1 large VMT | 1st pore 2–3, then 1, elongated | DAP and VAP contiguous | – | - |
|
Some species share morphological characters with the new species. Ophioplinthaca globata Koehler, 1922 is similar to O. brachispina sp. nov. by having similar disc spine shape, arm spine shape, radial shields separated proximally and connected distally, number of lateral oral papillae, and separated ventral and dorsal arm plates, but differs by number of arm spines (up to six), the disc spines being scattered across the disc, radial shields separated by disc scales, characters of the oral shield, and a smooth surface on the arm plates along the entire arm. Ophioplinthaca hastata Koehler, 1922 is similar to O. brachispina sp. nov. by having a slightly similar shape of the disc spines, separated dorsal and ventral arm plates, and similar tentacle scales on the distal end of the arm, but differs by number of arm spines (up to seven) and shape of dorsal arm spines, size of radial shields, characters of oral parts, and smooth arm surface. Ophioplinthaca athena A.H. Clark, 1949 is similar to O. brachispina sp. nov. by having similar disc spines with thorny tip, similar number of arm spines, separated radial shields, number of lateral oral papillae, but differs by large radial shields, thorny and leaf-like tentacle scales, separated dorsal and ventral arm plates. Ophioplinthaca amezianeae O’Hara & Stöhr, 2006 is similar to O. brachispina sp. nov. by having similar thorny tentacle scales, separated radial shields, separated dorsal and ventral arm plates, number of lateral oral papillae, but differs by number of arm spines, tall and thorny disc spines, and spiniform lateral oral papillae. Ophioplinthaca bythiaspis (H. L. Clark, 1911) is similar to O. brachispina sp. nov. by having separated radial shields and number of lateral oral papillae, but differs by oval tentacle scales, conical disc spines, number of arm spines and contiguous dorsal arm plates. Ophioplinthaca grenadensis John & A. M. Clark, 1954 is similar to O. brachispina sp. nov. by having similar number of arm spines, separated radial shields, number of lateral oral papillae, and separated arm plates but differs by leaf-like thornless tentacle scales, long and thick disc spines. Ophioplinthaca plicata (Lyman, 1878) is similar to O. brachispina sp. nov. by having similar disc and arm spines, and number of lateral oral papillae, but differs by continues dorsal arm plates, pointed tentacle scale with rounded base, and contiguous radial shields. Ophioplinthaca rudis (Koehler, 1897) is similar to O. brachispina sp. nov. by having similar thorny leaf-like tentacle scales, similar number of arm spines, separated radial shields, separated dorsal and ventral arm plates, but differs by number of lateral oral papillae, tall and thorny disc spines, and spiniform lateral oral papillae.
One of the most distinguishing characters to delimit the new species from almost all species in the genus Ophioplinthaca is the presence of spines with rough surface on lateral, ventral, and dorsal arm plates. The paratype (relatively smaller than the holotype) has thinner and denser spines on the arm. Although, some Ophioplinthaca species have a rough surface on dorsal arm plates or the distal margin covered with minute spines (Ophioplinthaca plicata and Ophioplinthaca incisa; (
Northwest Pacific • 1 specimen; near Mariana Trench, Southwest of Guam Island, seamount; 12°36.44'N, 140°51.73'E; depth 2779 m; 23 September 2019; Collecting event: stn. SC038; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043831; IDSSE-EEB-SW0108.
Disc diameter 9 mm, arm base width 2 mm (Fig.
Disc. Disc sub-pentagonal, incised interradially to nearly 1/5 disc radius, creating five wedge-shaped lobes over each arm base in contrast to sunken center and interradii of disc (Fig.
Ophioplinthaca sp. (IDSSE-EEB-SW0108) A dorsal disc B ventral disc C center of the disc D–F disc spines G radial shield H lateral disc I oral frame J ventral side of the arm base K dorsal arm L ventral arm M lateral arm. Abbreviations: as adoral shield, dap dorsal arm plate, das dorsal arm spine, dp disc plate, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 1 mm (A, B, M); 500 µm (C, E, G–L); 200 µm (D, F).
Arms. Five slightly moniliform arms, with smooth plates. Dorsal arm plates fan-shaped, as long as wide, widely separated, with convex distal edge, triangular proximal edge, straight lateral margins. Proximal edge of dorsal arm plate changes from obtuse to sharp triangular along arm (Fig.
Color. In live specimen, pale orange-brown (Fig.
Ossicle morphology. Arm spine articulations well developed, six in number, placed at slight angle to distal edge of lateral arm plate. A volute-shaped perforated lobe forms dorsal and distal parts of articulation (Fig.
Ophioplinthaca sp. (IDSSE-EEB-SW0108) A, B lateral arm plate C dorsal arm spine D–H vertebrae D proximal view E distal view F ventral view G dorsal view H lateral view. Abbreviations: d dorsal, de depression, dist distal, dl dorsal lobe, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, ri ridge, th thorns, v ventral, vl ventral lobe, vs volute-shape. Scale bars: 800 µm (B); 500 µm (A, C–H).
2779 m depth, Northwest Pacific, near Mariana trench, Southwest of Guam Island.
Ophioplinthaca sp. shares morphological characters with many other Ophioplinthaca species, but can easily be delimited by the number of arm spines, disc spine shape, radial shields, and tentacle scale characters (Table
The most similar species to Ophioplinthaca sp. is Ophioplinthaca clothilde sharing contiguous radial shields, similar number of arm spines (up to seven), number and shape of lateral oral papillae, similar tentacle scale, and separated ventral and dorsal arm plates, but differs in longer dorsal arm spines (up to four arm segments), disc spines with single cylindrical base ending in two or three crowns, or a stout disc spine with irregular crown of a dozen or more spinules, more or less ovoid radial shields with convex proximal side, slightly contiguous dorsal arm plates on proximal arm segments, and equal size of ventralmost tooth and lateral oral papillae. We refrain from naming our specimen, as these differences may suggest an undescribed species or fall within the insufficiently known variability of O. clothilde. This question may be answered, when more specimens have been collected, and molecular data are needed for O. clothilde.
Ophioplinthaca globata is similar to Ophioplinthaca sp. by having a similar number of arm spines (up to six), number of lateral oral papillae, and separated ventral and dorsal arm plate and shape, but differs by thorny disc spine and spine shape, separated radial shields and their shape, and tentacle scale longer than ventral arm plate. Ophioplinthaca laudator Koehler, 1930 shares with Ophioplinthaca sp. almost the same number of arm spines (up to seven), by size of radial shields, number and shape of lateral oral papillae, and separated dorsal and ventral arm plates, but differs in thorny disc spines, with two to three thorns or sub-thorns on their lateral surface, separated radial shields, and smooth arm spines. Ophioplinthaca grandisquama is similar to Ophioplinthaca sp. by having contiguous radial shields, closer number of arm spines (up to seven), and by the shape of arm and disc spines, but differs by tall (0.8 mm in high) long, thorny disc spines with two or three thorny sub-crowns, blunt tentacle scale, and contiguous ventral and dorsal arm plates. Ophioplinthaca manillae Guille, 1981 is similar to Ophioplinthaca sp. by having similar number and shape of arm spines, contiguous radial shields, shape of lateral oral papillae, and separated dorsal and ventral arm plates, but differs in an oval tentacle scale, and in height and shape of disc spines.
Ophioplinthaca amezianeae O’Hara & Stöhr, 2006: 77–78, fig. 9D–G.
Northwest Pacific • 1 specimen; near Mariana Trench, Southwest of Guam Island, seamount; 11°40.33'N, 141°20.57'E; depth 3600 m; 27 November 2020; Collecting event: stn. SC040; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043832; IDSSE-EEB-SW0109.
Disc diameter 11.5 mm, arm base width 2.5 mm (Fig.
Disc. Sub-pentagonal and incised interradially to 1/8 disc radius, creating five wedge-shaped lobes over each arm base in contrast to sunken center and interradii of disc (Fig.
Ophioplinthaca amezianeae O’Hara & Stöhr, 2006 (IDSSE-EEB-SW0109) A dorsal disc B ventral disc C center of the disc D–G disc spines H radial shield I oral frame J dorsal side of the arm base K dorsal arm L ventral arm, M lateral arm. Abbreviations: as adoral shield, ass adoral shield spine, dap dorsal arm plate, das dorsal arm spine, dp disc plate, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (A, B); 1 mm (H, I, K, M); 500 µm (C, J, L); 200 µm (D–G).
Arms. Five slightly moniliform arms, with smooth plates. Dorsal arm plates fan- to bell-shaped, with truncated proximal end on first dorsal arm plate, but following plates with obtuse proximal end, straight to slightly convex proximolateral margins, and convex distal margin (Fig.
Color. In live specimen, orange-brown dorsal disc, pale color on arms and ventral disc, arm spines orange, and disc spines red (Fig.
Ossicle morphology. Arm spine articulations well developed, four in number, and placed at slight angle to distal edge of lateral arm plate. Volute-shaped perforated lobe forms dorsal and distal part of articulation (Fig.
Ophioplinthaca amezianeae O’Hara & Stöhr, 2006 (IDSSE-EEB-SW0109) A, B lateral arm plate C ventral arm spine D–H vertebrae D proximal view E distal view F ventral view G dorsal view H lateral view. Abbreviations: d dorsal, de depression, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, ri ridge, th thorns, v ventral, vs volute-shape. Scale bars: 800 µm (A–E, G, H); 500 µm (F).
1618–3600 m depth, Southwest of Guam Island, Northwest Pacific, New Caledonia, New Zealand.
Ophioplinthaca amezianeae was described by
Ophioplinthaca amezianeae from the present study is similar to the holotype description, but it differs slightly in the disc spine shape and number of arm spines on the lateral arm plate. However, the number of arm spines differs between individuals (6–10 arm spines) according to the description of paratype variations of O. amezianeae (
Ophioplinthaca athena
A. H Clark, 1949: 23–24, fig. 9;
Northwest Pacific • 1 specimen; near Mariana Trench, Southwest of Guam Island, seamount; 12°8.83'N, 139°0.37'E; depth 1987 m; 27 November 2020; Collecting event: stn. SC041; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043833; IDSSE-EEB-SW0110.
Disc diameter 12.5 mm, arm base width 1.5 mm (Fig.
Disc. Sub-circular and incised interradially, creating five wedge-shaped lobes over each arm base in contrast to sunken center and interradii of disc (Fig.
Ophioplinthaca athena A. H. Clark, 1949 (IDSSE-EEB-SW0110) A dorsal disc B ventral disc C center of the disc D–E disc spines F radial shield G lateral disc H оral frame I ventral side of the arm base J dorsal side of the arm base K dorsal arm L ventral arm M lateral arm. Abbreviations: as adoral shield, ass adoral shield spine, dap dorsal arm plate, das dorsal arm spine, dp disc plate, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (A, B); 1 mm (C, F–K, M); 500 µm (L); 200 µm (D, E).
Arms. Five slightly moniliform arms, with smooth plates. Dorsal arm plates twice as long as wide, with truncated proximal end in first dorsal arm plate (Fig.
Color. In live specimen, orange-brown dorsal disc, light color in arms and ventral disc, arm spines orange, disc spines and papillae red (Fig.
Ossicle morphology. Arm spine articulations well developed, four in number, and placed at slight angle to distal edge of lateral arm plate. Volute-shaped perforated lobe forms dorsal and distal part of articulation, with large muscle opening and small nerve opening (Fig.
Ophioplinthaca athena A. H. Clark, 1949 (IDSSE-EEB-SW0110) A, B lateral arm plate C dorsal arm spine D dorsal arm plate E–I vertebrae E proximal view F distal view G ventral view H dorsal view I lateral view. Abbreviations: d dorsal, de depression, dist distal, dl dorsal lobe, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, ri ridge, th thorns, v ventral, vl ventral lobe, vs volute-shape. Scale bars: 800 µm (A–I).
1866–2157 m depth, Southwest of Guam Island, Northwest Pacific, Kupuai, Hawaii Islands.
Ophioplinthaca athena was described by A. H
Ophioplinthaca athena from the present study is similar to the holotype description, but it differs slightly by separated dorsal arm plates and the shape of the dorsal arm spines, although the latter varies within our individual. Therefore, the shape of the arm spines is not a suitable morphological character to delimit O. athena. The description of the holotype mentioned that dorsal arm plates were contiguous, but in our specimen, they are just separated along the arm, and there are no paratypes of O. athena. Therefore, this difference may be related to the size of the specimen (holotype 14.5 mm disc diameter; A. H.
Ophiocamax lithosora H. L. Clark, 1911: 191–193, fig. 89.
Ophiomitra lithosora:
China • 1 specimen; South China Sea, near Xisha Islands archipelago, seamount; 16°47.79'N, 113°15.04'E; depth 602 m; 31 March 2020; Collecting event: stn. SC009; Shenhaiyongshi msv leg; preserved in-80 °C; GenBank: OK043834 IDSSE-EEB-SW0111.
Japan • Holotype specimen; East China Sea, Osumi Islands, Kuchnioerabu Island; 30°22'N, 129°08.5'E; depth 660 m; 13 Aug 1906; Collecting event: stn. 4918; R/V Abatross, North Pacific Expedition leg; preserved dry;
Disc diameter 20 mm, arm base width 4.5 mm (Fig.
Disc. Sub-pentagonal and incised interradially, creating five wedge-shaped lobes over each arm base in contrast to sunken center and interradii of disc (Fig.
Ophioplinthaca cf. lithosora (H. L. Clark, 1911) (IDSSE-EEB-SW0111) A dorsal disc B ventral disc C center of the disc D–G disc spines H radial shield I оral frame J ventral side of the arm base K dorsal arm L ventral arm, M lateral arm. Abbreviations: ars arm spine, as adoral shield, ass adoral shield spine, dap dorsal arm plate, das dorsal arm spine, dp disc plate, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (A–C, K); 1 mm (H–J, L, M); 500 µm (D, E); 200 µm (F, G).
Arms. Dorsal arm plates pentagonal, wider than long, with truncated proximal end, weakly convex proximolateral margins, straight lateral margins, and convex to slightly wavy distal margins, on proximal to middle arm segments contiguous, but distally separated (Fig.
Color. In live specimen, orange-brown dorsal disc, pale color in arms and ventral disc, arm spines orange, disc spines and papillae red (Fig.
Ossicle morphology. Arm spine articulations well developed, five in number, and placed at slight angle to distal edge of lateral arm plate. Volute-shaped perforated lobe forms dorsal and distal part of articulation, with large muscle opening and small nerve opening, and decreasing in size ventralwards (Fig.
Ophioplinthaca cf. lithosora (H. L. Clark, 1911) (IDSSE-EEB-SW0111) A, B lateral arm plate C dorsal arm spine D ventral arm spine E–I vertebrae E proximal view F distal view G ventral view H dorsal view I lateral view. Abbreviations: d dorsal, de depression, dist distal, dl dorsal lobe, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, ri ridge, th thorns, v ventral, vl ventral lobe. Scale bars: 800 µm (A–I).
462–663 m depth, South China Sea, East China Sea, Japan Sea.
Ophioplinthaca lithosora was described by H. L.
Ophioplinthaca cf. lithosora from the present study concurs with the holotype description in most respects, but it differs slightly by having contiguous dorsal arm plates, long spines in the center of the disc and few granules in the mouth angle at only some jaws. These granules are present at the second tentacle pore at the adoral shield at all jaw angles in the holotype, paratype and an additional specimen, all of which we examined from digital photographs. They are more obvious than in any other species of Ophioplinthaca and H. L.
Ophiomitra semele A. H Clark, 1949: 20–23, fig. 8a, b.
Ophioplinthaca semele:
Northwest Pacific • 1 specimen; near Mariana Trench, Southeast of Guam Island, seamount, 12°6.67'N, 141°37.27'E; depth 1160 m; 03 September 2019; Collecting event: stn. SC033; Shenhaiyongshi msv leg; preserved in -80 °C; GenBank: OK043835, IDSSE-EEB-SW0113.
537–1987 m depth, southwest of Guam Island, Northwest Pacific, Hawaii Islands.
Ophioplinthaca semele was first described by A. H
Ophioplinthaca semele (A. H Clark, 1949) (IDSSE-EEB-SW0113: A–H) A dorsal disc B ventral disc C center of the disc D radial shield E оral frame F ventral arm G dorsal arm H lateral arm; Ophioplinthaca defensor Koehler, 1930 (IDSSE-EEB-SW0112: I–Q) I dorsal disc J ventral disc K center of the disc L disc spine M оral frame N lateral disc O dorsal arm P ventral arm Q lateral arm. Abbreviations: as adoral shield, dap dorsal arm plate, das dorsal arm spine, gs genital slit, j jaw, lap lateral arm plate, m madreporite, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (I); 1 mm (A, B, F–H, J, N–P); 500 µm (C–E, K, M, Q); 200 µm (L).
Ophioplinthaca defensor
Koehler, 1930: 84–86, pl. 9, figs1, 2;
Northwest Pacific • 1 specimen; near Mariana Trench, Southwest of Guam Island, seamount; 12°8.83'N, 139°0.37'E; depth 1987 m; 27 November 2020; Collecting event: stn. SC041; Shenhaiyongshi msv leg; preserved in -80°C; GenBank: OK043836; IDSSE-EEB-SW0112.
385–2000 m depth, Southwest of Guam Island, Caiwei Guyot, Weijia Guyot, Batiza Guyot, Northwest Pacific, New Caledonia, New Zealand, Tasman Sea.
Ophioplinthaca defensor was first described by
Ophiacantha cataleimmoida H. L. Clark, 1911
Included species:
Ophiophthalmus normani (Lyman, 1879)
Ophiophthalmus relictus (Koehler, 1904)
Ophiophthalmus hylacanthus (H. L. Clark, 1911)
Adapted from
100–2194 m depth, North Pacific, Australia, New Zealand, Papua New Guinea, South Africa. Substrate of mud, fine grey sand, Foraminifera, and small stones (
Ophiophthalmus was created by
Both names are available, because they have been published with either a description or mention of a type species, and they satisfy articles 10, 11, and 12 of the Code.
Ophiophthalmus belongs to one of the largest and diverse ophiuroid families, Ophiacanthidae in the order Ophiacanthida, and is delineated from most other genera by having minute granular coverage of the disc, smooth and somewhat finely serrated arm spines, ovoid radial shields, and by characters of the arm plates (
Holotype. China • 1 specimen; South China Sea, Haima cold seep; 16°42.45'N, 110°25.68'E; depth 1378 m; 05 February 2021; Collecting event: stn. SC036; Shenhaiyongshi msv leg; preserved in 95% ethanol; GenBank: OK043837; IDSSE-EEB-SW0136. Paratypes. China • 5 specimens; South China Sea, Haima cold seep; 16°42.45'N, 110°25.68'E; depth 1378 m; 05 February 2021; Collecting event: stn. SC036; Shenhaiyongshi msv leg; preserved in 95% ethanol; GenBank: OK043838; IDSSE-EEB-SW0137 to IDSSE-EEB-SW0141. • 9 specimens; South China Sea, Haima cold seep; 16°44.02'N, 110°27.61'E; depth 1388 m; 01 May 2018; Collecting event: stn. SC036; Shenhaiyongshi msv leg; preserved in 95% ethanol; IDSSE-EEB-SW0114 to IDSSE-EEB-SW0122. • 13 specimens; South China Sea, Haima cold seep; 16°43.75'N, 110°28.34'E; depth 1378 m; 05 February 2021; Collecting event: stn. SC037; Shenhaiyongshi msv leg; preserved in 95% ethanol; IDSSE-EEB-SW0123 to IDSSE-EEB-SW0135. • 2 specimens; South China Sea, Haima cold seep; 16°34.13'N, 110°42.55'E; depth 1408 m; 07 February 2021; Collecting event: stn. SC042; Shenhaiyongshi msv leg; preserved in 95% ethanol; IDSSE-EEB-SW0142, IDSSE-EEB-SW0143.
Disc circular to sub-pentagonal, covered by dense smooth granules. Radial shields ovoid, naked, and widely separated (Fig.
Ophiophthalmus serratus sp. nov., holotype (IDSSE-EEB-SW0136) A dorsal disc B ventral disc C center of the disc D radial shield E оral frame dorsal side of the arm base G dorsal arm (proximal half) H dorsal arm (distal half) I ventral side of the arm base J ventral arm (proximal half) K ventral arm (distal half) L lateral arm base M lateral arm (proximal half) N lateral arm (distal half). Abbreviations: ars arm spine, as adoral shield, dap dorsal arm plate, das dorsal arm spine, gra granules, gs genital slit, j jaw, lap lateral arm plate, os oral shield, rs radial shield, ts tentacle scale, vap ventral arm plate, vas ventral arm spine. Scale bars: 2 mm (A, B); 1 mm (D–F, J, L); 500 µm (C, G–I, K, M); 200 µm (N).
Disc diameter 9.5 mm, arm base width 1.65 mm, and arm length 45–50 mm (Fig.
Disc. Disc circular to sub-pentagonal, raised above arm base, and covered by overlapping irregular scales, bearing rounded to cylindrical stumps with blunt tip, and smooth granules (Fig.
Arms. Dorsal arm plates triangular to fan-shaped, twice as wide as long, distal edge slightly convex, contiguous at proximal end of arm, then separated (Fig.
Color. In ethanol, whole specimen pale brown-white. (Fig.
IDSSE-EEB-SW0137: Arm spine articulations well developed, five in number, and placed at slight angle to distal edge of lateral arm plate. Volute-shaped perforated lobe forms dorsal and distal part of articulation, but turns into two unequal subparallel curved lobes ventralwards; large muscle opening and small nerve opening (Fig.
Ophiophthalmus serratus sp. nov., paratype (IDSSE-EEB-SW0137) A, B lateral arm plate C dorsal arm spine D ventral arm spine E–J vertebrae E–F proximal view G distal view H ventral view I dorsal view J lateral view. Abbreviations: d dorsal, de depression, dist distal, dl dorsal lobe, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, v ventral, vl ventral lobe. Scale bars: 500 µm (A–C, E–J); 300 µm (D).
Here, we examined 29 paratypes, ranging in disc diameter from 4 mm to 17 mm, and found only few notable variations among them. Large specimens had five arm spines at proximal to middle regions of the arm, then reduced to four arm spines at distal end, but small specimens showed five arm spines only at arm base, then reduced to four along the distal half of the arm. However, the finely serrated surface of the arm spine was similar in both small and large specimens. The number of lateral oral papillae differed from three to four, but most specimens had three papillae. Most specimens had dense granular coverage of the disc except larger specimens (16–17 mm). Color ranges from creamy white to dark among specimens from our collection. The above mentioned variations depend mainly on the size of the disc, and specimens with similar disc diameter showed similar morphological characters.
1378–1408 m in depth, Haima cold seep, South China Sea.
The species name was derived from the Latin word serratus (saw like, serrate), alluding to the surface of the arm spine.
All specimens of Ophiophthalmus serratus sp. nov. were collected from a methane cold seep in the South China Sea. Ophiophthalmus serratus sp. nov. showed similar morphological characters to three congeners, except O. hylacanthus. Ophiophthalmus normani resembles O. serratus sp. nov. in having similar radial shield and arm plate characters, and granule coverage on the disc, but differs in number of arm spines (up to four), peg-like lateral oral papillae, smooth and slender arm spines, spaced granular coverage, arrangement of arm spines at lateral arm plate, and large oval tentacle scales (
The molecular phylogenetic analysis of the family Ophiacanthidae concurs with previous molecular studies (
Tabular key to all species of the genus Ophiophthalmus. Abbreviations: ASE arm segment, DAP dorsal arm plate, DAS dorsal arm spines, LOP lateral oral papillae, RS radial shield, TS tentacle scale, VAP ventral arm plate, VAS ventral arm spines, VMT ventralmost papillae.
Species | No. of arm spines | Radial shield | Oral frame | Tentacle scale | Dorsal arm plate (DAP) and Ventral arm plate (VAP) | Arm spine shape and length | Disc spine or granular | References |
---|---|---|---|---|---|---|---|---|
Ophiophthalmus cataleimmoidus (H. L. Clark, 1911) | up to 7 | small, ovoid, naked, as long as wide, widely separated | 3–4 LOP; 1 VMT equal of size | one, large, flat, rounded, and distinctly curved outward | 1st VAP rounded triangular shape, then wider than long, hexagonal or pentagonal, separated DAP wider than long, triangular shape with distal curve, first few DAP with single raw of rounded grain in distal margin, contiguous only in proximal half | smooth, slender, tapering spine, next to uppermost DAS longest, 3 × ASE length |
more or less sparsely with coarse, rounded granules | H. L. |
Ophiophthalmus hylacanthus (H. L. Clark, 1911) | up to 8 | small, ovoid, naked, widely separated | 3 LOP; 1 VMT, LOP smaller than VMT | one, large, flat, rounded, but become narrow and pointed along the arm | VAP wider than long, hexagonal or pentagonal, separated DAP wider than long, triangular shape with distal curve, first few DAP with rounded grain in distal margin, contiguous only at arm base | second or third form upper DAS longest more than 2 × ASE length, uppermost DAS and lowermost VAS smooth, intermediate ones with slightly rough tip | stout, pointed, rough spine, scattered coarse granules among spine near RS | H. L. |
Ophiophthalmus normani (Lyman, 1879) | up to 4 | small, ovoid, naked, as long as wide, widely separated | 3 LOP, widely spaced, cylindrical, tapering, peg-like, 1 VMT | one, large and oval | 1st VAP rounded triangular shape, then wider than long, separated DAP as wide as long, distal curve, 1–4 DAP with single raw of rounded grain in distal margin, contiguous only in proximal half | smooth, slender, blunt, and tapering spine, lowest VAS ≈ 1 × ASE, upper DAS 1–1½ × ASE length | rounded granules or short stump, sparsely spread on the disc |
|
Ophiophthalmus relictus (Koehler, 1904) | up to 6 | ovoid, naked, distal end well rounded, widely separated | 3–4 LOP, Conical to pointed tip, 1 VMT | one, pointed | 1st VAP rounded triangular shape, then wider than long, hexagonal or pentagonal, separated DAP wider than long, triangular shape with distal curve, DAP with rounded grain in distal margin and surface, contiguous only in proximal half | short, stout, longest one nearly 1 × ASE length, VAS quite rough near tip | dense, smooth or sometime rough minute granules |
|
Ophiophthalmus serratus sp. nov. | up to 5 | ovoid, naked, widely separated | 3–4 LOP, rugose, pointed tip, 1 VMT | one, slightly elongated blunt tipped, as long as VAP | 1st VAP rounded triangular shape, then slightly pentagonal, separated DAP twice as wide as long, triangular shape with distal curve, first DAP has few rounded grains in distal margin (only 2 or 3 arms), contiguous only in arm base then separated | finely serratus, blunt tip; DAS ≈ 1½–2 × ASE length, dorsalmost longest, next two similar in length, VAS shorter, 1–1½ × ASE length, rough and shorter at distal end of the arm | dense, rounded to cylindrical stumps-like smooth granules, except radial shield and small area at center of disc | this study |
The species in the genus Ophiophthalmus share many morphological features, and the main distinguishing characters were number and shape of arm spines and maximum size. However, they have high genetic distance variations between them. As an example, the main morphological difference between Ophiophthalmus cataleimmoidus and O. normani were number of arm spines, and lateral oral papillae (
The authors want to thank the crews of the vessel ‘Tansuo’ 1 and the pilots of the HOV ‘Shenhaiyongshi’. The authors also thank the members of the marine ecology and evolutionary biology laboratory at the Institute of Deep-sea Science and Engineering, CAS for their help in sample collection and analysis. Many thanks to Hou Xue and Zhi Zheng for their help in acquiring SEM images of specimens. We are grateful to C. Mah (
List of 36 references that use the name Ophiophthalmus as a valid ophiuroid genus name between 1971 and 2021
Data type: Docx file
Explanation note: List of 36 references that use the name Ophiophthalmus as a valid ophiuroid genus name between 1971 and 2021. We included the reference as evidence of prevailing usage of the name (Ophiophthalmus).