Research Article |
Corresponding author: Haibin Zhang ( hzhang@idsse.ac.cn ) Academic editor: Pavel Stoev
© 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) Order Euryalida (Echinodermata, Ophiuroidea), new species and new records from the South China Sea and the Northwest Pacific seamounts. ZooKeys 1090: 161-216. https://doi.org/10.3897/zookeys.1090.76292
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Ophiuroids were collected by the manned submersible ‘Shenhaiyongshi’ from the deep-sea seamounts in the South China Sea and Northwest Pacific regions at 602–1920 m depth, during 2018 to 2020. A total of nine species was identified, including two new species and seven new records from the South China Sea and one new record from the Northwest Pacific region. Two new species are described as Asteroschema shenhaiyongshii sp. nov. and Asteroschema domogranulatum sp. nov. The seven new records included five species from the genus Asteroschema, and one species each from the genera Asterostegus and Astrodendrum. Comprehensive descriptions of morphological features are provided, including characteristics of the arm skeleton, as well as a phylogenetic analysis based on 16S and COI sequences. Intraspecific genetic distance ranges of Euryalida species from the present study were 0.34% to 1.38%, which was relatively low compared to other orders in the class Ophiuroidea. The present study suggests a high probability that species of the order Euryalida are more widely spread around the Indo-Pacific region than previously expected.
Asteroschema, COI, molecular phylogeny, morphology, SEM, taxonomy
The order Euryalida Lamarck, 1816 (basket stars and snake stars) includes the families Euryalidae Gray, 1840, Asteronychidae Ljungman, 1867, and Gorgonocephalidae Ljungman, 1867, and these include the species with largest known body size in the class Ophiuroidea, the brittle stars (
This study presents species in the genera Asteroschema Örsted & Lütken in Lütken, 1856 and Asterostegus Mortensen, 1933 from Euryalidae, and Astrodendrum (Döderlein, 1902) from family Gorgonocephalidae, found in the South China Sea and on Northwest Pacific seamounts.
Asteroschema is one of the largest genera in the Euryalidae, but it is still ill-defined due to limited published information and high morphological similarity between the species. Currently, 33 species are included in Asteroschema and the most recently described one was Asteroschema sampadae Parameswaran & Abdul Jaleel, 2012 from the Indian Ocean. Most of the species are pentamerous, but two hexamerous species have been recorded from New Zealand waters (Asteroschema wrighti McKnight, 2000 and Asteroschema bidwillae McKnight, 2000). Previous studies differentiated Asteroschema species based on epidermal ossicle shape and arrangement on the disc and arms, size variance and shape of inner and outer arm spines, and starting point of the second arm spine on the proximal region of the arm (
The genus Asterostegus includes only three species and is morphologically related to the genus Astroceras Lyman, 1879, but differs in having the oral shield replaced by several small interradial plates (
The present study covers deep waters around the South China Sea (Xisha and Zhongsha Islands) and in the Northwest Pacific region (southwest of Guam Island). Here, we present an account of the Asteroschema, Asterostegus, and Astrodendrum species collection, with descriptions of new species and new records. Our goal is to present a detailed documentation of the morphological features of these species, to complement the limited original descriptions and the lack of figures in the literature. We present the first ever comprehensive tabular key for all species in the genus Asteroschema. Two new species are described and seven species are redescribed, including seven new records from the South China Sea and one new record from the Northwest Pacific, all richly illustrated. DNA barcoding was used to identify ophiuroid species in the past two decades (
Ophiuroid specimens were collected by the manned submersible vehicle ‘Shenhaiyongshi’, from 602 to 1920 m depth (Fig.
Specimens were photographed through a dissecting stereo microscope (OLYMPUS SZX7) or with a digital camera (Canon EOS 6DII) to identify morphological characters. Arm skeletons were examined with a scanning electron microscope (SEM) Phenom ProX. Skeletal elements were prepared by using undiluted NaOCl to dissolve the soft tissue of part of an arm. The excess NaOCl in skeletal elements was removed by repeated flushing with distilled water. Then, the ossicles were mounted on a stub using dissolved carbon tapes. Holotypes, paratypes and all other specimens are deposited at the Institute of Deep-sea Science and Engineering (
We extracted DNA from identified specimens by using the TIANamp Marine Animals DNA kit (TianGen, Beijing) following the manufacturer’s protocol. We sequenced cytochrome c oxidase I (COI) and the 16S partial gene for phylogenetic analysis by amplifying primer sets, with suitable PCR cycle (Suppl. material
Localities, voucher information, and GenBank accession numbers for all specimens used in this study.
Species | Locality | Voucher number | COI | 16S |
---|---|---|---|---|
Asteroschema shenhaiyongshii sp. nov. | South China Sea, near Xisha islands | IDSSE-EEB-SW0086 | OK044292 | OL712208 |
Asteroschema bidwillae | New Zealand | MVF188856 | KU895077 | - |
Asteroschema rubrum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0071 | OK044293 | OL712209 |
Asteroschema rubrum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0072 | OK044294 | OL712210 |
Asteroschema rubrum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0073 | OK044295 | OL712211 |
Asteroschema tubiferum | New Zealand | MVF188857 | KU895076 | - |
Asteroschema tubiferum | Mariana Trench, Southeast of Guam Isl. | IDSSE-EEB-SW0078 | OK044296 | OL712212 |
Asteroschema tubiferum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0106 | OK044297 | OL712213 |
Asteroschema tubiferum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0077 | OK044298 | - |
Asteroschema cf. lissum | Mariana Trench, Southeast of Guam Isl. | IDSSE-EEB-SW0081 | OK044299 | OL712207 |
Asteroschema cf. lissum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0079 | OK044300 | - |
Asteroschema salix | Australia | TOH_666 | HM400451 | - |
Asteroschema salix | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0082 | OK044301 | OL712214 |
Asteroschema sp. | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0092 | OK044302 | OL712215 |
Asteroschema sp.SO2392113 | Pacific Ocean: Clarion Clapperton Fracture Zone | SO2392113 | MN088049 | - |
Asteroschema clavigerum | North Atlantic seamounts | - | HM587852 | - |
Asteroschema sublaeve | Canada: British Columbia | RBCM EC00271 | HM400328 | - |
Asteroschema ajax | Australia: off Lord Howe Isl. | MVF99759 | AB758762 | AB605078 |
Asteroschema oligactes | Off Dominica | MNHN OM62 | AB758766 | AB758483 |
Asteroschema edmondsoni | Off Santa Isabel Isl., New Caledonia | MNHN OM13B | AB758831 | AB758486 |
Asteroschema horridum | Off Reunion Isl. | MNHN OM126 | AB758764 | AB758487 |
Asteroschema migrator | Off Santa Isabel Isl., New Caledonia | MNHN OM3 | AB758765 | AB758485 |
Ophiocreas ambonesicum | Off Amami-oshima Isl., Kagoshima, Japan | NSMT E-6502 | AB758813 | AB605084 |
Ophiocreas spinulosus | Caribbean Sea, USA | NMNH OM43 | AB758820 | AB758490 |
Ophiocreas glutinosum | Off Katsuura, Chiba, Japan | NSMT E-6710 | AB758815 | AB605086 |
Ophiocreas japonicus | New Zealand | NIWA T2494 | AB758816 | AB758488 |
Ophiocreas sibogae | South Norfolk Ridge, New Zealand | MV F99763 | AB758818 | AB605087 |
Ophiocreas caudatus | Sagami Sea, Japan | NSMT E-6259 | AB758814 | AB605085 |
Ophiocreas oedipus | Off Hachijo-jima Isl., Ogasawara, Japan | NSMT E-6375 | AB758817 | AB758489 |
Asterostegus maini | South China Sea, near Xisha islands | IDSSE-EEB-SW0076 | OK044303 | - |
Asterostegus tuberculatus | Western coast of Madagascar | SMNH-123461 | AB758769 | AB758515 |
Asterostegus sabineae | Madagascar: Off Reunion Island. | SMNH-Type-8333 | AB758768 | AB758511 |
Astrodendrum sagaminum | Japan: Sagami Sea | NSMT E-5645 | AB758795 | - |
Astrodendrum cf. sagaminum | South China Sea, near Zhongsha islands | IDSSE-EEB-SW0104 | OK044304 | - |
Gorgonocephalus pustulatum | New Zealand | MVF188859 | KU895114 | - |
Gorgonocephalus sundanus | Australia | MVF162682 | KU895115 | - |
Gorgonocephalus arcticus | Canada: Nunavut, Barrow Strait | HLC-30309 | HM543017 | - |
Gorgonocephalus caputmedusae | Sweden: Skagerrak | Echin 6305V | MG935270 | - |
Gorgonocephalus eucnemis | Japan: Iwate, Off Miyako | NSMT E-5640 | AB758809 | - |
Gorgonocephalus tuberosus | Antarctic Sea. | NIWA 38224 | AB758811 | - |
Gorgonocephalus chilensis | Antarctic Sea | NIWA 38714 | AB758812 | - |
Astrogymnotes irimurai | Seseko Beach, Okinawa, Japan | NSMT E-6716 | AB758829 | AB605123 |
Ophiomyxa anisacantha | Sagami Sea, Japan | NSMT E-6269 | AB758822 | AB605124 |
We constructed two maximum likelihood (ML) phylogenetic trees to represent the families Euryalidae and Gorgonocephalidae. Family Euryalidae: to construct the ML tree, we used 12 COI and nine 16S sequences from our collection and additionally 22 COI and 14 16S sequences from GenBank (Table
All sequences were aligned using the ClustalW algorithm in MEGA X. When constructing the Euryalidae ML tree, we used the concatenated sequence alignment function in MEGA X to input both COI and 16S sequences. The best-fit substitution model of the COI and 16S gene in the ML trees was the General Time Reversible + Gamma Distributed (GTR + G) model, estimated by the “Find Best DNA/Protein Models” Option of MEGA X. Phylogenetic trees were reconstructed using the maximum likelihood bootstrap method. ML analysis was run with MEGA X, and ML trees were constructed, including 1,000 bootstrap replicates (
ap articular pad of the base;
ars/ARS arm spine;
arsb arm spine base;
as adoral shield;
asa arm spine articulation;
ass/ASS adoral shield spine;
au auricle;
AUS Australia;
CAN Canada;
co/CO conical ossicle;
COI Cytochrome C oxide subunit I;
CS Caribbean Sea;
d dorsal;
de depression;
dist distal;
fo foramina of the base;
fs fossa between adjacent tubercles;
go/GO granular ossicle;
goc granular ossicles coat;
gs/GS genital slit;
hd head of the apophysis;
iars inner arm spine;
IDSSE Institute of Deep-sea Science and Engineering;
irp interradial plate;
j jaw;
JAP Japan;
lac lateral ambulacral canal;
MAD Madagascar;
lap lateral arm plate;
ML Maximum Likelihood;
mo muscle opening;
mp median plate;
msv manned submersible vehicle;
NAT North Atlantic;
no nerve opening;
NWP North-West Pacific;
NZ New Zealand;
oars outer arm spine;
ob oral bridge;
os oral shield;
PAO Pacific Ocean;
pb podial basin;
pd pedicel of the apophysis;
peb pedicellarial band;
po/PO plate-like ossicle;
prox proximal;
pt primary tooth of the blade;
rs/RS radial shield;
SCS South China Sea;
sh sheath of the base;
st secondary tooth;
su sulcus of tubercle head;
t teeth;
TEP terminal projection;
tp tentacle pore;
v ventral.
Seven species of Asteroschema were identified, among them two new to science that are described below. One species of each of the genera Asterostegus and Astrodendrum were identified, both of them are new to the South China Sea and described below. A tabular key to all species of Asteroschema is provided in Table
Tabular key to the species of Asteroschema and Ophiocreas. Abbreviations: ASS arm segment, ARS arm spine, GO granular ossicles, RS radial shield, CO conical ossicles, PO plate-like ossicles, TP terminal projection, GS genital slits.
Species | Disc diameter and arm length | Epidermal ossicles on the disc | Epidermal ossicles on the arm | ARS length | ARS shape | AS from segment 1st (2nd) | Reference | ||
---|---|---|---|---|---|---|---|---|---|
Dorsal | Ventral | Dorsal | Ventral | ||||||
Asteroschema ajax A. H. Clark, 1949 | 13 mm and 300 mm | fine GO; RS narrow, parallel, raised above the disc not meeting at center | fine GO | well-spaced annular bands when dried, covered with GO | covered with GO as dorsal | unknown | unknown | unknown | |
Asteroschema arenosum Lyman, 1878 | 8–9 mm and arm length unknown (arm width 4 mm) | coarse GO, 5 grains in 1 mm; RS wide, not meeting at center | coarse GO but near mouth area scattered, jaw covered with GO | coarse GO but denser than on disc | as dorsal | inner ≈ 2 × outer | inner spine: cylindrical, slightly swollen, thorny dark tip | 2 (4) |
|
Asteroschema bidwillae McKnight, 2000 | 5 mm and 50 mm (6 arms) | flat, small, very finely rugose GO, dense at center; RS and interradially (8–10 grains in 1 mm) but slightly spaced beside each RS; more or less extending to center | very small well-spaced GO, except on elongated oral plates | flat, small, very finely rugose GO, slightly spaced toward distal end, almost absent near tip, lateral surface always spaced | GO present on plates near arm base, then naked | inner > outer (inner 1 × ASE, outer 1/3 × ASE length) | inner spine: slightly flattened, denticulate over most of length, and proximal margin beset with small curved spines | 2 (8–14) |
|
outer spine: small and inconspicuous distally both spines flattened and pointed, but hooks absent | |||||||||
Asteroschema brachiatum Lyman, 1879 | 6–11 mm and 270 mm (arm base width 3 mm) | dense, uniform GO; RS elevated, extending nearly to center | similar to dorsal, inconspicuous GO, which simulate oral papillae | closely uniformly covered with GO; 6–9 grains in 1 mm | as dorsal | inner > outer (inner spine 2 mm) | inner spine: rough, slightly club-shaped | 2 (4) |
|
Asteroschema clavigerum Verrill, 1894 | 8–12 mm and arm length unknown (arm base width 3–3.5 mm) | small, smooth GO, 6 grains in 1 mm; RS large, extending to center, GO larger than on disc. | smooth skin lacking GO or minute, more spaced GO | small, smooth GO | only base of arm covered with minute, more spaced GO, and rest of arm naked | inner > outer | inner spine: large, long, elevated, and rough with spinules distally; somewhat swollen | 3–4 (4–5) |
|
outer spine: small | |||||||||
distally both spines small, slender, acute and nearly equal | |||||||||
Asteroschema domogranulatum sp. nov. | 9 mm and 165 mm | dense, large slightly domed GO, 4 or 5 grains in 1 mm; RS wide, parallel, raised above the disc close together | large polygonal PO except distal half of jaw | large polygonal PO in proximal arm; then slightly separated, decreasing in size GO | arm base concealed by polygonal PO; remainder naked | inner ≈ 2 × outer | inner spine: pointed thorny tip to cylindrical, slightly club shaped, flattened thorny | 2 (19–22) | This study |
outer spine: small with thorny tip | |||||||||
distally both compound hook with 3–6 secondary teeth | |||||||||
Asteroschema edmondsoni A. H. Clark, 1949 | 13 mm and 290 mm | GO & CO; dense GO on proximal half of RS, larger CO with TP on distal half | dense rounded GO | dense PO, swollen in the middle with TP; TP absent in distal end of arm | same as on ventral disc; but smaller | unknown | unknown | unknown | |
Asteroschema elongatum Koehler, 1914 | 7–11 mm and 300 mm | strongly excavated, GO rounded, unequal, slightly coarse near disc periphery; RS meeting at center, separated, GO larger and denser than on disc | minute GO, uniform, separated, slightly stronger near periphery | on first few segments GO like on RS then spaced, small, and uniform | GO much smaller and uniform, rapidly becoming fewer and finally disappearing after 30–40 mm from arm base | inner > outer | inner spine: cylindrical, strong, thinner at tip with TP | 2 (5) |
|
outer spine: conical, pointed tip | |||||||||
Asteroschema fastosum Koehler, 1904 | 6–13 mm and 180–300 mm (arm base width 5 mm) | high, CO including RS | small CO, more rounded, close-set at disc margin | small CO, more close-set than on disc, 6 or 7 grains in 1 mm | flattened CO | inner > outer (inner spine ≤ 4 mm) | inner spine: bluntly conical at arm base, then strongly club-shaped with TP | 2 (4–5) |
|
outer spine: cylindrical, thorny tip | |||||||||
distally both spines compound hook with 2–4 secondary teeth | |||||||||
Asteroschema flosculus Alcock, 1894 | – | GO & CO; scattered as uniform microscopic GO | uniform microscopic GO | GO & CO; scattered as uniform microscopic GO | uniform microscopic GO | large | unknown | 3 (3) |
|
Asteroschema glaucum Matsumoto, 1915 | 11 mm and 100 mm (4 mm width in arm base) | flat; coarser GO, 6 grains in 1 mm; RS mostly covered except distal end | coarser GO; near apex of jaw less GO | coarser GO, 6 grains in 1 mm, very stout at base, as high as wide | as dorsal | inner > outer | inner spine: cylindrical, club-shaped, rough end | 2–3 (8) |
|
distally both spines compound hook with four curved secondary teeth | |||||||||
Asteroschema hemigymnum Matsumoto, 1915 | 10 mm and 100 mm (3 mm width in arm base) | very fine, smooth, close-set GO | ventral: fine, rather sparse GO in skin, coarse, flat, smooth, pavement-like grains, corresponding to oral papillae | very fine, smooth, close-set GO; 5 grains in 1 mm; GO much finer distalwards and disappear at distal end. | entirely naked; LAP and VAP visible through skin | inner > outer (outer spine ½ × ASE length) | inner spine: cylindrical, club-shaped | 2 (5–6) |
|
outer spine: small, cylindrical, enclosed in skin, more or less rough tip | |||||||||
distally both spines compound hook with 3–6 secondary teeth | |||||||||
Asteroschema horridum Lyman, 1879 | 10–12.5 mm and 160–190 mm | tumid polygonal PO; mostly tall CO with terminal projections | PO & CO higher and thinner at disc periphery | PO, larger on arm base than on disc, 4 PO in 1 mm at arm base; weakly annulated | PO & CO lower and thinner | inner ≈ 2 × outer | inner spine: cylindrical with TP, slightly swollen | 1 (1–6) |
|
Asteroschema igloo Baker, 1980 | 5.7 mm and 68.4 mm (1: 12-disc diameter to arm length) | rounded or polygonal domed GO, 4–6 grains in 1 mm length; RS short, obscured, distally visible | closely packed rounded, domed GO | dorsal & ventral: rounded or polygonal domed GO; 4–6 grains in 1 mm length | as dorsal | inner ≈ 2 × outer (inner spine 2/3 × arm width) | inner spine: long, very fine, thorny blunt tip | 3: (8–10) |
|
distally both spines compound hook with 3–6 secondary teeth | |||||||||
Asteroschema inoratum Koehler, 1906 | 6–10 mm and 70+ mm | fine, contiguous GO (rounded or slightly conical); RS wider, extending to center | GO density similar to dorsal, slightly developed around GS | fine, rounded or slightly conical, contiguous GO | as dorsal | inner ≈ 1½ × ASE length | inner spine: slightly club-shaped, Swollen toward the end with conical point | 2 (5–7) |
|
outer spine: smooth, much smaller distally both spines small, but not transforming into a hook | |||||||||
Asteroschema intectum Lyman, 1878 | 5–11.5 mm and 280 mm (arm width 3 mm) | fine GO, 6–7 grains in 1 mm; RS long, meeting at center, GO fine than on disc, 8–9 grains in 1 mm | fine GO except jaw | GO scattered, and smaller than on disc. | lateral and ventral side naked or fewer GO | inner > outer | inner spine: blunt, spiniform, not club-shaped | 2 (3) |
|
Asteroschema laeve (Lyman, 1872) | 8.5 mm and 85 mm | flat; fine close-set GO, 7–8 grains in 1 mm; RS mostly covered with GO except distal end | minute, close, smooth GO, fewer GO near apex of jaw | fine close-set GO, 7–8 grains in 1 mm, thin skin, faint brown marking | as dorsal | inner > outer | inner spine: cylindrical, somewhat swollen, rough end | 2 (8) |
|
distally both spines compound hook with 4 curved secondary teeth | |||||||||
Asteroschema lissum H. L. Clark, 1939 | 7.5 mm and 110 mm | very fine, small GO; 50–60 grains in 1 mm2, but noticeably smaller at center and proximal end of RS; RS separated, narrow, straight, parallel, not meeting at center | naked with thin skin | fine GO similar on disc, laterally sparse, but continuous to base of ARS, distally sparse, and naked | naked with thin skin | inner ≈ 2–3 × outer | inner spine: long, thick, thorny tip | 2 (9–11) | H. L. |
Asteroschema migrator Koehler, 1904 | 11 mm and 200–300 mm | sparse, domed CO with terminal projections, CO dense on RS & disc margin | few small CO | close-set, small, tumid GO | few GO or CO | inner ≈ 2 × outer | inner spine: cylindrical, swollen, TP outer spine: small, with pointed tip | 3 (6–8) |
|
Asteroschema monobactrum H. L. Clark, 1917 | 8 mm and 80–90 mm (base arm width 2 mm) | GO, flat, slightly raised above arm, near center 7 grains in 1 mm (50 mm2), but disc periphery 5–6 grains 1 mm (30 mm2)); RS completely covered but rounded ridges appeared when dried | similar GO density as dorsal | GO on arm base similar to disc, then separated, very minute, distally almost naked | GO, from middle slightly naked | inner ≈ 2 × outer | unknown | 2 (11–16) | H. L. |
Asteroschema nuttingii Verrill, 1899 | 7 mm and 50 mm | minute rough GO/CO; close-set on RS | few GO near GS; minute rough GO/CO | minute GO/CO, distinct distally | minute rough GO/CO | inner > outer | inner spine: slender, tapering at arm base, then cylindrical, blunt, swollen distally, with TP | 1 (1–2) |
|
Asteroschema oligactes (Pallas, 1788) | 4–10 mm and 250 mm (length ≈ 17 × disc diameter) | CO | CO | CO; 4–5 CO in 1 mm on ventral arm base | as dorsal | inner > outer | unknown | unknown |
|
Asteroschema rubrum Lyman, 1879 | 12 mm and 160 mm | fine, close-set GO, 6–7 grains in 1 mm; RS faintly indicated as flat ridges | fine, close-set GO | fine, close-set GO, 6–7 grains in 1 mm | as dorsal | inner spine maximum length 1.4 mm | inner spine: small spiniform at arm base, then cylindrical, swollen with TP | 2 (5–6) |
|
distally both spines compound hook with secondary teeth | |||||||||
Asteroschema salix Lyman, 1879 | 5–8.5 mm and 55–85 mm | flat, fine, close-set GO, 7–8 grains in 1 mm; RS mostly covered with GO except distal end | fine, minute, close-set GO, less GO near apex of jaw | fine, close-set GO, 7–8 grains in 1 mm, thin skin | as dorsal | inner > outer | inner spine: cylindrical, somewhat swollen, rough end | 2–3 (11–12) |
|
distally both spines compound hook with 4 curved secondary teeth | |||||||||
Asteroschema sampadae Parameswaran & Jaleel, 2012 | 18 mm and 380–450 mm | spaced CO with terminal projections; RS covered with CO, extending to center | minute, spaced GO | spaced CO with terminal projections, denser at arm base | minute, spaced GO | inner ≈ 2 × outer, inner spine ≤ 2 × ASE (5 mm) | inner spine: bluntly conical at arm base; then cylindrical, with TP at inner edge | 2 (4) |
|
Asteroschema shenhaiyongshii sp. nov. | 10 mm and 220 mm (arm base width 3.4 mm) | small, finely rugose, rounded GO, similar in size, 8–9 grains in 1 mm; RS wide, parallel, close together, not meeting at center, distal end of RS raised above disc, swollen at center | GO similar on dorsal, spearhead-shaped teeth. GS narrow concealed with GO | dorsal: dense GO similar to disc; 8–9 grains in 1 mm; distally GO less rounded but dense | less rounded and more polygonal GO, concealing only proximal half of arm, in middle to distal ventral arm surface concealed with widely separated GO decreasing in size to completely naked | inner > outer (inner spine 2.2 mm long) | inner spine: cylindrical, thorny tip to less club-shaped with small sharp thorns on more than half its length | 2 (9–11) | This study |
outer spine: small in size with thorny tip similar to inner spine | |||||||||
distally both spines similar in size, compound hook with 4 or 5 secondary teeth | |||||||||
Asteroschema subfastostum Döderlein, 1930 | 8 mm and 9 × disc diameter | pointed CO, blunt at disc margin, 4–5 grains in 1 mm | smooth hemispherical GO | pointed CO | smooth hemispherical GO | inner > outer | unknown | unknown |
|
Asteroschema sublaeve Lütken & Mortensen, 1889 | 12 mm and 300 mm (arm base width 5 mm) | round, rugose GO variable size; RS covered with larger GO than on the disc | smooth, small GO, few GO lateral at jaw | round, rugose GO variable size, smaller at lateral side, larger on dorsal surface | naked | inner ≈ 2 × outer; in middle (inner ≈ 4 × outer) | inner spine: elongated, club shaped, enclosed with thick skin | 2–3 (3–4) |
|
Asteroschema sulcatum Ljungman, 1872 | 5 mm and arm length unknown | dense, small GO (9–15 grains in 1 mm); RS narrow, not meeting at center | dense, small GO, teeth rounded or distally lobed | dense, small GO | as dorsal | inner > outer | inner spine: strongly thorny tip, swollen, bent club shaped | (3–12) |
|
Asteroschema tenue Lyman, 1875 | 6 mm and 200 mm (arm base width 1.5 mm) | closely, smooth GO (8–9 grains in 1 mm); RS narrow, meeting at center and GO little coarser | coarser GO; large GO in jaw | slender arms; similar to dorsal disc, distally GO much finer and more scattered | as dorsal | inner > outer, inner spine 1 mm long in middle half | inner spine: spiniform at arm base, then large, fine thorny, club-shaped | 1 (3) |
|
Asteroschema tubiferum Matsumoto, 1911 | 14–16 mm and 230–300 mm | closely and evenly, small rounded or polygonal GO; RS narrow, not meeting at center but convergent | entirely covered with dense GO, slightly large, rounded GO corresponding to oral papillae | GO similar to disc, 4–5 grains in 1 mm | distally GO smaller, widely spaced on ventral side | inner > outer | inner spine: cylindrical, initially tapering to a blunt, thorny tip, middle club-shaped with small sharp thorns, first 10–12 covered by sheath | 2 (7) |
|
outer spine: small, pointed tip | |||||||||
distally both spines compound hook with secondary teeth | |||||||||
Asteroschema tumidum Lyman, 1879 | 8–13 mm and 120–180 mm | dense, rounded GO proximally, CO at disc margin regularly spaced pointed; RS covered with CO, extending to center | similar to dorsal but lower | regularly spaced pointed, CO; 4 grains in 1 mm, rarely touching each other | as dorsal | inner > outer, inner spine ≤2 mm long | inner spine: rough, slightly club-shaped | 2 (3) |
|
Asteroschema vicinum Koehler, 1907 | 7 mm and 93 mm | fine GO | fine GO, more than 9 grains in 1 mm, GO much larger around jaw | fine GO | as dorsal | ½ × ASE length | both sub-equal, fairly short, same morphology along the arm | - (2) |
|
Asteroschema wrighti McKnight, 2000 | 6.5 mm and at least 6 × disc diameter | fine and uniform GO, 8–10 grains in 1 mm; RS elongated, meeting at center | thin smooth skin, occasional small GO; relatively large irregular PO in GS | fine and uniform GO; 8–0 grains in 1 mm; extending to lateral surface | occasional small GO, thin and smooth skin | inner > outer, inner arm spine up to 2 × ASE length | inner spine: long, finely thorny, slightly club-shaped | 2(5–6) |
|
outer spine: relatively small and smooth | |||||||||
distally both spines compound hook with secondary teeth | |||||||||
Asteroschema yaeyamense Murakami, 1944 | 7 mm and 150 mm | dense, coarse CO | rounded GO | regularly spaced CO, distally swollen GO | as dorsal | inner > outer | inner spine: long, cylindrical with TP | 2 (3–6) |
|
Ophiocreas ambonesicum Döderlein, 1927 | 27–30 mm and 350–390 mm | coarse, thick, naked skin (when dry widely separated GO visible); RS narrow, not meeting at center | as dorsal | naked skin, when dry widely separated GO visible), annular band | naked skin, when dry widely separated GO visible) | inner ≈ 3 × outer; in middle 2 × ASS length | inner spine: elongated, thick, enclosed with thick skin, cylindrical, club-shaped | 2 (8–12) |
|
outer spine: cylindrical, pointed tip | |||||||||
distally both spines compound hook with 2–3 secondary teeth | |||||||||
Ophiocreas carnosus Lyman, 1879 | 15 mm and 200 mm (arm base width 7 mm) | thick, soft wrinkled skin; RS rounded distal end, narrow, meeting at disc center | as dorsal | smooth, soft wrinkled skin | as dorsal | inner ≈ outer, inner ≈ 3 mm long | inner spine: short, enclosed by thick skin, cylindrical, thorny tip | 2 (6) |
|
outer spine: cylindrical, thorny tip | |||||||||
Ophiocreas caudatus Lyman, 1879 | 22–25 mm and 300–420 mm (arm base width 5.5–7.5 mm) | covered with thick skin, when dry micro-GO visible; RS narrow, raised above the disc, meeting at center | as dorsal | covered by thick skin, when dry micro-GO visible at arm base, annular band. | as dorsal | inner 3 mm longer in middle | inner spine: elongated, enclosed by skin, stout, thorny tip | 2 (10–13) |
|
outer spine: short, peg-like | |||||||||
Ophiocreas oedipus Lyman, 1879 | 5–12 mm and 70–250 mm (arm base width 3.5 mm) | thin skin with small, fine GO; RS narrow, closer together, extending to disc center | small, closely set, rounded GO or naked, GS wide | thin skin with fine GO, first 5–8 ASS swollen | as dorsal | inner 1 × ASS length, outer ½ × ASS length | inner spine: slender, elongated, enclosed by skin, blunt, thorny tip | 2 (6–9) |
|
outer spine: short, cylindrical, pointed | |||||||||
distally both spines compound hook with 6 secondary teeth | |||||||||
Ophiocreas gilolense (Döderlein, 1927) | 22 mm and 290 mm (arm base width 9 mm) | naked skin; RS meeting at center | as dorsal | naked skin, annular band | as dorsal | inner ≈ 2 × outer; in middle 2 × ASS length | inner spine: elongated, slender, cylindrical | 2 (3–4) |
|
outer spine: cylindrical, pointed tip | |||||||||
Ophiocreas glutinosum (Döderlein, 1911) | 17 mm and unknown (arm base height 9 mm) | dense small GO (10 grains in 1 mm); RS large (nearly covering whole disc), long, close to each other, meeting at center | as dorsal | thick arms, thick skin covers arm plates completely, proximally dense small GO (10 grains in 1 mm), distally separated, | as dorsal | inner 1½ × ASS length, outer ≈ 1/3 × inner | inner spine: slender, elongated, swollen thorny tip | 2 (6–7) |
|
outer spine: small | |||||||||
distally both spines compound hook with 2–3 secondary teeth | |||||||||
Ophiocreas japonicus Koehler, 1907 | 4–33 and 210–655 mm (arm base width 7 mm) | smooth, thin, small specimen with dense GO coverage (4 mm disc diameter); RS thick, raised above the disc, meeting at disc center | as dorsal | smooth, thin, naked skin, annular, (small specimen with dense GO coverage (4 mm disc diameter) | somewhat fewer scattered GO | inner ≤6 mm, 3 × ASS length; outer 1 × ASS length | inner spine: elongated, thick base, cylindrical, thorny tip | 2 (3–12) |
|
outer spine: cylindrical, pointed tip | |||||||||
distally both spines compound hook with 2–3 secondary teeth | |||||||||
Ophiocreas lumbricus Lyman, 1869 | 4.5–17 mm and 50–240 mm (arm base width 2.5 mm) | covered by separated micro-thorny GO; RS meeting at center | as dorsal | covered by separated micro-thorny GO annular band | as dorsal | inner ≤ 1½–2 × ASS length outer 1 × ASS length | inner spine: cylindrical, enclosed by skin, blunt, rough surface, thorny tip | 2 (4) |
|
outer spine: cylindrical, enclosed with skin, blunt, rough surface, thorny tip | |||||||||
Ophiocreas mindorense (Döderlein, 1927) | 12–23 mm and 160–480 mm (arm base width 3–5.5 mm) | smooth, dense GO (8 grains in 1 mm); RS narrow, closer together, extending to disc center | as dorsal | similar to disc, smooth, dense GO (8 grains in 1 mm); GO absent on ventral side of younger specimens | as dorsal | inner 3–5.5 mm, in middle 2½ –3 × ASS length; outer 1 × ASS length | inner spine: slender, elongated, swollen thorny tip | 2 (8–11) |
|
outer spine: thick arm base with pointed tip | |||||||||
Ophiocreas mortenseni Koehler, 1930 | 7.5–25 mm and 110–400+ mm (arm base height 6 mm) | covered by thick, wrinkled, or folded skin; RS narrow, extending to disc center | covered by plate-like ossicles | skin thicker than dorsal, mostly thickened near arm spines, arched | as dorsal | inner 1 × ASS length; outer 2/3 × inner | inner spine: slightly flattened, rough in upper half, thorny tip | 2 (4–7) |
|
outer spine: short, cylindrical, thorny pointed | |||||||||
distally both spines compound hook with 3 or 4 secondary teeth | |||||||||
Ophiocreas sibogae Koehler, 1904 | 14–28 mm and 300–350 mm (disc diameter × 30) (arm base width 5 mm) | naked skin; RS narrow, parallel, not meeting at center | as dorsal | naked skin, annular band | as dorsal | inner ≈ 2 × outer, in middle 2 × ASS length | inner spine: elongated, slender, cylindrical, club-shaped, finely rugose | 2 (3–11) |
|
outer spine: cylindrical, pointed tip | |||||||||
distally both spines compound hook with 2–4 secondary teeth | |||||||||
Ophiocreas spinulosus Lyman, 1883 | 8–17 mm and 60–550 mm (arm base width 3 mm) | naked skin; RS strongly marked ridges with short, stout blunt spines, meeting at center | as dorsal | higher than wide, naked skin, annular band blunt spine at each pair of ASS | as dorsal | inner ≈ 2 mm, equal in size in proximal arms | inner spine: short, blunt, rough surface, cylindrical | 2 (3–4) |
|
outer spine: cylindrical, pointed tip, distally slender | |||||||||
distally both spines compound hook with 2 secondary teeth | |||||||||
Ophiocreas willsi McKnight, 2000 | 16 mm and 380 mm | covered by thick, wrinkled, or folded skin; RS narrow, extending to disc center, dense small GO cover in the center | covered by well separated small GO. | granulation similar to the disc, extending to the lateral arm, GO coverage dense proximally, but scattered distally | first 3–5 ASS with few GO, then naked | inner 1½ × ASS, outer shorter than ASS | inner spine: slightly flattened, enclosed by skin, rough, blunt tip | 2 (2–3) |
|
outer spine: short, cylindrical, thorny pointed | |||||||||
distally both spines compound hook with 3 or 4 secondary teeth |
In total, 34 COI sequences trimmed to 592 bp and 25 16S sequences trimmed to 453 bp were obtained after removing ambiguous aligned sites and successfully reconstructing an ML tree for the studied Euryalidae (Fig.
A total of 11 COI sequences trimmed to 730 bp were obtained after removing ambiguous aligned sites, and successfully reconstructing an ML tree for the genera Gorgonocephalus and Astrodendrum (Fig.
Superorder Euryophiurida O’Hara, Hugall, Thuy, Stöhr & Martynov, 2017
Order Euryalida Lamarck, 1816
Family Euryalidae Gray, 1840
Holotype : China • 1 specimen; South China Sea, East of Zhongsha Islands, seamount; 16°22.11'N, 113°6.01'E; depth 1742 m; 09 Aug. 2020; Collecting event: stn. SC028; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; IDSSE-EEB-SW0089.
Paratypes : China • 2 specimens; same data as for holotype; IDSSE-EEB-SW0090, IDSSE-EEB-SW0091.
Radial shields straight, parallel, close together, and raised above the disc and arms (Fig.
Asteroschema domogranulatum sp. nov., holotype (IDSSE-EEB-SW0089) A dorsal view B ventral view C dorsal disc D lateral disc E ventral disc F dorsal arm (proximal) G lateral arm (proximal) H lateral arm (distal) I ventral arm (base) J, K ventral arm (proximal) L ventral arm (middle) M, N arm spines (middle) O, P arm spines (distal). Abbreviations: ars arm spine, arsb arm spine base, as adoral shield, ass adoral shield spine, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, po plate-like ossicle, rs radial shields, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B); 1 mm (C–G, K, L); 500 µm (H–J, M, N); 200 µm (O, P).
Disc diameter 9 mm, length of arms 165 mm, arm base width 2.8–3.0 mm (Fig.
Disc. Disc star-shaped, pentagonal, raised high above the arms, incised interradially and swollen on radial shields (Fig.
Arms. Arms slender, arched at base, sub-cylindrical, increasingly cylindrical and narrower distalwards (Fig.
Color. In live specimen, light brown color (Fig.
IDSSE-EEB-SW090: Lateral arm plate curved around vertebrae, with strong curved rib with one arm spine articular structure, with single, completely separated large muscle and nerve openings (Fig.
Asteroschema domogranulatum sp. nov., paratype (IDSSE-EEB-SW0090) A, B lateral arm plate (external, internal) C arm spines (middle) D arm spine (distal) E skin from dorsal arm base, insert frame shows polygonal plate-like large ossicle F–J vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view. Abbreviations: d dorsal, de depression, dist distal, iars inner arm spine, lac lateral ambulacral canals, mo muscle opening, no nerve opening, oars outer arm spine, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (F–J); 500 µm (C); 300 µm (B, D, E); 200 µm (A).
Disc diameter 6.5 and 8 mm, and both basically identical to holotype. However, the segment at which the second arm spine first appeared varied (14–20 free segments), but is considered intraspecific variation.
1742 m depth. Zhongsha Islands, the South China Sea. Attached to coral host.
The species name is derived from the Latin words domus, meaning dome, and granulatus, meaning granulated, referring to the domed granular ossicles on the disc.
The here examined new species was collected on a deep-sea seamount, attached to an unidentified coral species. It concurs with the group that has domed and plate-like granular ossicles, in the genus Asteroschema. This clade included only one species, prior to this study (Asteroschema igloo Baker, 1980). Large polygonal plate-like ossicles were the most significant morphological character for delimiting most of the other Asteroschema species from A. domogranulatum sp. nov. (Table
Asteroschema domogranulatum sp. nov. strongly resembles A. igloo. They are similar in size according to
Holotype : China • 1 specimen; South China Sea, Northeast of Xisha Islands archipelago; 18°41.95'N, 113°33.08'E; depth 1070 m; 29 Mar. 2018; Collecting event: stn. SC004; ’Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044292, OL712208; IDSSE-EEB-SW0086.
Paratype : China • 1 specimen; South China Sea, Southeast of Zhongsha Islands; 13°55.30'N, 115°25.44'E; depth 1111 m; 04 Aug. 2020; Collecting event: stn. SC007; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; IDSSE-EEB-SW0087.
Disc raised high above the arm, concealed by highly dense, small, rounded, finely rugose granular ossicles (Fig.
Asteroschema shenhaiyongshii sp. nov., holotype (IDSSE-EEB-SW0086) A dorsal view B ventral view C dorsal disc D lateral disc E oral frame F dorsal arm (base) G lateral arm (proximal) H dorsal arm (distal) I ventral arm (base) J ventral arm (middle) K ventral arm (distal) L arm spine (arm base) M, N arm spines (middle) O, P arm spines (distal). Abbreviations: ars arm spine, go granular ossicle, goc granular ossicles coat, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B); 1 mm (C, D, F, I, J); 500 µm (E, G, H, K, M, N, P); 200 µm (L, O).
Disc diameter 10 mm, length of arms 220 mm, arm base width 3.3–3.5 mm (Fig.
Disc. Disc more or less pentagonal, raised high above arm, and swollen in center (Fig.
Arms. Arm width comparatively large in relation to body size, not arched, sub-cylindrical, width unchanged from base to middle half of arm (Fig.
Color. In live specimen, reddish brown (Fig.
Lateral arm plate curved around the vertebrae, with two arm spine articular structures, with completely separate large muscle and nerve openings (Fig.
Asteroschema shenhaiyongshii sp. nov., paratype (IDSSE-EEB-SW0087) A–C lateral arm plate (external, internal) D, E arm spines (middle) F, G arm spine (distal) H skin from dorsal arm base (rounded granular ossicles) I–M vertebrae I proximal view J distal view K lateral view L dorsal view M ventral view. Abbreviations: d dorsal, de depression, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 500 µm (D, I–M); 300 µm (A–C, E, G); 200 µm (F, H).
Paratype disc diameter 12 mm, similar to holotype. Second arm spine from segments 10–12 and disc slightly flatter than those of holotype; considered intraspecific variation.
1070–1111 m depth. Near Xisha and Zhongsha islands in the South China Sea. Attached to sponge host.
The specific name is dedicated to the manned submersible vessel ‘Shenhaiyongshi’ meaning deep sea warrior in Chinese, which collected the specimen.
Asteroschema shenhaiyongshii sp. nov. concurs with the group of Asteroschema that has only granular ossicles. This group includes nearly 20 species. Furthermore, they are divided by naked, widely separated granular ossicles on ventral disc and base of arm. Fifteen Asteroschema species have dense granular ossicles on the ventral disc. Asteroschema shenhaiyongshii sp. nov. is distinguished clearly by its unique dense, rounded, fine granular ossicles on both disc and arms, a thick sub-cylindrical proximal to middle half of the arms without annular bands, and cylindrical outer arm spine with visible thorns at middle arm segments (Fig.
Asteroschema ajax and A. laeve (Lyman, 1872) are similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but are easily differentiated by well-spaced annulated granular bands on the arms, and club-shaped inner arm spine (
Asteroschema arenosum Lyman, 1878 is similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but differs in having a swollen arm spine, sparser granular coverage (five grains in 1 mm), and a second arm spine from the fourth arm segment. Asteroschema vicinum Koehler, 1907 differs in its sub-equal arm spines and A. sulcatum Ljungman, 1872 in its highly dense granular ossicle coverage (9–15 grains in 1 mm). Asteroschema igloo and A. domogranulatum sp. nov. differ from A. shenhaiyongshii sp. nov. by large polygonal to domed granular ossicles (four or five grains in 1 mm; Table
Asteroschema glaucum Matsumoto, 1915, and A. hemigymnum Matsumoto, 1915 are similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but differ by sparser granular ossicle coverage (five or six grains in 1 mm), club-shaped inner arm spine at the middle arm segments and in A. hemigymnum the ventral disc is covered with pavement-like ossicles. Asteroschema inoratum Koehler, 1906 is similar to A. shenhaiyongshii sp. nov. by having a similar density of the granular coverage on both dorsal and ventral disc, but differs in having granular ossicles on the ventral surface along the arm, a slightly club-shaped inner arm spine at middle arm segments, and both spines not transforming into a compound hook (Table
Asteroschema monobactrum H. L. Clark, 1917 is similar to A. shenhaiyongshii sp. nov. in having granular ossicles on both dorsal and ventral surface and in start of the second arm spine, but differs by having separate, sparser granular ossicles (seven grains in 1 mm at disc center, five or six grains in 1 mm at periphery of disc and on arm), and by the granular ossicles on both sides distalwards along the arm becoming widely separated to almost naked (H. L.
Granular ossicle density of Asteroschema wrighti McKnight, 2000, A. bidwillae McKnight, 2000, and A. tenue (eight or ten grains in 1 mm) is similar to A. shenhaiyongshii sp. nov. However, Asteroschema tenue differs from A. shenhaiyongshii sp. nov. by having a club-shaped inner spine at middle arm segments, and slender long arms, and A. wrighti differs by having a club-shaped inner spine at middle arm segments, widely spaced granular ossicles on the ventral arm, irregular plate-like ossicles on the ventral disc, and smooth outer spines, and by being hexamerous (Table
Most Ophiocreas species differ from Asteroschema shenhaiyongshii sp. nov. by having naked or micro-granular ossicles in the skin in both disc and arms. (Table
Asteroschema bidwillae McKnight, 2000: 24–27, fig. 8.
China • 1 specimen; South China Sea, Zhongsha Islands, seamount; 13°36.20'N, 113°33.74'E; depth 1515 m; 30 Mar. 2020; Collecting event: stn. SC025; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; IDSSE-EEB-SW0105.
Disc diameter 13 mm, length of arms 195 mm, arm base width 4.5–5 mm (Fig.
Disc. Disc circular, hexamerous, raised above arms, deeply swollen in center (Fig.
Asteroschema cf. bidwillae McKnight, 2000 (IDSSE-EEB-SW0105) A dorsal side of the specimen B ventral side of the specimen C dorsal disc D skin on the disc E lateral disc F oral frame G dorsal arms (proximal) H dorsal arm (middle) I ventral arm (arm base) J outer arm spine (proximal) K arm spines (middle) L arm spines (distal). Abbreviations: ars arm spine, as adoral shield, ass adoral shield spine, go granular ossicle, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A–C, E, G); 1 mm (F, H, I); 500 µm (K, L); 200 µm (D, G, J).
Arms. Arms six, at base wide, not arched, dorsally flattened, and swollen in first few free arm segment (Fig.
Color. In live specimen, reddish brown (Fig.
Lateral arm plate with two arm spine articular structures, with slightly separated large muscle and relatively small nerve opening (Fig.
Asteroschema cf. bidwillae McKnight, 2000 (IDSSE-EEB-SW0105) A, B lateral arm plate (external, internal) C outer arm spine (middle) D arm spine (distal) E skin from dorsal arm base (rounded to irregular-shaped granular ossicles) F–J vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view. Abbreviations: asa arm spine articulation, d dorsal, de depression, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (F–J); 500 µm (C); 300 µm (A, B, E); 200 µm (D).
400–2000 m depth. New Zealand, Tasman Sea, Solomon Islands, South China Sea (
Asteroschema bidwillae was first described by
Asteroschema rubrum Lyman, 1879: 68–69, fig. 17, figs 454–457.
China • 3 specimens; South China Sea, near Zhongsha Islands, seamount; 13°55.44'N, 115°25.37'E; depth 958 m; 09 Mar. 2020; Collecting event: stn. SC007; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044293, OL712209, OK044294, OL712210, OK044295, OL712211; IDSSE-EEB-SW0071, IDSSE-EEB-SW0072, IDSSE-EEB-SW0073 • 1 specimen; South China Sea, near Zhongsha Islands, seamount; 14°21.93'N, 115°23.89'E; depth 922 m; 17 Mar. 2020; Collecting event: stn. SC035; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; IDSSE-EEB-SW0088.
IDSSE-EEB-SW0072: disc diameter 12 mm, length of arms from 165–175 mm (Fig.
Disc. Disc flat, slightly raised above arms, swollen in center, and small in relation to total body size of specimen (Fig.
Asteroschema rubrum Lyman, 1879 (IDSSE-EEB-SW0072) A dorsal view B ventral view C dorsal disc D skin on the disc E lateral disc F ventral disc G dorsal arm (proximal) H lateral arm (middle) I ventral arm (proximal) J outer arm spine (proximal) K arm spines (middle) L arm spines (distal). Abbreviations: as adoral shield, ass adoral shield spine, ars arm spine, go granular ossicle, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, ass adoral shield spine, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B); 1 mm (E–G, I); 500 µm (C, H, J, K); 200 µm (D, L).
Arms. Arms at base wide, not arched, dorsally flattened, and slightly swollen in first few free segments (Fig.
Color. In live specimen, reddish brown (Fig.
Lateral arm plate with two arm spine articular structures, with slightly separate large muscle and nerve openings (Fig.
Asteroschema rubrum Lyman, 1879 (IDSSE-EEB-SW0072) A, B lateral arm plate (external, internal), C outer arm spine (middle), D arm spine (distal), E skin from dorsal arm base (rounded to somewhat cone shaped granular ossicles), F–J vertebrae; F proximal view, G distal view, H lateral view, I dorsal view, J ventral view. Abbreviations: d dorsal, de depression, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (C); 500 µm (A, F, G); 300 µm (B, E, H–J); 200 µm (D).
730–958 m depth. Near Brandella, Chile and in the South China Sea.
Asteroschema rubrum was first described by
Asteroschema tubiferum
Matsumoto, 1911: 52; 1917: 44;
China • 1 specimen; South China Sea, Zhongsha Islands, seamount; 13°36.20'N, 113°33.74'E; depth 1515 m; 30 Mar. 2020; Collecting event: stn. SC025; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044298; IDSSE-EEB-SW0077 • 1 specimen; South China Sea, East of Zhongsha Islands, seamount; 16°22.11'N, 116°06.60'E; depth 1619 m; 09 Aug. 2020; Collecting event: stn. SC028; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044297, OL712213; IDSSE-EEB-SW0106. Northwest Pacific • 1 specimen; near Mariana Trench, Southeast of Guam Island, deepsea seamount, 11°57.20'N, 141°28.67'E; depth 1377 m; 03 Sep. 2019; Collecting event: stn. SC034; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044296, OL712212; IDSSE-EEB-SW0078.
IDSSE-EEB-SW0078: disc diameter 10 mm, length of arms 200 mm (Fig.
Disc. Disc flat, slightly raised above arms, swollen in center (Fig.
Asteroschema tubiferum Matsumoto, 1911 (IDSSE-EEB-SW0078) A dorsal view B ventral view C dorsal disc D skin on the arm E lateral disc F ventral disc G dorsal arm (proximal) H dorsal arm (middle) I ventral arm (proximal) J outer arm spine (proximal) K arm spines (middle) L arm spines (distal). Abbreviations: as adoral shield, ars arm spine, go granular ossicle, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B); 1 mm (E–G, I); 500 µm (C, H, J, K); 200 µm (D, L).
Arms. Arms at base wide, dorsally flattened, and swollen in first few free segments (Fig.
Color. In live specimen, reddish brown on dorsal disc and arm, light brown on ventral disc and arm (Fig.
Lateral arm plate with two arm spine articular structures, with large, separated muscle and nerve openings (Fig.
Asteroschema tubiferum Matsumoto, 1911 (IDSSE-EEB-SW0078) A lateral arm plate B outer arm spine (middle) C inner arm spine (middle) D arm spine (distal) E skin from dorsal arm base (granular ossicles) F–J vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view. Abbreviations: d dorsal, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (F, G, J): 500 µm (B, H, I); 300 µm (A, C–E).
325–1800 m depth. New Zealand, Tasman Sea, Kermadec Islands, Bay of Plenty, Hawaii, Sagami Sea, the South China Sea, and Northwest Pacific seamount.
Asteroschema tubiferum was first described by
Asteroschema salix
Lyman, 1879: 66–67, fig. 17, figs 466–469; 1882: 277, fig. 22, figs 13–15;
Disc diameter 10 mm, length of arms 145 mm (Fig.
Disc. Disc flat, strongly raised above arms (Fig.
Asteroschema salix Lyman, 1879 (IDSSE-EEB-SW0082) A dorsal view B ventral view C dorsal disc D skin on the arm E ventral disc F dorsal arm (proximal) G lateral arm (middle) H ventral arm (proximal) I ventral arm (distal) J outer arm spine (proximal) K arm spines (middle) L arm spines (distal). Abbreviations: as adoral shield, ass adoral shield spine, ars arm spine, go granular ossicle, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, ots oral tentacle scale, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B); 1 mm (C, E–H); 500 µm (J, K); 200 µm (D, I, L).
Arms. Arms sub-cylindrical, not swollen, narrower and more cylindrical in distal half of arm (Fig.
Color. In ethanol, pink but when dried, dull brown to whitish (Fig.
Lateral arm plate with two arm spine articular structures, with two large muscle and nerve openings (Fig.
Asteroschema salix Lyman, 1879 (IDSSE-EEB-SW0082) A lateral arm plate B outer arm spine (middle) C inner arm spine (middle) D arm spine (distal) E skin from dorsal arm base (granular ossicles) F–J vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view. Abbreviations: d dorsal, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (B, F–J); 300 µm (A, C, E); 100 µm (D).
341–1800 m depth. New Zealand, Tasman Sea, Kermadec Islands, Bay of Plenty, Solomon Island, Coral Sea, Timor Sea, South Africa (off Glenmore), the South China Sea.
Asteroschema salix was first described by
Asteroschema lissum H. L. Clark, 1939: 37–39, figs 1–3.
China • 2 specimens; South China Sea, Zhongsha Islands, seamount; 13°36.20'N, 113°33.74'E; depth 1515 m; 30 Mar. 2020; Collecting event: stn. SC025; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044300; IDSSE-EEB-SW0079, IDSSE-EEB-SW080. Northwest Pacific • 1 specimen; near Mariana Trench, Southeast of Guam Island, seamount, 12°6.67'N, 141°37.27'E; depth 1160 m; 03 Sep. 2019; Collecting event: stn. SC033; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044299, OL712207; IDSSE-EEB-SW0081.
IDSSE-EEB-SW0079: disc diameter 11.5 mm, length of arms 165 mm, arm base width 3–3.5 mm (Fig.
Disc. Disc flat, slightly raised above arms, swollen in center (Fig.
Asteroschema cf. lissum H. L. Clark, 1939 (IDSSE-EEB-SW0079) A dorsal view B ventral view C dorsal disc D skin on the disc E lateral disc F ventral disc G dorsal arm (middle) H lateral arm (middle) I ventral arm (proximal) J outer arm spine (proximal) K arm spines (middle) L arm spines (distal). Abbreviations: as adoral shield, ass adoral shield spine, ars arm spine, go granular ossicle, gs genital slit, iars inner arm spine, j jaw, oars outer arm spine, ots oral tentacle scale, rs radial shield, t teeth, tp tentacle pore. Scale bars: 2 mm (A, B, G); 1 mm (C, E, F, H, I); 500 µm (J, K); 200 µm (D, L).
Arms. Arms slightly arched, circular, from middle to distal half narrower and more cylindrical (Fig.
Color. In live specimen, reddish brown but radial shields slightly lighter in color due to thin skin (Fig.
Lateral arm plate with two arm spine articular structures, with large muscle and nerve openings (Fig.
Asteroschema cf. lissum H. L. Clark, 1939 (IDSSE-EEB-SW0079) A, B lateral arm plate (external, internal) C outer arm spine (middle) D arm spine (distal) E skin from dorsal arm base (granular ossicles) F–J vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view. Abbreviations: d dorsal, dist distal, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pb podial basin, prox proximal, st secondary teeth, v ventral. Scale bars: 800 µm (F–J); 500 µm (A, C); 300 µm (B, D); 200 µm (E).
797–1515 m depth. Maldives, South China Sea, Northwest Pacific.
Asteroschema lissum was first described by H. L.
Asterostegus maini McKnight, 2003: 386–389, figs 1, 2.
Astroceras elegans McKnight, 1989: 25 (non Astroceras elegans Bell, 1917).
China • 2 specimens; South China Sea, near Xisha Islands archipelago, seamount; 16°47.79'N, 113°15.04'E; depth 602 m; 31 Mar. 2020; Collecting event: stn. SC009; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044303; IDSSE-EEB-SW0075; IDSSE-EEB-SW0076.
IDSSE-EEB-SW0076: disc diameter 32.2 mm, length of arms 240–250 mm, height of arm base 9.8 mm (Fig.
Disc. Disc circular and slightly inflated radially, with sunken interradial margins (Fig.
Asterostegus maini McKnight, 2003 (A–M IDSSE-EEB-SW0076 N–P IDSSE-EEB-SW0075) A dorsal view B center of dorsal disc C dorsal disc (distal end of radial shields) D ventral disc E, F oral frame G lateral disc H dorsal arm (proximal) I dorsal arm (distal) J lateral arm (proximal) K ventral arm (middle) L, M arm spines (distal) N oral frame O periphery of the disc P oral frame (small transparent ossicles). Abbreviations: as adoral shield, ars arm spine, go granular ossicle, gs genital slit, j jaw, mp median plate, oip oral interradial plate, rs radial shield, t teeth, tp tentacle pore, ts tentacle scale. Scale bars: 6 mm (A); 2 mm (B–H, N); 1 mm (I–K, O, P); 500 µm (L); 200 µm (M).
Arms. Arms simple, strong, and not branching (Fig.
Color. In live specimen, dorsal disc interradially dark brown but radial shields light brown. Ventral and lateral disc whitish brown, dorsal surface of proximal and middle regions of arms bright brown/red. Lateral and ventral surface of arms whitish brown, granules creamy white (Fig.
Lateral arm plate with two arm spine articular structures, middle half of arm with large and wide, separated muscle and nerve openings, depression on inner side (Fig.
Asterostegus maini McKnight, 2003 (IDSSE-EEB-SW0076) A, B lateral arm plate (external, internal) C, D arm spine (middle) E, F vertebrae (middle) E proximal view F distal view G–K vertebrae (distal) G proximal view H distal view I lateral view J dorsal view K ventral view. Abbreviations: asa arm spine articular structure, d dorsal, de depression, dist distal, mo muscle opening, ob oral bridge, prox proximal, v ventral. Scale bars: 800 µm (E, F); 500 µm (A, C, D, I, K); 300 µm (B, G, H, J).
417–602 m in depth. New Zealand (Cook Island), South China Sea.
Asterostegus maini was first described by
Subfamily Gorgonocephalinae Döderlein, 1911
Astrodendrum sagaminum
Döderlein, 1902: 321–322; 1911: 38–39, figs 2, 3–5, 7, 8; 1927: 32, 92; H.L.
China • 1 specimen; South China Sea, East side from Zhongsha Islands, seamount; 16°22.11'N, 116°06.60'E; depth 1619 m; 09 Aug. 2020; Collecting event: stn. SC028; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044304; IDSSE-EEB-SW0104.
Disc diameter 62 mm (Fig.
Disc. Dorsal disc slightly inflated, swollen in the center (Fig.
Astrodendrum cf. sagaminum (Döderlein, 1902) (IDSSE-EEB-SW0104) A dorsal view B ventral view C dorsal disc (center) D dorsal disc (distal edge) E radial shield F, G ventral disc H oral frame I, J ventral view of arm base K ventral view of after second arm branch L, M dorsal view of second arm branch N lateral view of arm (middle) O lateral view of arm (pedicellariae with baseplate) P, Q variations of arm spine on distal end of the arm. Abbreviations: ars arm spine, co conical ossicles gs genital slit, os oral shield, peb = pedicellarial band, rs radial shield, t teeth, tp tentacle pore. Scale bars: 16 mm (A, B); 2 mm (C, D, F, L); 1 mm (E, H–K, M, N); 500 µm (G, O); 200 µm (P, Q).
Arms. Arms branched at least eight to nine times, flexible dorso-ventrally, flat ventrally, arched dorsally (Fig.
Color. In live specimen, whole specimen brown, but radial shields, oral regions, and ventral arms lighter than disc (Fig.
On middle half of arm, lateral arm plates with perforations on ventral side, large muscle opening and small nerve opening (Fig.
Astrodendrum cf. sagaminum (Döderlein, 1902) (IDSSE-EEB-SW0104) A lateral arm plate (middle) B plan view of baseplate C pedicellariae D arm spine on distal end E–J vertebrae on middle half of arm E proximal view of branch vertebrae F proximal view G distal view H lateral view I dorsal view J ventral view K–N vertebrae on distal end of arm K distal view L proximal view M lateral view N ventral view. Abbreviations: ap articular pad of the base, au auricle, d dorsal, dist distal, fo foramina of the base, fs fossa between adjacent tubercles, hd head of the apophysis, lac lateral ambulacral canals, mo muscle opening, no nerve opening, pd pedicel of the apophysis, prox proximal, pt primary tooth of the blade, sh sheath of the baseplate, su sulcus of tubercle head, v ventral. Scale bars: 800 µm (E–J); 500 µm (A, B); 300 µm (K–N); 200 µm (D); 80 µm (C).
90–1300 m depth. South China Sea, Japan, East China Sea, Sri Lanka.
The specimen is similar to the holotype description by Döderlein (1902), and the redescriptions of
The molecular phylogenetic trees of these species of Gorgonocephalidae and Euryalidae were in agreement with previous studies (
The genus Asterostegus includes only three species, and is closely related to Astroceras, but a previous phylogenetic analysis recognized it as monophyletic and belonging in the family Euryalidae (
Most of the species from the present study were collected from deep water in the South China Sea. Previous studies from the South China Sea recorded only few Asteroschema species, but found no representatives of the genera Astrodendrum and Asterostegus. According to the present study, the ophiuroid diversity of the South China Sea may be higher than previously known and future expeditions to the South China Sea deep-sea seamounts may discover even more species. The present study suggests a wider distribution of Euryalida species from the South-Pacific to the North-Pacific regions than previously expected.
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,
Table S1
Data type: Primers (text)
Explanation note: COI and 16S primers and PCR cycles used in this study (
Table S2
Data type: Genetic distance % (COI)
Explanation note: Genera Asteroschema, Ophiocreas and Asterostegus, pairwise distance values based on 592 bp mitochondrial COI sequences, calculated using the Kimura 2-parameter method with 1,000 bootstrap replicates (Value in blue color represent Standard Error). Abbreviations: AUS Australia, CAN Canada, CS Caribbean Sea, JAP Japan, MAD Madagascar, NCA New Caledonia, NWP Northwest Pacific, NZ New Zealand, PAO Pacific Ocean, SCS South China Sea.
Table S3
Data type: Genetic distance % (COI)
Explanation note: Genera Gorgonocephalus and Astrodendrum, pairwise distance values based on 730 bp mitochondrial COI sequences, calculated using the Kimura 2-parameter method with 1,000 bootstrap replicates (Value in blue color represent Standard Error). Abbreviations: AN Antarctic Sea, AUS Australia, CAN Canada, JAP Japan, NZ New Zealand, SCS South China Sea, SWE Sweden.