Research Article |
Corresponding author: Hiroshi Yamasaki ( h.yamasaki@meiobenthos.com ) Academic editor: Pavel Stoev
© 2018 Hiroshi Yamasaki, Katarzyna Grzelak, Martin V. Sørensen, Birger Neuhaus, Kai Horst George.
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:
Yamasaki H, Grzelak K, Sørensen MV, Neuhaus B, George KH (2018) Echinoderes pterus sp. n. showing a geographically and bathymetrically wide distribution pattern on seamounts and on the deep-sea floor in the Arctic Ocean, Atlantic Ocean, and the Mediterranean Sea (Kinorhyncha, Cyclorhagida). ZooKeys 771: 15-40. https://doi.org/10.3897/zookeys.771.25534
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Kinorhynchs rarely show a wide distribution pattern, due to their putatively low dispersal capabilities and/or limited sampling efforts. In this study, a new kinorhynch species is described, Echinoderes pterus sp. n., which shows a geographically and bathymetrically wide distribution, occurring on the Karasik Seamount and off the Svalbard Islands (Arctic Ocean), on the Sedlo Seamount (northeast Atlantic Ocean), and on the deep-sea floor off Crete and on the Anaximenes Seamount (Mediterranean Sea), at a depth range of 675–4,403 m. The new species is characterized by a combination of middorsal acicular spines on segments 4–8, laterodorsal tubes on segment 10, lateroventral tubes on segment 5, lateroventral acicular spines on segments 6–9, tufts of long hairs rising from slits in a laterodorsal position on segment 9, truncated tergal extensions on segment 11, and the absence of any type-2 gland cell outlet. The specimens belonging to the populations from the Arctic Ocean, the Sedlo Seamount, and the Mediterranean Sea show morphological variation in the thickness and length of the spines as well as in the presence/absence of ventromedial sensory spots on segment 7. The different populations are regarded as belonging to a single species because of their overlapping variable characters.
meiofauna, meiofauna paradox, morphological variation, taxonomy
The meiofauna, defined as the assemblage of microscopic benthic organisms passing through a 1 mm-sieve mesh and collected on a 40–63 µm-sieve mesh, is composed of various taxonomic groups, and occurs in diverse habitats including extreme environments such as polar regions, the deep sea, and seamounts (
Kinorhyncha is an ecdysozoan phylum which is exclusively composed of marine meiofaunal species. To date, more than 260 kinorhynchs species are known from around the world (
In the present study, we describe a new kinorhynch species with a geographically and bathymetrically wide distribution, ranging from the Arctic Ocean to the Mediterranean Sea and from upper bathyal to lower abyssal depths. The interpopulational morphological variation of the new species is also discussed.
Kinorhynchs were obtained from meiofauna samples collected from the central mount of the Karasik Seamount, Langseth Ridge in the Arctic Ocean (by the R/V Polarstern during the expedition PS101,
Map of the sampling localities. A map of the Northern hemisphere, including the Arctic Ocean, Atlantic Ocean, and Mediterranean Sea B enlarged map of the Karasik Seamount C enlarged map of the north of Svalbard D enlarged map of the Sedlo Seamount E enlarged map of the deep-sea canyon off Crete in the Mediterranean Sea F enlarged map of the Anaximenes Seamount. Scale bars: 20 km (B), 50 km (C), 30 km (D–F).
Sampling region | Station | Cruise | Date | Depth [m] | Latitude | Longitude | Gear |
---|---|---|---|---|---|---|---|
Langseth Ridge, central mount on Karasik Seamount | 152-1 | PS101 | 28.09.2016 | 903 | 86°49'23"N, 61°40'10"E | multicorer | |
North of Svalbard | 31 | PS92 | 04.06.2015 | 1,656 | 81°28'11"N, 18°10'27"E | box corer | |
North of Svalbard | 43 | PS92 | 15.06.2015 | 790 | 82°12'19"N, 7°38'4"E | box corer | |
Sedlo Seamount | 717 | M60/1 | 24.11.2003 | 2,721 | 40°11'00"N, 26°33'6"W | box corer | |
Mediterranean deep sea | 24 | M71/2 | 04.01.2007 | 2,789 | 33°43'41"N, 26°32'55"E | multicorer | |
Mediterranean deep sea | 51 | M71/2 | 07.01.2007 | 4,323 | 34°30'19"N, 26°11'30"E | multicorer | |
Mediterranean deep sea | 52 | M71/2 | 07.01.2007 | 4,326 | 34°30'18"N, 26°11'31"E | multicorer | |
Mediterranean deep sea | 55 | M71/2 | 07.01.2007 | 4,332 | 34°30'19"N, 26°11'30"E | multicorer | |
Mediterranean deep sea | 56 | M71/2 | 08.01.2007 | 4,327 | 34°30'19"N, 26°11'31"E | multicorer | |
Mediterranean deep sea | 62 | M71/2 | 08.01.2007 | 4,396 | 34°25'5"N, 26°7'6"E | multicorer | |
Mediterranean deep sea | 63 | M71/2 | 08.01.2007 | 4,395 | 34°24'56"N, 26°6'59"E | multicorer | |
Mediterranean deep sea | 64 | M71/2 | 08.01.2007 | 4,399 | 34°24'59"N, 26°6'57"E | multicorer | |
Mediterranean deep sea | 65 | M71/2 | 09.01.2007 | 4,403 | 34°25'00"N, 26°6'59"E | multicorer | |
Mediterranean deep sea | 66 | M71/2 | 09.01.2007 | 4,401 | 34°25'00"N, 26°6'59"E | multicorer | |
Mediterranean deep sea | 94 | M71/2 | 12.01.2007 | 4,147 | 34°21'29"N, 25°58'30"E | multicorer | |
Mediterranean deep sea | 1167.1 | MSM14/1 | 11.01.2010 | 4,353 | 34°24'36"N, 26°7'31"E | multicorer | |
Mediterranean deep sea | 1169.1 | MSM14/1 | 12.01.2010 | 4,344 | 34°24'34"N, 26°7'30"E | multicorer | |
Anaximenes Seamount | 918 | M71/1 | 17.12.2006 | 2,043 | 35°30'14"N, 30°8'58"E | multicorer | |
Anaximenes Seamount | 930 | M71/1 | 19.12.2006 | 675 | 35°26'4"N, 30°9'53"E | multicorer |
Specimens for light microscopy (LM) were dehydrated in glycerol and mounted as glycerol-paraffin slides on Cobb aluminum frames or mounted in Fluoromount G™ between two cover slips attached to a plastic H-S slide. LM specimens were observed with a Zeiss Axioskop 50 microscope, or with an Olympus BX51 microscope, and a Nikon E600 microscope. All microscopes were equipped with Nomarski differential interference contrast. A camera lucida equipped with a Zeiss Axioskop 50 microscope was used to make drafts for line art illustrations. Final line art illustrations were drawn with Adobe Illustrator CS6 based on the drafts. Measurements were made through a camera lucida or with Cell^D software. Specimens were photographed with a Zeiss AxioCam MRc5 or an Olympus DP27 camera.
Five specimens from the Karasik Seamount and 23 specimens from the Mediterranean deep sea were used for scanning electron microscopy (SEM) observation. The specimens were transferred from ethanol to distilled water through a graded series of ethanol, postfixed with OsO4 in 0.05 M phosphate buffer (pH = 7.3) with 0.3 M sodium chloride and 0.05% sodium azide for 2.5 hours, dehydrated through a graded series of ethanol, critical-point dried with a BalTec CPD 030, mounted on aluminum stubs, sputter-coated with gold-palladium with a Polaron SC 7640, and observed with a Zeiss EVO LS 10 scanning electron microscope.
The terminology follows
Echinoderes with middorsal acicular spines on segments 4–8; laterodorsal tubes on segment 10; lateroventral tubes on segment 5; lateroventral acicular spines on segments 6–9; tufts of long hairs arising from slits in a laterodorsal position on segment 9; truncated tergal extensions on segment 11; without type-2 gland cell outlet.
The species name is derived from the Latinized Greek pterón (wing or feather), referring to the tufts of hairs on segment 9 which look like wings.
Holotype: Adult male (ZMB 11608), collected at station 55 in the Mediterranean deep sea off Crete (Fig.
Paratypes: Adults, collected in the Mediterranean Sea off Crete; four males and one female, collected at station 24 (ZMB 11609–11613); one female, collected at station 51 (ZMB 11614); one female, collected at station 52 (ZMB 11615); one male, collected at station 56 (ZMB 11616); one male and three females, collected at station 62 (ZMB 11617–11620); one female, collected at station 64 (ZMB 11621); one male, collected at station 65 (ZMB 11622); one male, collected at station 66 (ZMB 11623); one male, collected at station 94 (ZMB 11624); four males and seven females, collected at station 1167.1 (ZMB 11628–11638); one male and one female, collected at station 1169.1 (ZMB 11639–11640); one female, collected at station 918 (ZMB 11625); one male and one female, collected at station 930 (ZMB 11626–11627); (Fig.
Additional material for LM: all adults; seven males and 12 females, collected at station 152 on Karasik Seamount, mounted as glycerol-paraffin slides on Cobb aluminum frames (ZMB 11642–11660); one male and one female, collected at station 31 north of Svalbard, mounted in Fluoromount G (NHMD-202798 and NHMD-202799); one male and one female, collected at station 43 north of Svalbard, mounted in Fluoromount G (NHMD-202800 and NHMD-202801); one male, collected at station 717 on the Sedlo Seamount, mounted as a glycerol-paraffin slide on a glass slide (ZMB 11641) (Fig.
Additional material for SEM: adults, mounted on aluminum stubs; five males and nine females, collected at station 63 (ZMB 11664a–d, 11665a–d, 11666a, 11667a–d, 11668a), Mediterranean deep sea off Crete; five males and four females, collected at station 66, Mediterranean deep sea off Crete (ZMB 11661a–c, d, 11662a–c, 11663a, c); one male and four females, collected at station 152, the Karasik Seamount (ZMB 11669a, b, 11670b, d, 11671e) (Fig.
Deep-sea trench off Crete, Mediterranean Sea, (34°30'19"N, 26°11'30"E), 4,332 m depth (Fig.
Adult with head, neck, and eleven trunk segments (Figs
Echinoderes pterus sp. n., camera lucida drawings. A, B Holotype, male (ZMB 11608), collected at station 55 (Mediterranean deep sea off Crete), entire animal, segments 1–11 in dorsal and ventral view, respectively C, D paratype, female (ZMB 11614), collected at station 51 (Mediterranean deep sea off Crete), segments 9–11, dorsal and ventral view, respectively E non-type, male (ZMB 11653), collected at station 152-1 (Karasik Seamount), segments 8–11, left side of ventral view. Characters drawn in gray color are overlapped by the preceding segment. Abbreviations: gco1, type-1 gland cell outlet; ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvs, lateroventral acicular spine; lvt, lateroventral tube; mds, middorsal acicular spine; pe, penile spine; si, protonephridial sieve plate; ss, sensory spot; th, tuft of long hairs. Digits after abbreviations indicate the corresponding segment number except in connection with a gland cell outlet. Scale bar: 100 µm.
Measurements of adult Echinoderes pterus sp. n. Measurements are given in micrometers, except for the ratios, and are summed for all specimens and listed separately for each population. Columns N and SD indicate sample size and standard deviation, respectively. Abbreviations: (f), length in females; ldt, length of laterodorsal tube; ltas, length of lateral terminal accessory spine; lts, length of lateral terminal spine; lvs, length of lateroventral spine; lvt, length of lateroventral tube; (m), length in males; mds, length of middorsal spine; msw, maximum sternal width; n.a., data not available; s, segment length; sw, standard width; tl, trunk length. Digits after abbreviation indicate segment number.
Total | Anaximenes Seamount | Mediterranean deep-sea off Crete | Sedlo Seamount | North of Svalbard | Karasik Seamount | |||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
N | Range | Mean | SD | N | Range | Mean | SD | N | Range | Mean | SD | N | N | Range | Mean | SD | N | Range | Mean | SD | ||
tl | 56 | 186–253 | 219.3 | 15.5 | 3 | 205–234 | 215.4 | 15.9 | 30 | 186–253 | 217.8 | 16.5 | 0 | n.a. | 4 | 208–241 | 224.5 | 14.0 | 19 | 196–250 | 221.2 | 15.0 |
msw-5/6 | 30 | 42–59 | 50.2 | 4.3 | 2 | 48–48 | 47.9 | 0.3 | 13 | 42–54 | 48.0 | 3.5 | 1 | 49 | 4 | 56–59 | 58.0 | 1.4 | 10 | 46–56 | 50.5 | 2.5 |
msw/tl | 29 | 19–28% | 22.9% | 2.2% | 2 | 21–23% | 21.9% | 1.9% | 13 | 19–26% | 21.9% | 1.7% | 0 | n.a. | 4 | 23–28% | 25.9% | 2.1% | 10 | 21–26% | 23.2% | 1.7% |
sw-10 | 38 | 35–50 | 42.8 | 4.0 | 2 | 41–41 | 41.0 | 0.3 | 19 | 35–49 | 40.8 | 4.2 | 1 | 41 | 4 | 48–50 | 49.0 | 0.8 | 12 | 41–45 | 44.2 | 1.3 |
sw/tl | 37 | 16–24% | 19.7% | 1.6% | 2 | 18–20% | 18.7% | 1.6% | 19 | 16–22% | 19.2% | 1.6% | 0 | n.a. | 4 | 21–24% | 21.9% | 1.2% | 12 | 18–22% | 19.9% | 1.3% |
s1 | 46 | 25–38 | 31.8 | 2.9 | 2 | 29–31 | 29.9 | 1.0 | 25 | 25–37 | 31.6 | 3.1 | 1 | 30 | 4 | 27–29 | 28.3 | 1.0 | 14 | 31–38 | 33.6 | 1.6 |
s2 | 45 | 16–31 | 25.2 | 3.2 | 2 | 21–25 | 22.9 | 2.9 | 25 | 16–31 | 24.6 | 3.1 | 0 | n.a. | 4 | 19–23 | 21.3 | 1.7 | 14 | 23–29 | 27.6 | 1.7 |
s3 | 44 | 20–26 | 23.3 | 1.4 | 2 | 22–23 | 22.5 | 0.3 | 24 | 20–25 | 22.6 | 1.4 | 0 | n.a. | 4 | 23–26 | 24.5 | 1.3 | 14 | 23–26 | 24.1 | 1.1 |
s4 | 45 | 20–30 | 24.7 | 1.9 | 2 | 24–25 | 24.1 | 0.7 | 25 | 20–26 | 23.8 | 1.4 | 0 | n.a. | 4 | 27–30 | 28.0 | 1.4 | 14 | 24–27 | 25.7 | 1.1 |
s5 | 46 | 22–33 | 25.8 | 2.5 | 2 | 24–25 | 24.5 | 0.7 | 25 | 22–27 | 24.4 | 1.1 | 1 | 24 | 4 | 30–33 | 31.3 | 1.3 | 14 | 25–31 | 27.3 | 1.5 |
s6 | 46 | 25–36 | 28.7 | 2.5 | 2 | 25–28 | 26.6 | 2.3 | 25 | 25–32 | 27.4 | 1.7 | 1 | 27 | 4 | 32–36 | 33.8 | 1.7 | 14 | 27–32 | 29.9 | 1.4 |
s7 | 46 | 25–38 | 30.5 | 2.7 | 2 | 29–30 | 29.2 | 0.7 | 25 | 25–32 | 28.9 | 1.5 | 1 | 30 | 4 | 36–38 | 36.8 | 1.0 | 14 | 30–33 | 31.8 | 1.3 |
s8 | 46 | 29–43 | 33.8 | 3.0 | 2 | 30–34 | 31.9 | 2.6 | 25 | 29–37 | 32.5 | 2.0 | 1 | 30 | 4 | 40–43 | 41.3 | 1.3 | 14 | 32–36 | 34.4 | 1.3 |
s9 | 46 | 31–40 | 34.8 | 2.2 | 2 | 32–34 | 33.3 | 1.3 | 25 | 31–37 | 34.0 | 1.5 | 1 | 31 | 4 | 39–40 | 39.8 | 0.5 | 14 | 33–38 | 35.2 | 1.5 |
s10 | 46 | 32–50 | 39.3 | 4.8 | 2 | 32–37 | 34.5 | 2.9 | 25 | 34–39 | 36.4 | 1.4 | 1 | 36 | 4 | 36–41 | 38.3 | 2.2 | 14 | 40–50 | 45.8 | 3.1 |
s11 | 45 | 19–27 | 22.8 | 2.2 | 2 | 19–21 | 19.9 | 2.0 | 24 | 19–27 | 23.3 | 1.9 | 1 | 19 | 4 | 20–25 | 22.8 | 2.2 | 14 | 19–26 | 22.6 | 2.2 |
mds4 | 53 | 25–44 | 33.1 | 5.0 | 3 | 27–29 | 28.2 | 0.9 | 28 | 25–36 | 30.1 | 3.3 | 1 | 35 | 4 | 33–36 | 34.8 | 1.3 | 17 | 33–44 | 38.5 | 3.0 |
mds5 | 53 | 34–60 | 44.5 | 6.6 | 3 | 38–42 | 39.5 | 1.9 | 28 | 34–47 | 39.8 | 3.1 | 1 | 50 | 4 | 44–50 | 47.8 | 2.6 | 17 | 45–60 | 52.1 | 3.9 |
mds6 | 52 | 44–69 | 54.0 | 7.0 | 3 | 51–52 | 51.5 | 0.8 | 27 | 44–57 | 48.8 | 3.4 | 0 | n.a. | 4 | 48–60 | 55.0 | 5.6 | 18 | 56–69 | 62.0 | 3.6 |
mds7 | 53 | 56–92 | 71.4 | 11.5 | 3 | 60–69 | 63.7 | 4.6 | 29 | 56–69 | 63.0 | 3.4 | 1 | 68 | 3 | 75–76 | 75.3 | 0.6 | 17 | 79–92 | 86.6 | 4.4 |
mds8 | 48 | 71–108 | 88.0 | 11.2 | 2 | 84–85 | 84.5 | 0.3 | 27 | 71–88 | 79.5 | 4.6 | 1 | 101 | 4 | 89–99 | 95.5 | 4.7 | 14 | 95–108 | 101.9 | 4.2 |
ldt10 | 31 | 5–13 | 9.5 | 2.3 | 0 | n.a. | n.a. | n.a. | 12 | 5–9 | 7.2 | 1.3 | 0 | n.a. | 0 | n.a. | n.a. | n.a. | 19 | 8–13 | 10.9 | 1.2 |
lvt5 | 49 | 6–15 | 9.3 | 1.8 | 1 | 10–10 | 10.2 | n.a. | 28 | 6–15 | 9.7 | 2.1 | 0 | n.a. | 1 | 12–12 | n.a. | n.a. | 19 | 7–11 | 8.5 | 1.0 |
lvs6 | 51 | 22–43 | 31.7 | 5.4 | 3 | 27–32 | 29.6 | 2.3 | 27 | 22–38 | 28.0 | 3.6 | 1 | 35 | 4 | 30–35 | 33.5 | 2.4 | 16 | 32–43 | 37.7 | 3.0 |
lvs7 | 55 | 30–49 | 38.0 | 4.7 | 2 | 32–37 | 34.5 | 3.6 | 29 | 30–41 | 34.8 | 2.9 | 1 | 42 | 4 | 37–41 | 39.0 | 1.8 | 19 | 38–49 | 42.8 | 3.0 |
lvs8 | 56 | 37–65 | 48.4 | 7.0 | 3 | 42–46 | 43.7 | 2.1 | 29 | 37–50 | 43.9 | 3.7 | 1 | 45 | 4 | 47–61 | 54.5 | 7.0 | 19 | 46–65 | 55.0 | 5.2 |
lvs9 | 57 | 49–90 | 61.9 | 11.4 | 3 | 50–57 | 54.5 | 3.6 | 30 | 49–64 | 55.9 | 3.8 | 1 | 83 | 4 | 58–88 | 72.8 | 15.9 | 19 | 55–90 | 69.1 | 12.8 |
lvs9 (m) | 25 | 50–90 | 66.2 | 14.9 | 1 | 56–56 | n.a. | n.a. | 15 | 50–62 | 55.5 | 3.1 | 1 | 83 | 2 | 85–88 | 86.5 | 2.1 | 7 | 80–90 | 84.9 | 3.9 |
lvs9 (f) | 32 | 49–83 | 58.6 | 6.1 | 2 | 50–57 | 53.9 | 4.9 | 15 | 49–64 | 56.4 | 4.4 | 0 | n.a. | 2 | 58–60 | 59.0 | 1.4 | 12 | 55–64 | 59.9 | 3.2 |
lts | 56 | 114–184 | 154.4 | 14.5 | 3 | 153–155 | 153.4 | 1.4 | 29 | 114–176 | 155.8 | 17.1 | 1 | 184 | 4 | 138–161 | 147.0 | 9.8 | 19 | 129–165 | 152.6 | 10.4 |
ltas | 25 | 44–61 | 54.7 | 4.4 | 2 | 57–61 | 59.1 | 2.8 | 10 | 44–60 | 52.4 | 5.1 | 0 | n.a. | 2 | 51–52 | 51.5 | 0.7 | 11 | 52–61 | 56.7 | 2.5 |
lts/tl | 55 | 52–86% | 70.5% | 7.2% | 3 | 65–75% | 71.5% | 5.3% | 29 | 57–86% | 71.9% | 8.2% | 0 | n.a. | 4 | 63–69% | 65.5% | 3.1% | 19 | 52–78% | 69.3% | 5.9% |
ltas/tl | 25 | 20–29% | 25.2% | 2.5% | 2 | 28–29% | 28.7% | 1.1% | 10 | 20–28% | 23.9% | 2.4% | 0 | n.a. | 2 | 22–25% | 23.6% | 1.9% | 11 | 22–29% | 26.0% | 2.1% |
Summary of locations of cuticular structures and appendages in Echinoderes pterus sp. n. Underlined structure was observed only in specimens from the Anaximenes Seamount and the Mediterranean deep sea off Crete. Abbreviations: ac, acicular spine; (f), female condition of sexually dimorphic character; gco1, type-1 gland cell outlet; la, lateral accessory; ld, laterodorsal; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lv, lateroventral; (m), male condition of sexually dimorphic character; md, middorsal; ml, midlateral; pd, paradorsal; pe, penile spine; sd, subdorsal; si, sieve plate; sl, sublateral; ss, sensory spot; tu, tube; vl, ventrolateral; vm, ventromedial.
Position | md | pd | sd | ld | ml | sl | la | lv | vl | vm |
---|---|---|---|---|---|---|---|---|---|---|
segment | ||||||||||
1 | gco1, gco1 | ss | ss | gco1 | ||||||
2 | gco1, ss | ss | gco1, ss | |||||||
3 | gco1 | gco1 | ||||||||
4 | ac | gco1 | gco1 | |||||||
5 | ac | gco1 | tu | gco1 | ||||||
6 | ac | gco1, ss | ss | ac | ss, gco1 | |||||
7 | ac | gco1 | ac | ss, gco1 | ||||||
8 | ac | gco1, ss | ac | gco1 | ||||||
9 | gco1 | ss | si | ac | ss | gco1 | ||||
10 | gco1, gco1 | ss | tu | ss | gco1 | |||||
11 | gco1, gco1 | ss | pe×3 (m), ltas (f) | lts |
Head consisting of retractable mouth cone and introvert (Fig.
Echinoderes pterus sp. n., scanning electron micrographs. Male (A, DZMB 11662c), collected at station 66 (Mediterranean deep sea off Crete) and females (BZMB 11669b; CZMB 11671e), collected at station 152-1 (Karasik Seamount). A entire animal, lateral view (left side) B head, ventral view C close-up of mouth cone, subdorsal view D close-up of introvert, lateral view (left side). Abbreviations: bsp, bifurcated spinose processes; hea, head; int, introvert; ios, inner oral style; mc, mouth cone; ne, neck; oos, outer oral style; pc, pharyngeal crown; pss, primary spinoscalid; sec, sector; sp, spinoscalid; tr, trichoscalid; tru, trunk. Digits after abbreviations indicate the sector or ring number. White arrows point to spinose structures at basal part of ring -01 inner oral styles. White double arrowheads indicate short spinose processes. Scale bars: 50 µm (A), 10 µm (B), 2 µm (C), 3 µm (D).
Neck with 16 placids (Figs
Echinoderes pterus sp. n., Nomarski photomicrographs. The holotype male (A, FZMB 11608), collected at station 55 (Mediterranean deep sea off Crete), a male (EZMB 11609), collected at station 24 (Mediterranean deep sea off Crete), and a female (B–DZMB 11635), collected at station 1167.1 (Mediterranean deep sea of Crete). A entire animal, ventral view B neck, dorsal view C neck, ventral view D segments 1–6, dorsal view E segments 3–7, ventral view F segments 4–7, dorsal view. Abbreviations: lts, lateral terminal spine; lvs, lateroventral acicular spine; lvt, lateroventral tube; mdp, middorsal placid; mds, middorsal acicular spine; mvp, midventral placid; trp, trichoscalid plate. Digits after abbreviations indicate the corresponding segment number. Black arrows mark sensory spots; white arrowheads point to type-1 gland cell outlets. Scale bars: 100 µm (A), 20 µm (B–D).
Segment 1 consisting of complete cuticular ring. Sensory spots located in subdorsal and laterodorsal position (Figs
Polar-coordinate diagram of mouth cone, introvert, and placids in Echinoderes pterus sp. n. Grey area and heavy line arcs show mouth cone and placids respectively. The table lists the arrangement of styles and scalids by sector. Inner oral styles of ring 01 showing spinose processes at basal part indicated by black circle in grey outer circle. Abbreviation: sec, sector.
Echinoderes pterus sp. n., scanning electron micrographs. Females (A, BZMB 11669a, collected at station 152-1 (Karasik Seamount) DZMB 11661c, collected at station 66 (Mediterranean deep sea of Crete) FZMB 11669b, collected at station 152-1 (Karasik Seamount)) and a male (C, EZMB 11661a, collected at station 66 (Mediterranean deep sea off Crete)). A segments 1–4, laterodorsal view (left side) B close-up of laterodorsal sensory spot on segment 1 C segments 1–4, ventral view D segments 3–7, lateral view (right side) E sternal plates on segments 6 and 7 F sternal plates on segments 6 and 7. Abbreviations: lvs, lateroventral acicular spine; lvt, lateroventral tube; mds, middorsal acicular spine. Digits after abbreviations indicate the corresponding segment number. Black arrows point to sensory spots; white arrowheads mark type-1 gland cell outlets. Scale bars: 10 µm (A, C–F), 2 µm (B).
Segment 2 with complete cuticular ring as segment 1. This and following eight segments with thick pachycyclus at anterior margin of each segment (Figs
Segment 3 and following eight segments consisting of one tergal and two sternal plates (Fig.
Segment 4 with middorsal acicular spine (Figs
Segment 5 with middorsal acicular spine and lateroventral tubes (Figs
Segment 6 with middorsal and lateroventral acicular spines (Figs
Echinoderes pterus sp. n., scanning electron micrographs. Females (AZMB 11661b, collected at station 66 (Mediterranean deep sea off Crete) BZMB 11669a, collected at station 152-1 (Karasik Seamount) CZMB 11664a, collected at station 63 (Mediterranean deep sea off Crete) DZMB 11665d, collected at station 63 (Mediterranean deep sea off Crete)). A segments 6–8, dorsal view B segments 6–9, lateral view (left side) C segments 8–11, lateral view (left side) D close-up of tuft of hairs on segment 9. Abbreviations: ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvs, lateroventral acicular spine; mds, middorsal acicular spine; th, tuft of long hairs. Digits after abbreviations indicate the corresponding segment number. Black arrows point to sensory spots. Scale bars: 10 µm (A–C), 2 µm (D).
Segment 7 with middorsal and lateroventral acicular spines (Figs
Segment 8 with middorsal and lateroventral acicular spines (Figs
Segment 9 with lateroventral acicular spines (Figs
Echinoderes pterus sp. n., Nomarski photomicrographs. The holotype male (BZMB 11608, collected at station 55, Mediterranean deep sea off Crete), non-type males (AZMB 11641, collected at station 717, Sedlo Seamount CZMB 11653, collected at station 152-1, Karasik Seamount), and a female (DZMB 11635, collected at station 1167.1, Mediterranean deep sea off Crete). A segments 7–9, dorsal view B segments 8–11, ventral view C segments 8–11, ventral view D segments 8–11, ventral view. Abbreviations: ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvs, lateroventral acicular spine; mds, middorsal acicular spine; pe, penile spine; th, tuft of long hairs. Digits after abbreviations indicate the corresponding segment number. Black arrows point to sensory spots. Scale bars: 20 µm (A–C), 10 µm (D).
Echinoderes pterus sp. n., scanning electron micrographs. Males (AZMB 11662b BZMB 11662a, both collected at station 66 (Mediterranean deep sea off Crete)). A segments 9–11, ventral view B left side of sternal plates on segments 10 and 11. Abbreviations: ldt, laterodorsal tube; lts, lateral terminal spine; lvs, lateroventral acicular spine; pe, penile spine. Digits after abbreviations indicate the corresponding segment number. Black arrows point to sensory spots. Scale bars: 10 µm (A), 1 µm (B).
Segment 10 with laterodorsal tubes (Figs
Segment 11 with lateral terminal spines (Figs
Echinoderes pterus sp. n. can be easily distinguished from all the other congeners by the presence of the tufts of hairs on segment 9. Such a structure has never been described for any other kinorhynch, and is thus a unique character for the new species. This is also the case for the conspicuously thick and long lateroventral spines on segment 9, although this character appears to be restricted to males in the Karasik Seamount, Svalbard, and the Sedlo Seamount populations.
With respect to other characters, the spine/tube pattern of E. pterus sp. n., i.e., with middorsal acicular spines on segments 4–8, laterodorsal tubes on segment 10, lateroventral tubes on segment 5, and lateroventral acicular spines on segments 6–9, but without any other spine and tube is not shared with any of 109 congeners.
The head morphology of E. pterus sp. n. seems to be shared with only a few species of Kinorhyncha. In the new species, the ring -02 and -03 inner oral styles occur in odd and even sectors, respectively. Such an arrangement is known for Dracoderes abei Higgins & Shirayama, 1990 (see
Echinoderes pterus sp. n. shows a geographically and bathymetrically wide distribution, from near the North Pole to the eastern Mediterranean Sea through the northeast Atlantic Ocean, and from 675 m to 4,403 m depth (Fig.
There are few other kinorhynchs which have been reported to show either a geographically or a bathymetrically wide distribution. Species with a geographically wide distribution are e.g., Ce. barbanigra found in the Gulf of Mexico, the Caribbean Sea, Bermuda, and the Dominican Republic at a depth ranging from 2 m to 57.5 m, E. ohtsukai found on both the eastern and western coasts of the Pacific Ocean in the intertidal zone, and E. tchefouensis found in the East China Sea, South China Sea, Celebes Sea, Singapore Strait, and Mariana Islands at a depth ranging from 0 m to 140 m (
The morphological comparison between populations of E. pterus sp. n. reveals that the new species shows an inter-population variation (Fig.
Box plot for the spine-lengths comparison among populations of Echinoderes pterus sp. n. Each color represents one population. The numbers above a box indicate the number of measured specimens for each character and population. Abbreviations: Ana, population from the Anaximenes Seamount; (f), length in females; Kar, population from the Karasik Seamount; lvs, lateroventral acicular spine; (m), length in males; Med, population in the Mediterranean deep sea off Crete; mds, middorsal acicular spine; Sed, population from the Sedlo Seamount; Sva, population north of Svalbard. Digits after mds and lvs indicate the corresponding segment number.
Considering the geographically and bathymetrically wide distribution of E. pterus sp. n., the presence of inter-population variation in morphological characters, as well as the potentially low-distribution ability of kinorhynchs, it should be considered whether E. pterus sp. n. represents one or multiple species. In the case of the other geographically and bathymetrically wide distribution kinorhynchs, intra- and inter-populational variation of several morphological characters, e.g., body length, arrangement of gland cell outlets, and sensory spots, has been detected in Cam. vanhoeffeni. However, it was still regarded as a single species due to the overlapping characters between/within populations and the absence of the type material (
Echinoderes pterus sp. n. may on the one hand represent two species, e.g., one species in the Arctic Ocean and on the Sedlo Seamount and the second species in the Mediterranean, or it may even belong to three species, i.e., one in the Arctic Ocean, another on the Sedlo Seamount, and the third in the Mediterranean, with only a few morphological differences. However, there is the possibility that the different populations belong to the same species with the observed morphological variations, which gradually change from the Arctic Ocean via the Sedlo Seamount to the Mediterranean populations or vice versa. Although we cannot reject these possibilities, we currently regard all populations as a single species. Further investigations of the species, for instance the sampling and observation of populations in intermediate localities and/or molecular phylogeographic studies, should provide more information about the population connectivity of the species and support one of the two hypotheses.
Whichever hypothesis is correct, all populations in this study are undoubtedly closely related to each other. They have expanded their habitat range with or without speciation, however, their distribution process is open to question: did they distribute from the Arctic Ocean via the Atlantic Ocean to the Mediterranean, from the Mediterranean via the Atlantic Ocean to the Arctic Ocean, or from the Atlantic Ocean to both the Arctic Ocean and the Mediterranean? Indeed the species represents interesting material for studying the “meiofauna paradox” or the “everything is everywhere hypothesis”. We cannot provide a strongly-supported answer based on our current data. Further data about the species distribution range and population connectivity would also enable us to approach the question in future studies.
We greatly appreciate Prof. Pedro Martínez Arbizu (Senckenberg am Meer, Abt. Deutsches Zentrum für Marine Biodiversitätsforschung DZMB) for providing the specimens collected during the expedition M71/2 by R/V METEOR, Kristine Kämpf (Museum für Naturkunde Berlin) for assisting in the preparation of LM specimens, Anke Sänger (Museum für Naturkunde Berlin) for the technical support at the SEM, and Dr Jason Dunlop (Museum für Naturkunde Berlin) for English editing. This study was supported by a grant from the Deutsche Forschungsgemeinschaft DFG to KHG (GE 1086/20-1) and to BN (NE 931/6-1) and by the SYNTHESYS Projects (DK-TAF-5319 and DK-TAF-6523) to KG, which were financed by European Community Research Infrastructure Action under FP7 (http://www.synthesys.info/). The study was completed also thanks to funding provided by the National Science Centre, Poland (grant no. 2016/20/S/NZ8/00432 and 2015/19/B/NZ8/03945). Material collected during R/V Polarstern TRANSSIZ cruise (ARK XXIX/1; PS92) was carried out under grant number AWI_PS92_00 and organized by Arctic in Rapid Transition (ART).