Echinoderes xiphophorus sp. nov. - the first deep-water representative of Echinoderidae in the Sea of Japan (Kinorhyncha: Cyclorhagida) Author Adrianov, Andrey V. 8D252A04-2DE8-48A9-85BE-353CE8DE70C0 ZhiRmUnsky National Scientific CenteR of MaRine Biology, Far Eastern Branch of Russian Academy of Sciences, Vladivostok 690041, Russia. avadr@mail.ru Author Maiorova, Anastassya S. C7691069-EC28-4FBE-A80D-02902686C364 ZhiRmUnsky National Scientific CenteR of MaRine Biology, Far Eastern Branch of Russian Academy of Sciences, Vladivostok 690041, Russia. anastasia.mayorova@gmail.com text European Journal of Taxonomy 2021 2021-10-04 773 1 169 186 http://dx.doi.org/10.5852/ejt.2021.773.1523 journal article 10.5852/ejt.2021.773.1523 2118-9773 8172912 CA23F2C2-38F7-47B8-ABAC-F447A775E9E4 Echinoderes xiphophorus sp. nov. urn:lsid:zoobank.org:act: 3E80E789-3AC9-410F-9137-7CF7EC541568 Figs 1–8 Diagnosis TRUnk length (TL) 290–305 µm; lateRal teRminal spines (LTS) 142–185 µm; tRUnk segments 1–2 consisting of closed cuticular rings, and trunk segments 3–11 of one tergal and two sternal plates; trunk segment 2 with three pairs of well-developed tubes in subdorsal, midlateral, and ventrolateral positions; trunk segment 5 with tubes in lateroventral position; trunk segment 8 with tubes in sublateral position; middorsal spines on trunk segments 4, 6, 8; lateroventral acicular spines on trunk segments 6–9; trunk segment 11 with RemaRkably long teRgal extensions (TE) aboUt 15–16% of TL; males with thRee paiRs of penile spines and RemaRkably long swoRd-like extensions (aboUt 80% of TE) doRsally to penile spines; females with pair of laterodorsal tubes on trunk segment 10. Etymology The species name is deRived fRom the GReek ʻ xiphos ʼ (swoRd) and ʻ phorus ʼ (caRRy) becaUse of veRy long sword-like appendages in males dorsally to penile spines. Material examined Holotype ( Fig. 2A–E ) RUSSIA • 1 ♂ ; Sea of Japan ; 44.7942° N , 137.2550° E ; depth 1530 m ; 14 AUg. 2010 ; SoJaBio cRUise; stn A3-7; multiple corer; oxidized brown clay; MIMB 41347 . Paratypes ( Fig. 3A–B ) RUSSIA • 4 adUlt ♂♂ ; same locality and station as foR holotype ; MIMB 41348 , MIMB 41349 , MIMB 41350 , MIMB 41351 • 1 adUlt ♂ ; Sea of Japan ; 44.9439950° N , 137.2017717° E ; depth 515 m ; 13 AUg. 2010 ; SoJaBio cruise; stn A2-5; multiple corer; oxidized brown clay; MIMB 41352 . Other material RUSSIA • 2 adUlt ♂♂ , 2 adUlt ♀♀ (moUnted foR SEM ); same locality and station as foR holotype . Table 1. MeasURements (µm) of the main chaRacteRs of six adUlt specimens of Echinoderes xiphophorus sp. nov. : holotype and five paRatypes. NUmbeR afteR abbReviation indicates nUmbeR of tRUnk segment.

Character	MIMB 41347 holotype, ♂ Sea of Japan	MIMB 41348 paRatype, ♂ 1 Sea of Japan	MIMB 41349 paRatype, ♂ 2 Sea of Japan	MIMB 41350 paRatype, ♂ 3 Sea of Japan	MIMB 41351 paRatype, ♂ 4 Sea of Japan	MIMB 41352 paRatype, ♂ 5 Sea of Japan
TL	304	305	295	295	290	broken tergal extensions
MSW-7	56	58	58	63	58	59
MSW-7/TL	18%	19%	20%	21%	20%	–
SW	52	47	46	45	50	53
SW/TL	17%	15%	16%	15%	17%	–
S1	29	29	32	29	31	28
S2	22	23	26	26	22	24
S3	21	23	23	24	23	24
S4	24	26	24	24	23	29
S5	26	28	27	25	27	32
S6	30	31	31	32	30	35
S7	32	31	32	32	32	40
S8	36	36	37	35	33	37
S9	34	39	37	40	35	43
S10	33	31	37	42	32	40
S11 (including TE)	63	60	60	59	54	broken
MD 4	24	24	27	17	12	broken
MD 6	32	33	broken	30	18	29
MD 8	35	40	broken	36	31	31
SDT 2	17	11	14	12	11	17
LVT 5	18	18	15	21	12	17
LVS 6	28	27	27	29	29	32
LVS 7	32	30	28	34	29	34
LVS 8	33	34	37	28	32	36
SLT 8	16	19	20	19	3	15
LVS 9	37	39	39	39	35	31
LTS	185	160	163	142	143	168
LTS/TL	61%	52%	55%	48%	49%	–
TE	51	45	40	45	44	–
TE/TL	17%	15%	14%	15%	15%	–
TE/S11	80%	75%	67%	76%	81%	–
PS1	41	42	40	33	40	39
SWA	35	32	24	broken	28	31
SWA/TE	68%	71%	60%	–	63%	–

Table 2. Summary of nature and location of sensory spots, glandular cell outlets, tubes and spines arranged by series in Echinoderes xiphophorus sp. nov. Abbreviations: ac = acicular spine; exs = excretory sieve plate; gco1 = glandular cell outlet type 1; LA = lateral accessory; LD = laterodorsal; ltas = lateral terminal accessory spine; lts = lateral terminal spine; LV = lateroventral; MD = middorsal; ML = midlateral; PD = paradorsal; pe = penile spines; SD = subdorsal; SL = sublateral; ss = sensory spot; swa = swordlike appendage; tU = tUbe; VL = ventRolateRal; VM = ventRomedial; (♀) = female condition of sexUally dimoRphic chaRacteR; (♂) = male condition of sexUally dimoRphic chaRacteR.

Segment	MD	PD	SD	LD	Position ML SL	LA	LV	VL	VM
1	gco1	ss	ss	ss, gco1
2	ss	tu	ss	tu	ss	tu	ss, gco1
3	gco1	ss	ss	gco1
4	ac	gco1	ss	gco1
5	gco1	ss	ss	tu	ss, gco1
6	ac	ss, gco1	ss	ac	ss, gco1
7	gco1	ss	ss	ac	gco1
8	ac	ss, gco1	tu	ac	gco1
9	ss, gco1	ss	ss	exs	ac	ss	gco1
10	gco1	ss	swa (♂)	ss	gco1
11	2 × gco1	2 × ss	tU (♀)	3× pe (♂)	ltas (♀)	lts	ss, gco1

Description BODY. AdUlt specimen consists of head, neck and 11 tRUnk segments. MeasURements (µm) and Ratios (%) aRe pRovided in Table 1 . Head consists of RetRactable moUth cone and eveRsible intRoveRt. InneR oRal styles are arranged in two circlets (5 large tooth-like outer styles + 10 minute innermost styles). External mouth cone bears nine articulated outer oral styles. Head bears seven rings of spinoscalids and one ring of six trichoscalids. Neck consists of 16 placids. All placids trapezoid in shape, distinctly articulating with the fiRst tRUnk segment. MidventRal placid widest; Remaining ones naRRoweR. Two ventRal and foUR dorsal trichoscalid plates present, ventral ones being broader than four dorsal ones. TRUNK SEGMENT 1. Closed cuticular ring, with three pairs of sensory spots located close to the anterior segment margin in subdorsal and laterodorsal and more posteriorly in ventromedial position ( Figs 1A–B , 2A , 3B , 5 , 6A–B , 7A ); sensory spots rounded in shape, with 15–20 very short petals and one or two pores ( Fig. 6A ); single glandular cell outlet of type 1 in middorsal position and two outlets in ventromedial position ( Figs 1A–B , 2A , 3A–B , 5 , 6A–C ); glandular cell outlets of type 2 absent as in all trunk segments; posterior margin of segment with pectinate fringe with fringe tips from midventral to ventrolateral position being shorter than others ( Fig. 7A ); long cuticular hairs on dorsal surface regularly arranged forming a continuous belt of 3–4 distinct transverse rows and irregularly arranged on ventral side ( Figs 6A–B , 7B ). TRUNK SEGMENT 2. Closed cUticUlaR Ring, withoUt any paRtial intRa- oR extRacUticUlaR fissURes; thRee paiRs of tubes in subdorsal, midlateral and ventrolateral positions; each tube with short and smooth basal part and longer distal part with two wing-like lateral projections ( Fig. 6B ); one sensory spot in middorsal position and three pairs in laterodorsal, lateroventral and ventromedial position, sensory spots on this and following segments with 10–15 very short petals and 1–2 very long posteriormost petals similar to cilia ( Figs 6B , 7C–E ); one pair of glandular cell outlets of type 1 in ventromedial position anterior to ventromedial sensory spots ( Fig. 3B ); ventral hairs on the trunk segment 2 seem to be more regularly arranged than those on trunk segment 1; pectinate fringe as in the preceding segment. It should be noted that glandular cell outlets at the anterior margin of tergal and sternal plates are usually hidden beneath posterior cuticular fringe of previous segment and seen more easily with DIC (see Figs 2–3 ). Fig. 1. Echinoderes xiphophorus sp. nov. , ♂. A . Whole animal, dorsal view. B . Whole animal, ventral view. C . Lateral terminal spine.Abbreviations: ldss = laterodorsal sensory spot; lts = lateral terminal spine; lvs = lateroventral spine; lvss = lateroventral sensory spot; lvt = lateroventral tube; mdgo = middorsal glandular cell outlet type 1; mds = middorsal spine; mdss = middorsal sensory spot; mlss = midlateral sensory spot; mlt = midlateral tube; pdgo = paradorsal glandular cell outlet type 1; pdss = paradorsal sensory spot; ps = penile spine; sdss = subdorsal sensory spot; sdt = subdorsal tube; slt = sublateral tube; swa = sword-like appendage; tex = tergal extension; vlss = ventrolateral sensory spot; vlt = ventrolateral tube; vmgo = ventromedial glandular cell outlet type 1; vmss = ventromedial sensory spot. Numbers indicate the nUmbeR of the tRUnk segment. Scale baR = 50 µm. Fig. 2. Echinoderes xiphophorus sp. nov. , holotype, ♂ (MIMB 41347), light micRogRaphs. A–C . Dorsal view. D–E . Ventral view. A . Trunk segments 1–8. B . Trunk segments 7–10. C . Trunk segments 10– 11. D . Trunk segments 1–8. E . Trunk segments 7–11. Abbreviations: lts = lateral terminal spine; lvs = lateroventral spine; mdgo = middorsal glandular cell outlet type 1; mds = middorsal spine; mdss = middorsal sensory spot; pdgo = paradorsal glandular cell outlet type 1; pdss = paradorsal sensory spot; sdss = subdorsal sensory spot; sdt = subdorsal tube; slt = sublateral tube; spe = spermatozoa; swa = sword-like appendage; tex = tergal extension; vlgo = ventrolateral glandular cell outlet type 1; vls = ventrolateral spine; vlss = ventrolateral sensory spot; vmgo = ventromedial glandular cell outlet type 1; vmss = ventromedial sensory spot. White circles indicate sensory spots, dotted white circles indicate glandUlaR cell oUtlets. NUmbeRs indicate the nUmbeR of the tRUnk segment. Scale baRs = 50 µm. TRUNK SEGMENT 3. One tergal and two sternal plates, with distinct tergosternal and midventral articulations, as in all remaining trunk segments; with two pairs of sensory spots in subdorsal and midlateral position ( Figs 1A–B , 2A , 3B , 6B ); single glandular cell outlet of type 1 in middorsal position located close to the anterior segment margin and hidden under preceding segment; with a pair of glandular cell outlets in ventromedial position; long cuticular hairs absent in ventromedial position, being replaced by much shorter cuticular hairs ( Fig. 7B ); other cuticular hairs and pectinate fringe as in the preceding segment. TRUNK SEGMENT 4. With acicular spine in middorsal position ( Figs 2A , 4A ); with two pairs of glandular cell outlet of type 1 in paradorsal and ventromedial positions, paradorsal outlets usually hidden under previous segment ( Figs 2A, D , 3 ); long cuticular hairs absent in middorsal position beneath acicular spine; other cuticular hairs and pectinate fringe as in the preceding segment. Fig. 3. Echinoderes xiphophorus sp. nov. , paRatype ♂ (MIMB 41348), tRUnk segments 1–6, light micrographs. A . Dorsal view. B . Ventral view. Abbreviations: cut = cuticular scars; dvm = dorsoventral muscle attachment site; mdgo = middorsal glandular cell outlet of type 1; mdss = middorsal sensory spot; pdgo = paradorsal glandular cell outlet of type 1; vlt = ventrolateral tube; vmgo = ventromedial glandular cell outlet type 1; vmss = ventromedial sensory spot. White circles indicate sensory spots. Dotted white circles indicate glandular cell outlets. Numbers indicate the number of the trunk segment. Scale baRs = 50 µm. TRUNK SEGMENT 5. No acicular spine in middorsal position; one pair of tubes in lateroventral position ( Figs 4C , 7B ); three pairs of sensory spots in subdorsal, laterodorsal and ventromedial position; single glandular cell outlet of type 1 in middorsal position located close to the anterior segment margin and usually hidden under previous segment; with one pair of glandular cell outlets of type 1 in ventromedial positions; pectinate fringe and cuticular hairs as in the trunk segment 3. TRUNK SEGMENT 6. With acicular spine in middorsal position ( Figs 2A , 4A , 6D ); with a pair of acicular spines in lateroventral position ( Fig. 4B ); with three pairs of sensory spots in paradorsal, laterodorsal and ventromedial position; with two pairs of glandular cell outlets of type 1 in paradorsal and ventromedial position, paradorsal outlets usually hidden under previous segment; pectinate fringe and cuticular hairs as in the trunk segment 4. Fig. 4. Echinoderes xiphophorus sp. nov. , ♂, SEM micRogRaphs. A . Dorsal view. B–C . Ventral view, uncoated SEM specimens.Abbreviations: lvt = lateroventral tube; mds = middorsal spine; mlt = midlateral tube; sdt = subdorsal tube; slt = sublateral tube; vlss = ventrolateral sensory spot; vlt = ventrolateral tube; vmgo = ventromedial glandular cell outlet type 1; vmss = ventromedial sensory spot. White circles indicate sensory spots. Dotted white circles indicate glandular cell outlets. White arrowhead indicates cuticular hole of broken sword-like appendage. Numbers indicate the number of the trunk segment. Scale baRs: A = 20 µm; B–C = 10 µm. Fig. 5. Echinoderes xiphophorus sp. nov. , ♂, SEM micRogRaph of Uncoated specimen, ventRal view. Abbreviations: lvss = lateroventral sensory spot; mdgo = middorsal glandular cell outlet type 1; swa = sword-like appendage; vlt = ventrolateral tube; vmgo = ventromedial glandular cell outlet type 1; vmss = ventromedial sensory spot. White circles indicate sensory spots. Dotted white circles indicate glandular cell oUtlets. NUmbeR afteR vlt indicates the nUmbeR of the tRUnk segment. Scale baR = 10 µm. TRUNK SEGMENT 7. No acicular middorsal spine; with two pairs of sensory spots in subdorsal and laterodorsal position; with single glandular cell outlets of type 1 in middorsal position (usually hidden under previous segment) and one pair of outlets in ventromedial position; other spines, pectinate fringe and cuticular hairs as in the preceding segment. TRUNK SEGMENT 8. With acicular spine in middorsal position ( Figs 2A , 4A , 6E ); with a pair of tubes in sublateral position ( Figs 2E , 4C , 7D ); with one pair of sensory spots in paradorsal position ( Figs 6E , 7C ); with two pairs of glandular cell outlets of type 1 in paradorsal and ventromedial position ( Fig. 2B, D ); other spines, pectinate fringe and cuticular hairs as in the preceding segment. Fig. 6. Echinoderes xiphophorus sp. nov. , ♂, SEM micRogRaphs. A, D . Dorsolateral view. B, C, E . Dorsal view. A . Head, neck, and trunk segment 1. B . Trunk segments 1–4. C . Middorsal glandular cell outlet type 1 on trunk segment 1. D . Trunk segments 5–7. E . Trunk segments 8–10.Abbreviations: ldss = laterodorsal sensory spot; mdgo = middorsal glandular cell outlet type 1; mds = middorsal spine; mdss = middorsal sensory spot; mlss = midlateral sensory spot; mlt = midlateral tube; pdss = paradorsal sensory spot; sdss = subdorsal sensory spot; sdt = subdorsal tube; slt = sublateral tube. White circles indicate sensory spots. Dotted white circles indicate glandular cell outlets. Numbers indicate the number of the trunk segment. Scale baRs: A–B, D–E = 10 µm; C = 1 µm. TRUNK SEGMENT 9. No acicular middorsal spine; no tubes; with four pairs of sensory spots in paradorsal, subdorsal, laterodorsal and ventrolateral position ( Figs 2E , 6E , 7C–E , 8C ); with two pairs of glandular cell outlets of type 1 in paradorsal and ventromedial positions ( Fig. 2B, E ); pair of excretory sieve plates in lateral accessory position; other spines, pectinate fringe and cuticular hairs as in the preceding segment. TRUNK SEGMENT 10. No acicular spines; with two pairs of sensory spots in subdorsal and ventrolateral position ( Figs 2E , 6E , 8C ); with single glandular cell outlets of type 1 in middorsal position and one paiR in ventRomedial position ( Figs 2B, E , 5 ); males possess a paiR of veRy long and flattened swoRd-like appendages (similar in shape to Japanese swords katana or wakizashi) in laterodorsal position, dorsally to penile spines, only slightly shoRteR than teRgal extensions (aboUt 80% of TE) ( Fig. 8A–B ); females with a pair of short tubes/ spines in laterodorsal position corresponding to sword-like appendages of male ( Fig. 8C–D ); other characters as in the preceding segment. Fig. 7. Echinoderes xiphophorus sp. nov. , SEM micrographs. A–B . ♂, ventRal view. A . Trunk segments 1–2. B . Trunk segments 2–5. — C–E . ♀, doRsal view. C . Trunk segments 6–9. D . Trunk segment 9. E . Subdorsal sensory spot on trunk segment 9. Abbreviations: ldss = laterodorsal sensory spot; lvs = lateroventral spine; lvt = lateroventral tube; mds = middorsal spine; pdss = paradorsal sensory spot; sdss = subdorsal sensory spot; slt = sublateral tube; vlt = ventrolateral tube; vmss = ventromedial sensory spot. White circles indicate sensory spots. Numbers indicate the number of the trunk segment. Scale bars: A–D = 10 µm; E = 2 µm. Fig. 8. Echinoderes xiphophorus sp. nov. , SEM micrographs. A–B . ♂, tRUnk segments 10–11. A . Dorsolateral view. B . Dorsal view. — C–D . ♀, tRUnk segments 9–11. C . Lateral view. D . Posterior view. Abbreviations: lds = laterodorsal spine/tube; ldss = laterodorsal sensory spot; ltas = lateral terminal accessory spine; lts = lateral terminal spine; mde = middorsal elevation; pdss = paradorsal sensory spot; ps = penile spine; sdss = subdorsal sensory spot; slt = sublateral tube; swa = sword-like appendage; tex = tergal extension. White circlets indicate sensory spots. Numbers after ps indicate the number of the pair, the nUmbeR afteR slt indicates the nUmbeR of the tRUnk segment. Scale baRs: A, C–D = 10 µm; B = 20 µm. TRUNK SEGMENT 11. One pair of long lateral terminal spines ( Fig. 1C ); tergal extensions very long, about 15–16% of TL ( Figs 4–5 , 8 ); teRgal plate with neaRly RoUnded middoRsal elevation ( Fig. 8B, D ); with two pairs of sensory spots in subdorsal and ventromedial position, and additional pair of sensory spots present at the base of tergal extensions ( Fig. 8A, C–D ); with two glandular cell outlets of type 1 in middorsal position and one paiR ventRolateRal position ( Figs 2C, E , 5 ); males with thRee paiRs of penile spines, fiRst and thiRd paiRs thin and flexible, spine of second paiR shoRteR and cone-shaped with teRminal tUft of cUticUlaR hairs ( Figs 5 , 8A–B ); female with a pair of long and thin lateral terminal accessory spines; sexes can be also recognized by observation of gonads.