Expanding the Echinoderes coulli group (Kinorhyncha: Cyclorhagida) with a new species from the Chuuk Islands, Micronesia Author Herranz, María Author Moreleon, Alexis D. Author Rho, Hyun Soo Author Sørensen, Martin V. text Zoologischer Anzeiger 2023 2023-01-31 302 67 74 http://dx.doi.org/10.1016/j.jcz.2022.11.010 journal article 56571 10.1016/j.jcz.2022.11.010 5b10a3d9-1d42-4874-abfe-ef46cd21e183 1873-2674 8164163 Species E. inaequalis sp. nov. urn:lsid:zoobank.org:act:41BC4BF8- E3B4–445C–87F1–9C6D2CC97AA2. ( Figs. 2–4 , Tables 1–2 ). 3.1.1. Etymology The species name comes from the Latin in- (un or not) and -aequ¯alis (equal or even), meaning, the uneven one, referring to the distinctive asymmetric distribution of subdorsal tubes on segments 5 to 7. 3.1.2. Diagnosis Echinoderes with a single, minute middorsal spine on segment 4. Lateroventral tubes on segments 5, 7–9, midlateral tubes on segment 8, and sexually dimorphic laterodorsal tubes on segment 10. Single subdorsal tubes usually in alternating positions on segments 5–7 with intraspecific variation. Small glandular cell outlets type 2 in subdorsal, laterodorsal and ventrolateral positions on segment 2, subdorsal position on segment 4, and midlateral positions on segments 5–7; large, conspicuous, laterodorsal glandular cell outlets type 2 are present on segment 8. Large nephridial areas composed of elongated sieve plates and a posterior pore in sublateral position on segment 9. Short and stout lateral terminal spines with fringed edges. Males with three pairs of slender penile spines, and well-developed laterodorsal tubes on segment 10. Females with short and thin lateral terminal accessory spines, and reduced laterodorsal tubes on segment 10. 3.1.3. Material examined Holotypic female collected by HSR on March 21st, 2007 from coral sand at 1–2 m depth at Chuuk Islands , Micronesia (locality MAP-19: 007 ◦ 27’11’’N , 151 ◦ 54’15’’E ) ( Fig. 1 ); mounted in Fluoromount G on a glass slide and deposited at the Natural History Museum of Denmark, under catalogue number NHMD-1176540 . Paratypes series include five specimens , three females and two males all of them mounted in Fluoromount G on glass slides and deposited at the Natural History Museum of Denmark , under catalogue numbers NHMD-1176541 to 45. Of those, male paratypes NHMD-1176542, NHMD-1176545 and female paratype NHMD-1176541 were collected at the same locality as the holotype; whereas the two remaining female paratypes, NHMD-1176543 and NHMD-1176544, were collected on March 9th, 2007 from subtidal sediment at 30 m depth (locality MAP-01: 007 ◦ 27’27’’N , 151 ◦ 53’52’’E ) . Additional material includes 17 specimens mounted for SEM and stored in MVS personal reference collection . 3.1.4. Description Adults with head, neck and eleven trunk segments ( Figs. 2 , 3A and 4A ). Measurements and dimensions are given in Table 1. A summary of sensory spots, spines, tubes and glandular cell outlet positions is provided in Table 2 . Mouth cone and introvert could not be studied in detail due to the poor condition of the SEM specimens prepared 14 years ago. The neck consists of 16 placids numbered clockwise from the midventral 1 ( Fig. 3B and C ). Placids 2–16 are trapezoid measuring 9 μm at the base while the midventral placid is more rectangular and wider measuring 15 μm (Fig.. 2B, 3B–C). All placids articulate with the first trunk segment. Trichoscalid plates bearing trichoscalids appear dorsally on placids 6, 8, 10, 12 and ventrally on placids 2 and 16. Ventral trichoscalid plates are triangular with rounded edges, while dorsal trichoscalid plates are rounded and smaller ( Figs. 2 , 3B–C ). Trunk segments 1 and 2 consist of one closed cuticular ring ( Figs. 2 , 3 A-C, 4A-B) while segments 3–11 are composed of one tergal and two sternal plates ( Figs. 2 , 3A and 4A ). Glandular cell outlets type 1 consist of numerous minute pores arranged in a circle, situated in the anterior part of the segments, usually hidden under the posterior part of the previous segment and quite inconspicuous. Dorsal glandular cell outlets type 1 are located middorsally on segments 1–3, 10–11 and paradorsally on segments 4–9 ( Fig. 2 ). Ventral glandular cell outlets type 1 are lateroventral on segment 1 and ventromedial on segments 2–10 ( Fig. 2 ). Primary pectinate fringe well developed in all segments, composed of very short fringe tips on segments 1 and 2 ( Figs. 2 and 4B ) and long and flexible tips in remaining segments ( Figs. 2 and 4B ). Secondary pectinate fringe absent on segment 1, and on segments 2–11 consisting of a single line of minute and regular teeth usually hidden under the primary pectinate fringe of previous segment ( Fig. 4B ). Fig. 1. Map showing (A) the position of the Chuuk Islands, and (B) zoom of the sampling localities. Fig. 2. Line art illustrations of Echinoderes inaequalis sp. nov. (A) Female, dorsal view. (B) Female, ventral view. (C) Male, detail of segments 10–11, dorsal view. (D) Male, detail of segments 10–11, ventral view. Abbreviations: ldgco2, laterodorsal glandular cell outlet type 2; ldss, laterodorsal sensory spot; ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvgco1, lateroventral glandular cell outlet type 1; lvt, lateroventral tube; mds, middorsal spine; mlgco2, midlateral glandular cell outlet type 2; mlss, midlateral sensory spot; mlt, midlateral tube; pe, penile spine; sdgco2, subdorsal glandular cell outlet type 2; sdt, subdorsal tube; si, sieve plate; vlgco2, ventrolateral glandular cell outlet type 2; vlss, ventrolateral sensory spot; vmss, ventromedial sensory spot. Scale bar, 100 μm. Segment 1 with rounded sensory spots formed by a collar of short papillae surrounding at least one pore ( Fig. 4B ); sensory spots are located near the anterior segment margin in subdorsal and laterodorsal positions, and centrally in ventromedial position ( Figs. 2 , 3B–C , 4B ). Cuticular hairs are abundant and distributed forming a wide belt covering most of the dorsal and ventral surface of the segment, except for the anterior margin of the segment, ventral area with a less dense hair covering ( Figs. 2 , 3B–C , 4B ). All cuticular hairs emerging from round perforation sites in this and the following segments. The posterior segment margin is straight along the dorsal and lateral side but extends slightly posteriorly in the ventromedial and midventral areas. Segment 2 with glandular cell outlets type 2, located in subdorsal, laterodorsal and ventrolateral positions ( Fig. 2A and B , 3B–C , 4B, E ). These are small with delicate fringed margins. Sensory spots present in middorsal, laterodorsal, midlateral and ventromedial positions; sensory spots on this and the following segments are oval. Hairs densely distributed in a belt covering the segment showing hairless areas in the anterior margin of the segment in ventromedial position ( Fig. 4B–C, E ). Hairs increasing in length posteriorly. Segment 3 with sensory spots in subdorsal and sublateral positions ( Fig. 2A and B ). Dorsal hair pattern dense, cuticular hairs on the ventral side are covering the sternal plates except for hairless areas on the anterior margin of the sternal plates and narrow patches in ventromedial positions in this and the following segments. Segment 4 with a very short acicular middorsal spine (ca. 11 μm measured from SEM) ( Fig. 2A and B , 3E , 4C ). Glandular cell outlets type 2 present in subdorsal position ( Figs. 2A , 3E and 4C ). Sensory spots present in laterodorsal position. Other characters similar to previous segment. Segment 5 with lateroventral tubes and a single additional tube in subdorsal position ( Fig. 2A and B , 3 D-E, 4D, G). Each tube consists of a short and smooth basal part, and a longer distal part in this and the following segments ( Fig. 4G ). Glandular cell outlets type 2 present in midlateral position ( Figs. 2A and 4G ). Sensory spots present in subdorsal, laterodorsal and ventromedial positions ( Fig. 2A and B ). Other characters similar to previous segment. Fig. 3. Light micrographs (DIC) showing traits in Echinoderes inaequalis sp. nov. Male paratype NHMD-1176545 (A, B, D, E, H), female holotype NHMD-1176540 (C, K, I) female paratype NHMD-1176543 (F, G), and male paratype NHMD-1176542 (J). (A) Male overview, ventral view. (B) Segments 1–2, ventral view. (C) Segments 1–2, dorsal view. (D) Segments 5–7, ventral view. (E) Segments 4–5, dorsal view. (F) Segments 7–8, lateroventral view. (G) Segments 6–7, dorsolateral view. (H) Male, segments 10–11 ventral view. (I) Female, segment 11, ventral view. (J) Segments 9–10, ventral view. (J’) Detail of sieve plate. (K) Segment 8, focused on laterodorsal area. Abbreviations: ldgco2, laterodorsal glandular cell outlet type 2; ldss, laterodorsal sensory spot; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvgco1, lateroventral glandular cell outlet type 1; lvt, lateroventral tube; mdgco1, middorsal glandular cell outlet type 1; mlgco2, midlateral glandular cell outlet type 2; mlt, midlateral tube; mvp, midventral placid; pdgco1, paradorsal glandular cell outlet type 1; pe, penile spine; sdgco2, subdorsal glandular cell outlet type 2; sdss, subdorsal sensory spot; sdt, subdorsal tube; si, sieve plate; te, tergal extension; tp, trichoscalid plate; vlgco2, ventrolateral glandular cell outlet type 2; vmgco1, ventromedial glandular cell outlet type 1; vmss, ventromedial sensory spot. Circles indicate the position of glandular cell outlets type 1. Dashed circles indicate the position of sensory spots. Digits after abbreviations refer to segment number. Fig. 4. Scanning electron micrographs (SEM) showing overviews and details of Echinoderes inaequalis sp. nov. (A) Male, lateroventral overview. (B) Segments 1–2 ventral view. (C) Segments 2–4, dorsal view. (D) Segments 5–6, lateroventral view. (E) Segment 2, laterodorsal view. (F) Detail of segment 8, lateral view. (G) Detail of segment 5, lateroventral view. (H) Segments 6–7, middorsal view. (I) Detail of sieve plate. (J) Female, segments 10–11, dorsal view. (K) Segments 9–11, ventral view. (L) Male, detail of penile spines, lateral view. (M) Male, detail of penile spines and laterodorsal tube, laterodorsal view. Abbreviations: ldgo2, laterodorsal glandular cell outlet type 2; ldss, laterodorsal sensory spot; ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvgco1, lateroventral glandular cell outlet type 1; lvt, lateroventral tube; mds, middorsal spine; mdss, middorsal sensory spot; mlgco2, midlateral glandular cell outlet type 2; mlss, midlateral sensory spot; mlt, midlateral tube; pe, penile spine; sdgco2, subdorsal glandular cell outlet type 2; sdss, subdorsal sensory spot; sdt, subdorsal tube; si, sieve plate; spf, secondary pectinate fringe; te, tergal extension; vlgco2, ventrolateral glandular cell outlet type 2; vlss, ventrolateral sensory spot; vmgco1, ventromedial glandular cell outlet type 1; vmss, ventromedial sensory spot. Circles indicate the position of glandular cell outlets type 1. Dashed circles indicate the position of sensory spots. Digits after abbreviations refer to segment number. Table 1 Measurements (in μm) from light microscopy (except for the middorsal spine of segment 4) of adult Echinoderes inaequalis sp. nov. Abbreviations: LTAS, lateral terminal accessory spine; LTS, lateral terminal spine; LVT, lateroventral tube; MD, middorsal spine; MLT, midlateral tube; MSW, maximum sternal width; n, number of specimens; SD, standard deviation; SDT, subdorsal tube; SI, sieve plate length; SW, standard width; S, segment lengths; TL, trunk length.Numbers, where inserted, indicate segment number.

Character	n	Range	Mean	SD
TL	6	359–386	372	10.6
MSW (8)	6	64–72	69	3.3
MSW/TL (%)	6	18–19	18	0.5
SW	6	57–65	61	2.8
SW/TL (%)	6	16–17	16	0.6
S1	6	29–31	30	0.9
S2	6	26–31	29	2.0
S3	6	30–34	32	1.4
S4	6	33–36	34	1.2
S5	6	36–40	37	1.5
S6	6	41–44	43	1.4
S7	6	44–48	46	1.5
S8	6	49–55	52	2.2
S9	6	46–55	51	3.1
S10	6	39–50	43	4.0
S11	6	33–41	38	3.6
MD4	1	11	–	–
SDT5	1	18	–	–
SDT6	2	12–17	15	2.8
SDT7	1	15	–	–
MLT8	3	10–20	16	5.1
LVT5	4	10–22	14	5.5
LVT7	3	10–15	13	2.5
LVT8	2	15–16	16	0.7
LVT9	2	20	20	0
SI	2	13–15	14	1.4
LTS	6	41–47	43	2.4
LTS/TL (%)	6	11–13	12	0.7
LTAS	2	20–22	21	1.4

Segment 6 with a single subdorsal tube usually, but not consistently, in alternating position in respect to the single tube on segment 5 ( Figs. 2A , 3G and 4H ). Glandular cell outlets type 2 present in midlateral position ( Figs. 2A and 3G ). Sensory spots present in subdorsal, sublateral and ventromedial positions ( Fig. 2A and B ). Remaining characters as on previous segments. Segment 7 with lateroventral tubes, and an additional single tube located in subdorsal position, the latter usually alternating in position with the unpaired tube of the preceding segment ( Fig. 2A and B , 3 F-G, 4H). Glandular cell outlets type 2 present in midlateral position ( Fig. 3G ). Sensory spots present in subdorsal, laterodorsal and ventrolateral positions ( Fig. 2A and B , 4H ). Remaining characters as on previous segments. Segment 8 with tubes in lateroventral and midlateral positions ( Fig. 2A and B , 4F ). Large glandular cell outlets type 2 with fringed edges present in laterodorsal position ( Fig. 2A and B , 3K , 4F ). Sensory spots present in subdorsal position. Other characters similar to previous segments. Segment 9 with tubes in lateroventral position. Sensory spots present in subdorsal, laterodorsal, midlateral and ventrolateral positions ( Fig. 2A and B , 3J ). Elongated nephridial areas present in sublateral position, and consisting of an oval perforated sieve plate (ca. 12 μm) with a posterior round pore ( Fig. 3 J- J’, 4I). Other characters similar to previous segments. Segment 10 with tubes in laterodorsal positions, at or near the posterior segment margin. In males the tubes are long and similar of those described on segments 5–9 (Fig.. 2C and 4M), whereas in females the tubes lack the basal part, showing just a flexible and short tubular structure ( Figs. 2A and 4J ). Very elongated sensory spots composed of two or three rows of short parallel papillae present in subdorsal and ventrolateral positions ( Figs. 2 , 4 J-K). The posterior segment margin of the tergal plate is straight and with a small, but well-developed, pectinate fringe, whereas the margins of the sternal plates are concave, extending posteriorly near the midventral junction, and with well-developed fringe tips ( Fig. 2B, D , 4K ). Segment 11 with short and stout lateral terminal spines with lateral fringes, and a short fringe wrapping the spine medially ( Figs. 2 and 3A, H–I , 4J ). Males with three pairs of tubular, and flexible penile spines, two of them long, and one slightly shorter ( Fig. 2B and C , 3H , 4 L-M). Females with a pair of short, thin and hairy lateral terminal accessory spines ( Fig. 2A and B , 3I , 4 J-K). Sensory spots are present in subdorsal position (two pairs) and in ventromedial position. The ventromedial sensory spots are very small, and located at the posterior margin of the sternal plate ( Fig. 4K ). One of the subdorsal pairs of sensory spots is also small and located on the margin of the tergal extensions ( Fig. 2 ). The tergal plate is covered in hair-like extensions without perforation sites; sternal plates with a ventromedial fringed area ( Fig. 2B, D , 4K ). The margins of the sternal plates are curved and covered by long hairs that get shorter towards the lateroventral area ( Fig. 4K ). Tergal extensions are pointed extending further than the sternal plates and with a small distal notch ( Figs. 2 , 3H–I , 4 J-K).