Two new species of mud dragons (Scalidophora: Kinorhyncha) inhabiting a human-impacted mangrove from Mayotte (Southwestern Indian Ocean) Author Cepeda, Diego Author González-Casarrubios, Alberto Author Sánchez, Nuria Author Spedicato, Adriana Author Michaud, Emma Author Zeppilli, Daniela text Zoologischer Anzeiger 2022 2022-11-30 301 23 41 http://dx.doi.org/10.1016/j.jcz.2022.09.001 journal article 10.1016/j.jcz.2022.09.001 1873-2674 10375202 3.1. Echinoderes cyaneafictus sp. nov Zoobank code: urn:lsid:zoobank.org:act: AD7E82A4-F389-485E- 8B7B-2E53437B09C1 ( Figs. 2–4 , Tables 2 and 3 ) 3.1.1. Material examined Holotype , adult male, collected on October 6th, 2018 , at Chirongui Bay , Grande-Terre Island , Mayotte Archipelago, SW Indian Ocean: 12 Ǫ 55 ′ 17.5 ′′ S, 45 Ǫ 09 ′ 10.4 ′′ E 12 Ǫ 55 ′ 22.8 ′′ S, 45 Ǫ 09 ′ 09.1 ′′ E in black organic mud at the intertidal zone; mounted in Fluoromount G ®, deposited at MNHN under catalogue number: 623 Ma . Paratypes , 23 adult males and 14 adult females, same collecting data as holotype; mounted in Fluoromount G ®, deposited at MNHN under catalogue numbers: 587 Ma-589 Ma, 594 Ma-595 Ma, 597 Ma-599 Ma, 601 Ma- 606 Ma, 608 Ma-612 Ma, 614 Ma, 616 Ma, 618 Ma-620 Ma, 622 Ma, 626 Ma-628 Ma and 630 Ma-636 Ma. Additional, non-type material : 12 juveniles , same collecting data as holotype and paratypes ; mounted in Fluoromount G ®, deposited at MNHN under catalogue numbers: 590 Ma-593 Ma, 596 Ma, 600 Ma, 607 Ma, 615 Ma, 617 Ma, 621 Ma and 624 Ma-625 Ma . Fig. 1. Map showing the location of the study site in the Indian Ocean (A), the Comoros Archipelago (B), the Mayotte Archipelago (C) and the Chirongui Bay (D). An illustration of the study site structure is represented in the horizontal profile (E). The mangrove cover was mapped by photo-interpretation and manual digitizing by D. Cepeda using the Adobe® Photoshop CS6 software. 3.1.2. Diagnosis Echinoderes with spines that are short, poorly sclerotized and weakly articulated in middorsal position on segment 4 and sublateral position on segments 6–7, plus large tubes in lateroventral position on segment 5, lateral accessory position on segment 8 and laterodorsal position on segment 10. Enlarged, oval sieve plate openings in sublateral position on segment 9, consisting of an anterior, slightly convex region bearing numerous pores, and a posterior, slightly concave area bearing a single pore. 3.1.3. Etymology The species name derives from Cyanea P´eron & Lesueur, 1810, which is a genus of scyphozoan cnidarians characterized by having multiple, elongated tentacles (resembling the elongated hairs of the segment 1 sensory spots of the species) and the Latin fictus (meaning feigned, false, counterfeit). 3.1.4. Description See Table 2 for measurements of selected morphological traits and dimensions, and Table 3 for summary of acicular spine, tube, nephridiopore, glandular cell outlet and sensory spot locations. Head: only a few specimens were found with a completely everted head, hence only a few details in some structures can be provided. Ring 00 of mouth cone with nine outer oral styles alternating in size between slightly larger and smaller ones. Outer oral styles composed of two jointed subunits: a rectangular, basal piece with proximal fringed sheath bearing a tuft of 5–7 spinous processes; and a triangular, hooked, distally pointed and curved end-piece ( Fig. 3F ). Triangular, strongly sclerotized, basally fringed cuticular thickenings flanking the outer oral styles. Outer oral styles located anterior to each introvert sector, except in the middorsal sector 6. Introvert with six rings of scalids (one ring of primary spinoscalids and five rings of regular-sized scalids) and 10 longitudinal sectors delimited by the arrangement of the primary spinoscalids. Ring 01 of introvert with 10 primary spinoscalids, larger than remaining ones, laterally compressed, composed of a medially fringed basal sheath and a distal, elongated, flexible, distally blunt end-piece ( Fig. 3F ). Remaining rings of introvert with regular-sized scalids, composed of a rectangular basal sheath and a distal, elongated, acicular, distally pointed end-piece ( Fig. 3F ). Scalids tend to collapse when mounted for LM ( Fig. 3F ), and specimens for SEM were not available, so details on the scalid arrangement are not provided. Neck: 16 trapezoidal placids, wider at base, closely adjacent, with distinct joint between the neck and first trunk segment. Midventral placid widest (ca. 9–10 μm wide at base), remaining ones slightly narrower (ca. 6–8 μm wide at base). A ring of six long, superficially haired trichoscalids associated with the placids, attached to large, bottleshaped trichoscalid plates ( Fig. 2A–B , D-E; 3B, D, F). Trunk: fusiform, composed of 11 segments, heart-shaped in cross-section. Segments 1–2 closed, ring-like cuticular plates, remaining ones with one tergal and two sternal cuticular plates ( Fig. 2A–B , D-E; 3A; 4A). Maximum sternal width at segment 7, trunk progressively tapering toward anterior and posterior ends. Cuticular hairs throughout segments 2–10, emerging from rounded to slightly oval perforation sites. Cuticular hairs arranged as 6–8 approximately straight transversal rows densely covering the cuticular surface of segment 2; as 5–7 transversal, uninterrupted rows that become wavy at laterodorsal, sublateral and ventrolateral to ventromedial regions on segment 3; as 7–12 transversal rows interrupted at the laterodorsal region that become wavy at sublateral and ventrolateral to ventromedial regions on segments 4–10; segments 1 and 11 without hairs ( Fig. 2A–E ; 3 B-D; 4B-F). Posterior segment margins straight, with a long, conspicuous, strongly serrated primary pectinate fringe ( Fig. 2A–E ; 3 B-C; 4B-F). Secondary pectinate fringes not detected. Fig. 2. Line art drawing of Echinoderes cyaneafictus sp. nov. A: Ventral male overview; B: Dorsal male overview; C: Dorsal female overview of segments 10–11. D: Ventral female overview of segments 1–3. E: Dorsal female overview of segments 1–3. Abbreviations: dpl; dorsal placid; epo, enlarged pore; lat, lateral accessory tube; ldrss, laterodorsal rounded sensory spot; ldt, laterodorsal tube; lts, lateral terminal spine; lvgco1, lateroventral type 1 glandular cell outlet; mddss, middorsal droplet-shaped sensory spot; mdgco1, middorsal type 1 glandular cell outlet; mds, middorsal spine; mldss, midlateral droplet-shaped sensory spot; mvpl, midventral placid; pddss, paradorsal droplet-shaped sensory spot; pdgco1, paradorsal type 1 glandular cell outlet; ppf, primary pectinate fringe; ps; penile spine (followed by number of corresponding pair); S, segment (followed by number of corresponding segment); sddss; subdorsal droplet-shaped sensory spot; sdrss, subdorsal rounded sensory spot; slne, sublateral nephridiopore; sls, sublateral spine; te, tergal extension; tp, trichoscalid plate; vldss, ventrolateral droplet-shaped sensory spot; vmdss, ventromedial droplet-shaped sensory spot; vmgco1, ventromedial type 1 glandular cell outlet; vmrss, ventromedial rounded sensory spot. Segment 1: type 1 glandular cell outlets in middorsal and lateroventral positions, the former near the anterior segment margin, the latter located at the anterior half of the segment ( Fig. 2A–E ; 3B ). Rounded sensory spots (sensu Lundbye et al., 2011 ) in subdorsal, laterodorsal and ventrolateral positions, the former two located near the anterior segment margin, the latter located near the posterior segment end; these sensory spots are characterized by having the posterior part of the papillae area with a transversal row of conspicuously elongated hairs ( Fig. 2A–B , D-E; 3 B, D, E). Table 2 Morphological measurements and dimensions (in μm) of adult specimens of Echinoderes cyaneafictus sp. nov. from the type locality, including number of measured specimens ( n ), mean value and standard deviation (Sd) of each feature, depicted for the holotype and all the type series. Abbreviations: ac, acicular spine; LA, lateral accessory; LD, laterodorsal; LTAS, lateral terminal accessory spine length; LTS, lateral terminal spine length; LV, lateroventral; MD, middorsal; MSW,maximum sternal width; S, segment length; SL, sublateral; SW, standard sternal width; t, tube; TL, total trunk length; numbers after abbreviations indicate the corresponding segment.

Character	Holotype	Range	Mean	Sd, n
TL	250.6	194.1–268.7	231.2	21.9, 29
MSW-7	45.1	39.6–46.6	44.5	1.4, 27
MSW-7/TL (%)	18.0	16.6–23.3	19.4	1.8, 27
SW-10	39.9	37.5–41.6	39.6	1.0, 28
SW-10/TL (%)	15.9	14.6–20.8	17.3	1.8, 28
S1	21.6	17.7–28.6	22.1	3.0, 30
S2	21.2	16.5–23.7	20.4	2.1, 30
S3	17.9	13.9–26.8	19.7	2.9, 30
S4	24.7	17.9–27.9	23.0	2.7, 29
S5	29.3	20.0–32.7	25.2	3.0, 30
S6	36.6	21.5–36.6	27.0	3.8, 30
S7	32.8	24.0–40.8	30.6	4.0, 30
S8	33.0	23.8–39.8	33.9	4.1, 30
S9	40.4	27.2–44.6	37.2	3.8, 30
S10	36.5	28.8–37.8	33.7	2.4, 29
S11	25.3	22.0–32.3	27.2	2.7, 29
MD4 (ac)	5.3	4.2–10.2	6.5	1.7, 24
LV5 (t)	9.2	6.9–11.7	9.5	1.3, 23
SL6 (ac)	5.7	4.0–6.6	5.1	0.7, 28
SL7 (ac)	5.1	4.6–7.6	5.7	0.7, 27
LA8 (t)	9.0	7.7–14.8	11.7	2.0, 26
LD10 (t)	12.7	10.3–14.9	12.2	1.5, 8
LTS	56.4	51.4–59.0	54.9	2.0, 29
LTS/TL (%)	22.5	20.3–28.5	23.8	2.3, 29
LTAS	/	9.4–12.7	11.1	1.0, 12
LTAS/LTS (%)	/	4.4–5.8	5.0	0.5, 12

Segment 2: type 1 glandular cell outlets in middorsal and ventromedial positions ( Fig. 2A–B , D-E; 3D). Droplet-shaped sensory spots (sensu Lundbye et al., 2011 ) in middorsal position only in males, in paradorsal and midlateral positions only in females, and also in subdorsal and laterodorsal positions in both sexes ( Fig. 2A–B , D-E; 3B). Segment 3: type 1 glandular cell outlets in middorsal and ventromedial positions ( Fig. 2A–B , D-E; 3D). Droplet-shaped sensory spots in middorsal and subdorsal positions, and also in midlateral position only in females ( Fig. 2B , D-E). Segment 4: short (ca. 4–10 μm long), poorly sclerotized, weakly articulated, acicular spine in middorsal position ( Fig. 2B ; 3 B ). Type 1 glandular cell outlets in paradorsal and ventromedial positions ( Fig. 2A–B ). Segment 5: tubes in lateroventral position ( Fig. 2A ; 3C ). Type 1 glandular cell outlets in paradorsal and ventromedial positions ( Fig. 2A–B ; 4B ). Droplet-shaped sensory spots in subdorsal, midlateral and ventromedial positions ( Fig. 2A–B ; 3C ; 4B ). Segment 6: short (ca. 4–7 μm long), poorly sclerotized, weakly articulated, acicular spines in sublateral position ( Fig. 2A ; 3C ). Type 1 glandular cell outlets in paradorsal and ventromedial positions ( Fig. 2A–B ; 4B ). Droplet-shaped sensory spots in subdorsal, midlateral and ventromedial positions, the former slightly more mesial than those of the precedent segment but still in subdorsal position ( Fig. 2A–B ; 3C ; 4B ). Segment 7: similar to segment 6 in the arrangement of spines, glandular cell outlets and sensory spots ( Fig. 2A–B ; 3C ; 4B ). Segment 8: tubes in lateral accessory position ( Fig. 2A ; 3C ). Type 1 glandular cell outlets in paradorsal and ventromedial positions ( Fig. 2A–B ; 4 B-C). Droplet-shaped sensory spots in paradorsal and ventrolateral positions ( Fig. 2A–B ; 4 B-C). Segment 9: type 1 glandular cell outlets in paradorsal and ventromedial positions ( Fig. 2A–B ; 4C ). Droplet-shaped sensory spots in paradorsal, subdorsal and ventrolateral positions ( Fig. 2A–B ; 4C ). Nephridiopores in sublateral position as oval, enlarged sieve plate openings consisting of an anterior, elongated, slightly convex area with numerous pores, and a posterior, slightly concave region with a single pore (sensu Lundbye et al., 2011 ) ( Fig. 2A ; 4F ). Segment 10: tubes in laterodorsal position ( Fig. 2B ). Two longitudinally aligned type 1 glandular cell outlets in middorsal position; type 1 glandular cell outlets also in ventromedial position ( Fig. 2A–C ; 4C, E ). Droplet-shaped sensory spots in subdorsal and ventrolateral positions ( Fig. 2A–C ; 4C, E ). Posterior margins of sternal plates midventrally extended, forming an elongated, V-shaped extension over the following segment ( Fig. 2A ; 4 D-E). Segment 11: relatively short lateral terminal spines (LTS:TL average ratio = 23.8%), apparently well sclerotised but still quite flexible, distally pointed, with a hollow central cavity ( Fig. 2A–C ; 3A ; 4A , D-E). Males with three pairs of penile spines, dorsal and ventral pairs longer and slender, smooth and distally rounded, medial pair shorter and stouter, hairy with a distal tuft of hairs ( Fig. 2A–B ; 4E ); females with short (LTAS:LTS average ratio = 5.0%), slender, occasionally distally frayed, lateral terminal accessory spines ( Fig. 2C ; 4D ). Type 1 glandular cell outlet in middorsal position ( Fig. 2B–C ). Rounded sensory spots in subdorsal and ventromedial positions, the latter near the basal insertion of the lateral terminal spines ( Fig. 2A–C ; 4E ). Tergal extensions forming projections laterally, with blunt tips in males and pointed tips in females; posterior margin between the tergal extensions densely fringed ( Fig. 2A–C ; 4 D-E). Sternal extensions short, distally rounded ( Fig. 2A ; 4E ). Table 3 Summary of nature and arrangement of spines, tubes, sensory spots, glandular cell outlets and nephridiopores in adults of Echinoderes cyaneafictus sp. nov. Abbreviations: ac, acicular spine; dss, droplet-shaped sensory spot; gcoI, type 1 glandular cell outlet; LD, laterodorsal; ltas, lateral terminal accessory spine; lts, lateral terminal spine; LV, lateroventral; MD, middorsal; ML, midlateral; ne, nephridiopore; PD, paradorsal; ps, penile spines; rss, rounded sensory spot; SD, subdorsal; SL, sublateral; t, tube; VL, ventrolateral; VM, ventromedial; Ƌ/♀ indicate sexually dimorphic structures.

Segment	MD	PD	SD	LD	ML	SL	LA	LV	VL	VM
1	gcoI	rss	rss	gcoI	rss
2	gcoI, dss (Ƌ)	dss (♀)	dss	dss	dss (♀)	gcoI, dss
3	gcoI, dss	dss	dss (♀)	gcoI, dss
4	Ac	gcoI	gcoI
5	gcoI	dss	dss	t	gcoI, dss
6	gcoI	dss	dss	ac	gcoI, dss
7	gcoI	dss	dss	ac	gcoI, dss
8	gcoI, dss	t	dss	gcoI
9	gcoI, dss	dss	ne	dss	gcoI
10	gcoI, gcoI	dss	t	dss	gcoI
11	gcoI	rss	lts, ps x3 (Ƌ), ltas (♀)	rss

Fig. 3. Light micrographs of male holotype MNHN-623 Ma (A-B, D), and female paratype MNHN-602 Ma (C, E-F) of Echinoderes cyaneafictus sp. nov. , showing trunk overview and details on the head, neck, and segments 1–8. A: Ventral trunk overview; B: Dorsal view on segments 1–4; C: Midlateral to ventrolateral view on left side of cuticular plates of segments 5–8; D: Ventral view on segments 1–4; E: Detail of elongated micropapillae sensory spot on segment 1; F: Mouth cone and introvert. Abbreviations: ba, bacteria; bs, basal sheath; dpl, dorsal placid; ep, distal end-piece; lat, lateral accessory tube; ldess, laterodorsal elongated micropapillae sensory spot; lvt, lateroventral tube; mds, middorsal spine; mvpl, midventral placid; oos, outer oral style; phc, pharyngeal crown; ppf, primary pectinate fringe; psc, primary spinoscalid; rsc, regular-sized scalid; sdess, subdorsal elongated micropapillae sensory spot; sls, sublateral spine; tsp, trichoscalid plate; vmess, ventromedial elongated micropapillae sensory spot; numbers after abbreviations indicates corresponding segment; glandular cell outlets are marked as continuous circles, and sensory spots as dashed circles/droplet-shaped figures. 3.1.5. Remarks The holotype of the species (MNHN-623 Ma) was found carrying epibiont, filamentous bacteria attached to the lateral margins of segment 11 tergal plate ( Fig. 3A ).