Two new species of the Echinoderes coulli-group (Kinorhyncha: Cyclorhagida: Echinoderidae) from a low human-impacted mangrove swamp in French Guiana (western Atlantic Ocean) Author Cepeda, Diego Author Gayet, Nicolas Author Spedicato, Adriana Author Michaud, Emma Author Zeppilli, Daniela text Zoologischer Anzeiger 2022 2022-11-30 301 179 195 http://dx.doi.org/10.1016/j.jcz.2022.10.008 journal article 281831 10.1016/j.jcz.2022.10.008 cbc8d1b2-efdd-488e-9c9a-04d8e5740627 1873-2674 10375291 3.2. Echinoderes angelae sp. nov urn:lsid:zoobank.org:act: 482926BC-199C-4168-BB67- 92E21CB0ACF5 . ( Figs. 2–8 , Tables 1 and 2 ) 3.2.1. Material examined Holotype , adult female, collected in November 2017 at the confluence of the Cayenne and Montsin´ery Rivers , French Guiana ( western Atlantic Ocean ): 04 ◦ 53 ′ 49.2288 ′′ N , 52 ◦ 22 ′ 27.714 ′′ W at the intertidal zone in mud; mounted in Fluoromount G ®, deposited at MNHN under catalogue number: 655 Ma . Paratypes , three adult males and five adult females, same collecting data as holotype; mounted in Fluoromount G ®, deposited at MNHN under catalogue numbers: 656Ma–663Ma . Additional material, 29 adult males, 23 adult females, 3 adults of unknown sex, 83 juveniles and 12 exuvia , some of them with same collecting data as type material, mounted in Fluoromount G ®, others collected in November 2017 ca. 14 km upstream of the Cayenne River , French Guiana ( western Atlantic Ocean ): 04 ◦ 51 ′ 31.9716 ′′ N , 52 ◦ 23 ′ 59.5248 ′′ W at the intertidal zone in mud; mounted in Fluoromount G ®, deposited at MNHN under catalogue numbers: 666Ma–815Ma; seven adult males, eight adult females, three adults of unknown sex and eight juveniles , same collecting data as type and remaining additional material, mounted for SEM , deposited at IFREMER . Fig. 1. Map showing the sampling location in South America (top left), French Guiana (top right) and the Cayenne Estuary (bottom). Sampling stations are marked red circles; mangrove cover is coloured in dark green. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) 3.2.2. Diagnosis Echinoderes with short, poorly sclerotized, weakly articulated spines in middorsal position on segment 4 and sublateral position on segments 6–7. Tubes in lateroventral position on segment 5, lateral accessory position on segment 8 and laterodorsal position on segment 10. Modified type 2 glandular cell outlets in subdorsal position on segments 2 and 5–8, laterodorsal position on segments 2, 4 and 10, midlateral position on segments 2, 6 and 8, and lateroventral position on segments 7–8. Large, rounded sensory spots on segment 1 with a transversal row of conspicuously elongated hairs at the posterior edge of the papillae area. Enlarged, oval sieve plate in sublateral position on segment 9, consisting of an anterior, slightly convex region with numerous pores and a posterior, slightly concave area with a single, central pore. 3.2.3. Etymology The species is dedicated to Angela´Cepeda Gomez´, sister of the first author, for all these years of unconditional support. 3.2.4. Description See Table 1 for measurements of selected morphological features and body dimensions, and Table 2 for summary of spine, tube, nephridiopore, glandular cell outlet and sensory spot locations. Despite the high number of studied specimens, only a few had the head everted, hence only some data of the morphology and appendage arrangement are 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 sheath with distal fringe and a triangular, hooked, distally pointed end-piece. Outer oral styles located anterior to each introvert sector, except in the middorsal sector 6 where a style is missing ( Fig. 2 ; 4B ). Introvert with seven concentric rings of spinoscalids (one ring of primary spinoscalids and six rings of regular-sized spinoscalids) and 10 longitudinal sectors defined by the arrangement of the primary spinoscalids. Ring 01 with 10 primary spinoscalids, larger than remaining scalids, composed of a basal sheath and a distal, elongated, flexible end-piece. Ring 02 with 10 spinoscalids, arranged as one medially in each sector; spinoscalids on this and following rings are morphologically similar to the primary spinoscalids but smaller. Ring 03 with 20 spinoscalids, arranged as two in each sector. Ring 04 with 10 spinoscalids, arranged as one medially in each sector. Ring 05 with 20 spinoscalids, arranged as two in each sector. Ring 06 with five spinoscalids, arranged as one medially in each odd-numbered sector. Ring 07 with an unknown number of smaller spinoscalids, as only those of sectors 1, 3 and 4 could be observed (sectors 1 and 3 with three spinoscalids, sector 4 with two leaving space for the corresponding trichoscalid and its plate); sectors 9 and 8 are likely similar to sectors 3 and 4 in this arrangement due to the typical radial symmetry of the kinorhynch introvert. Scalid arrangement identical in all sectors from rings 02–05, with one unpaired scalid in ring 02 followed by a quincunx in rings 03–05; in sector 1 (and likely 9), ring 06 with an unpaired scalid followed by three smaller scalids in ring 07; in sector 4 (and likely 8), ring 06 without scalids followed by two smaller scalids in ring 07 leaving space for the corresponding trichoscalid and its plate; rings 06–07 unknown for remaining sectors. A fringed ring around the introvert at the level of rings 04–05, with tips more elongated in sectors where a spinoscalid is missing in ring 06 ( Fig. 2 ; 6B–C ). Fig. 2. Diagram of mouth cone, introvert and neck placids in Echinoderes angelae sp. nov. Grey area and thicker line arcs indicate mouth cone and neck placids, respectively. Spinoscalid positions that are inferred by radial symmetry are marked in grey with dashed line. Fig. 3. Line art drawing of Echinoderes angelae sp. nov. A: Ventral female overview; B: dorsal female overview; C: ventral male overview of segments 10–11; D: dorsal male overview of segments 10–11. Abbreviations: dpl, dorsal placid; go, gonopore; lat, lateral accessory tube; lddss, laterodorsal droplet-shaped sensory spot; ldmgco2, laterodorsal modified type 2 glandular cell outlet; ldrss, laterodorsal rounded sensory spot; ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; lvgco1, lateroventral type 1 glandular cell outlet; lvmgco2, lateroventral modified type 2 glandular cell outlet; lvt, lateroventral tube; mddss, middorsal droplet-shaped sensory spot; mdgco1, middorsal type 1 glandular cell outlet; mds, middorsal spine; mldss, midlateral droplet-shaped sensory spot; mlmgco2, midlateral modified type 2 glandular cell outlet; ms, muscular scar; mvpl, midventral placid; ppf, primary pectinate fringe; ps, penile spines; S, segment (followed by number of corresponding segment); sddss, subdorsal droplet-shaped sensory spot; sdgco1, subdorsal type 1 glandular cell outlet; sdmgco2, subdorsal modified type 2 glandular cell outlet; sdrss, subdorsal rounded sensory spot; slne, sublateral nephridiopore; sls, sublateral spine; te, tergal extension; tsp, 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. Neck with 16 trapezoidal placids, wider at the base, closely adjacent each other, with distinct joint between the neck and first trunk segment. Midventral placid widest (ca. 10–11 μm at base), remaining ones slightly narrower (ca. 6–8 μm at base). A ring of six short, superficially haired trichoscalids associated with the placids, attached to quadrangular trichoscalid plates in sectors 2, 4, 5, 7, 8 and 10 ( Fig. 2 ; 3 A-B; 4C-D; 6A- D). Trunk fusiform, heart-shaped in cross-section, composed of 11 segments. Segments 1–2 closed, ring-like cuticular plates; remaining ones with one tergal and two sternal cuticular plates ( Fig. 3A–D ; 4A ; 5 A-F; 6A; 7B). Maximum sternal width at segment 8, relatively narrow compared to total trunk length (MSW8/TL average ratio = 19.6%). Cuticular hairs throughout segments 2–11 (absent on segment 1), acicular, non-bracteate, emerging from rounded to slightly oval perforation sites. Cuticular hairs arranged as 6–12 transversal, uninterrupted rows covering the cuticular surface of segments 2–3 (except in the ventromedial region where hairs are missing); as 6–16 transversal rows that become wavy at subdorsal and ventrolateral to ventromedial regions, interrupted by large, oval, muscular scars in laterodorsal position throughout segments 4–10; as 6–8 transversal, uninterrupted rows covering the cuticular surface of segment 11 (hairs of this segment conspicuously shorter) ( Fig. 3A–D ; 5 A-F; 7B, D, F, H, L). Posterior segment margins straight, with serrated primary pectinate fringe ( Fig. 3A–D ); primary pectinate fringe of segment 1 with larger tips ( Fig. 7B ); segments 2 and 10 with posterior segment margin extended as a triangle in the ventrolateral to ventromedial region, with tips of primary pectinate fringe conspicuously shorter and tighter than those on other regions on the same segment ( Fig. 3A–D ; 7B, L ); segments 3–9 with tips of primary pectinate fringes noticeable shorter and tighter in the ventromedial region than those on other regions on the same segment ( Fig. 7B ); segment 11 with elongated tips of primary pectinate fringe in middorsal to subdorsal and lateroventral to ventrolateral regions ( Fig. 3A–D ; 6 F-G). Secondary pectinate fringes finely serrated ( Fig. 7K ). Fig. 4. Light micrographs of female holotype MNHN- 655Ma (A, C-D), male paratype MNHN-661Ma (B, E), female paratypes MNHN-656Ma (H) and MNHN-657Ma (F), and additional specimens (G, I) of Echinoderes angelae sp. nov. showing trunk overview, details of mouth cone and neck, epibionts and ingested diatoms. A: Ventral trunk overview; B: mouth cone, showing the outer oral styles; C: dorsal neck view; D: ventral neck view; E: middorsal to laterodorsal view on right side of tergal plate of segments 10–11; F: lateral view of segment 11; G: ingested diatom; H: unknown type of epibionts attached to the posterior edge of segment 11; I: filamentous bacteria attached to the posterior edge of segment 11. Abbreviations: ba, bacteria; bs, basal sheath; dpl, dorsal placid; ep, end-piece; ldt, laterodorsal tube; ltas, lateral terminal accessory spine; lts, lateral terminal spine; mvpl, midventral placid; ps, penile spines; te, tergal extension; tsp, trichoscalid plate. Segment 1 with type 1 glandular cell outlets in middorsal and lateroventral positions ( Fig. 3A and B ; 5A ). Large, rounded sensory spots in subdorsal, laterodorsal and ventromedial positions, the former two located near the anterior segment margin, the latter near the posterior segment edge; these sensory spots have a transversal row of conspicuously elongated hairs at the posterior edge of the papillae area (except in seven specimens mounted for SEM that lacked these hairs, see subsection 3.1.5 Notes on intraspecific variability ) ( Fig. 3A and B ; 5A ; 7A ) . Segment 2 with one pair of droplet-shaped sensory spots in middorsal and ventromedial positions, and two pairs in laterodorsal position ( Fig. 3A and B ; 5A ); on this and following segments, these sensory spots usually have one or two central pores with emerging cilia ( Fig. 7D ). Modified type 2 glandular cell outlets in subdorsal, laterodorsal and midlateral positions ( Fig. 3B ; 5A ; 7D ); on this and following segments, modified type 2 glandular cell outlets are minute, oval, glandular openings surrounded by a tuft of short cuticular extensions ( Fig. 7C ). Segment 3 with type 1 glandular cell outlets in middorsal and ventromedial positions ( Fig. 3A and B ). Droplet-shaped sensory spots in subdorsal and midlateral positions ( Fig. 3B ; 7H ). Segment 4 with short (ca. 4–8 μm length), poorly sclerotized, weakly articulated, acicular spine in middorsal position ( Fig. 3B ; 7G ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B ). Modified type 2 glandular cell outlets in laterodorsal position ( Fig. 3B ; 7C ). Segment 5 with tubes in lateroventral position ( Fig. 3A ; 5C ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B ). Modified type 2 glandular cell outlets in subdorsal position ( Fig. 3B ). Droplet-shaped sensory spots in subdorsal, midlateral and ventromedial positions; subdorsal sensory spots more lateral than subdorsal modified type 2 glandular cell outlets ( Fig. 3A and B ; 5B–C ; 7B ). Segment 6 with short (ca. 4–6 μm length), poorly sclerotized, weakly articulated, acicular spines in sublateral position ( Fig. 3A ; 5C ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B ). Modified type 2 glandular cell outlets in subdorsal and midlateral positions ( Fig. 3B ; 5B ). Droplet-shaped sensory spots in subdorsal, midlateral and ventromedial positions; subdorsal sensory spots more mesial than subdorsal modified type 2 glandular cell outlets ( Fig. 3A and B ; 5B–C ; 7B ). Segment 7 similar to segment 6 regarding spine, glandular cell outlet and sensory spot arrangement, but with modified type 2 glandular cell outlets in lateroventral instead of midlateral position and sensory spots in ventrolateral instead of ventromedial position ( Fig. 3A and B ; 5B, F ; 7J ). Segment 8 with tubes in lateral accessory position ( Fig. 3A ; 5F ; 7J ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B ). Modified type 2 glandular cell outlets in subdorsal, midlateral and lateroventral positions ( Fig. 3A and B ; 5D, F ; 7F ). Droplet-shaped sensory spots in subdorsal position ( Fig. 3B ; 5D ; 7F ). Segment 9 with type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B ; 7K ). One pair of droplet-shaped sensory spots in midlateral and ventrolateral positions, and two pairs in subdorsal position ( Fig. 3A and B ; 5 D-E; 7F, M). Nephridiopores in sublateral position as enlarged sieve plate openings with an anterior, elongated, slightly convex area with numerous pores and a posterior, slightly concave region with a single, central pore ( Fig. 3A ; 5E ; 7E ). Segment 10 with tubes in laterodorsal position, larger in males ( Fig. 3B, D ; 4E ; 7I ). Two type 1 glandular cell outlets in middorsal position, longitudinally arranged; type 1 glandular cell outlets also in ventromedial position ( Fig. 3A and B ). Modified type 2 glandular cell outlets in laterodorsal position, anterior to the tubes ( Fig. 3B ). Droplet-shaped sensory spots in subdorsal and ventrolateral positions ( Fig. 3A–D ; 5E ; 7L ). Fig. 5. Light micrographs of female holotype MNHN- 655Ma (E), male paratype MNHN-661Ma (C–D), and additional specimens (A-B, F) of Echinoderes angelae sp. nov. showing trunk cuticular details. A: Middorsal to midlateral view on right side of tergal plate of segments 1–2; B: midlateral to ventromedial view on left side of cuticular plates of segments 5–7; C: ventral view of segments 5–6; D: dorsal view of segments 8–9; E: midlateral to ventromedial view on right side of cuticular plates of segments 9–10 (inset shows the intraspecific variability of the nephridiopore); F: midlateral to ventromedial view on right side of cuticular plates of segments 7–8. Abbreviations: lat, lateral accessory tube; lvt, lateroventral tube; ms, muscular scar; ppf, primary pectinate fringe; slne, sublateral nephridiopore; sls, sublateral spine; numbers after abbreviation indicate corresponding segment; glandular cell outlets are marked with continuous circles, and sensory spots with dashed circles or teardrop-like figures. Segment 11 with relatively short lateral terminal spines (LTS:TL average ratio = 17.9%), distally pointed, with hollow central cavity, superficially covered by hairs ( Fig. 3A–D ; 4A , E-F, H–I; 6A, E-G). Males with three pairs of penile spines that emerge from laterodorsal position in the intersegmental joint with the preceding segment; penile spines tube-like, covered by hairs, abruptly tapering near their distal tips ( Fig. 3D ; 4E ; 6F ). Females with short (LTAS:LTS average ratio = 28.5%), distally frayed, covered by hairs, lateral terminal accessory spines, and oval, ventrolateral gonopores near the intersegmental joint with the preceding segment ( Fig. 3A and B ; 4F ; 6G ). Droplet-shaped sensory spots in subdorsal and ventromedial positions ( Fig. 3A–D ; 7L ). Tergal extensions triangular, distally pointed, covered by hairs, distally elongated as hair-like extensions ( Fig. 3A–D ; 4F ; 6E ). 3.2.5. Notes on intraspecific variability Echinoderes angelae sp. nov. shows certain degree of intraspecific variability not related to sex or sampling station. One of the most remarkable features of the species is the presence of three pairs of large sensory spots on segment 1 with a transversal row of conspicuously elongated hairs at the posterior edge of the papillae area ( Fig. 3A and B ; 5A ; 7A ). However, seven specimens mounted for SEM ( four males and three females ) showed these sensory spots without such kind of hairs ( Fig. 7A ). Neither juveniles of the species possess the elongated hairs, Fig. 6. Scanning electron micrographs of additional specimens of Echinoderes angelae sp. nov. showing trunk overview and details of introvert, neck, lateral terminal spines and sexually dimorphic features. A: Lateral trunk overview; B: introvert, sector 3; C: introvert, sector 4; D: ventral neck view; E: lateral terminal spine; F: male penile spines; G: female lateral terminal accessory spine. Abbreviations: ba, bacteria; ftz, fringed transverse zone; ltas, lateral terminal accessory spine; lts, lateral terminal spine; mvpl, midventral placid; ne, neck; ps, penile spines; psp, primary spinoscalid; sp, spinoscalid (followed by number of corresponding ring); te, tergal extension; ts, trichoscalid; tsp, trichoscalid plate; lambda marks (̂) indicate attachment point of spinoscalids. which suggests that the observed specimens could be pre-adults that did not develop the structures yet. Shape and position of nephridiopores also showed variation among the studied specimens. This structure varies from completely oval or slightly triangular, located near the anterior margin of segment 9 without rows of hairs on top (ca. 70% of the examined specimens) to more buttonhole-shaped, posteriorly displaced having a few rows of hairs on top (ca. 30% of the examined specimens) ( Fig. 5E ; 7E ). These differences were observed in both LM and SEM specimens. Segments 10 and 11 also showed conspicuous intraspecific variability regarding the length of the tergal extensions and the primary pectinate fringe. Thus, some specimens had shorter tergal extensions, without the hair-like distal end, as well as a primary pectinate fringe with barely elongated tips (ca. 20% of the examined specimens) ( Fig. 6E ). Others had tergal extensions with an elongated, hair-like distal end and primary pectinate fringes with longer tips (ca. 80% of the examined specimens) ( Fig. 3A–D ; 4 E-F; 6F-G). The primary pectinate fringe of segment 10 also showed some intraspecific variation concerning the length of the tips at the ventrolateral region, with ca. 30% of the examined specimens showing conspicuously elongated tips (reaching the edge of segment 11) at this area. Finally, the relative length of the lateral terminal spines also showed intraspecific variability (LTS:TL ratio of 6–10% in 15 out of 52 measured specimens vs. 15–25% in 37 out of 52 measured specimens). These differences were observed in both LM and SEM specimens. 3.2.6. Other remarks Several specimens (ca. 15% of the total number) had epibionts. The most common ones were filamentous bacteria of different lengths ( Fig. 4I ; 6G ; 8 A-C, F-G), but unicellular bacteria were also observed ( Fig. 8D–E , H-I). Finally, unknown, rod-shaped epibionts, with a distal constriction, were also detected ( Fig. 4H ). Epibionts were more commonly found attached to the ventral surface of the posterior segments, the nephridiopore and the lateral terminal spines ( Fig. 4H and I ; 6G ; 8G ), but some of them were also present at the anterior segments near sensory spots, tubes, muscular scars and glandular cell outlets ( Fig. 8A–F, H–I ). Fig. 7. Scanning electron micrographs of additional specimens of Echinoderes angelae sp. nov. showing trunk segments and details of cuticular appendages. A: Subdorsal and laterodorsal sensory spots of segment 1, with the enlarged external ring of micropapillar (inset shows the intraspecific variability of these structures without such kind of external ring); B: ventral view of segments 2–6; C: subdorsal (top) and laterodorsal (bottom) modified type 2 glandular cell outlets of segments 2 and 4 respectively; D: laterodorsal view on left side of tergal plate of segment 2; E: nephridiopore and midlateral dropletshaped sensory spot of segment 9; F: subdorsal to midlateral view on right side of tergal plates of segments 8–9; G: middorsal spine of segment 4; H: subdorsal to midlateral view on left side of tergal plates of segments 3–4; I: laterodorsal tube of segment 10; J: lateral accessory tube of segment 8 (left) and sublateral spine of segment 7 (right); K: subdorsal type 1 glandular cell outlet of segment 9; L: ventral view of segments 10–11; M: subdorsal droplet-shaped sensory spot of segment 9. Abbreviations: go, gonopore; ms, muscular scar; spf, secondary pectinate fringe; modified type 2 glandular cell outlets are marked with continuous circles, and sensory spots with dashed teardrop-like figures. Some specimens (ca. 10% of the total number) had ingested clusters of diatoms at the gut, and even though their frustules seemed to be unaltered, a partially digested, green content was observed ( Fig. 4G ). This could suggest that the specimens were able to extract the content of the diatom to digest it.