Echinoderes angelae, Cepeda & Gayet & Spedicato & Michaud & Zeppilli, 2022

Cepeda, Diego, Gayet, Nicolas, Spedicato, Adriana, Michaud, Emma & Zeppilli, Daniela, 2022, Two new species of the Echinoderes coulli-group (Kinorhyncha: Cyclorhagida: Echinoderidae) from a low human-impacted mangrove swamp in French Guiana (western Atlantic Ocean), Zoologischer Anzeiger 301, pp. 179-195 : 180-186

publication ID	https://doi.org/ 10.1016/j.jcz.2022.10.008
DOI	https://doi.org/10.5281/zenodo.10374756
persistent identifier	https://treatment.plazi.org/id/AE098789-C674-FF80-2552-FD917902FA23
treatment provided by	Felipe
scientific name	Echinoderes angelae
status	sp. nov.

Treatment

3.2. Echinoderes angelae View in CoL sp. nov urn:lsid:zoobank.org:act:482926BC-199C-4168-BB67-92E21CB0ACF5 .

( Figs. 2–8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig , 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 GoogleMaps . 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 GoogleMaps . 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 GoogleMaps 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.

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 View Fig ; 4B View Fig ).

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 View Fig ; 6B–C View Fig ).

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 View Fig ; 3 View Fig 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 View Fig ; 4A View Fig ; 5 View Fig 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 View Fig ; 5 View Fig A-F; 7B, D, F, H, L). Posterior segment margins straight, with serrated primary pectinate fringe ( Fig. 3A–D View Fig ); primary pectinate fringe of segment 1 with larger tips ( Fig. 7B View Fig ); 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 View Fig ; 7B, L View Fig ); 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 View Fig ); segment 11 with elongated tips of primary pectinate fringe in middorsal to subdorsal and lateroventral to ventrolateral regions ( Fig. 3A–D View Fig ; 6 View Fig F-G). Secondary pectinate fringes finely serrated ( Fig. 7K View Fig ).

Segment 1 with type 1 glandular cell outlets in middorsal and lateroventral positions ( Fig. 3A and B View Fig ; 5A View Fig ). 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 View Fig ; 5A View Fig ; 7A View Fig ) .

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 View Fig ; 5A View Fig ); on this and following segments, these sensory spots usually have one or two central pores with emerging cilia ( Fig. 7D View Fig ). Modified type 2 glandular cell outlets in subdorsal, laterodorsal and midlateral positions ( Fig. 3B View Fig ; 5A View Fig ; 7D View Fig ); 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 View Fig ).

Segment 3 with type 1 glandular cell outlets in middorsal and ventromedial positions ( Fig. 3A and B View Fig ). Droplet-shaped sensory spots in subdorsal and midlateral positions ( Fig. 3B View Fig ; 7H View Fig ).

Segment 4 with short (ca. 4–8 μm length), poorly sclerotized, weakly articulated, acicular spine in middorsal position ( Fig. 3B View Fig ; 7G View Fig ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B View Fig ). Modified type 2 glandular cell outlets in laterodorsal position ( Fig. 3B View Fig ; 7C View Fig ).

Segment 5 with tubes in lateroventral position ( Fig. 3A View Fig ; 5C View Fig ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B View Fig ). Modified type 2 glandular cell outlets in subdorsal position ( Fig. 3B View Fig ). 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 View Fig ; 5B–C View Fig ; 7B View Fig ).

Segment 6 with short (ca. 4–6 μm length), poorly sclerotized, weakly articulated, acicular spines in sublateral position ( Fig. 3A View Fig ; 5C View Fig ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B View Fig ). Modified type 2 glandular cell outlets in subdorsal and midlateral positions ( Fig. 3B View Fig ; 5B View Fig ). 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 View Fig ; 5B–C View Fig ; 7B View Fig ).

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 View Fig ; 5B, F View Fig ; 7J View Fig ).

Segment 8 with tubes in lateral accessory position ( Fig. 3A View Fig ; 5F View Fig ; 7J View Fig ). Type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B View Fig ). Modified type 2 glandular cell outlets in subdorsal, midlateral and lateroventral positions ( Fig. 3A and B View Fig ; 5D, F View Fig ; 7F View Fig ). Droplet-shaped sensory spots in subdorsal position ( Fig. 3B View Fig ; 5D View Fig ; 7F View Fig ).

Segment 9 with type 1 glandular cell outlets in subdorsal and ventromedial positions ( Fig. 3A and B View Fig ; 7K View Fig ). One pair of droplet-shaped sensory spots in midlateral and ventrolateral positions, and two pairs in subdorsal position ( Fig. 3A and B View Fig ; 5 View Fig 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 View Fig ; 5E View Fig ; 7E View Fig ).

Segment 10 with tubes in laterodorsal position, larger in males ( Fig. 3B, D View Fig ; 4E View Fig ; 7I View Fig ). Two type 1 glandular cell outlets in middorsal position, longitudinally arranged; type 1 glandular cell outlets also in ventromedial position ( Fig. 3A and B View Fig ). Modified type 2 glandular cell outlets in laterodorsal position, anterior to the tubes ( Fig. 3B View Fig ). Droplet-shaped sensory spots in subdorsal and ventrolateral positions ( Fig. 3A–D View Fig ; 5E View Fig ; 7L View Fig ).

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 View Fig ; 4A View Fig , 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 View Fig ; 4E View Fig ; 6F View Fig ). 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 View Fig ; 4F View Fig ; 6G View Fig ). Droplet-shaped sensory spots in subdorsal and ventromedial positions ( Fig. 3A–D View Fig ; 7L View Fig ). Tergal extensions triangular, distally pointed, covered by hairs, distally elongated as hair-like extensions ( Fig. 3A–D View Fig ; 4F View Fig ; 6E View Fig ).

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 View Fig ; 5A View Fig ; 7A View Fig ). However, seven specimens mounted for SEM (four males and three females) showed these sensory spots without such kind of hairs ( Fig. 7A View Fig ). Neither juveniles of the species possess the elongated hairs,

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 View Fig ; 7E View Fig ). 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 View Fig ). 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 View Fig ; 4 View Fig 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 View Fig ; 6G View Fig ; 8 View Fig A-C, F-G), but unicellular bacteria were also observed ( Fig. 8D–E View Fig , H-I). Finally, unknown, rod-shaped epibionts, with a distal constriction, were also detected ( Fig. 4H View Fig ). 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 View Fig ; 6G View Fig ; 8G View Fig ), 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 View Fig ).

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 View Fig ). This could suggest that the specimens were able to extract the content of the diatom to digest it.