Echinoderes zacharyi, Kennedy & Sørensen & Landers, 2022

Kennedy, Madison C., Sørensen, Martin V. & Landers, Stephen C., 2022, Echinoderes zacharyi sp. nov., a new kinorhynch in the E. coulli species group (Kinorhyncha: Cyclorhagida) from the Gulf of Mexico, Zoologischer Anzeiger (Zool. Anz.) 301, pp. 91-99 : 92-96

Genus Echinoderes Clapar`ede, 1863

Species Echinoderes zacharyi sp. nov.

Zoobank codes:

urn:lsid:zoobank.org:act:57671314-AF1F–41FC-BCE7-0E80583670E3

urn:lsid:zoobank.org:pub:97E7ECBB-8B9B-4CD8-83B8-7930EC5C0D41 .

Figs. 2–6 .

Synonymy. Echinoderes coulli group – Landers et al. 2020: page 496; Table III.

Material. Holotype: Adult male collected at Station 09–2020 from sediment on March 9, 2020 at 15.4 m (30.2911 ◦ N, 88.0330 ◦ W), and deposited in the Natural History Museum of Denmark (Copenhagen) under catalogue number NHMD–1174539. Three paratype specimens from the nGOM ( NHMD –1174540 - 1174542) include adult females, one collected from the same site as the holotype ( NHMD –1174540), and two at station 00–2020 (30.2654 ◦ N, 88.0733 ◦ W), at a depth of 4.46 m ( NHMD –1174541 and 1174542). All type material was fixed in 5–10% buffered formalin and mounted with Fluoromount G ®. One non-type specimen ( SEM) was collected on March 16, 2018 in the nGOM at site 10–2018 (30.1354 ◦ N, 88.0768 ◦ W), at a depth of 16.3 m. Five additional non-type specimens were collected from the sGOM, which came from the two most-shallow locations that were sampled in Mexican waters (stations LT1 and LT2). This material includes four non-type specimens (1 SEM, 3 LM) collected on August 4, 2015 at site LT1 (18.8484 ◦ N, 92.0705 ◦ W) at 16m depth, and one non-type specimen (LM) collected on August 4, 2015 at site LT2 (19.0564 ◦ N, 92.1245 ◦ W) at 21m depth.

Diagnosis: Echinoderes without acicular spines, except for lateral terminal ones. Midlateral and lateroventral tubes on segment 5; midlateral and lateral accessory tubes on segment 8. Large oval sublateral sieve plate on segment 9. Males with 3 sublateral penile spines, with the lateral-most spine twice as long as the others. Females without lateral terminal accessory spines. Segments 10 and 11 retractable into segment 9.

Description: Adults with head, neck, and trunk, with eleven trunk segments ( Figs. 2–6 ). Trunk length (segments 1–11) ranging from 214 to 265 μm, measured from anterior-most location on segment 1 to the posterior tip of the tergum (measured from animals with segments 10 and 11 retracted into segment 9). All specimens had segments 10 and 11 retracted into segment 9. Complete measurements are listed in Table 2. Location of glandular cell outlets, sensory spots, spines, and tubes are listed in Table 3.

The head has a retractable mouth cone and an introvert composed of scalids ( Figs 3A and B ; 5A, B ). The mouth cone has a ring of 9 outer oral styles, each with a proximal portion which articulates with an elongated distal tip, with the total length of the two approximately 17 μm. A fringe with spikes is located at the base of each outer oral style. The introvert sectors are defined by 10 primary spinoscalids in the first ring. The primary spinoscalids are composed of a basal sheath and a distal end piece. The distal end piece of each primary spinoscalid is elongated and extends posteriorly to segment 1. Six rings of spinoscalids are visible by SEM.

The neck has 16 placids ( Figs. 2A and B ; 3B,D ). The midventral placid is the largest, measuring 15 μm in length and 16 μm in width, with the remaining placids measuring 10 μm in width at their bases. Trichoscalid plates are narrow, but otherwise well developed ( Fig. 2 ).

Segment 1 ( Figs. 2A and B ; 3A, B, D ; 5A, B, C ; 6A ) is a complete cuticular ring. Sensory spots are located at the anterior margin of the segment, in subdorsal and laterodorsal positions. Sensory spots are located in a circular indentation with fine, stubby hairs. Glandular cell outlets type 1 are located anteriorly in the segment, in the middorsal and lateroventral position. Cuticular hairs are evenly distributed. Pectinate fringe with delicate filiform extensions transitioning from longer extensions (3 μm) along the ventral surface to shorter extensions (1.2 μm) along the dorsal surface, with the transition occurring approximately at the midlateral position.

Segment 2 ( Figs. 2A and B ; 3A, B, D ; 5A, C, D ; 6A ) is a complete cuticular ring. Two pairs of sensory spots are located in tandem in laterodorsal positions, and a single pair is present in the ventromedial position. Sensory spots are round at the anterior end, and posteriorly form an oblong field of hairs that taper to a point, and have an approximate length of 6.6–8.0 μm. Glandular cell outlets not observed on this segment or subsequent segments. Cuticular hairs are evenly distributed. Pectinate fringe as on the preceding segment and on subsequent segments 3–6. Pachycyclus of the anterior segment of regular thickness.

Segment 3 ( Figs 2A and B ; 3A, B, D ; 5A, C, D ; 6A ) and remaining segments consist of one tergal and two sternal plates. Sensory spot shape on this and subsequent segments are consistent with segment 2; sensory spots located in the subdorsal and sublateral positions. Pachycyclus of the anterior segment disrupted along margins at the middorsal, midventral, and at the tergosternal junctions. Cuticular hairs evenly distributed across tergal and sternal plates of segment with a hairless midventral area on this and segments 4–10.

Segment 4 ( Figs 2A and B ; 3A, B, D ; 5A, C, D ; 6A ) with sensory spots located in the laterodorsal position. Pachycyclus as on preceding segment.

Segment 5 ( Figs 2A and B ; 3A–D ; 5A, D ; 6A ) with tubes in midlateral and lateroventral positions; tubes positioned medially in the segment. Tube morphology consists of a flattened basal portion that is wider than the distal portion (a cylindrical distal portion extends for approximately 2/3 of the length of the tube). Sensory spots located in subdorsal and ventromedial positions. Pachycyclus as on preceding segment.

Segment 6 ( Figs 2A and B ; 3A–D ; 4A ; 5A, D ; 6A ) with sensory spots in subdorsal, sublateral, and ventromedial positions. Pachycyclus as on preceding segment.

Segment 7 ( Figs 2A and B ; 3A–C ; 4A ; 5A ; 6A ) with sensory spots in subdorsal, midlateral, and ventrolateral positions. Pectinate fringe with delicate filiform extensions uniform in length across the posterior margin, approximately 1.8 μm. Pachycyclus as on preceding segment.

Segment 8 ( Figs 2A and B ; 3A–C ; 4A ; 5A ; 6A ) with tubes in the midlateral and lateral accessory positions; tubes positioned medially in the segment. Sensory spots present in subdorsal and ventrolateral positions. Pachycyclus and pectinate fringe as on preceding segment.

Segment 9 ( Fig. 2A–D ; 3A, C ; 4A–C ; 5A ; 6A–C ) with a pair of sensory spots in tandem in the subdorsal position. Additional sensory spots present in the sublateral and ventrolateral positions. Oval sieve plates positioned medially at the sublateral position; sieve plates measure 11 μm in length, corresponding to 18.7% of the total segment length. Sieve plate accompanied by a cuticular pore approximately 0.25 μm posterior to the plate. Pachycyclus, and pectinate fringe as on preceding segment.

Segment 10 ( Fig. 2A–D ; 4B, C ) nearly fully retracted into segment 9; sensory spots and glandular cell outlets not observed. Pectinate fringe with uniform filiform extensions.

Segment 11 ( Fig. 2A–D ; 3A, C ; 4A–C ; 5A ; 6A, C ) nearly fully retracted into segment 10; with lateral terminal spines that extend for 20–30% of the total trunk length. Sensory spots and glandular cell outlets not observed. Lateral terminal accessory spines not observed on females. Males with three pairs of sublateral penile spines, with one pair stout and extending well past the tergal and sternal posterior margins (when the last two segments are contracted into segment 9). Cuticular hairs sparsely distributed. Tergal extensions blunt and end in short narrowtipped hairs at the posterior margin. Posterior margin of the sternum with very short, rounded extensions on each side of the midline, with fine hairs on the edge.

Etymology. This species is named after the late Zachary J. Kennedy, brother of Madison C. Kennedy, first author of this publication.

Figures

Fig. 2. Line art illustrations of Echinoderes zacharyi sp. nov. A. Male, dorsal view. B. Male, ventral view. C. Segments 9 to 11 in female, dorsal view. D. Segments 9 to 11 in female, ventral view. Abbreviations: lat, lateral accessory tube; ldss, laterodorsal sensory spot; lts, lateral terminal spine; lvgco1, lateroventral glandular cell outlet type 1; lvt, lateroventral tube; mdgco1, middorsal glandular cell outlet type 1; mlt, midlateral tube; pe, penile spines; s10, segment 10; sdss, subdorsal sensory spot; si, sieve plate; slss, sublateral sensory spot; vlss, ventrolateral sensory spot; vmss, ventromedial sensory spot.

Fig. 3. Light microscopy of head and trunk morphology of Echinoderes zacharyi sp. nov. A. An overview of male holotype (NHMD-1174539), dorsal view. B. Segments 1 to 9 of female paratype (NHMD-1174541), dorsal view. Arrow, placids. C. Segments 5 to 11 of male holotype, dorsal view. Arrows, midlateral tubes on segment 5; arrowheads, midlateral tubes on segment 8. D. Segments 1 to 6 of female paratype (NHMD-1174540), ventral view. Arrow, midventral placid; arrowhead, lateroventral tube.

Fig. 4. Light micrographs showing overviews and details in trunk morphology of Echinoderes zacharyi sp. nov. A. An overview of female paratype specimen (NHMD-1174540), posterior view. Arrow, lateral accessory tube on segment 8; arrowhead, sieve plate. Inset: enlargement of sieve plate. B. Segments 9 to 11 of male holotype (NHMD- 1174539), dorsal overview. Arrows, penile spines; arrowhead, lateral terminal spine. C. Segments 9 to 11 of female paratype specimen (NHMD- 1174541KIN), ventral overview. Arrow, pectinate fringe on segment 10.

Fig. 5. Scanning electron micrographs showing overviews and details in head and trunk morphology of Echinoderes zacharyi sp. nov. A. Midlateral overview. B. The oral cone and introvert region. Arrow, outer oral style; arrowhead, primary spinoscalid. C. Segments 1 to 4, laterodorsal overview. Arrowheads, sensory spots. D. Segments 2 to 6, midlateral overview. Arrow, midlateral tube on segment 5; arrowheads, lateroventral tubes on segment 5.

Fig. 6. Scanning electron micrographs showing overviews and details of head and trunk morphology of Echinoderes zacharyi sp. nov. A. Lateral overview. Arrows, midlateral tubes on segments 5 and 8; arrowheads, lateroventral tubes on segment 5; double arrowhead, lateral accessory tube on segment 8. B. Segment 9 enlargement showing sieve plate (arrow) with distinctive posterior cuticular pore (arrowhead). C. Lateral enlargement of posterior region. Arrow, lateral terminal spine.