Echinoderes songae Sørensen & Chang, 2020

Sørensen, Martin V., Goetz, Freya E., Herranz, María, Chang, Cheon Young, Chatterjee, Tapas, Durucan, Furkan, Neves, Ricardo C., Yildiz, N. Özlem, Norenburg, Jon & Yamasaki, Hiroshi, 2020, Description, redescription and revision of sixteen putatively closely related species of Echinoderes (Kinorhyncha: Cyclorhagida), with the proposition of a new species group - the Echinoderes dujardinii group, European Journal of Taxonomy 730, pp. 1-101 : 56-65

Echinoderes songae Sørensen & Chang sp. nov.

urn:lsid:zoobank.org:act:7C168528-B97E-4D7E-A725-4C74B4C0D2BF

Figs 19–21 ; Tables 14–16

Echinoderes lanceolatus – Chang & Song 2002: 204, 206.

Echinoderes sp . A – Yamasaki et al. 2014: 421–428, figs 1, 3, tables 1, 4–5.

Diagnosis

Echinoderes with short middorsal spines on segments 4 to 8, and lateroventral spines on segments 6 to 9; middorsal spine on segment 8 reaches the pectinate fringe of its posterior margin, but does not extend beyond it. Tubes present in lateroventral positions on segments 2 and 5, and in midlateral positions on 10. Minute glandular cell outlets type 2 in midlateral positions on segment 8. Tergal extensions of segment 11 short, pointed and well-spaced; sternal extensions short, with ventrolateral seta-like tuft of extended fringe tips. Both sexes with ventrolateral sensory spots on segment 10, but sensory spots in females are located closer to the posterior segment margin. Females with female papillae showing indistinct crescentic intracuticular substructure in ventrolateral positions on segments 7 and with tubular to rhomboid substructure in ventromedial positions on segment 8.

Etymology

The species is dedicated to Dr Young Hee Song who co-authored the description of Echinoderes lanceolatus Chang & Song, 2002 , and assisted during collecting of much of the material used for the present description.

Material examined

Holotype

REPUBLIC OF KOREA • ♀; Korean south coast , Yeosu , Geumodo Island ; 34°31′38″ N, 127°47′21″ E; 0 m b.s.l.; 16 Jun. 2000; C.Y. Chang, J. Lee and Y.H. Song leg.; intertidal macroalgae; NHMD-662101 . Specimen mounted for LM in Hoyer’s medium.

Paratypes

Paratypes include 22 specimens, collected from a total of 18 localities around the Korean Peninsula, and all mounted as the holotype. 11 paratypes, four females and seven males, are deposited at NHMD under catalogue numbers NHMD-662102 to 662102 . Another 11 paratypes, two females and nine males, are deposited at NIBR under catalogue numbers NIBRIV0000866873 to NIBRIV0000866883 .

Additional material

Additional LM material includes three non-types, stored in the personal reference collection of C.Y. Chang. Material mounted for SEM includes nine females and thirteen males from five different localities; SEM material stored in the personal reference collection of M.V. Sørensen. Further species, not used in the description but with identity confirmed as E. songae Sørensen & Chang sp. nov., were collected by H. Yamasaki and included as Echinoderes sp. A in his population genetic study of Echinoderes species across the Tsugaru Strait in Northern Japan (Yamasaki et al. 2014). See Table 1 for a summary of studied material, and Table 14 for a detailed overview of stations yielding types or nontypes for the description.

Description

Adults with head, neck and eleven trunk segments ( Figs 19 A–B, 20A, 21A). Secondary pectinate fringe present near anterior segment margin of segments 2 to 10. For complete overview of measurements and dimensions, see Table 15. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, is summarized in Table 16.

The head consists of a retractable mouth cone and an introvert ( Fig. 21B ). Mouth cone with ten helioscalids; other inner oral styles could not be examined in detail. The external mouth cone armature consists of nine outer oral styles; bases of outer oral styles each with a transverse row of short fringe tips; two central, distally bifurcated bristles are present more posteriorly. The introvert sectors are defined by the ten primary spinoscalids in Ring 01. Each primary spinoscalid consists of a basal sheath and a distal end piece with a blunt tip. The sheaths have a well-defined basal, transverse fringe, overhanging a second, more distal transverse fringe. End pieces are smooth and flexible. Rings 02 and 04 have 10 spinoscalids and Rings 03 and 05 have 20. All spinoscalids in these rings are well-developed, and consist of a basal sheath and a pointed end piece. The basal sheaths terminate into fine, fringed margins in spinoscalids of Rings 02 to 05, and those of Rings 03 to 05 have in addition a basal median spike also. Ring 06 has only six spinoscalids, located in sectors 1, 3, 5, 6, 7, and 9; Ring 06 spinoscalids resemble those in preceding sectors, but without a distinct differentiation into sheath and end piece. Ring 07 also has 6 spinoscalids, located as pairs in sectors 3 and 9, and unpaired but laterally displaced in sectors 5 and 7 (trichoscalids are taking up the space in the opposite side of each sector); ring 07 spinoscalids resemble those in preceding sector.

Described sector-wise, sectors 1 and 6 are similar, having spinoscalids arranged as two double diamonds anterior. Sectors 2, 4, 8 and 10 all have spinoscalids arranged as a quincunx, located in between a medial anterior spinoscalid (Ring 02) and a trichoscalid plate. Sectors 3 and 9 have spinoscalids forming double diamonds anterior to a pair of spinoscalids. Sectors 5 and 7 also have spinoscalids forming double diamonds, but anterior to an unpaired, laterally spinoscalid (see Fig. 13 for species with similar outer oral style and scalid pattern).

Regular trichoscalids with trichoscalid plates are present in sectors 2, 4, 5, 7, 8, and 10. In addition, a single trichoscalid without trichoscalid plate is present in sector 1.

The neck has 16 placids, measuring 13 µm in length. The midventral placid is broadest, measuring 12 µm in width at its base, whereas all other are narrower, measuring 7 µm in width at their bases. The trichoscalid plates are well-developed, subdorsal and laterodorsal ones narrow and elongated, and ventromedial ones broadly oval.

Segment 1 consists of a complete cuticular ring. Sensory spots are located on the anterior segment half in subdorsal, laterodorsal, and sublateral positions, and slightly more posterior in ventromedial positions ( Figs 19 A–B, 21C–E); sensory spots are large, and rounded to oval, with numerous micropapillae, two pores, and often a cilium emerging from one of the pores. Glandular cell outlets type 1 present in middorsal and lateral accessory positions ( Figs 19 A–B, 20B–C, 21C). Dorsal and lateral sides, and posterior half of ventral side, with scattered cuticular hairs emerging through rounded perforation sites. The posterior segment margin is straight around the segment, terminating into a pectinate fringe with short, uniform fringe tips.

Segment 2 consists of a complete cuticular ring. Pachycyclus of the anterior segment margin is of medium thickness and not interrupted ( Fig. 20 B–C). Sensory spots are located in middorsal (but slightly laterally displaced), laterodorsal (twin pair) and ventromedial positions ( Figs 19 A–B, 21C–E); sensory spots on this and all following segments rounded, but with less papillae than on segment 1. Glandular cell outlets type 1 present in middorsal and ventromedial positions, and long and slender tubes present in lateroventral positions ( Figs 19 A–B, 20B–C, 21C–E). The segment is densely covered with bracteate hairs, but interrupted by hairless areas anterior to laterodorsal sensory spots and posterior to lateroventral tubes ( Fig. 21 C–E). The posterior segment margin is nearly straight; pectinate fringe from middorsal to midlateral positions with short fringe tips, as on segment 1; fringe tips from midlateral to ventromedial positions conspicuously longer and with trifurcate tips (two short lateral tips, and a long medial tip), and then slightly shorter but still trifurcate between ventromedial positions.

Segment 3, and remaining segments, consisting of one tergal and two sternal plates. Pachycyclus of the anterior segment margin of medium thickness, and interrupted only at tergosternal junctions. Sensory spots present in subdorsal, laterodorsal and sublateral positions ( Figs 19 A–B, 21C). Glandular cell outlets type 1 present in middorsal and ventromedial positions ( Figs 19 A–B, 20B–C). Bracteate cuticular hairs are densely covering the segment from middorsal to ventromedial positions (except in a hairless V-shaped patch anterior on segment in laterodorsal positions); paraventral areas densely covered by non-bracteate, hair-like extensions. Pectinate fringe of posterior margin hairs as on preceding segment, but with ventromedial fringe tips being slightly longer.

Segment 4 with short acicular spine in middorsal position, not reaching the posterior margin of the segment ( Figs 19A , 21F ); this and all middorsal spines on following segments with finely serrated lateral edges. Sensory spots present in subdorsal, midlateral and ventromedial positions ( Figs 19 A–B, 21F); midlateral and ventromedial sensory spots considerably smaller than all other sensory spots in the species, but they occur consistently in all examined specimens. Glandular cell outlets type 1 present in subdorsal and ventromedial positions ( Figs 19 A–B, 20E). Pectinate fringe of posterior segment margin with long fringe tips from middorsal to ventromedial positions, and with only slightly shorter tips between ventromedial positions. Pachycycli and cuticular hairs as on preceding segment.

Segment 5 with short acicular spine in middorsal position ( Figs 19A , 21F ), not reaching the posterior margin of the segment, and long, slender tubes in lateroventral positions ( Figs 19B , 20E , 21H ). Sensory spots present in subdorsal, midlateral and ventromedial positions ( Figs 19 A–B, 21F). Pectinate fringe of posterior segment margin with equally long fringe tips around the segment. Glandular cell outlets type 1, pachycycli, and cuticular hairs as on preceding segment.

Segment 6 with short acicular spines in middorsal and lateroventral positions ( Figs 19 A–B, 20E, 21F, H), not reaching the posterior margin of the segment; lateral edges of lateroventral spines on this following segments with stronger serration. Sensory spots present in paradorsal, subdorsal, midlateral and ventromedial positions ( Figs 19 A–B, 21F, H). Glandular cell outlets type 1, pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 7 with short acicular spines in middorsal and lateroventral positions ( Figs 19 A–B, 20D–E, 21H), barely or just reaching the posterior margin of the segment. Females with female papillae in ventrolateral positions ( Figs 19B , 20E, G , 21H ); openings of papillae with fine fringes around their margins ( Fig. 21H ); intracuticular substructures each form an indistinct crescentic structure, but without a clearly visible protuberance in the curved part ( Fig. 20G ). Sensory spots, glandular cell outlets type 1, pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 8 with short acicular spines in middorsal and lateroventral positions ( Figs 19 A–B, 20D, F–G), barely or just reaching the posterior margin of the segment. Minute glandular cell outlets type 2 present in midlateral positions ( Figs 19A , 20F , 21G ), but very close to the laterodorsal areas. Sensory spots present in paradorsal, subdorsal and midlateral (posterior to glandular cell outlets) positions ( Figs 19 A– B, 21G). Females with female papillae in ventromedial positions ( Figs 19B , 20G , 21H ); openings of papillae form short tubes with fine fringes around their margins ( Fig. 21H ); intracuticular substructures each form a very short tubular or rhomboid structure ( Fig. 20G ). Glandular cell outlets type 1 as on preceding segment, but subdorsal ones are situated slightly closer to each other. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 9 with acicular spines in lateroventral positions ( Figs 19B , 21G ), just reaching the posterior margin of the segment. Sensory spots present in paradorsal, subdorsal, laterodorsal, and ventrolateral positions ( Figs 19 A–B, 21G). Female papillae absent. Glandular cell outlets type 1 as on preceding segment, but with subdorsal ones situated even closer to each other, very close to paradorsal positions. Small, rounded nephridial sieve plates present in lateral accessory positions. Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 10 with long, slender midlateral tubes near posterior segment margin ( Figs 19 , 20 H–J, 21I, K). Sensory spots present in subdorsal (but close to paradorsal) and ventrolateral positions ( Figs 19 , 21 I–K); ventrolateral sensory spots are present in both sexes, but differ in appearance and longitudinal position: male sensory spots resemble other sensory spots, and are positioned about ¼ from the posterior segment margin, in the posterior limit of the hair covering ( Figs 19D , 21J ); female sensory spots are more elongate, have less but longer micropapillae, and are located at the posterior segment margin ( Figs 19B , 21K ). Glandular cell outlets type 1 present as two longitudinally arranged middorsal ones and in ventromedial positions. The posterior segment margin of the tergal plate is straight, whereas margins of sternal plates are concave and extend midventrally into a point that almost reaches the posterior margin of the terminal segment ( Fig. 21 J–K); fringe tips of pectinate fringe are considerably shorter than those on preceding segments. Cuticular hairs as on preceding segments from middorsal to ventromedial positions, but the paraventral areas are only covered by very thin and delicate, non-bracteate, hair-like extensions. Pachycycli as on preceding segment.

Segment 11 with lateral terminal spines ( Figs 19 A–B, 20A, 21I). Males with three pairs of penile spines ( Figs 19 C–D, 20H, 21J); dorsal and ventral penile spines are thin, flexible tubes, whereas the median ones are slightly thicker, conical, and more rigid; females with short, thin lateral terminal accessory spines ( Figs 19 A–B, 20I–J, 21I–K). Two pairs of sensory spots present in subdorsal positions and one pair in ventrolateral positions ( Figs 19 , 21I ); one pair of subdorsal sensory spots medially on segment, other pair at posterior margin. A single, oval glandular cell outlets type 1 is present in middorsal position, anterior on segment. The dorsal side of the segment is densely covered with non-bracteate hair-like extensions; ventral side has hair-like extensions in paraventral areas, and as a dense covering along the posterior margins of the sternal plates. Tergal extensions are well-spaced, short and pointed ( Figs 19 , 20 H–J, 21I–K); sternal extensions short, with ventrolateral seta-like tuft of extended fringe tips ( Figs 19 , 21 J–K).

Notes on distribution and habitat

The species was found at numerous localities around the Korean Peninsula, at Jeju Island in the Korea Strait, at Dokdo/Takeshima Islands, Korean East Sea/Sea of Japan, and in northern Japan (around Hokkaido Island and the northernmost area of Honshu Island), suggesting that it has a pan-KoreanJapanese distribution. It is noteworthy that it apparently is highly opportunistic in its habitat choice, and often can be found associated with growth on macroinvertebrates and on macroalgae, as well as in mud, sand and mixed sediments.

Figures

Fig. 19. Line art illustrations of Echinoderes songae Sørensen & Chang sp. nov. A. Female, dorsal view. B. Female, ventral view. C. Segments 10 to 11 in male, dorsal view. D. Segments 10 to 11 in male, ventral view.

Fig. 20. Light micrographs showing overviews and details of Echinoderes songae Sørensen & Chang sp. nov. A–B, E–G, I–J. Holotype, ♀ (NHMD-662101). C. Paratype, ♀ (NHMD-662102). D. Paratype, ♀ (NHMD-662103). H. Paratype, ♂ (NHMD-662104). A. Ventral overview. B. Segments 1 to 3, dorsal view. C. Segments 1 to 3, ventral view. D. Segments 7 to 9, dorsal view. E. Segments 4 to 7, ventral view, showing female sexual dimorphism. F. Segments 8 to 9, dorsal view. G. Segments 7 to 8, ventral view, showing female sexual dimorphism. H. Segments 10 to 11, ventral view, showing male sexual dimorphism. I. Segments 10 to 11, dorsal view, showing female sexual dimorphism. J. Segments 10 to 11, ventral view, showing female sexual dimorphism.

Fig. 21. Scanning electron micrographs showing overviews and details ofEchinoderes songae Sørensen & Chang sp. nov. A–B, D, F–I, K. ♀ (MVS, personal reference collection). C, E, J. ♂ (MVS, personal reference collection). A. Lateroventral overview. B. Introvert sectors 5 and 4 (laterodorsal). C. Segments 1 to 3, dorsal view. D. Segments 1 to 2, laterodorsal view. E. Segments 1 to 2, ventral view. F. Segments 4 to 6, laterodorsal view. G. Segments 8 to 9, lateral view; inset show glandular cell outlets type 2. H. Segments 5 to 8, ventral view, showing female sexual dimorphism; insets show outlets of female papillae on segment 7 (upper inset) and segment 8 (lower inset), scale on insets = 1 µm. I. Segments 10 to 11, dorsal view, showing female sexual dimorphism. J. Segments 10 to 11 ventral view, showing male sexual dimorphism. K. Segments 10 to 11 ventral view, showing female sexual dimorphism.

Fig. 13. Diagram of mouth cone (grey area), introvert and placids in Echinoderes sensibilis Adrianov et al., 2002, showing distribution of inner oral styles (full circles), outer oral styles (diamonds), primary scalids (triangles), spinoscalids (thick open circles) and trichoscalids (stars), with positions of trichoscalid plates and placids indicated. Table shows the scalid arrangement by sector; single-lined boxes mark quincunxes, double-lined boxes mark ‘double diamonds’.