Echinoderes pilosus Lang, 1949

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 : 32-39

Echinoderes pilosus Lang, 1949

Figs 9–10 ; Tables 9–10

Emended diagnosis

Echinoderes with middorsal spines on segments 4 to 8, and lateroventral spines on segments 6 to 9; all middorsal spines slender and flexible and projecting well beyond the posterior margin of their respective segments. Long and slender tubes present in ventrolateral positions on segment 2, lateroventral positions on segment 5, and in laterodorsal positions on 10. Incomplete midventral, intracuticular fissure present on anterior half of segment 2. Two middorsal, longitudinally aligned glandular cell outlets type on segment 1. Minute glandular cell outlets type 2 in subdorsal positions on segment 2, and in laterodorsal positions on segments 8 and 9. Tergal extensions of segment 11 short and pointed; margin of sternal extensions straight, with ventrolateral seta-like tuft of extended fringe tips. Females with female papillae with tubular substructure in ventrolateral positions on segment 7 and ventromedial positions on segment 8; males with ventrolateral sensory spots on segment 10.

Material examined

Lectotype (here designated)

SOUTH GEORGIA ISLANDS • ♀; Grytviken ; 54°16′59″ S, 36°30′29″ W; 22–23 May 1902; collected during the Swedish Antarctic Expedition in Grytviken; SMNH 3930 . Specimen mounted for LM.

Paralectotypes

SOUTH GEORGE ISLANDS • 15 ♀♀, 18 ♂♂, 3 uncertain sex; same collection data as for lectotype; SMNH-1007 , SMNH-9256 to 9282 . SMNH-1007 , SMNH-9256 to 9282 . 9 ♀♀, 13 ♂♂ and 3 uncertain sex mounted for LM; 6 ♀♀, 5 ♂♂ mounted for SEM ;

Remarks

Higgins (1986) mentions that he accessed the type material of E. pilosus in SMNH , mounted and observed two paratypic specimens. However, such mounted specimens were found in neither the SMNH nor the USNM.

After examining the syntypes and providing the present redescription we choose, in the interest of assuring future taxonomic stability, to designate one of the female syntype as lectotype for Echinoderes pilosus with the catalogue number SMNH-3930, and consequently designate the remaining specimens as paralectotypes (SMNH-1007, 9256–9282).

Description

The species was described by Lang (1949), and more recently redescribed by Higgins (1986). However, since information from SEM not previously has been available for the species, and since the present examinations with LM and SEM resulted in substantial new information about the morphology of the species, we are here providing a full redescription.

Adults with head, neck and eleven trunk segments. The anterior part of the trunk is relatively stout, and maximum width is reached around segments 6 and 7 ( Fig. 9 A–B). From segment 8 the segments taper significantly, giving the species an appearance of a pointed hind end ( Fig. 9 A–B). The trunk cuticle appears thin in SEM specimens ( Fig. 10A ), and tends to collapse posterior to the stronger pachycycli. Secondary pectinate fringe present near anterior segment margin on segments 2 to 10. For complete overview of measurements and dimensions, see Table 9. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, is summarized in Table 10.

The head consists of a retractable mouth cone and an introvert. Inner oral styles could not be examined. Nine outer oral styles are present; nine tufts with ca. six long, rigid and distally bifurcated tips in each, attach basally on the mouth cone, posterior to each outer oral style. The exact arrangement of scalids could not be examined.

The neck has 16 placids, measuring 19 µm in length. The midventral placid is broadest, measuring 17 µm in width at its base, whereas all other are narrower, measuring 10 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 medially on segment, in ventromedial positions ( Figs 9C , 10 B–C); sensory spots on this all following segments are small, and rounded, with numerous micropapillae. Two longitudinally arranged glandular cell outlets type 1 are present in middorsal position ( Figs 9C , 10B ); anteriormost outlet appears narrower and more elongate than the posterior one; an additional pair of glandular cell outlets type 1 is present in ventrolateral positions ( Fig. 10C ). Dorsal and lateral sides, with scattered cuticular hairs emerging through rounded perforation sites; posterior half of ventral side with similar hair covering, but anterior part with large, W-shaped hairless area ( Fig. 10 B–C). The posterior segment margin is straight along the dorsal and lateral sides, and slightly convex ventrally, terminating into a pectinate fringe with short and very flexible fringe tips. Pachycyclus thin to medium thickness, and not interrupted.

Segment 2 consists of a complete cuticular ring, but with indication of an intracuticular, partial, midventral fissure ( Figs 9F , 10C ). Sensory spots are located in middorsal (but slightly laterally displaced), laterodorsal (twin pair) ( Figs 9E , 10B ) and ventromedial positions ( Fig. 10C ). Minute glandular cell outlets type 2 present in subdorsal positions ( Figs 9C , 10B ), and tubes present in ventrolateral positions ( Figs 9D , 10C ). Glandular cell outlets type 1 present in middorsal and ventromedial positions ( Figs 9 C– D, 10B). The segment is densely covered with bracteate hairs, but interrupted by hairless areas posterior to ventrolateral tubes, and in paraventral areas. Pachycyclus of the anterior segment margin is of medium thickness and not interrupted. The posterior segment margin is straight along dorsal and lateral sides, and extend into V-shaped flap on the ventral side; pectinate fringe from middorsal to midlateral positions with short fringe tips, as on segment 1; fringe tips from midlateral to ventromedial positions longer and very flexible, and then very short 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 ( Figs 9E , 10D ) and sublateral positions. Glandular cell outlets type 1 present in middorsal ( Fig. 9E, H ) and ventromedial positions. Bracteate cuticular hairs are densely covering the segment from middorsal to ventromedial positions (except in V-shaped areas in laterodorsal positions anterior on segment); paraventral areas that are devoid of any hair-like structures. Pectinate fringe of posterior margin as on preceding segment, but with ventromedial fringe tips being slightly longer.

Segment 4 with acicular spine in middorsal position, reaching attachment point of middorsal spine on following segment ( Fig. 10D ); this and all other spines on following five segments are slender and flexible. Sensory spots present in subdorsal ( Figs 9H , 10D ), midlateral and ventromedial positions; midlateral and ventromedial sensory spots considerably smaller than most other sensory spots in the species, but they occur consistently in all examined specimens. Glandular cell outlets type 1 present in subdorsal ( Fig. 9H ) and ventromedial positions. Pectinate fringe of posterior segment margin, pachycycli and cuticular hairs as on preceding segment.

Segment 5 with acicular spine in middorsal position, reaching attachment point of middorsal spine on following segment, and long, slender tubes in lateroventral positions ( Fig. 10E ). Sensory spots present in subdorsal, midlateral ( Figs 9H , 10E ) and ventromedial positions; ventromedial sensory spots considerably smaller than most other sensory spots in the species. Glandular cell outlets type 1, pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 6 with acicular spine in middorsal position, reaching attachment point of middorsal spine on following segment, and in lateroventral positions ( Fig. 10 E–F), reaching beyond the posterior margin of the segment. Females with female papillae in ventrolateral positions; openings of papillae with fine fringes around their margins ( Fig. 10F inset); intracuticular substructures each form an indistinct tubular structure ( Fig. 9G ). Sensory spots present in paradorsal, midlateral and ventromedial ( Fig. 10F ) positions. Pectinate fringe of posterior segment margin with uniform long fringe tips on tergal plate and on most lateral halves of sternal plates; fringe tips shorter between ventromedial positions. Glandular cell outlets type 1, pachycycli and cuticular hairs as on preceding segment.

Segment 7 with acicular spine in middorsal position, extending about halfway over the following segment, and in lateroventral positions, reaching beyond the posterior margin of the segment. Female papillae ( Figs 9G, J , 10F, I ), sensory spots, glandular cell outlets type 1, pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 8 with acicular spine in middorsal position, extending more than halfway over the following segment ( Fig. 10G ), and in lateroventral positions ( Fig. 9J ), reaching beyond the posterior margin of the segment ( Fig. 10I ). Minute glandular cell outlets type 2 present in laterodorsal positions ( Figs 9L , 10H ). Sensory spots present in paradorsal, laterodorsal (posterior to glandular cell outlets) and ventrolateral positions ( Fig. 10 G–I). Females with female papillae in ventromedial positions ( Figs 9J , 10I ); openings of papillae with fine fringes around their margins ( Fig. 10I inset); intracuticular substructures each form an indistinct tubular structure. Glandular cell outlets type 1 as on preceding segment, but subdorsal ones are situated slightly closer to each other ( Fig. 9I ). Pachycycli, pectinate fringe of posterior margin and cuticular hairs as on preceding segment.

Segment 9 with acicular spines in lateroventral positions, extending about halfway over the following segment. Minute glandular cell outlets type 2 present in laterodorsal positions ( Figs 9L , 10H ). Sensory spots present in paradorsal, subdorsal, laterodorsal ( Fig. 10 G–H), and ventrolateral positions. 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 laterodorsal tubes near posterior segment margin ( Figs 9M , 10J, L ). Sensory spots present in paradorsal positions ( Fig. 10J ); males with additional pair of sensory spots in ventrolateral positions ( Fig. 10K ). 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 into a midventral point ( Fig. 10K ); fringe tips of pectinate fringe are as on preceding segment on tergal plate, but considerably shorter on sternal plates. Cuticular hairs as on preceding segments on tergal plates, but more sparse on sternal plates. Pachycycli as on preceding segment.

Segment 11 with lateral terminal spines ( Fig. 9B, K, M ). Males with three pairs of penile spines ( Figs 9M , 10K ); dorsal and ventral penile spines are stout but still flexible tubes, whereas the median ones are slightly thicker and more rigid; females with short, and relatively stout lateral terminal accessory spines ( Figs 9K , 10J, L ). Sensory spots present in subdorsal positions medially on segment. Two longitudinally arranged glandular cell outlets type 1 present in middorsal position, anterior on segment. The dorsal side of the segment is sparsely covered with thin, non-bracteate hair-like extensions; ventral side is almost hair-less. Tergal extensions are well-spaced, short and pointed; sternal extensions short, with ventrolateral seta-like tuft of extended fringe tips ( Fig. 10 K–L).

Figures

Fig. 9. Light micrographs showing overviews and details of Echinoderes pilosus Lang, 1949. A–B, G–L. Lectotype, ♀ (SMNH-3930a). C–F, M. Paralectotype, ♂ (SMNH-3930b). A. Dorsal overview. B. Ventral overview. C. Segments 1 to 2, dorsal view. D. Segments 1 to 2, ventral view. E. Segments 1 to 3, dorsal view. F. Segments 2 to 4, ventral view. G. Segments 6 to 7, ventral view, showing female sexual dimorphism. H. Segments 3 to 5, dorsal view. I. Segments 8 to 9, dorsal view. J. Segments 7 to 8, ventral view, showing female sexual dimorphism. K. Segments 10 to 11, ventrolateral view, showing female sexual dimorphism.L. Segments 8 to 9, dorsal view but deeper focal plane than (I). M. Segments 10 to 11, ventral view, showing male sexual dimorphism.

Fig. 10. Scanning electron micrographs showing overviews and details of Echinoderes pilosus Lang, 1949. A–J, L. ♀ (SMNH-9262, SMNH-9281). K.♂ (SMNH-9262). A. Lateral overview. B. Segments 1 to 2, dorsal view. C. Segments 1 to 2, ventral view. D. Segments 3 to 4, dorsal view. E. Segments 5 to 6, lateral view. F. Segments 6 to 7, ventral view, showing female sexual dimorphism; inset shows ventrolateral female papilla on segment 6, scale on inset = 1 µm. G. Segments 8 to 9, dorsal view. H. Segments 8 to 9, laterodorsal view. I. Segments 7 to 8, ventral view, showing female sexual dimorphism; inset shows ventromedial female papilla on segment 8, scale on inset = 2 µm. J. Segments 10 to 11 dorsal view, showing female sexual dimorphism. K. Segments 10 to 11 ventral view, showing male sexual dimorphism. L. Segments 10 to 11 ventral view, showing female sexual dimorphism.