Setaphyes elenae, Cepeda & González-Casarrubios & Sánchez & Pardos, 2020

Cepeda, Diego, González-Casarrubios, Alberto, Sánchez, Nuria & Pardos, Fernando, 2020, Setaphyes elenae sp. nov., a new species of mud dragon (Kinorhyncha: Allomalorhagida) from Skagerrak (north-eastern Atlantic Ocean), European Journal of Taxonomy 637, pp. 1-15 : 4-11

Setaphyes elenae sp. nov.

urn:lsid:zoobank.org:act:6C4FE50F-E39A-451E-B805-60B709B9B9B4

Figs 2–4 , Tables 1–3

Diagnosis

Setaphyes with shortened, distally rounded middorsal processes on segments 1 and 9, and middorsal elevations on segments 2–9, superficially covered by tufts of elongated, thick hairs whose tips sometimes surpass the posterior margin of segment. Unpaired setae in paradorsal position on segments 1–9. Laterodorsal setae on segments 3, 5, 7 and 9; paralateral setae absent. Lateroventral setae on segments 2–10. Ventromedial setae on segments 3, 5 and 7. Paired, small, dot-shaped intracuticular structures (maybe outlets of glandular cells) present in several positions throughout the trunk, with a specific arrangement that differs from males to females. Males with paired, sexually dimorphic ventromedial tubes on segment 2, and females with paired, sexually dimorphic ventrolateral setae on segment 2. Lateral terminal spines present, relatively short, slender. Segment 11 retractable into segment 10.

Etymology

The species is dedicated to Ms Elena González, sister of the second author.

Material examined

Holotype

ATLANTIC OCEAN • ♀ adult (mounted in Fluoromount G ®); near Syd-Hällsö Island, Skagerrak ( Fig. 1B ); 58°56.846′ N, 11°4.896′ E; 55–65 m depth; Ulf Jondelius and Fredrik Pleijel leg.; very fine mud; NHMD 655358 .

Paratypes

ATLANTIC OCEAN • 3 adult ♂♂, 2 adult ♀♀ (all mounted in Fluoromount G ®); same collection data as for holotype; NHMD 655359 to 655363 .

Additional non-type material

ATLANTIC OCEAN • 8 specs (four mounted for LM and four mounted for SEM); same collection data as for holotype; Meiofauna Collection UCM.

Description

See Table 1 for measurements and dimensions, Table 2 for summary of cuticular elevation, process, seta, tube, nephridiopore and sensory spot locations, and Table 3 for summary of intracuticular, dot-shaped structure locations.

Head with retractable mouth cone and introvert. The collected specimens were not suitable for head examinations, hence data on number and arrangement of scalids and oral styles are not available.

Neck with four dorsal and two ventral sclerotized placids ( Fig. 2 A–B, D). Dorsal placids rectangular, with a slightly convex anterior margin; mesial ones broader than lateral ones ( Fig. 2B ). Ventral placids morphologically similar to dorsal ones but much more elongated, getting thinner towards the lateral sides ( Fig. 2A, D ).

Trunk with eleven segments ( Figs 2 A–B, 3A, H, 4A). Segment 1 with one tergal, two episternal and one sub-trapezoidal, midsternal plate; remaining ones with one tergal and two sternal cuticular plates ( Figs 2 A–D, 3A, H). Tergal cuticular plates slightly bulging middorsally. Sternal plates reach their maximum width at segment 5, but are almost constant in width across the trunk, slightly tapering at the last three trunk segments ( Figs 2 A–B, 3A, H). Sternal cuticular plates are relatively narrow in the ratio maximum width to total trunk length (MSW-5: TL average ratio = 27.2%), giving the animal a slender appearance ( Figs 2 A–B, 3A, H, 4A). Middorsal processes on segments 1 and 9, shortened and distally rounded ( Figs 2B , 3B, M , 4G, I); middorsal elevations on segments 2–8, pentagonally-shaped, distally rounded, with intracuticular, butterfly-like atria of paradorsal sensory spots ( Figs 2B , 3D, F, I, K , 4B, E). Middorsal elevations superficially covered by tufts of elongated, thick cuticular hairs whose tips sometimes surpass the posterior margin of the segments ( Fig. 4B, E ). Intracuticular, minute, dot-shaped, rounded to oval structures (maybe outlets of glandular cells) throughout the cuticle on segments 1–10 ( Figs 2 A–D, 3B–G, I–N). Location and pairs of these structures per segment differ from males to females ( Table 3), and deviations from the bilateral symmetry of their arrangement have been observed in some specimens. Up to three pairs of conspicuous laterodorsal cuticular ridges on segments 2–10 ( Figs 2 A– B, 3D–G, I–N). Cuticular hairs acicular, elongated, emerging from oval perforation sites, distributed all over the trunk cuticle. Pachycycli and ball-and-socket joints only conspicuous on segments 2–3, reduced on posterior segments ( Fig. 2 A–B, D). Apodemes on segments 7–10 ( Fig. 2 A–C). Primary pectinate fringe finely serrated; secondary pectinate fringe as a double tranverse, hairy-like, wavy row; free flaps covering the anterior part of subsequent segment ( Figs 2 A–D, 4D). Muscular scars as rounded to oval, hairless areas in laterodorsal and ventromedial positions on segments 1–10 (those of segment 1 in subdorsal and ventrolateral positions), quite inconspicuous ( Fig. 2 A–D).

Segment 1 with shortened, distally rounded middorsal process still extending beyond the posterior margin of segment ( Figs 2B , 3B , 4G). Anterolateral margins of the tergal plate as horn-shaped, short, wide, distally curved and pointed extensions ( Figs 2 A–B, D, 3A–C, H, 4A). Anterior margin of segment with a reticule-like ornamentation dorsally ( Figs 2B , 3B , 4C). Setae absent. Two pairs of sensory spots

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in ventrolateral position longitudinally arranged, and one pair in paradorsal, subdorsal and laterodorsal positions ( Figs 2 A–B, D, 3B–C, 4G). Sensory spots on this and subsequent segments as oval areas with several rows of cuticular micropapillae surrounding a single pore ( Fig. 4B, G, J ).

Segment 2 with middorsal elevation not projecting beyond the posterior margin of segment ( Figs 2B , 3D , 4E). Unpaired seta in paradorsal position, on this and following segments indifferently located to the right or to the left of the middorsal cuticular specialization, not following any particular pattern, near the anterior margin of the segment ( Figs 2B , 3D , 4E); paired setae in lateroventral position ( Figs 2 A–B, D, 3E); females furthermore with paired, sexually dimorphic setae in ventrolateral position ( Figs 2A , 3E ). Sexually dimorphic male tubes in ventromedial position ( Fig. 2D ); detailed morphology of these tubes not determined. Paired sensory spots in paradorsal, laterodorsal and ventrolateral position, the latter near the ventrolateral-ventromedial limit, not longitudinally aligned with the following ventromedial sensory spots ( Figs 2 A–B, D, 3D–E).

Segment 3 with middorsal elevation as on the preceding segment ( Figs 2B , 3F ). Unpaired seta in paradorsal position ( Figs 2B , 3F ); paired setae in laterodorsal, lateroventral and ventromedial positions ( Figs 2 A–B, 3F–G). Paired sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions, the latter mesially shifted compared to the previous ones, aligned with those of the following segments ( Figs 2 A–B, 3F–G).

Segment 4 with middorsal elevation as on the preceding segment ( Figs 2B , 3I , 4B). Unpaired seta in paradorsal position ( Figs 2B , 3I ); paired setae in lateroventral position ( Figs 2 A–B, 3J). Paired sensory spots in paradorsal, subdorsal, laterodorsal and ventromedial positions ( Figs 2 A–B, 3I–J).

Segment 5 similar to segment 3 in the arrangement of the cuticular elevation, setae and sensory spots ( Figs 2 A–B, 4F, H).

Segment 6 similar to segment 4 in the arrangement of the cuticular elevation, setae and sensory spots ( Fig. 2 A–B).

Segment 7 similar to segments 3 and 5 in the arrangement of the cuticular elevation, setae and sensory spots ( Fig. 2 A–B).

Segment 8 with middorsal elevation as on the preceding segment ( Figs 2B , 3K ). Unpaired seta in paradorsal position ( Figs 2B , 3K ); paired setae in lateroventral position ( Fig. 2 A–B). Two pairs of sensory spots in subdorsal position, and one pair in paradorsal, laterodorsal and ventromedial positions ( Figs 2 A–B, 3K–L, 4J).

Segment 9 with middorsal process as that of segment 1 ( Figs 2B , 3M , 4I). Unpaired seta in paradorsal ( Figs 2B and 3M ); paired setae in laterodorsal and lateroventral positions ( Fig. 2 A–B). Two pairs of sensory spots in subdorsal position, and one pair in paradorsal, laterodorsal and ventromedial positions ( Figs 2 A–B, 3M–N, 4I). Nephridiopores in lateroventral position.

Segment 10 without middorsal cuticular specialization. Paired setae in lateroventral position ( Figs 2 A– C, 4I). Two pairs of sensory spots in subdorsal position, and one pair in laterodorsal and ventrolateral positions, the latter near the tergosternal junction ( Figs 2 A–C, 4I).

Segment 11 without cuticular appendages, partly retractable into segment 10 ( Fig. 4A, I ). Tergal plate triangular, with a concave and distally pointed posterior margin; sternal plates form a pair of ventral extensions rounded distally ( Figs 2 A–C, 4I). Males with two sexually dimorphic pairs of stout, thick penile spines ( Fig. 2C ). Lateral terminal spines’ length differs from males (relatively longer, LTS average ratio = 158.93 μm) to females (relatively shorter, LTS average ratio = 100.9 μm)

Figures

Fig. 2 (opposite page). Line art illustrations of adult Setaphyes elenae sp. nov. A. ♀, ventral overview. B. ♀, dorsal overview. C. ♂, segments 10–11, ventral view. D. ♂, segments 1–2, ventral view. Abbreviations: bsj = ball-and-socket joint; dpl = dorsal placid; gcoI = type I glandular cell outlet; ldcr = laterodorsal cuticular ridge; ldse = laterodorsal seta; ldss = laterodorsal sensory spot; lts = lateral terminal spine; lvse = lateroventral seta; mde = middorsal elevation; mdp = middorsal process; ms = muscular scar; pdse = paradorsal seta; pdss = paradorsal sensory spot; ppf = primary pectinate fringe; ps = penil spine; pvap = paraventral apodeme; sdss = subdorsal sensory spot; spf = secondary pectinate fringe; vlcr = ventrolateral cuticular ridge; vlse = ventrolateral seta; vlss = ventrolateral sensory spot; vmse = ventromedial seta; vmss = ventromedial sensory spot; vmt = ventromedial tube; vpl = ventral placid. Scale bar = 100 µm

Fig. 3 (opposite page). Light micrographs showing trunk overviews and details of cuticular trunk characters of ♀, holotype (NHMD 655358) (A–L, N) and ♂, paratype (NHMD 655361) (M) of Setaphyes elenae sp. nov. A. Dorsal overview. B. Dorsal view on right half of segment 1. C. Ventral view on left half of segment 1. D. Dorsal view on right half of segment 2. E. Ventral view on left half of segment 2. F. Dorsal view on right half of segment 3. G. Ventral view on left half of segment 3. H. Ventral overview. I. Dorsal view on right half of segment 4. J. Ventral view on left half of segment 4. K. Dorsal view on right half of segment 8. L. Ventral view on left half of segment 8. M. Dorsal view on right half of segment 9. N. Ventral view on left half of segment 9. Abbreviations: ldse = laterodorsal seta; lts = lateral terminal spine; lvse = lateroventral seta; mde = middorsal elevation; mdp = middorsal process; pdse = paradorsal seta; vlse = ventrolateral seta; vmse = ventromedial seta. Numbers after abreviations indicate correspong segment; sensory spots are marked as dashed circles, and glandular cell outlets as continuous circles. Scale bars: A, H = 100 µm; B–G, I–N = 20 µm.

Fig. 4. Scanning electron micrographs showing general overview and details of the cuticular trunk morphology of a non-type specimen of Setaphyes elenae sp. nov. A. Dorsal overview. B. Middorsal elevation of segment 4. C. Cuticular ornamentation of anterior margin of segment 1. D. Detail of primary and secondary pectinate fringes of segment 5. E. Middorsal to paradorsal view of segment 2. F. Laterodorsal seta of segment 5. G. Middorsal process of segment 1. H. Ventral view of segments 4–5. I. Dorsal view of segment 10. J. Subdorsal sensory spots of segment 8. Abbreviations: mde = middorsal elevation; mdp = middorsal process; pdse = paradorsal seta; ppf = primary pectinate fringe; s = segment; vmse = ventromedial seta. Numbers after abbreviations indicate corresponding segment; sensory spots are marked as dashed circles. Scale bars: A = 100 µm; B, D, F–G, J = 1 µm; C, E, H–I = 10 µm.

Fig. 1. A. Map showing the sampling area of Syd-Hällsö Island (Strömstad, Sweden). B. Detail. Red point shows the specific sampling point.

Tables

Table 1. Measurements of nine adult specimens of Setaphyes elenae sp. nov. (four males and five females) from Skagerrak. Abbreviations: LTS = lateral terminal spines; MSW = maximum sternal width (measured at segment 5); S = segments’ length (followed by number of corresponding segment); Sd = standard deviation; SSW = standard sternal width (measured at segment 10); TL = total length.

Character	Range ♀	Mean ♀	Range ♂	Mean ♂	Total range	Total mean	Sd
TL (µm)	612.67–722.64	679.192	614.32–647.86	625.51	612.67–722.64	655.33	44.06
MSW–5 (µm)	179.55–188.89	183.422	168.06–176.25	170.72	168.06–188.89	177.78	7.61
MSW–5/TL (%)	26–29.5	27	26.2–28.4	27.3	26–29.5	27.2	1.22
SSW (µm)	141.41–152.44	144.178	124.68–133.65	131.065	124.68–152.44	138.35	8.23
SSW/TL (%)	19.7–23	21.3	19.2–21.9	21	19.2–23	21.1	1.14
S1 (µm)	87.74–108.41	96.584	89.16–96.28	91.548	87.74–108.41	94.35	6.31
S2 (µm)	59.74–82.08	69.712	62.45–68.07	65.068	59.74–82.08	67.65	6.42
S3 (µm)	57.56–79.22	70.068	63.54–68.8	66.655	57.56–79.22	68.55	6.04
S4 (µm)	70.27–79.51	74.618	68.79–81.68	74.51	68.79–81.68	74.57	4.48
S5 (µm)	69.77–83.01	77.1	69.3–76.08	74.438	69.3–83.01	75.92	5.84
S6 (µm)	73.96–81.58	78.504	73.81–83.53	77.013	73.81–83.53	77.84	3.51
S7 (µm)	74.47–85.94	80.752	73.33–80.37	75.385	73.33–85.94	78.37	4.70
S8 (µm)	69.57–86.82	80.846	77.08–79.98	78.138	69.57–86.82	79.64	5.31
S9 (µm)	70.24–84.44	79.61	68.76–78.56	74.463	68.76–84.44	77.32	5.43
S10 (µm)	64.87–77.97	73.66	60.93–71.98	67.165	60.93–77.97	70.77	5.92
S11 (µm)	27.93–39.81	32.3	27.49–34.23	30.615	27.49–39.81	31.55	3.74
LTS (µm)	90.64–105.7	100.9	149.06–168.74	158.928	90.64–168.74	126.69	31.29
LTS/TL (%)	13.9–15.8	14.9	24–26	25.4	13.9–26	19.6	5.60