Pseudechiniscus dastychi Roszkowska & Grobys & Bartylak & Gawlak & Kmita & Kepel & Kepel & Parnikoza & Kaczmarek 2020, sp. nov.

2. Pseudechiniscus dastychi sp. nov. Roszkowska, Grobys, Bartylak & Kaczmarek

(Table 3, Figs 1, 5–6)

Pseudechiniscus suillus (Ehrenberg, 1853) (Dastych (1984)

Pseudechiniscus sp. 2 (Grobys et al. 2020)

Material examined: 80 animals (holotype and 79 paratypes, all females) mounted on microscope slides in Hoyer’s medium, 40 animals prepared for SEM and 7 prepared for barcoding.

Description

Animals (measurements and statistics in Table 3)

Females. Body (Fig. 5) orange in living specimens (transparent after mounting on slides), black eyes present after mounting on slides. Apart from the head appendages (cirri interni and externi and elongated cephalic papillae [secondary clavae]), only lateral cirrus A present (with finger-like clavae near the base [primary clava]) (Fig. 5 A–B,D). Cephalic papillae smaller than clavae.

Dorsal plates with small hemispherical granules/upper ends of cuticular pillars (dots in PCM) 0.5–1.2 μm in diameter, densely (spaces between granules 0.5–0.8 μm) and uniformly distributed and joined by thin striae forming indistinct hexagonal pattern (which are in fact thin stripes positioned under epicuticle) (Fig. 5A). Granules/upper ends of cuticular pillars slightly larger in the anterior and posterior parts of the plates.

Dorsal plates typical for the genus Pseudechiniscus (cephalic plate (cp), neck plate (np), scapular plate (scp), median plates (m1, m2, m3), paired segmental plates I and II (s1, s2), pseudosegmental plate (psp) and the caudal plate (cap), see also Dorsal and ventral plates and sculpture in Grobys et al. (2020)) well developed. The cp with Wshaped pattern divided into five parts (Fig. 6A, filled arrowhead). The scp divided by transversal fold which forms a long narrow stripe in posterior part of the plate. This narrow stripe is often divided by three longitudinal folds forming four plate parts/subplates (Fig. 5A). The entire scp divided by median longitudinal fold into two parts (Fig. 5 A–B, empty arrow). Additionally, lateral portions of the scp appear detached from the dorsal plate, forming small plate-like structures separated from the scp by a thin bright stripe. Plates m1 and m2 divided in two portions by transverse fold, plate m3 undivided (Fig. 5 A–B, filled indented arrowheads). Laterally to the median plates, lateral intersegmental plates (lip) present. The psp divided by a longitudinal fold. Posterior margin of the psp straight, i.e. without projections, teeth or spines (Fig. 5 A–B, empty indented arrowhead). The cap concave with two Y-shaped bifurcated ridges (Fig. 5 A–B, filled arrowhead). Ventral cuticle with tiny granulation (formed by dense granules/upper ends of cuticular pillars, 0.1–0.4 μm) forming unique pattern (Figs 1, 5 C–D, 6B). Ventral PGs present (granula- tion 0.4–0.5 μm in diameter, spaces between granules 0.4–0.5 μm) with configuration PG:I-II-III-IV-V-VI-VII-VIII a (Figs. 1, 5 C–D). The female gonopore with the typical six-petal rosette. (Fig. 5 C–D, asterisks).

The outer cuticle on legs I–III with round patches of granulation (with larger granules but more sparse in the centre and smaller and denser in peripheral parts), on legs IV with uniform, wide stripes of granulation (slightly larger in the centre of these stripes) (Fig. 6 C–D). Triangular spine on leg I and dentate collar on leg IV absent. A finger-like papillae on leg IV present (Fig. 6D, filled arrow). External claws of all legs smooth, internal with spurs directed downwards, identical in legs I–IV (Fig. 6 E–F).

Males. Unknown.

Juveniles. Unknown.

Larvae. Unknown.

DNA sequences

We obtained good quality sequences for the applied molecular markers:

– COI sequence (GenBank: MN528469), 641 bp long;

– ITS-2 sequence (GenBank: MN537865), 452 bp long.

Etymology.

We dedicated this species to the distinguished Polish tardigradologist Dr Hieronymus Dastych, who originally reported specimens of this species from Antarctica as Pse. suillus.

Type locality.

65°14’57.30”S, 64°15’13.20”W, 8 m asl: maritime Antarctic, Argentine Islands, Galindez Island, Carolina Point, Charybda Tover, 15 m from sea, moss (Sanionia georgicouncinata) and lichens (Cladonia sp.), 29.01.2016, coll. Ivan Parnikoza.

Type depositories.

Holotype: slide AT2940/2 and 67 paratypes (slides: AT2940/*, where the asterisk can be substituted by any of the following numbers: 2, 3, 4, 6, 7, 8, 9, 10, 12, 19, 5/S) are deposited at the Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 6, 61-614 Poznań, Poland; 12 paratypes (slides: AT2940/5 and AT2940/18) are deposited at the collection of Binda and Pilato, Museum of the Department of Animal Biology ‘Marcello La Greca’, University of Catania, Italy.

Morphological differential diagnosis*

*only measurements of adult females are used in differential diagnosis

Pseudechiniscus dastychi sp. nov. differs specifically from:

1. Pse. angelusalas sp. nov., by: different ventral pattern (Figs 1, 5 C–D for Pse. dastychi sp. nov. vs Figs 1, 7B for Pse. angelusalas sp. nov.), different ventral PG configuration (PG:I-II-III-IV-V-VI-VII-VIII a in Pse. dastychi sp. nov. vs PG:I-II-III-IV-VI-VIII a in Pse. angelusalas sp. nov.), larger body length (167.0–202.0 μm in Pse. dastychi sp. nov. vs 113.0–143.0 μm in Pse. angelusalas sp. nov.), wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 17.4–20.9 μm in Pse. angelusalas sp. nov.), longer cirri interni (10.4–12.7 μm, [sp=36.9–41.0] in Pse. dastychi sp. nov. vs 6.0–7.3 μm, [sp=34.4–36.6] in Pse. angelusalas sp. nov.), lower sp of cephalic papillae (14.7–16.9 in Pse. dastychi sp. nov. vs 18.3–20.8 in Pse. angelusalas sp. nov.), longer cirri externi (15.9–19.1 μm, [sp=54.7–61.4] in Pse. dastychi sp. nov. vs 9.1–10.4 μm, [sp=49.0–54.3] in Pse. angelusalas sp. nov.), lower sp of clavae (16.4–18.6 in Pse. dastychi sp. nov. vs 22.4–25.7 in Pse. angelusalas sp. nov.), longer cirri A (40.0–45.0 μm in Pse. dastychi sp. nov. vs 24.1–28.0 μm in Pse. angulusalus sp. nov.), longer papillae on leg IV (2.6–3.5 μm in Pse. dastychi sp. nov. vs 2.0–2.4 μm in Pse. angelusalas sp. nov.) and longer claws (see Tables 3 and 4).

2. Pse. beasleyi, by: the scp not divided in the anterior part (the scp divided into four parts in Pse. beasleyi), longer clavae (4.5–5.7 μm in Pse. dastychi sp. nov. vs 3.1–3.9 μm in Pse. beasleyi sp. nov.), longer cephalic papillae (4.2–5.3 μm in Pse. dastychi sp. nov. vs 2.6–3.9 μm in Pse. beasleyi sp. nov.) and longer cirri A (40.0–45.0 μm in Pse. dastychi sp. nov. vs 23.5–31.3 μm in Pse. beasleyi sp. nov.) and different claws length arrangement (shortest claws II and III, and longest claws IV in Pse. dastychi sp. nov. vs shortest claws I and II, and longest claws III and IV in Pse. beasleyi).

3. Pse. chengi, known only from China (Xue et al. 2017), by: dorsal granules joined by striae, plates m1 and m2 divided in two portions by transverse fold (unndivided in Pse. chengi), wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 20.8–25.7 μm in Pse. chengi), longer cephalic papillae (4.2–5.3 μm in Pse. dastychi sp. nov. vs 2.8–3.7 μm in Pse. chegi), longer cirri interni and externi (10.4–12.7 μm and 15.9–19.1 μm respectively in Pse. dastychi sp. nov. vs 3.2–8.5 μm and 10.5–14.2 μm respectively in Pse. chegi), longer cirri A (40.0–45.0 μm [sp=135.2–149.1] in Pse. dastychi sp. nov. vs 21.4–27.5 μm [sp=96.0 –111.1] in Pse. chengi) and higher cirrus A /body length ratio (22–26% in Pse. dastychi sp. nov. vs 13–17% in Pse. chengi).

4. Pse. clavatus, by: different shape of clavae (finger-like in Pse. dastychi sp. nov. vs club-shaped in Pse. clavatus) and normally developed cephalic papillae (reduced in Pse. clavatus).

5. Pse. ehrenbergi sp. nov. see Morphological differential diagnosis of Pse. ehrenbergi sp. nov. above.

6. Pse. facettalis, known from distant localities throughout the world (McInnes 1994). Based on present study, an inaccurate description of this species makes it impossible to differentiate this taxon from Pse. dastychi sp. nov.. See also Morphological differential diagnosis of Pse. suillus and Discussion in the paper by Grobys et al. (2020).

7. Pse. indistinctus sp. nov., by: different ventral pattern (Figs 1, 5 C–D for Pse. dastychi sp. nov. vs Figs 1, 13 C–D for Pse. indistinctus sp. nov.), different ventral PG configuration (PG:I-II-III-IV-V-VI-VII-VIII a in Pse. dastychi sp. nov. vs PG:I-II-III-IV-V-VI-VIII a in Pse. indistinctus sp. nov.), granules on the cap similar in size to other dorsal plates (granules visibly larger on the cap in comparison with other dorsal plates in Pse. indistinctus sp. nov.), larger body size (167.0–202.0 μm in Pse. dastychi sp. nov. vs 140.0–166.0 μm in Pse. indistinctus sp. nov.), wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 20.5–24.9 μm in Pse. indistinctus sp. nov.), longer cirri interni (10.4–12.7 μm in Pse. dastychi sp. nov. vs 7.0–9.2 μm in Pse. indistinctus sp. nov.), longer cirri externi (15.9–19.1 μm in Pse. dastychi sp. nov. vs 11.3–14.4 μm in Pse. indistinctus sp. nov.), lower sp of clavae (16.4–18.6 in Pse. dastychi sp. nov. vs 19.3–22.5 in Pse. indistinctus sp. nov.), longer cirri A (40.0–45.0 μm in Pse. dastychi sp. nov. vs 27.6–34.2 μm in Pse. indistinctus sp. nov.) and longer claws (see Tables 3 and 7).

8. Pse. juanitae, known from Austria, Brazil (type locality), Italy and Galapagos Islands (McInnes 1994). Based on present study, an inaccurate description of this species makes it impossible to differentiate this taxon from Pse. dastychi sp. nov.. See also Morphological differential diagnosis of Pse. suillus and Discussion in the paper by Grobys et al. (2020).

9. Pse. lacyformis sp. nov., by: different ventral pattern (Figs 1, 5 C–D for Pse. dastychi sp. nov. vs Figs 1, 10B for Pse. lacyformis sp. nov.), different ventral PG configuration (PG:I-II-III-IV-V-VI-VII-VIII a in Pse. dastychi sp. nov. vs PG:I-II-III-IV-VI-VIII a in Pse. lacyformis sp. nov.), dorsal granules joined by striae, wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 20.4–26.0 μm in Pse. lacyformis sp. nov.), lower sp of cirri interni (36.9–41.0 in Pse. dastychi sp. nov. vs 48.4–53.9 in Pse. lacyformis sp. nov.), lower sp of cirri externi (54.7–61.4 in Pse. dastychi sp. nov. vs 66.5–77.8 in Pse. lacyformis sp. nov.), lower sp of clavae (16.4–18.6 in Pse. dastychi sp. nov. vs 23.4–26.8 in Pse. lacyformis sp. nov.), longer cirri A (40.0–45.0 μm in Pse. dastychi sp. nov. vs 26.5–35.0 μm in Pse. lacyformis sp. nov.), higher cirrus A /body length ratio (22–26% in Pse. dastychi sp. nov. vs 15–20% in Pse. lacyformis sp. nov.), lower sp of papillae on leg IV (8.9–11.6 in Pse. dastychi sp. nov. vs 14.7–17.2 in Pse. lacyformis sp. nov.), longer spurs on all legs (2.1–2.8 μm in Pse. dastychi sp. nov. vs 1.3–1.7 μm in Pse. lacyformis sp. nov.) and lower spur/branch length ratio of all claws (23–30% in Pse. dastychi sp. nov. vs 15–20% in Pse. lacyformis sp. nov.).

10. Pse. megacephalus, by: different shape of cephalic papillae (elongated in Pse. dastychi sp. nov. vs mushroom-like in Pse. megacephalus), absence of papilliform projection between external buccal cirri and cirri A.

11. Pse. suillus, by: a small papilla-like structure on leg I absent, different ventral pattern (Figs 1, 5 C–D for Pse. dastychi sp. nov. vs Figs 1 herein and 4C–D in Grobys et al. (2020) for Pse. suillus), well-developed ventral patches of granulation, different ventral PG configuration (PG:I-II-III-IV-V-VI-VII-VIIIa in Pse. dastychi sp. nov. vs PG: I-II-III-IV-VI-VIIIg in Pse. suillus), dorsal granules joined by striae, wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 18.8–23.5 μm in Pse. suillus), lower sp of cirri interni (36.9–41.0 in Pse. dastychi sp. nov. vs 44.0– 49.6 in Pse. suillus), lower sp of cephalic papillae (14.7–16.9 in Pse. dastychi sp. nov. vs 19.1–24.3 in Pse. suillus), lower sp of cirri externi (54.7–61.4 in Pse. dastychi sp. nov. vs 62.1–75.0 in Pse. suillus), lower sp of clavae (16.4–18.6 in Pse. dastychi sp. nov. vs 20.9–26.8 in Pse. suillus), higher cirrus A /body length ratio (22–26% in Pse. dastychi sp. nov. vs 17–21% in Pse. suillus), lower sp of papillae on leg IV (8.9–11.6 in Pse. dastychi sp. nov. vs 14.7–18.4 in Pse. suillus) and longer claws (see Table 3 herein and Table 4 in Grobys et al. 2020).

12. Pse. xiai, known only from China (Wang et al. 2018), by: different ventral pattern (Figs 1, 5 C–D for Pse. dastychi sp. nov. vs Figs 1B, F and 2E in Wang et al. (2018) for Pse. xiai), dorsal granules joined by striae, wider scp (27.5–33.0 μm in Pse. dastychi sp. nov. vs 11.3–26.7 μm in Pse. xiai), longer cephalic papillae (4.2–5.3 μm in Pse. dastychi sp. nov. vs 1.4–3.9 μm in Pse. xiai), longer cirri A (40.0–45.0 μm in Pse. dastychi sp. nov. vs 24.7–31.9 μm

in Pse. xiai), and higher cirrus A /body length ratio (22–26% in Pse. dastychi sp. nov. vs 13–16% in Pse. xiai). Genotypic differential diagnosis

The ranges of genetic distances between Pse. dastychi sp. nov. and species of the genus Pseudechiniscus, for which DNA sequences are available in GenBank, are as follows:

COI: 2.0–28.5% (24.0% on average), with the most similar being Pseudechiniscus sp. (KJ857005, Velasco- Castrillón et. al. 2015 (described in GenBank as Echiniscus sp.); for more details see Discussion in Grobys et al. 2020) and the least similar being Pse. aff. suillus (MK804907, Cesari et al., 2020).

ITS-2: 7.7–36.8% (26.5% on average), with the most similar being Pse. ehrenbergi sp. nov. (MN537866, present study) and the least similar being Pse. lacyformis sp. nov. (MN537868, present study).