Pseudechiniscus suillus, (EHRENBERG, 1853) SENSU

Grobys, Daria, Roszkowska, Milena, Gawlak, Magdalena, Kmita, Hanna, Kepel, Andrzej, Kepel, Marta, Parnikoza, Ivan, Bartylak, Tomasz & Kaczmarek, Łukasz, 2020, High diversity in the Pseudechiniscus suillus-facettalis complex (Heterotardigrada: Echiniscidae) with remarks on the morphology of the genus Pseudechiniscus, Zoological Journal of the Linnean Society 188 (3), pp. 733-752 : 740-741

PSEUDECHINISCUS SUILLUS ( EHRENBERG, 1853) SENSU STRICTO

( TABLE 4, FIGS 3–5 )

Material examined: Forty-five females (neotype and 44 neoparatypes) mounted on microscope slides in Hoyer’s medium, ten females prepared for SEM and 11

females prepared for barcoding (exoskeletons mounted in Hoyer’s medium as vouchers).

Redescription: animals (measurements and statistics in Table 4)

Females: Body ( Fig. 4 ) yellow-orange in living specimens (transparent after mounting), eyes black after mounting. Apart from the head appendages [cirri interni and externi and spherical or slightly elongated cephalic papillae (secondary clava)], only lateral cirrus A present [with finger-like clava near the base (primary clava)] ( Fig. 4A, B ). Cephalic papillae smaller than primary clava.

Dorsal plates with small hemispherical granules/ upper ends of cuticular pillars (dots in LM) 0.3–0.7 μm in diameter, densely (spaces between granules 0.3– 1.1 μm) and uniformly distributed and not joined by striae ( Fig. 5B ). Granules/upper ends of cuticular pillars are slightly larger in the centre of the plates.

Dorsal plates typical for the genus Pseudechiniscus [single 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 ‘Dorsal and ventral plates and sculpture’ above] well developed. The cp facetted (with W-shaped pattern) divided into five parts ( Fig. 4A , empty arrowhead). The scp divided by a transversal fold, which forms a long, narrow stripe in the posterior part of the plate. This narrow stripe is often divided by three longitudinal folds, resulting in four plate parts/subplates ( Fig. 4A, B ). Besides, the entire scp is divided by a median longitudinal fold into two parts ( Fig. 4A, B , empty arrow). Additionally, lateral portions of the scp appear to be detached from the dorsal plate, forming small plate-like structures separated from the scp by a thin, bright stripe ( Fig. 4A ). Plates m1 and m2 are divided in two portions by a transverse fold; plate m3 is undivided ( Fig. 4A, B , filled indented arrowheads). Laterally to the median plates, lateral intersegmental plates (lip) are present. On plates s1 and s2, darker stripes (folds in SEM) are also visible ( Fig. 4A , filled arrow). The psp is divided by a longitudinal fold. Posterior margin of psp is straight, i.e. without projecting teeth or spines ( Fig. 4A, B , empty indented arrowheads). The cap is concave with two Y-shaped bifurcated ridges ( Fig. 4A, B , filled arrowhead). Ventral cuticle with tiny granulation (formed by dense granules/upper ends of cuticular pillars, 0.2–0.4 μm) forming a unique pattern ( Figs 3 , 4C, D , 5C ). Ventral patches of granulation present, but most of them poorly marked and visible sometimes as a smooth areas almost without granulation (if granulation is present it is 0.3–0.5 μm in diameter, spaces between granules 0.2–0.3 μm), with configuration PG:I-II-III-IV-VI-VIII

g

( Figs 3 , 4C, D ). The female gonopore with the typical six-petal rosette ( Fig. 4C, D , asterisks).

The outer cuticle on legs I–III has round patches of granulation (with larger granules but sparser in the centre and smaller and denser in peripheral parts); on legs IV, uniform wide stripes of granulation (slightly larger in the centre of these stripes) ( Fig. 5D–F ). Triangular spine on leg I absent, instead a small papilla-like structure present, but very hardly visible under LM ( Fig. 5A ). Dentate collar on leg IV absent. A finger-like papilla on leg IV present ( Fig. 5E , filled arrow). External claws of all legs smooth, internal with spurs directed downwards ( Fig. 5F ).

Figures

Figure 3. A schematic illustration of ventral patterns of the Pseudechiniscus species presented in this study. PG I–VIII, patches of granulation I–VIII. Scale bars in micrometres (μm).

Figure 4. Pseudechiniscus suillus s.s., female. A, B, dorsal image of the entire animal: empty arrowhead indicates the W-shaped pattern on the cephalic plate (cp); empty arrow indicates a median longitudinal fold dividing scapular plate (scp) into two parts; filled indented arrowheads indicate transverse folds dividing m1 and m2 in two portions; filled arrows indicate stripes (folds) on plates s1 and s2; empty indented arrowheads indicate straight pseudosegmental plate (psp); filled arrowheads indicate notches on caudal plate (cap) (neotype, PCM and neoparatype, SEM respectively). C, D, the characteristic pattern on the ventral side of the body; asterisks indicate female gonopore (neotype, PCM and neoparatype, SEM, respectively). Scale bars in micrometres (μm).

Figure 5. Pseudechiniscus suillus s.s., female. A, front view of the individual (neoparatype, SEM). B, focus on dorsal plates s1 and s2, and m3 with visible upper ends of cuticular pillars (neotype, PCM). C, focus on characteristic pattern on the ventral side of the body above 3rd pair of legs (neoparatype, PCM). D, granulation on leg III (neotype, PCM). E, granulation and papillae (arrow) on leg IV (neotype, PCM). F, claws of leg III (neoparatype, PCM). Scale bars in micrometres (μm).