Echiniscus pardalis, Degma & Schill, 2015

Degma, Peter & Schill, Ralph Oliver, 2015, Echiniscus pardalis n. sp., a new species of Tardigrada (Heterotardigrada, Echiniscidae, arctomys group) from the Parco Naturale delle Alpi Marittime (NW Italy), Zoosystema 37 (1), pp. 239-249 : 241-244

Echiniscus pardalis n. sp.

( Figs 1-4 ; Tables 1-3)

TYPE LOCALITY. — North-western Italy, Maritime Alps, Parco Naturale delle Alpi Marittime, EDIT ATBI +M focal site 2a – Vallone di Brocan valley, about 1100 m SE of the hydroelectric dam of Lago del Chiotas, GPS position 44°09’44.9”N 07°20’36.9”- 07°20’37.7”E, 2063-2064 m asl.

TYPE MATERIAL. — Holotype: from moss sample ( Polytrichum piliferum Hedw. ) on a rock, GPS position 44°09’44.9”N 07°20’37.7”E, position accuracy ± 27 m, 2063 m asl., collected 05.VIII.2007, leg. R. Schill (slide with the label “# 71c, 9449 377”). Paratypes: 6 specimens from same sample as the holotype (3 paratypes on slide “# 71a, 9449 377” and 3 paratypes on slide “# 71b, 9449 377”) and 5 specimens from another moss sample from a rock, GPS position 44°09’44.9”N 07°20’36.9”E, position accuracy ± 27 m, 2064 m asl, 05.VIII.2007, leg. R. Schill (3 paratypes on slide “# 70a, 9449 369” and 2 paratypes on slide “# 70c, 9449 369”).

TYPE DEPOSITORIES. — The type material is deposited in the collection of Roberto Bertolani (Department of Life Sciences, University of Modena and Reggio Emilia, Italy – holotype and 5 paratypes on slides “70a” and “70c”) and in the collection of Maria Grazia Binda & Giovanni Pilato (Department of Animal Biology “Marcello La Greca”, University of Catania, Italy – 6 paratypes on slides “71a” and “71b”).

ETYMOLOGY. — The species name refers to the similarity of the subsurface dorsal plates pattern (when observed using 100× PhC) to a leopard’s spots.

DIAGNOSIS

Echiniscus species with lateral cirri in position A, shorter than half of body length. Other appendages absent with the exceptions of cephalic cirri, clava and sensorial papilla on hind legs. All dorso-lateral plates undivided and without facetation. Each lateral side of median plates 1 and 2 with joined lateral platelet visible in small specimens. Median plate 3 and ventral plates absent. Surface of cuticular plates (with the exception of the neck plate, leg plates and lateral platelets) with flat polygonal tubercles arranged in the manner of tiling. Narrow space between individual tubercles with a crown of shallow dimples. Unequal sparse deep pores irregularly distributed on plates. Under the cuticle surface, the perimeter of each tubercle is reinforced by a rosette of cuticular pillars, visible as dark spots (in PhC) and forming a pattern resembling that of a leopard (sometimes also their interior with several pillars, especially under larger tubercles). Spine or papilla absent on the first three pairs of legs. Papilla and dentate collar present on hind legs. All internal claws with well developed protruding spur.

DESCRIPTION OF THE HOLOTYPE

Adult female, orientated ventro-laterally. Body of prepared holotype indistinctly reddish and without visible eye spots, 258.1 Μm long ( Fig. 1 ).

Internal cephalic cirrus 11.9 Μm long (length of cirrophorus 1.9 Μm) and external cephalic cirrus 17.2 Μm long (cirrophorus 1.8 Μm long). Broad cephalic papilla with broadly rounded apex 7.7 Μm long, with basal diameter 3.6 Μm and maximal width 5.4 Μm half-way along its length. Lateral cirrus A in the shape of a filament, 76.6 Μm long (29.7% of body length; its cirrophorus 3.5 Μm long). Clava with rounded apex, 6.8 Μm long, with basal diameter 2.2 Μm and maximal width 2.9 Μm in its basal third ( Fig. 2A, B ). Apart from cirrus A, no other trunk appendages present ( Fig. 1 ).

Dividing line between cephalic plate and neck plate weakly visible in the holotype. Scapular plate 40.4 Μm long and without any ridges ( Fig. 2C ). Segmental paired plates II and III shortest along saggital line. Posterior margin of segmental plate II forming a distinct angle (c. 150°) in its lateral third on both sides, while the posterior margin of segmental plate III is moderately arched ( Fig. 2D, E ). Terminal plate with two postero-lateral incisions, 12.4 Μm long, without facetation and with indistinct depression in central part of plate ( Fig. 2 F-H). Cephalic, neck, scapular, median 1, median 2 and terminal plates undivided. Four narrow lateral platelets apparent, each connected with lateral margin of median plate 1 or median plate 2, but these have faint edges in the holotype ( Fig. 1 ). Median plate 3 ( Figs 1 ; 2 F-H) and ventral plates absent. Anterior and posterior margins of dorso-lateral plates well marked (with the exception of neck plate and lateral platelets), but lateral margins marked only by their sculpture. Similarly, edges of leg plates indistinct in the holotype, especially for the first three pairs of legs ( Fig. 1 ).

Sculpture of surface of plates (with some exceptions described below) consists of simple, rather flat, polygonal (mostly hexagonal) tubercles up to 1.9 Μm in diameter (up to 1.3 Μm on cephalic plate, both median plates 1 and 2 and both segmental plates, up to 1.6 Μm on scapular plate, largest on caudal plate), densely spaced in a manner like tiling. This sculpture has the appearance of a system of dark patches when using a 40 × PhC lens. Similar, but less distinct, sculpture in narrow areas between median plate 1 and segmental paired plate II, between median plate 2 and segmental paired plate III and in area corresponding to median plate 3 ( Fig. 1 ). Only tiny granulation (0.2-0.4 Μm in diameter), instead of tubercles, covers a narrow transverse band on the neck plate just before the scapular plate, the posterior margin and posterior corners of the sculptured field on the cephalic plate, the whole of the lateral platelets (where the granulation is only faint) and the leg plates on outer surface of legs. Anterior notch in the shape of an hourglass on the cephalic plate; rest of neck plate, narrow posterior margins of both median plates 1 and 2 and of segmental paired plate II and wider anterior margins of both segmental paired plates II and III unsculptured ( Figs 1B ; 2A , C-H; 4C).

Deeper focusing an oil immersion 100 × lens on a space separating surface tubercles reveals a crown of round, not perfectly focusable in PhC (apparently just weakly sloped), shallow dimples (0.2-0.5 Μm in diameter) that form a more or less distinct hexagonal pattern around each tubercle ( Fig. 2G, H ). Apart from above mentioned surface sculpture (large tubercles and tiny granulation), there are very irregularly and widely distributed deep pores of different sizes (having an appearance of round or elongated white spots in PhC), up to 1.3 Μm, on the plates with the exception of the leg plates, on which there is a small group of about 5-7 pores on each plate ( Figs 1 ; 4C ). When a 100× PhC oil immersion lens is focused under the surface of the plates, the above-mentioned shallow dimples, as well as deeper pores, disappear and the subsurface structure of each tubercle appears in the form of a rosette of several more or less round and well-focusable dark spots under its perimeter. Some other spots can also be present in a space delimited by the peripheral spots, especially under larger tubercles (about 0.2 Μm in diameter, about 1-10 spots per tubercle, depending on its size) ( Fig. 3 ). These spots are apparently cuticular pillars that reinforce the tubercles internally.Rest of cuticle, including that of ventral body side, has an appearance of tiny, dense and regularly distributed dots not protruding above the cuticle surface (thus formed by cuticular pillars; 0.1-0.2 Μm in diameter) ( Fig. 2B ).

Leg claws well developed, straight in their basal portion, bent in their distal third and thereafter in a fluent arc to their apex ( Fig. 4A, B ). External claws slightly shorter than internal ones, claws on the hind legs longest (external and internal claws on the first pair of legs 11.6 and 12.4 Μm long, respectively, those of fourth pair of legs 13.7 and 15.6 Μm long, respectively). Internal claws of all legs with a well-developed, rather protruding spur orientated downwards (4.1 Μm long on first legs, 4.8 Μm long on hind legs, angle between claw and spur c. 45°), situated at about 2/5 of claw height (spurs of first and fourth pairs of legs respectively 4.4 Μm and 6.8 Μm from base, representing 36% and 44% of claw height respectively) ( Fig. 4A, B ). All external claws without spurs. First three pairs of legs without spine or papilla. Broadly drop-shaped papilla with rounded apex (3.5 Μm long, with maximal width 3.0 Μm) and a dentate collar with 8 and 12 tall triangular sharp teeth of unequal height (1.2-3.5 Μm; each tooth always higher than broad) and unequally spaced (however, the space between adjoining teeth is always shorter than the width of their base) present on fourth pair of legs ( Fig. 4C ).

Eggs unknown.

VARIABILITY

Paratypes similar to the holotype, except the edges of their neck plates and lateral platelets, which are much more distinct in paratypes than in the holotype ( Fig. 4D, E ).

The variability of specimens manifests itself primarily in the arrangement and density of deep pores (perforations) on plates, which is diverse without any common pattern (e.g., pores in Fig. 4E ).

In both the paratypes orientated in a lateral position (slides “70a” and “71b”) lateral continuations of both median plates 1 and 2 are well visible in the form of lateral platelets (one on each side of each median plate 1 and 2) although they fluently join with the rest of cuticle in their lower end, without a distinct margin. Anterior margin of first pair of these lateral platelets is angular ( Fig. 4E ). Similarly, leg plates appear to be well delimited in these laterally orientated paratypes. However, it should be noted that all paratypes have more or less crumpled cuticle around the plates and for this reason it is difficult to decide whether a clearer delimitation of leg plates, as well as lateral platelets, is natural in small specimens (all paratypes are distinctly smaller than the holotype with body length 113.7-183.3 Μm) or if it is instead a consequence of deformations.

Measurements and morphometric indices of the holotype and all paratypes are given in Tables 1-3.

Figures

FIG. 1. — Echiniscus pardalis n. sp., habitus of holotype: A, PhC; B, DIC. Scale bars: 50 μm.

FIG. 2. — Echiniscus pardalis n. sp., holotype: A, cephalic papilla, clava and surface sculpture of cephalic plate (dorso-lateral view), PhC; B, cephalic cirri, ce- phalic papilla and cuticular pillars in ventral cuticle (ventro-lateral view), PhC; C, scapular plate, PhC; D, median plate 1 and segmental plate II (note its angular posterior margin), PhC; E, median plate 2 and segmental plate III, PhC; F, area corresponding to median plate 3 and caudal plate, PhC; G, H, shallow dimples around tubercles on caudal plate; G, PhC; H, DIC. C-F, focused on subsurface structures and posterior body part orientated towards upper side of pictures; G-H, focused on surface of plate. Scale bars: 20 μm.

FIG. 3. — Echiniscus pardalis n. sp., details of subsurface structure of plates, holotype, PhC: A, scapular plate; B, caudal plate. Scale bars: 2 μm.

FIG. 4. — Echiniscus pardalis n. sp.: A, claws of first pair of legs, holotype, PhC; B, claws of hind legs, holotype, PhC; C, papilla and dentate collar on hind legs, holotype, DIC; D, cephalic plate and neck plate (note clear delimitation of neck plate), paratype on slide “71a”, DIC; E, lateral view (note distinct neck plate, an- gular posterior margin of segmental plate II and both lateral platelets with angular anterior margin of the first one; white spots are deep punctures in the cuticle), paratype on slide “71b”, PhC. Scale bars: A-D, 20 μm; E, 40 μm.