Introduction

Although the first studies on water bears (Tardigrada) of the Svalbard Archipelago took place as early as in the nineteenth century (Scourfield 1897) and were continued by a number of researchers throughout the twentieth century (e.g. Richters 1903, 1904, 1911; Murray 1907; Marcus 1928; Węglarska 1965; Dastych 1985; Pugh and McInnes 1998; Łagisz 1999), our knowledge about the tardigrade fauna of this region is still relatively poor. The most comprehensive work on Spitsbergen tardigrades (Dastych 1985) provided a complete species list, new records and also investigated the ecology of these microscopic invertebrates. A decade later, Pugh and McInnes (1998) analysed the origin of the Arctic Tardigrada. Other papers were published sporadically, and the majority were limited to reports and descriptions of new species from the Svalbard Archipelago (e.g. Binda et al. 1980; Pilato et al. 1982; Dastych 1983; De Smet et al. 1987, 1988; Pilato and Binda 1987; Van Rompu and De Smet 1988, 1991, 1994; De Smet and Van Rompu 1994; Maucci 1996; Tumanov 2007; Smykla et al. 2011). In the region of Hornsund, studies were previously conducted by Węglarska (1965), Dastych (1985), Maucci (1996), Janiec (1996) and Łagisz (1999). Up to now, only 84 species were recorded from the Svalbard Archipelago, but none specifically from the Revdalen (Coulson 2011).

Here, we provide a list of tardigrades species from the Revdalen, including two new records from the Svalbard Archipelago and descriptions of two species new for science, Bryodelphax parvuspolaris sp. nov. and Isohypsibius coulsoni sp. nov. The genus Bryodelphax consists of only 17 species, but its distribution is global—it has been recorded from the polar regions to tropical rain forests (Kaczmarek and Michalczyk 2004; Kaczmarek et al. 2005; Kristensen et al. 2010; Degma et al. 2011). In contrast, the genus Isohypsibius is one of the largest in the phylum Tardigrada, with more than 130 species and subspecies described from all over the world (McInnes 1994; Degma et al. 2011).

Materials and methods

Moss and lichen samples for this study were collected from the Revdalen and the Rotjesfjellet, which are located on the north coast of Hornsund (Spitsbergen, Svalbard Archipelago; Fig. 1). The total of forty-one moss and lichen samples were collected on the 26th June 2010 from the Revdalen and on the 29th June 2010 from the south-east slopes of the Rotjesfjellet (see Table 1). Twenty-nine (over 70%) of the samples provided a total of 461 specimens and 83 eggs.

Table 1 The list of localities in the Hornsund area, from which samples containing tardigrades were collected
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Fig. 1
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The study area: a Svalbard Archipelago b Hornsund, West Spitsbergen, c Revdalen and Rotjesfjellet (maps from Norsk Polarinstitute)

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All specimens and eggs were mounted on microscopic slides in Hoyer’s medium and then examined and photographed with a Phase Contrast Microscope (PCM). Species were identified using the key to the World Tardigrada (Ramazzotti and Maucci 1983) and original descriptions from the literature.

All measurements are given in micrometres (μm). Structures were measured only if their orientations were suitable. Body length was measured from the anterior to the posterior end of the body, excluding the hind legs. Measurements of the species used in differential diagnoses are given or calculated according to the original descriptions (i.e. Pilato 1972, 1974; Bertolani et al. 1995; Kristensen et al. 2010). Claws of Isohypsibius coulsoni sp. nov. were measured according to Beasley et al. (2008).

In eutardigrades, the pt ratio is the ratio of the length of a given structure to the length of the buccal tube, expressed as a percentage (Pilato 1981). Similarly, to provide relative measurements in echiniscids, the sc ratio of the length of a given structure to the length of the scapular plate is used (e.g. Fontoura and Morais 2011). Both values are always provided in italics, in order to differentiate them from other measurements and ratios.

The configuration of ventral plates in the genus Bryodelphax is described using an analogous system to that used for the description of cuticular gibbosities in some eutardigrades (Michalczyk and Kaczmarek 2010), i.e. a Roman number with a colon at the beginning of the sequence indicates the total number of rows of ventral plates and following Arabic numbers separated by dashes refer to the numbers of plates in each row, starting from the most anterior row.

All the investigated material is preserved in the collection of the first author, at the Department of Animal Taxonomy and Ecology, A. Mickiewicz University, Poznań, Poland.

Results

Taxonomic accounts of the new species found in the study

Bryodelphax parvuspolaris sp. nov. (Figs. 2–8; Table 2)

Material examined Holotype (female) (slide 14.2/20) and 8 paratypes (females) (slides: 14.2/4, 14.2/8, 14.2/9, 14.2/12, 14.2/13, 14.2/14, 14.2/16, 14.2/19).

Description (measurements in Table 2 ) Body (Figs. 2–4) transparent to slightly rose, eyes absent or not visible after the preparation. Apart from the head appendages (cirrus internus and externus and drop-shaped cephalic papillae (secondary clava)), only lateral cirrus A (with clava near the base (primary clava) present).

Table 2 Measurements and sc values of selected morphological structures of nine specimens (including the holotype) from the type population of Bryodelphax parvuspolaris sp. nov.
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Figs. 2–4
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Bryodelphax parvuspolaris sp. nov. habitus. Fig. 2. dorso-lateral view (holotype). Fig. 3. lateral view (paratype). Fig. 4. ventro-lateral view (holotype). Scale in μm, on 3–4 same as on 2

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Dorsal plates covered with fine, but distinct dark dots that appear as granulation under PCM, but are in fact cuticular pillars within cuticle (Michalczyk and Kaczmarek 2006, 2007). “Granulation” distinctly larger on the scapular and the terminal plate. In addition to the “granulation”, slightly larger and irregularly distributed pores are visible mainly on the margins of all dorsal plates (Fig. 5). Scapular plate facetted with a median longitudinal fold and a few smaller transverse folds. Paired plates divided into two unequal anterior and posterior parts by a transverse stripe without “granulation”. Median plates 1 and 2 divided, and median plate 3 undivided. Twelve supplementary plates poorly visible near median plates 1–3. The terminal plate facetted with two longitudinal folds.

Figs. 5–7
figure 5-7

Bryodelphax parvuspolaris sp. nov. Fig. 5. sculpture on the scapular plate. Fig. 6. ventral plates. Fig. 7. claws III. Scale in μm, on 6 same as on 5

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Ventral plates arranged in eight rows: 1 plate in row I (between legs I), 1 plate in row II (between legs I and II), 2 plates in row III (between legs I and II), 2 plates in row IV (between legs II), 2 plates in row V (between legs II and III), 2 plates in row VI (between legs III), 2 plates in row VII (in line with the gonophore) and 1 plate in row VIII (below the gonophore); i.e. the ventral plate configuration VIII:1-1-2-2-2-2-2-1 (Figs 4, 8). All ventral plates with fine and indistinct “granulation” (Fig. 6).

Fig. 8
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Configurations of ventral plates in all known species of the Bryodelphax weglarskae group. Roman numbers indicate the rows in which the ventral plates are arranged

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Spine on legs I and papilla on legs IV absent or not visible under PCM. Collar on legs IV with poorly developed and irregular teeth. External claws of all legs smooth, internal claws with very small spurs directed downwards (Fig. 7).

Eggs unknown.

Remarks In some specimens, ventral plates are indistinct; thus, an examination of at least several specimens to ensure correct identification is strongly recommended.

Etymology The name ‘parvuspolaris’, meaning ‘a small dweller from the polar regions’, was chosen by the participants of the XXXIII Polar Expedition of the Polish Academy of Sciences, who provided us with logistical support and helped collecting samples from Spitsbergen.

Type locality Hornsund, northern part of the Revdalen, near the Revvatnet and the Revelva, mosses from soil, 67 m asl, 77°01′41″N, 15°22′21″E, 26.06.2010, coll. Łukasz Kaczmarek and Jerzy Smykla.

Type depositories Holotype (slide 14.2/20) and paratypes (slides: 14.2/4, 14.2/8, 14.2/9, 14.2/12, 14.2/13, 14.2/14, 14.2/16, 14.2/19) are deposited at the Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań.

Differential Diagnosis Bryodelphax parvuspolaris sp. nov. has ventral plates and thus belongs to the weglarskae group (Kristensen et al. 2010); we therefore only compared other species of this group (see Fig. 8), using the ventral plates and other characters. The new species differs from:

  • B. aaseae Kristensen et al., 2010 by: a different ventral plate configuration (VIII:1-1-2-2-2-2-2-1 in the new species and X:2-1-4-4-2-4-2-1-2-1 in B. aaseae) and the presence of dentate collars on hind legs.

  • B. iohannis Bertolani et al., 1995 by: a different ventral plate configuration (VIII:1-1-2-2-2-2-2-1 in the new species and X:2-1-1-5-2-4-2-2-2-1 in B. iohannis), a slightly smaller body size (87.4–125.0 in the new species and 113.9–179.5 in B. iohannis), and the presence of dentate collars on hind legs.

  • B. sinensis Pilato, 1974 by: a different ventral plate configuration (VIII:1-1-2-2-2-2-2-1 in the new species and VII:2-2-2-2-2-2-1 in B. sinensis), slightly longer lateral appendages A (up to 37.4 in the new species and up to 27.0 in B. sinensis), and the presence of dentate collars hind legs.

  • B. weglarskae Pilato, 1972 by: a different ventral plate configuration (VIII:1-1-2-2-2-2-2-1 in the new species and IX:2-1-5-2-4-2-2-2-1 in B. weglarskae) and by not bifurcated appendages.

Isohypsibius coulsoni sp. nov. (Figs. 9–13; Table 3)

Material examined Holotype (slide 34.2/29) and 80 paratypes (slides: 31.4/1, 31.4/3, 34.2/6, 34.2/7, 34.2/8, 34.2/9, 34.2/10, 34.2/11, 34.2/12, 34.2/13, 34.2/14, 34.2/15, 34.2/16, 34.2/17, 34.2/18, 34.2/19, 34.2/20, 34.2/21, 34.2/22, 34.2/23, 34.2/24, 34.2/25, 34.2/26, 34.2/28, 34.2/29, 34.2/30, 34.2/31, 34.2/32, 34.2/33, 34.2/34).

Description (measurements in Table 3 ) Body transparent/white, eyes present (in live and mounted animals) in 83% of the examined specimens (Fig. 9). Dorso-lateral cuticle without gibbosities but covered with a reticular pattern (polygons diameter 0.9–3.2) (Fig. 10). Ventral cuticle smooth.

Table 3 Measurements and pt values of selected morphological structures of eleven specimens (including the holotype) from the type population of Isohypsibius coulsoni sp. nov.
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Figs. 9−10
figure 9-10

Isohypsibius coulsoni sp. nov. Fig. 9. habitus (ventral view, holotype). Fig. 10. sculpture on the dorsal cuticle (paratype). Scale in μm

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Bucco-pharyngeal apparatus of the Isohypsibius type, without ventral lamina (Fig. 11). Oral cavity armature absent or not visible under PCM. Pharyngeal bulb oval with three macroplacoids and a microplacoid. All macroplacoids without constrictions. Macroplacoid length sequence (smallest-medium-largest): 2-1-3.

Figs. 11–13
figure 11-13

Isohypsibius coulsoni sp. nov. Fig. 11. buccal apparatus (ventral view, holotype). Fig. 12. claws III (paratype). Fig. 13. claws IV (paratype). Scale in μm, on 12–13 same as on 11

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Claws of the Isohypsibius type, similar in size and shape on all legs (Figs. 12, 13). All main branches with well-developed accessory points. Smooth lunules present on all claws, slightly larger on claws IV. Cuticular bars present under internal claws I–III.

Eggs white, smooth and deposited in exuvium (4–6 eggs per exuvium).

Etymology The new species is named in honour of Dr. Steve Coulson of the Department of Arctic Biology (UNIS) who helped us in collecting tardigrades from Spitsbergen.

Type locality Hornsund, the top of the Rotjesfjellet, mosses from rock, 437 m asl, 77°00′40″N, 15°22′20″E, 29.06.2010. coll. Łukasz Kaczmarek and Jerzy Smykla.

Additional localities Hornsund, south-east slope of the Rotjesfjellet, mosses and lichens from soil, 301 m asl, 77°00′31″N, 15°23′21″E, 29.06.2010. coll. Łukasz Kaczmarek and Jerzy Smykla.

Type depositories Holotype (slide 34.2/29) and 80 paratypes (slides: 34.2/9, 34.2/12, 34.2/13, 34.2/14, 34.2/15, 34.2/16, 34.2/22, 34.2/23, 34.2/25, 34.2/26) are deposited at the Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań.

Differential diagnosis Isohypsibius coulsoni sp. nov. differs from all other known Isohypsibius species with sculptured dorsal cuticle and three macroplacoids in the pharynx by a unique combination of the following characters: the presence of a microplacoid, the absence of cuticular gibbosities and the presence of accessory points on primary branches of all claws. The new species differs from the most similar:

  • Isohypsibius glazovi Biserov, 1999 (known only from Novaya Zemlya) by the absence of the cuticular gibbosities.

  • Isohypsibius ceciliae Pilato and Binda, 1987 (which is also known from Spitsbergen) by: the absence of the reticular sculpture on the ventral side of the body, a distinctly smaller diameter of the reticular mesh on the dorsal cuticle (0.9-3.2 in the new species and about 5.0–6.0 in I. ceciliae) and the absence of the oral cavity armature.

  • Isohypsibius lineatus (Mihelčič, 1969) (known only from Austria) by: a different shape and composition of the reticular sculpture (reticular mesh in the new species and irregular undulating lines in I. lineatus), different macroplacoid length sequence (2-1-3 in the new species and equal lengths in I. lineatus), the presence of accessory points on the primary branches of external claws and the presence of smooth lunules on all claws.

Other tardigrade species recorded from the Revdalen

In total, we found 25 species, including two new to science (described above) and two recorded from the Svalbard Archipelago for the first time (Milnesium asiaticum Tumanov, 2006 and Diphascon (Adropion) prorsirostre Thulin, 1928). All species with notes on their previous records from the Svalbard Archipelago and zoogeographic and taxonomic remarks are listed in Table 4.

Table 4 A list of all species found in the present study with information on previous records from Svalbard and zoogeographic and taxonomic remarks
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