﻿The pseudoscorpions of the Caucasian Sphagnum bogs: part I. Description of Neobisium (Neobisium) adjaricum sp. nov. and redescription of the holotype of N. (N.) vilcekii Krumpál, 1983 (Arachnida, Pseudoscorpiones, Neobisiidae)

﻿Abstract A new species of pseudoscorpions, Neobisium (Neobisium) adjaricumsp. nov., is described and diagnosed. It was collected in the Sphagnum habitats of Ispani lowland mires in Transcaucasia (Republic of Adjara, Georgia). The habitat of N. (N.) adjaricumsp. nov. is described. The holotype of N. (N.) vilcekii Krumpál, 1983, a species most similar morphologically to N. (N.) adjaricumsp. nov., known from the North Caucasus (Republic of North Ossetia–Alania, Russia), is redescribed. Diagnostic characters of the relative Caucasian species of the subgenus Neobisium Chamberlin, 1930 are analysed.


Introduction
Pseudoscorpions are well known to inhabit peat bogs, but the fauna of pseudoscorpions in bogs is peculiar and poor. It includes both specialised tyrphophilous bryobionts (i.e., species associated mostly with moss habitats in mires) and eurytopic species (Turbanov et al. 2017). The pseudoscorpions of the Caucasus are relatively well studied, but they were not investigated as a component of the biodiversity of Sphagnum bogs in this region.
The Caucasus is one of the biodiversity hotspots (Myers et al. 2000), with a high variety of landscapes and habitats. The mires of the Caucasus, including Sphagnum bogs, are relatively rare, isolated, mostly small-sized ecosystems with specific conditions Masing 1979, 1983). Peat bogs in the Caucasus are peculiar also because they are situated near the southernmost limit of the occurrence of this habitat type in the Palaearctic Region. Most of Caucasian bogs are located at an altitude between 600 and 3,400 m a.s.l. In contrast, the Sphagnum bogs of western Georgia (Transcaucasia) strongly differ from other Caucasian bogs in many important features (Krebs et al. 2017;Sirin et al. 2017). They are situated in the Kolkheti (= Colchis) Lowland, near the Black Sea coast, at an altitude of less than 10 m a.s.l. These bogs are unique as they are the only Sphagnum bogs situated in the subtropical climatic zone, representing a separate Kolkheti (= Colchis) mire region (Botch and Masing 1983;Tanneberger et al. 2021). Both montane Caucasian and lowland Transcaucasian bogs are considered to contain relict biotic components and to serve as postglacial refugia for species of boreal origin, primarily plants (Denk et al. 2001;Kaffke 2008;Doroshina and Nikolajev 2018). Hitherto, terrestrial arthropods remain almost unstudied in the peat bogs of the Caucasus and, consequently, any contribution to their knowledge is important.
The present paper is first contribution to the knowledge of pseudoscorpions inhabiting the mires of the Caucasus, based on the original material collected in the scope of ecological and faunal studies of ten bogs. A species new to science described below, Neobisium (Neobisium) adjaricum sp. nov., has been collected from Ispani 1 and Ispani 2 (Figs 1A, 2A) bogs situated in the Kolkheti Lowland of Georgia. In addition, we re-examined and redescribed holotype of N. (N.) vilcekii Krumpál, 1983, species most similar morphologically to N. (N.) adjaricum sp nov., described from the North Caucasus (near Karmadon in the Republic of North Ossetia-Alania, Russia; Krumpál 1983). Nassirkhani and Snegovaya (2021) recently redescribed N. (N.) vilcekii based on the new material collected near Mozdok, Republic of North Ossetia-Alania, ca. 100 km far away from the type locality. However, redescription of the holotype highlights important diagnostic characters and demonstrates an intraspecific variability of this species as compared with the redescription provided by Nassirkhani and Snegovaya (2021).
The subgenus Neobisium Chamberlin, 1930 Krumpál, 1983 (Republic of North Ossetia-Alania, Russia) (Dashdamirov and Schawaller 1992;Nassirkhani et al. 2020;World Pseudoscorpiones Catalog 2022). Dashdamirov and Schawaller (1992) and Nassirkhani et al. (2020) indicated that the distribution of the subgenus Neobisium within the Caucasus was poorly known and this taxon is likely to be more diverse in the area than indicated by the published records. The results of our study confirm this and contribute to the diversity of pseudoscorpions in the Caucasus.

Study bogs
The Sphagnum bogs Ispani 1 and Ispani 2 (Figs 1A, 2A) are situated in the Kolcheti Lowland, near the town of Kobuleti in the Republic of Adjara, Georgia, western Transcaucasia, ca. 1 km of the Black Sea coast. This area is characterised by a high mean annual temperature (13-14 °C), it is almost without frosts in winter, with very high levels of mean annual precipitation (ca. 1,500-2,500 mm), with ca. 50% of the precipitation falling from May to October, and with high air humidity (Kaffke 2008;de Klerk et al. 2009).
The Ispani 1 bog ( Fig. 2A) is strongly modified due to human activity during the 20 th century (drainage and peat excavation) and is now considered as "degraded"; it has a well-developed relief of hummocks and interspaces (Fig. 2B). The Ispani 2 bog (Fig. 1A) is relatively undisturbed and retains its natural state. It is famous for belonging to a unique mire type, percolation bog, which does not have surficial, but predominantly only vertical water flow through the entire peat body. As a consequence, the surface is nearly flat over most of the bog, without explicit microhabitats (Fig. 1B).

Materials and methods
Four specimens of a new species of the subgenus Neobisium (3 ♂ and 1 ♀) were collected from the bogs Ispani 1 and Ispani 2 briefly described above. All specimens were taken from quantitative samples of substrate consisting mostly of Sphagnum, taken up to a depth of 20-30 cm from the surface. Samples were washed in sieves (the smallest mesh size 0.25 × 0.25 mm), and then macroinvertebrates were extracted by flotation in a strong solution of NaCl combined with hand-sorting of the coarse fraction (see e.g., Khalin et al. (2022) for further details of flotation). All specimens were kept in 85% ethyl alcohol. Habitat parameters were measured in the water squeezed from Sphagnum at the sample point: pH value by a Hanna pHep + pH meter and mineralisation (ppt) by a Hanna DIST 2 conductometer.
For morphological examination using light microscopy, Neobisium (Neobisium) adjaricum sp. nov. was cleaned in pure lactic acid and was temporarily mounted on microscopic slides in glycerol. Some specimens were dissected for a more detailed study of the chelicerae, pedipalps and legs I and IV. The drawings were made under a Biomed 6 microscope (variant 3). The photographs of habitus were taken with a Leica MC170 HD (12MPs) digital microscope camera using the extended focus technology (Helicon Focus 7.7.4). After the study, each specimen including the dissected body parts was returned to the vial containing 85% ethanol.
The holotype of N. (N.) vilcekii, deposited in the zoological collection of the Slovak National Museum (SNM) in Bratislava, Slovakia, is redescribed. A permanent slide mount containing the dissected type species was studied ( Fig. 3B) (pedipalps, chela, chelicera, leg IV, and abdomen separated). The slide bears the following labels: "Neobisium (N.) vilcekii, male, Holotypus, det. M. Krumpál" (right) and "ZSSR, Osetínsko nad Karmadonom, 01.06.1976, lgt. M. Lisický" (left). Morphological and morphometric analyses were performed using a Leica DM1000 compound microscope with an ICC50 Camera Module (LAS EZ application, 1.8.0). Measurements were taken from digital images using the AxioVision 40LE application. Drawings were generated using a Leica DM1000 drawing tube. Image stacks were produced manually, combined using the Zerene Stacker software, and edited with Adobe Photoshop CC.
The type material of N. (N.) adjaricum sp. nov. is deposited in the following collections: Zoological Institute of the Russian Academy of Sciences, Saint Petersburg (ZISP); Zoological Museum of the Moscow University (ZMMU); and Institute of Systematics and Ecology of Animals, the Siberian Branch of the Russian Academy of Sciences, Novosibirsk (ISEA).
The measurements were made with an ocular micrometre using the reference points proposed by Chamberlin (1931) and those are given in millimetres (mm). All measurements are presented either as length/width ratios (carapace, chelicera, and pedipalp) or as length/depth ratios (legs). Proportions are indicated by the symbol "×". The data on paratypes are given in parentheses, after the holotype data.
Diagnosis. Carapace with moderately long and apically rounded epistome; two pairs of eyes present, lenses of posterior eyes with low convexity; movable cheliceral finger without large median tooth; pedipalpal femur and patella smooth (sometimes very rare and weak granules on outer side of femur); chelal hand with faint reticulate ornament; notch on median side of patella reaching almost middle of patellar club length; movable finger distinctly longer than hand + but almost equal to femur in length; trichobothrium ist situated distal to middle of fixed chelal finger; distal half of fixed chelal finger with teeth almost equal in size and shape; anterolateral process of coxa of leg I pointed and slightly enlarged, its mediolateral process slightly prominent, denticulate; sternite II with 5 setae; pedipalpal femur 4.5-5.1× as long as broad (0.77-1.00/0.15-0.22), chelal hand + 1.62 × as long as broad (0.62-0.71/0.38-40); movable chelal finger length 0.79-0.95.
Pedipalp (Figs 5A-C, 6B, D, E, G, I): femur and patella smooth (in one paratype, outer side of femur finely granulate), hand of chela covered with fine reticulate ornament ( Fig. 6D), pedicel of chela with distinct ornament; trochanter with small dorsal tubercle, 2.0 × (1.60-1.85 ×) as long as broad; femur with short pedicel, its margins of femur without tubercles, some setae mostly located in basal half of segment, without enlarged alveoli, one glandular pore located dorsodistally, 4.5 × (5-5.1 ×) as long as broad; patella with short and stout pedicel (0.20-0.22), patella distinctly shorter than femur, 1.43 × (1.54-1.66 ×) as long as broad, with 3 lyrifissures basally and 2 lyrifissures distally, notch on median side reaching very close to middle of club length. Chela + 3.8 × (3.68-3.87 ×) and chela -3.7 × (3.52-3.75 ×) as long as broad; movable finger distinctly longer than hand + , 1.31 × (1.27-1.33 ×), but almost equal to femur in length, 0.95 × (0.95-1.02 ×); hand + 1.62 × (1.63-1.77 ×) and hand -1.52 × (1.57-1.62 ×) as long as broad; retrolateral surface of hand with 3 glandular pores located around trichobothria eb and esb (two pores close to each other, one distant); fixed finger with 3 lyrifissures: fa located close to base in retrolateral view, fb located slightly proximal to ib, fd located distal to it; movable finger with 3 lyrifissures in retrolateral view: ma 2 located closer to trichobothrium b than to sb, ma 1 nearly at same level with sb (slightly proximal to sb), ma 3 closer to st than to sb, ma 1 slightly closer to ma 3 than to ma 2 ; one or two sensilla pc located between trichobothria sb and st, close to dental canals (one sensillum closer to sb, other closer to st; latter not present in all specimens); fixed finger with 48 (48-51) contiguous triangular teeth reaching level of trichobothrium ib, two outer distal teeth smallest, other teeth almost equal in size, all teeth with dental canal; movable finger with 45 (44-47) contiguous teeth not reaching level of trichobothrium b, teeth slightly reduced in size from tip of base of, distal 10-12 teeth triangular, other blunt and apically rounded, teeth with dental canal (except basal 6 or 7 small teeth); nodus ramosus of venom duct in fixed chelal finger short, situated very close to finger tip.
Trichobothriotaxy: fixed finger with 8 trichobothria, movable finger with 4 trichobothria; fixed finger with trichobothria esb and eb located close to each other and slightly proximal to ib, with isb on retrolateral surface, with ib closer to isb than to esb (in lateral and dorsal views), trichobothrium ist distinctly closer to est than to isb, distance ist-est similar to distance est-it, but less than twice as long as distance est-et in lateral view,  trichobothrium ist situated distal to middle of finger (T = 0.57-0.60), ist located distinctly proximal to t, et located posterior to it, at approximately the same distance between est and it (in lateral and dorsal views), ist situated distal to middle of finger; movable finger with trichobothrium st situated slightly closer to t than to sb, trichobothrium sb slightly closer to b than to st (at almost equal distances), distance b-sb almost equal to distance st-t.
Distribution. Known only from two adjacent Sphagnum bogs, Ispani 1 and Ispani 2, situated near the town of Kobuleti in the Republic of Adjara (Georgia).
In Ispani 2 bog, N. (N.) adjaricum sp. nov. was collected from a flat site in its (site 3; Fig. 1A) covered by a flat carpet of Sphagnum, with S. papillosum and S. palustre predominant, and with the thinned stands of M. caerulea arundinacea (Fig. 1B). Sphagnum was wet to moist, with a pH of 4.0 and mineralization of 0.07 ppt.
The new species seems to be rare, considering that only 1-3 specimens were collected at each site, in 10 quantitative samples (sample size of 0.05 m 2 ). As distinct from other pseudoscorpion species, all specimens of N. (N.) adjaricum sp. nov. were collected only from quantitative samples and no specimens were collected by other techniques (sifting, pitfall trapping, and/or rearing from substrata in the lab).
Etymology. The Latin adjective adjaricum indicates that the new species is named after the Republic of Adjara (= Ajaria), Georgia, where it was discovered. Table 1. Numbers of setae on the coxae of some species of the subgenus Neobisium from the Caucasus and adjacent territories.
Trichobothriotaxy (Fig. 8C): fixed finger with 8 trichobothria, movable finger with 4 ones; fixed finger with close-set trichobothria esb and eb located slightly proximal to ib, with isb on retrolateral surface, ib closer to isb than to esb, ist distinctly closer to est than to isb, distance ist-est approximately the same as distance est-it, but less than twice as long as distance est-et in lateral view, trichobothrium ist situated distal to middle of finger, ist located distinctly proximal to t, et located proximal to it, at approximately the same distance between est and it (in lateral and dorsal views), ist situated distal to middle of finger; movable finger with trichobothrium st situated slightly closer to t than to sb, trichobothrium sb slightly closer to b than to st, distance b-sb almost equal to distance st-t.
Remarks. The states of several characters reported here slightly differ from those in the original description of N. (N.) vilcekii (Krumpál 1983), viz. the number of setae on the posterior carapace margin (7 vs. 8); number of setae on the tergites III (11 vs. 10), V (11 vs. 12) and VIII (13 vs. 12); number of setae on the sternites III [(5)38(6) vs. (6)37(6)], VI (17 vs. 16), VIII and IX (each with 15 vs. each with 14); number of internal setae in the genital opening (8 + 7 vs. 7 + 7); number of teeth on the fixed and movable cheliceral fingers (13 and 6 vs. 11 and 4); number of setae on the coxae II of legs (10-12 vs. 11-12) and pedal coxae III (8-9 vs. 9-11) and IV (13 vs. 12-13); body length (3.65 vs. 3.04); carapace (0.92/1.30 vs. 0.69/0.95); pedipalpal trochanter (0.69/0.34 vs. 0.60/0.32). The numbers of setae on two last tergites and sternites are missing in the present redescription because these segments were damaged on the slide mount, but the respective data are given in the original description (tergites X with 12, XI with 10 and sternites X with 16, XI with 12 setae; see Krumpál 1983). Several new characters were added in the present redescription, namely, the measurements and ratio of length to width of chelicera, measurements and ratio of length to depth of trochanters of leg I and leg IV, presence of glandular pores, number of lyrifissures on carapace, number of blades on serrula exterior and interior, presence of tooth tis on chelicera, number of lyrifissures on palps and coxae.
Distribution. The species is known only from two localities in the Republic of North Ossetia-Alania (Russia) in the North Caucasus: the type locality near Karmadon (ca. 1500 m a.s.l.), and another locality in the valley of the Terek River in the environs of Mozdok (115 m a.s.l.) that was reported by Nassirkhani and Snegovaya (2021). The localities are situated at different altitudes, hence they should strongly differ from each other in the landscape and climatic conditions.
Habitats. The habitat of N. (N.) vilcekii near Karmadon is unclear (Krumpál 1983). It is questionable whether the species is confined to mire or wet habitats. The material from the environs of Mozdok that was used by Nassirkhani and Snegovaya (2021) for redescription was collected in a floodplain, in litter consisting of leaves of broad-leaved trees mixed with wood pieces. Hence, it is possible that N. (N.) vilcekii is a hygrophilous species.

Discussion
Various characters are used in the taxonomy of species belonging to the subgenus Neobisium (genus Neobisium), but the value of some characters is questionable. For example, Nassirkhani et al. (2020) discussed the morphological features of N. (N.) anatolicum from different locations (records of this species from several regions are doubtful and require confirmation) and indicated the high variability of many characters in the specimens from different regions. The diagnostic characters of Neobisium s. str. are poor and descriptions of many species are with insufficient data. Hence, it is important to study in detail the characters and intraspecific variability for as many species of the subgenus as possible.
The variation reported in the above-mentioned species does not take into account possible differences between males and females. In this regard, it is possible to state that number of setae on male sternite II is stable enough to distinguish species, with some variability being possible. It should be noted that none of the 13 specimens of N. (N.) vilcekii collected from the floodplain of the Terek River had 15 setae on the sternite II (as was the case with the holotype of the same species), but all had between 10 and 14 setae (Nassirkhani and Snegovaya 2021).
In contrast, the number of setae on the carapace (anterior and posterior rows) in the type specimens of N. (N.) adjaricum sp. nov. varies noticeably, i.e., 4 or 6 in the anterior row (microsetae present or absent), 6, 7, or 9 in the posterior row. Variability in the number of setae in the posterior row was previously observed in some species in the subgenus Neobisium, i.e., N. (N.) carcinoides (4-10), N. (N.) kovalevskayae (5-6) and N. (N.) artaxerxesi (7-9) (Mahnert 1988;Nassirkhani et al. , 2019, but such variability in the anterior row was recorded here for the first time. Interestingly, none of the 13 specimens of N. (N.) vilcekii from the floodplain of the Terek River contained 6 setae in the anterior row on the carapace (Nassirkhani and Snegovaya 2021). Keeping this in mind one should use the number of setae in the anterior and posterior rows on the carapace for species diagnostics with caution, if other good distinguishing characters are missing.
Examination of the type series of N. (N.) adjaricum sp. nov. also demonstrated relative stability of the shape and position of teeth on the chelicera, primarily the presence or absence of the large median tooth/teeth on the movable finger. In this character, N. (N.) adjaricum sp. nov. clearly differs from N. (N.) vilcekii, which only sometimes possesses a small median tooth on the movable finger (Nassirkhani and Snegovaya 2021).
The position of the sensillum pc is rarely mentioned descriptions of species belonging to the subgenus Neobisium. Recently the position of pc in relation to trichobothria on the movable chelal finger is considered a character for distinguishing species in some families of pseudoscorpions (e.g., Chthoniidae) (Zaragoza 2017;Turbanov and Kolesnikov 2021). In N. (N.) adjaricum sp. nov., variability in the number of pc (one or two) is observed, however, two pc were found only in one specimen, with the anterior pc indistinct (shifted apart from the level of the teeth line). In the holotype of N. (N.) vilcekii, two pc are distinctly visible between st and sb, whereas Nassirkhani and Snegovaya (2021) reported for this species only one pc (as se) proximal to sb. At the same time, the former authors illustrated an unnamed structure near st (Nassirkhani and Snegovaya 2021: fig. 1H), which resembles the second pc in N. (N.) adjaricum sp. nov. (Fig. 6G). Additional studies on other related species are necessary to reveal the variability or stability of this character.
We have demonstrated that N. (N.) adjaricum sp. nov. and N. (N.) vilcekii noticeably differ in the number of setae on the coxae of pedipalps and legs, as well as in the number of setae on the pedipalpal manducatory process. Although these numbers partially overlap (i.e., minimum values for one species with maximum ones for another), the upper and lower limits of variation strongly differ. In Table 1, numbers of setae on the coxae of pedipalps and legs are listed for 11 species of Neobisium s. str. from the Caucasus and adjacent territories (Nassirkhani and Doustaresharaf 2018;Nassirkhani et al. , 2019Nassirkhani et al. , 2020Nassirkhani and Snegovaya 2021;Nassirkhani 2022). It is worth mentioning that the number of setae on the pedipalpal manducatory process does not vary within species, so it can be used for species diagnostics (this study). It should be noted that Mahnert (1988) points to the variability of this trait in European populations of N. (N.) carcinoides (4-5 or 3-6), while leaving open the question of the possibility of the existence of a cryptic species complex. Some species [e.g., N. (N.) vilcekii] are characterised by an increased number of setae on the coxae of legs, however, this is noticeable only when the number of setae differs considerably between species. To objectively assess this character, it is necessary to examine a large series of specimens from the same population for different species.
An isolated tooth tis is present close to the interior seta of the chelicera in N. (N.) adjaricum sp. nov. and the holotype of N. (N.) vilcekii. Other researchers did not mention the presence of this tooth for Neobisium s. str., including Nassirkhani and Snegovaya (2021), who redescribed N. (N.) vilcekii. However, it may be hardly visible due to its small size and close position to the seta is. We found the same tooth in the genus Microbisium Chamberlin, 1930 from the Sphagnum bogs of Georgia (this study), but did not observe it in many species of the families Syarinidae Chamberlin, 1930and Chthoniidae Daday, 1888(Kolesnikov and Turbanov 2018Kolesnikov et al. 2019;Kolesnikov 2020, 2021). At present, the question remains whether this tooth is present in all species of Neobisiidae or it exists only in some genera and species. The shape of the tooth in N. (N.) adjaricum sp. nov. differs from that in N. (N.) vilcekii (triangular and rounded, respectively; Figs 6F, 9F).