Lithuania is one of the three Baltic states situated on the eastern shore of the Baltic Sea: i.e. Estonia, Latvia and Lithuania.The Estonian pseudoscorpion fauna currently consists of 15 species belonging to 13 genera and five families (Sammet et al. 2016), that of Latvia comprises 11 species belonging to 11 genera and five families (WPC 2022), and of Lithuania nine species belonging to six genera and three families (Krajčovičová et al. 2018b, 2020). Recently, the first study dedicated to the pseudoscorpion fauna of Belarus, neighbouring Lithuania to the east, was published and filled the gap in the knowledge on pseudoscorpion distribution in Europe. The known pseudoscorpion fauna of Belarus consists of seven species belonging to six genera and two families (Ostrovsky 2020).

The first data about pseudoscorpions from Lithuania were published only recently and consist mostly of random collections, which is reflected in the low number of known species (Krajčovičová et al. 2018b, 2020). Krajčovičová et al. (2018b) documented pseudoscorpion occurrence at 25 localities throughout the country. The collection contained specimens sampled by sieving of litter and moss, from pitfall traps and collected individually, mostly under deadwood bark. The species composition of eight species from three families reflected the choice of sampling methods (Krajčovičová et al. 2018b). Part of the material published by Krajčovičová et al. (2018b) was collected at localities that are situated in the Curonian Spit National Park. The occurrence of Neobisium carcinoides (Hermann, 1804), Neobisium crassifemoratum (Beier, 1928) and Pselaphochernes scorpioides (Hermann, 1804) was recorded from the area (Krajčovičová et al. 2018b). Recently, Chernes similis (Beier, 1932) was added to the list of the Lithuanian fauna, it was found in tree hollow in the Botanical Garden of Vilnius University (Krajčovičová et al. 2020).

The Curonian Spit NP is located in a long thin curved sand spit in the Baltic Sea stretching from Zelenogradsk (Russia) to Klaipeda (Lithuania) (Fig. 1). It is the largest accumulative sandy formation with linear dunes of the swell-shaped type in the Baltic region. A distinctive feature of the Curonian Spit is the presence of blow sands (Nikitina et al. 2019). The main forest-forming species are pine (Pinus sylvestris L.) and black alder (Alnus glutinosa (L.)) (Nikitina et al. 2019).

In 1989, the Great cormorant (Phalacrocorax carbo (Linnaeus, 1758)) started to nest near Juodkrantė and expanded into the largest breeding colony in Lithuania (Motiejūnaitė et al. 2014), representing a potential habitat for pseudoscorpions living in bird nests and influencing the vegetation and biodiversity around and below the colony. The aim of the present paper is to summarize data on pseudoscorpions assembled from the Curonian Spit National Park, partly collected as bycatch from research on environmental effects of the abovementioned, newly established colony of Great cormorants, and to provide a summary of the species known from this valuable, protected area.

Fig. 1.

The sampling sites (red and yellow circles) in the Curonian Spit National Park, Lithuania (red circle represents the locality of Dinocheirus panzeri). Detail: open and solid circles: Smiltynė (open circle: the locality of D. panzeri), inverse triangle: Alksnynė, solid triangle: Nagliai Reserve, solid square: Juodkrantė, open squares: Nida. The map was produced with SimpleMappr (Shorthouse 2010)

Fig. 2.

Sampling sites. a. Great cormorant colony in the old forest; b. the old part of the cormorant colony in the old forest; c. white sand dune with Leymusarenarius

Material and methods

Pseudoscorpions were collected by Povilas Ivinskis and Jolanta Rimšaitė in the Curonian Spit National Park, Lithuania (Figs 1-2). A part of the material was collected during the research on long-term changes in vegetation affected by nesting of the Great cormorants and their influence on ground-dwelling predatory arthropods (Fig. 2). During the research pitfall traps were selected as the sampling method (Machač et al. 2022). The rest of the material was collected during the study of the insect fauna across the national park using window traps.

Pseudoscorpions were preserved in 75% ethanol. They were studied as temporary slide mounts, prepared by immersing specimens in lactic acid for clearing. After the study, they were rinsed in water and returned to 75% ethanol. The digital photograph (Fig. 3) was taken using a Canon EOS 5D Mark II camera attached to a Zeiss Axio Zoom V16 stereomicroscope. Image stacks were produced manually, combined using the Zerene Stacker software, and subsequently edited in Adobe Photoshop CC. Pseudoscorpion species were identified using the key in Christophoryová et al. (2011). The nomenclature follows WPC (2022). The material is deposited in the zoological collections of Dr. Povilas Ivinskis at the Nature Research Centre, Vilnius, Lithuania. The newly recorded species Dinocheirus panzeri is deposited in the Kaunas T. Ivanauskas Zoological Museum (KZM), Kaunas, Lithuania.

Results

A list of the taxa is given below with locality name, habitat, sampling method, date and the number of developmental stages (A – adult with unidentified sex, TN – tritonymph, DN – deutonymph, PN – protonymph).

Fig. 3.

Dinocheirus panzeri, male. Arrow indicates the pseudotactile seta on the tarsus of leg IV. Scale line: 1 mm

Discussion

The discovery of Dinocheirus panzeri in the Curonian Spit NP brings the pseudoscorpion species number in Lithuania to ten, within seven genera and three families. The genus Dinocheirus Chamberlin, 1929 contains 27 species with the highest diversity and distribution in North America. Only three species are known to occur outside the American continent (WPC 2022). Dinocheirus bulbipalpis (Redikorzev, 1949) and D. transcaspius (Redikorzev, 1922) have been recorded from Central Asia (WPC 2022) with an isolated finding of D. transcaspius in the European part of Russia (Krajčovičová et al. 2018a). Besides the single record of D. transcaspius in Moscow (Krajčovičová et al. 2018a), D. panzeri is the only known species of the genus that is widespread in Europe (WPC 2022). Among the main diagnostic characters of the genus are the female spermathecae with a pair of long tubes each ending with terminal bulb and relatively long pseudotactile seta situated distally on the tarsus of leg IV (Fig. 3) (Beier 1963).

Dinocheirus panzeri can be distinguished from D. transcaspius by the presence of a pair of long tactile setae on tergite XI, which is absent in D. transcaspius (Schawaller 1986, Christophoryová et al. 2011, Krajčovičová et al. 2018a). The affiliation of the species with the presence of a pair of long tactile setae on tergite XI, versus species with the absence of those, to one genus was questioned by Schawaller (1986). Recently, a study based on DNA barcoding (Muster et al. 2021) split D. panzeri into two deeply diverged clades; specimens from synanthropic sites were restricted to one clade, while specimens from the mould of trees were distributed across both clades. The existence of two separate species, namely D. panzeri and D. rufeolus (Simon, 1879), was discussed in Muster et al. (2021). The current synonymy of the two species was justified by the presence of transitional morphotypes in the males and the indistinguishability of the females (Mahnert 1978, Ressl 1983). However, the abovementioned study by Muster et al. (2021) revealed mitochondrial variation in analysed specimens and supported the hypothesis that D. panzeri and D. rufeolus might be two separate species (Muster et al. 2021).

The Neobisium carcinoides complex represents a unique case. The study of Muster et al. (2021) included 36 European pseudoscorpion morphospecies and revealed the highest intraspecific diversity within this species among all those analysed. Muster et al. (2021) showed that there are potentially 10–20 cryptic species within the N. carcinoides complex. In future, taxonomic revisions following an integrative approach combining molecular, karyological, morphometric data and including consideration of type material will be needed to discover the true pseudoscorpion species diversity here.

From a faunistic point of view, the known pseudoscorpion species composition of Lithuania is comparable to that of other Baltic countries (WPC 2022), but there is still a large gap in the knowledge of pseudoscorpions in this country. For example, no representatives from the Chthoniidae Daday, 1889, Cheiridiidae Hansen, 1894 or Larcidae Harvey, 1992 have been discovered in Lithuania so far. Future, systematic pseudoscorpion research focusing on different habitats would probably reveal new discoveries for the country.