1✉ Wielkopolska Wyższa Szkoła Społeczno-Ekonomiczna, Środa Wielkopolska, Poland.
2Department of Water Protection, Collegium Biologicum, Adam Mickiewicz University, Poznań, Poland.
3Department of Animal Taxonomy and Ecology, Collegium Biologicum, Adam Mickiewicz University, Poznań, Poland.
2021 - Volume: 61 Issue: 1 pages: 148-153https://doi.org/10.24349/acarologia/20214423
Despite several surveys, the Polish fauna of Oribatida is not fully known and new taxa are still being found (for example, Konecka and Olszanowski 2019). During ecological studies carried out in the Drawa National Park, an oribatid mite species new for Poland (Xenillus salamoni Mahunka, 1996), was found in a heavily transformed habitat below a former cormorant colony.
The study was performed on two islands: Lech (LI) (53°04'42''N, 15°57'47''E) and Okrzeja (OI) (53°05'10''N, 15°58'44''E) on the Lake Ostrowiec in the Drawa National Park (Poland). The islands are small in surface (\textless5 ha), domed and primarily overgrown by acidophilus oak forests with pine, and they are 1.3 km away from each other. Since 1950, a colony of cormorants has been present on LI. Over the past 60 years, the activity of the cormorants led to the deforestation of a large part of the island and the disappearance of herbal plants. Occasionally the cormorants visited OI, but never bred there. In 2015, the cormorants abandoned the island and the slow recolonisation of plants (mainly nitrophilous species) began. Nowadays, a significant part of the island is still bare. The topsoil horizon is rich in wooden detritus and well exposed to sunlight. The soil chemistry is also a distinguishing feature of the studied island. According to Klimaszyk et al. (2015), the nitrogen and phosphorus concentrations in the soils beneath the colony LI compared to OI are several dozen and several hundred times higher, respectively.
On both islands, 20 soil samples were collected from steep slopes. After extraction with a Tullgren apparatus (which lasted five days), all specimens were preserved in 85% ethanol and cleared on slides with 80% lactic acid. Microscopic slides were prepared with Hoyer's mounting medium. Pictures were taken with a Nikon DS-Ri2 microscope camera and obtained with the aid of Nikon NIS-Elements D software (Nikon Corporation) and rendered with the Helicon Focus 7 program (Kozub et al. 2008).
To prepare the identification key of European Xenillus, the following publications were used: Csiszár 1961; Kulijev 1963, 1968; Mahunka 1979, 1996; Pérez-Íñigo 1987; Morell 1987, 1989; Gil-Martín and Subías 1997; Mahunka and Mahunka-Papp 1999; Subías and Arillo 2000; Grobler et al. 2003; Schatz 2004; Weigmann 2006; 2011; Ermilov and Kalúz 2013. Only species which were found in Europe, according to Subías (2004, updated 2020) were included in the key.
In total, 44 specimens of X. salamoni were found, of which 40 were from LI and 4 from OI. The average frequency of X. salamoni on OI was 0.2 specimens per sample, while on LI, it was tenfold higher.
In Poland, only two species of Xenillus have been recorded so far: X. clypeator Robineau-Desvoidy, 1839 and X. tegeocranus (Hermann, 1804) (Niedbała and Olszanowski 2008). Xenillus salamoni differs from these species primarily by the morphology of its prodorsum (Figs. 1 and 2). The lamellar cusps of X. salamoni are fused at their bases, without intercuspidal mucro, which is present in many Xenillus species (Fig. 2A). Lamellar setae are ciliate and directed anteromedially, similar to the setae of X. clypeator, while interlamellar setae are short (but longer than in X. clypeator)(Fig. 2B, C). Sensillus is clavate with a long stalk. Another characteristic feature of X. salamoni is the reduced exobothridial setae, represented only by small alveoli and lack of interlamellar tubercules (which are present in X. tegeocranus). The body length of X. salamoni is 695–932 μm (Mahunka 1996; Schatz 2004).
Xenillus salamoni is considered to be a xerophilous and silvicolous species, which was first recorded in Hungary. Mahunka (1996) described this species from dry Tilio-Sorbetum in the Bükk National Park, and later, it was also recorded in a commercial beech forest stand in the Mátra Mountains (Kreszivnik and Mahunka 2000). X. salamoni was also noted in dry grassland and in downy scree slope oaks of the Italian and Austrian parts of the Tyrol region, which are located in the Eastern Alps (Schatz and Fischer 2015; Schatz 2016). Subías (2004, updated 2020) reported X. salamoni in material from Abkhazia (Caucasus), but this information was not published (L. S. Subías, personal communication). Thus, X. salamoni is only known from a few locations in Europe and the Caucasus. Islands on Lake Ostrowiec are the first location outside mountain areas (Alps, Bükk and Caucasus mountains) on which this species was found.
Likely, the range of occurrence of X. salamoni in Poland is not limited to the islands on the Lake Ostrowiec, and this species might be present in other parts of the country. Because of their narrow ecology niche, X. salamoni and their habitats could have been overlooked during previous research. A higher abundance of this mite on LI might have been caused by previous cormorant activity that led to the deforestation of the island and changed soil chemistry (Klimaszyk et al. 2015). It could create better conditions for xerophilous species like X. salamoni.
Cormorants can also be hypothesised as an expansion vector for this species. Xenillus tegeocranus was recorded in cormorant feathers by Lebedeva et al. (2004), so the presence of X. salamoni in cormorant plumage is probable.
To verify these assumptions, further surveys on dry environments and cormorants (their colonies and feathers) should be carried out.
1. Notogastral setae short, dilated (or fan-shaped), well visible. Interlamellar setae long, not attached to lamellae or reduced
— Notogaster setae of different lengths and not dilated
2. Interlamellar setae reduced. Notogastral and adanal setae - fan-shaped. Body length: 775–1000 μm
...... Xenillus arilloi Gil-Martín & Subías, 1997. Distribution: Spain
— Interlamellar setae long
3. Sensillus with a long stalk. Interlamellar setae dilated at the end. Setae c1 and c2 short and similar in size. Body length: 824 μm
...... Xenillus penicilliger Csiszár, 1961. Distribution: Southeast Europe
— Sensillus with a short stalk. Setae c1 and c2 long. Seta c1 visibly longer than c2. Body length: 900–1250 μm
...... Xenillus clavatopilus Mihelčič, 1966. Distribution: Western part of the Mediterranean Sea
4. Interlamellar setae arising from lamellae
— Interlamellar setae not fused with lamellae and arising from the interlamellar region
5. Setae c1 and c2 bacilliform. Body length: 997 μm
...... Xenillus mutabilis Mahunka & Mahunka-Papp, 1999. Distribution: Hungary
— Setae c1 and c2 setiform. Body length: 860–1155 μm
...... Xenillus discrepans discrepans Grandjean, 1936. Distribution: Southern Palearctic
6. Sensillus with a short stalk
— Sensillus with a long stalk
7. Interlamellar setae minute (20–30 μm). Rostral setae facing each other. Sensillus with a short stalk, club-shaped. Body length: 1200– 1400 μm
...... Xenillus clypeator Robineau-Desvoidy, 1839. Distribution: Holarctic and Mexico
— Interlamellar setae longer
8. Rostrum oval. Rostral setae facing each other. Big and well visible mucro between lamellae. Body length: 990–1200 μm
...... Xenillus discrepans azorensis Pérez-Íñigo, 1987. Distribution: Southern Palearctic (Mediterranean and Central West Asia)
— Rostrum apically slightly concave with small irregular teeth. Rostral setae facing forward. Small mucro between lamellae or a lacking. Body length: 815–1000 μm (female), 610–770 μm (male)
...... Xenillus halophilus Weigmann, 2011. Distribution: Portugal
9. Lamellae completely fused or fused only with each other medially. Mucro between lamellae lacking
— Lamellae not fused. Usually, the presence of at least small mucro between lamellae.
10. Lamellae fused completely. Sensillus with a long stalk. Notogaster and interlamellar setae very short. Body length: 857–1005 μm
...... Xenillus confusus Mahunka, 1979. Distribution: Greece
— Lamellae not completely fused
11. Inner cuspis curved. Interlamellar setae long. Body length: 709–866 μm
...... Xenillus matskasii Mahunka, 1996. Distribution: Hungary
— Interlamellar setae short
12. Lamellar cuspidal short, pointed teeth, pointed, directed medially, inner margins of cusps curved. Lamellae setae long, smooth, directed medially. Exobothridial setae club-shaped. Body length: 670–870 μm (female), 410–540 μm (male)
...... Xenillus athesis Schatz, 2004. Distribution: Italian Alps
— Lamellar cuspidal teeth weakly expressed, directed anteriad, inner margins of cusps almost parallel. Lamellar setae shorter, ciliate, directed anteromedial. Exobothridial setae reduced. Body length: 695–932 μm
...... Xenillus salamoni Mahunka, 1996. Distribution: Central Europe and Caucasus
13. Lamellar, interlamellar and notogaster setae distally ciliate
— Setae smooth and slightly ciliate along entire length
14. Cusp with one tooth. Body length: 612–984 μm.
...... Xenillus selgae Morell, 1987. Distribution: Western part of Mediterranean Sea and Vietnam
— Cusp with two teeth. Body length: 648–912 μm
...... Xenillus ybarrai Morell, 1987. Distribution: Spain
15. Rostrum round. Prodorsal and notogastral seatae long and ciliate. Body length: 624–900 μm
...... Xenillus fernandoi Morell Zandalinas, 1989. Distribution: Western part of Mediterranean Sea
— Rostrum with a recess in the middle or two teeth along the entire length
16. Notogaster nearly oval. Body sculpture tuberculate. Body length: 900 μm
...... Xenillus tuberculatus Subías & Arillo, 2000. Distribution: Spain
— Punctate body sculpture
17. Setae c1 and c2 setae short, bacilliform, both similar in size. Rostrum medially slightly or distinctly concave, laterally with small teeth. Body length: 720–1100 μm
...... Xenillus tegeocranus (Hermann, 1804). Distribution: Palearctic and Oriental
— Setae c1 and c2 long, c2 considerably longer than c1
18. Rostrum apically oval, with two side projections on which rostral setae are situated. Ventral setae short, needle-like. Body length: 945 μm
...... Xenillus sculptrus Kulijev, 1963. Distribution: Southern Palearctic: Caucasus, Spain and Iran
— Rostrum apically slightly concave, with two small teeth. Ventral setae long, ciliate (except genital setae). Body length: 940 μm
...... Xenillus setosus Grobler, Ozman & Çobanoglu, 2003. Distribution: Turkey and Iran
The authors would like to thank Mateusz Zmudziński from the Department of Animal Morphology, at the Adam Mickiewicz University in Poznań for his help in preparing the photographs of mites, the management of the Drawa National Park for enabling the collection of material for our research, and Luis S. Subías from the Department of Zoology and Physical Anthropology at the Complutense University of Madrid for sharing information about the Caucasian record of X. salomoni. Our greatest thanks go to Professor Ziemowit Olszanowski for his help in confirming the identification of the new species and organizing the research.
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