Water mites (Acariformes: Hydrachnidia, Halacaroidea) of bogs of Western Siberia (Russia)

Water mites (Acariformes, Hydrachnidia, Halacaroidea) were studied in 8 different bogs and fens of Western Siberia. 28 species of Hydrachnidia and 5 species of Halacaridae were found in them. The species composition in the bogs was very different. In the fens the abundance and species diversity were higher than in sphagnum bogs and the fauna were based on spring species. The representatives of the halacarid mites dominated in sphagnum bogs, which were not found in the fens. The specific similarity of the studied bogs was low. At the same time, the peculiarities of seasonal dynamics in bogs and fens were similar and resembled temporary water bodies: high numbers in the spring and an abruptly decline in the summer, with a slight increase in autumn.


Introduction
Water mites are widespread in almost all types of fresh water bodies, including bogs of different types (Sokolow 1940;Di Sabatino et al. 2002). Mites can have high species diversity in bog habitats. For example, in Canada, of more than 500 species of water mites known in the country, about one hundred occur in different types of bogs (Smith 1987).
In Europe, where acarofauna as a whole has been studied most well, there are a large number of works on faunal composition of water mites inhabiting bogs and marshy water bodies (Biesiadka et al. 2005;Cichocka 1996bCichocka , 1998Smit & Van der Hammen 2000;Stryjecki 2010). There is a number of large works devoted to the ecological characteristics of water mites inhabiting bogs (Tuzovskij 1974(Tuzovskij , 1996Wiecek et al. 2013a). The fauna of water mites of the bogs is very specific, typical for a certain type of biotope and can be used for monitoring the state of bogs ecosystems (Wiecek et al. 2013b). However, even in Europe, not all types of wetland habitats and features of the ecology of water mites living in them have been studied (Wiecek et al. 2013a). In other regions the state of the water mite's study is much lower.
In Western Siberia (the Asian part of Russia), such studies have not previously been conducted. At the same time, the West Siberian Plain (one of the largest plains of the world) is most rich in bogs. Wetlands occupy more than 50% of its territory (Bogs of West Siberia 1976). Certainly, sphagnum bogs have a Ecologica Montenegrina 18: 102-109 (2018) This journal is available online at: www.biotaxa.org/em tremendous impact on the climate of the region. In the territory of Western Siberia sphagnum bogs ecosystems are subject to increased anthropogenic pollution in connection with oil and gas production. Therefore, their conservation is an important task, the solution of which is impossible without studying all the components of bog ecosystems, one of which are water mites.

Material and Methods
Studies were conducted in 2016-2017 in the vicinity of Lake Kuchak (Nizhnetavdinsky district of the Tyumen region). The study area is located in the southwest of the West Siberian Plain. Eight different types of bogs were investigated, their description and location are shown in table 1. Sphagnum mesotrophic and eutrophic bogs, sedge and grassy fens were taken for the study, which differed in their characteristics: electrical conductivity, depth, pH. Samples were taken for studing the variety of mites and the hydrochemical characteristics of water at the end of June and the beginning of July 2016 and 2017, also examined the seasonal dynamics of mites during the entire season of 2017 from the thawing of bogs in early April to their freezing in late October.
A total of 47 samples were taken, of which 1501 specimens of water mites were extracted and studied. To collect samples in fens used hydrobiological net with mesh size 250 μm. Samples were taken from the same area equal to 2 m 2 , raking the entire thickness of water from the surface to the bottom, capturing the upper part of the soil. In the sphagnum bogs, in areas where there were no open water patches, the method of trampling moss was used, creating a water-filled micro-depression in which mites was caught by a small net (Fillipov et al. 2017). In the sphagnum bogs, while milling, mosses were selected, which were then washed in a net.
For the construction of a dendrogram of faunal similarity, the single-attachment method was used based on calculating the Jacquard coefficient in the PAST 3.01 program.

Results and discussion.
In total, 28 species of water mites from seven families, and five species of halacarid mites, were identified in 8 investigated bogs in the vicinity of Lake Kuchak (table 2).
Among the species of mites marked in the bogs, representatives of spring fauna characteristic of temporary water bodies prevailed, which was noted by other researchers (Smith 1987;Tuzovskij 1974Tuzovskij , 1990Tuzovskij , 1996. Euribiotic species were less, and they appeared only in the summer, if there was a lot of water left in the bog. Parathyas colligera (Viets, 1923) - In general, the number and occurrence of mites in different bogs varied greatly. So, only one specimen of mites was met in two bogs (No. 4 and 7). In general, in sphagnum bogs, especially those that lacked open water, the number and variety of mites were low, as was noted by other researchers in Europe (Cichocka 1998;Wiecek et al. 2013a). Indicators of abundance and species richness in them were usually significantly lower than in sedge and grass fens. In this case, they usually dominated one species. Number of species was significantly higher in fens and pronounced dominants were absent.
The species composition of the mites also varied: Hydrachnidia are noted mainly in fens, their abundance and species diversity were low in sphagnum bogs, they were absent in 30% of the samples. Only a few species of Hydrachnidia were found in both bogs and fens this is primarily Limnesia connata Koenike, 1895, which had the highest rates of occurrence from all mites (marked in 5 of 8 bogs).
Most of the species of Hydrachnidia, noted in sphagnum bogs, did not occur in fens. Thus, these species (Tiphys scaurus (Koenike, 1892), Acercopsis pistillifer (Koenike, 1908), Arrenurus stecki Koenike, 1894) can be considered typical representatives of the semi-aquatic fauna of sphagnum bogs, as noted by other researchers in Europe (Besseling 1959;Cichocka 1996a;Wiecek et al. 2013a). At the same time, in our collections there were no species of water mites typical of sphagnum bogs in Europe -Piersigia spp., Zschokkea oblonga Koenike, 1892 (Besseling 1959;Wiecek et al. 2013a). Perhaps this is due to the insufficient study of the marshes of Western Siberia, the rarity of these species or the peculiarities of their distribution.
For sphagnum bogs, five species of halacarid mites were found, while in most samples they dominated in numbers. In this case, in the fens, the halacarid mites were not noted. Halacaridae often inhabit sphagnum bogs, and their numbers can be very high here (Bartsch 1989(Bartsch , 2007(Bartsch , 2008(Bartsch , 2009(Bartsch , 2011. As can be seen, in the bogs of Western Siberia, halacarid mites are numerous, often dominate in numbers and are represented not only by widespread species, but also rare enough, such as Parasoldanellonyx parviscutatus (Walter, 1917).
The faunal similarity of the studied bogs was not high and did not exceed 60%. (Fig. 1). Mesotrophic sphagnum bogs differed in the greatest similarity with each other, in which there were practically no open water areas. Close to them was a bog near the lake Tangach (No. 6), in which there were also no open water areas, but there were grassy plants with a small share of sphagnum prevailed. Conversely, eutrophic sedge and grassy fens had low rates of similarity with sphagnum bogs, in both groups there were practically no common species. At the same time, the similarity of the two fens to each other was also low. In two bogs, in which were noted the highest abundance and species diversity of water mites, we conducted studies of seasonal dynamics of abundance. Two typical bogs were selected for the study of seasonal dynamics: the mesotrophic sphagnum bog Chertankul (No 1) and the eutrophic sedge fen in the vicinity of Torgili (No 2).
In the mesotrophic sphagnum bog of Chertankul (No 1) prevailed representatives of the halacarid mites, they also determined the features of seasonal dynamics (Fig. 2). Porolohmannella violacea (Kramer, 1879) prevailed in all terms of the collection, its share varied from 51 to 98% at different times, in the same year in 2017 this species had a 100% occurrence. Hydrachnidia, on the contrary, were few in species composition and in number, only Tiphys scaurus and Limnesia connata were regularly enough noted. In contrast to the fen No 2, which already had high numbers of mites at the end of April, the sphagnum bog did not completely melt during these periods, and the mites were not marked in it. However, already since the beginning of May, the mites were numerous. The greatest abundance and species diversity were recorded from late May to early June, after which the number rapidly declined. In July-August, Hydrachnidia were not observed and mites were represented only by Halacaridae. After the maximum decrease in the number in August, in autumn the number and species richness of mites increased slightly, again the deutonymphs and females of Tiphys were again noted. Mites were found right up to the freezing of the swamp.
In the sedge fen near the village of Torgili (No. 2), the seasonal dynamics of abundance and species diversity of mites was also well pronounced (Fig. 3): already in late April, shortly after ice melt, mites were found in large quantities.
Deutonymphs of Tiphys and Piona were dominated, representatives of Hydryphantidae were numerous. In May, the highest indicators of species richness and abundance of water mites were revealed. All species diversity occurs in typical spring species of mites, but there were individual representatives of summer species -Piona alpicola (Neuman, 1880), Arrenurus globator (Muller, 1776). Among the dominant representatives -Hydryphantes ruber (De Geer, 1778), adults Tiphys, the number of nymphs decreased. By the end of May, the number of mites decreased: the nymphs practically disappeared, Hydryphantidae, Tiphys and Piona were noted among the dominant species, among the Piona, many dead individuals, mostly males, were caught in the samples. On water plants, numerous egg layings of water mites have been recorded. By the beginning of June, the number of water mites rapidly declined: only a few adult specimens were recorded, as well as a large number of dead Piona nodata (Muller, 1776) females. Tiphys and Piona predominated, Hydryphantes are marked by single representatives. At the end of June, a change in species composition occurs -summer species of the genus Arrenurus and Piona alpicola appear. There are also numerous egg laying. The number was low. In July and August, the numbers decreased even further due to a strong water level reduction in the bog. Summer species predominated, but their abundance and species diversity were small. In autumn a slight increase in the number of mites was observed due to two summer species of the genus Arrenurus. Also, in the samples of the end of September-October, the deutonymphs of the spring species of the genera Tiphys and Piona of the second generation are again marked.
Thus, despite the significant differences in the taxonomic composition, species richness and abundance of mites in different types of bogs, the features of seasonal dynamics in them were similar, which can be explained by similar conditions of existence. The features of seasonal dynamics in many respects resemble those in temporary water bodies (Tuzovskij 1974, 1996, Wiggins et al. 1980Stryjecki 2006) and similar in many respects to the species composition of bog-inhabiting mites.