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Groundwater dependent ecosystems are recognized as biodiversity hotspots, being,apart many negative human impacts, highly threatened also by ongoing climate warming. Clitellata (Annelida) are dominant invertebrates of permanent fauna in spring habitats, representing a heterogeneous group including both specialized cold stenothermic and ubiquitous eurythermic species. Therefore, they seem to be a good model group to compare the effects of local spring water temperature (recorded in situ by data loggers) and mesoclimate (i.e., local) air temperature. By the analysis of clitellate assemblages at 41 isolated Western Carpathian spring fens, we found that their species composition was significantly driven by mesoclimate air temperature and springwater temperature independently of other important environmentalvariables (i.e., water mineralization, oxygen content, and total organic carbon). Theeffect of various environment related and temperature related variables on thenumber of clitellate species was analyzed separately for two categories, that is,substrate dwellers (endobenthic species) and surface active (epibenthic) species. The decrease of the number of species with the increasing amount of inorganic particles in substrate was observed in the substrate dwellers. Mesoclimate air temperature had no significant effect on the number of species of substrate dwellers.However, water temperature, specifically its daily fluctuation, turned out to have a strong effect. Only the sites with no or moderate fluctuation were inhabited by cold stenotherm spring specialists and cold water species. In contrast, no significant response to any temperature parameter was found for the number of surface active species, which was driven only by other environmental variables. Our results suggest that climatically induced increase in temperature fluctuation of spring waters can result in notable reduction of cold adapted clitellate species (mainly the family Lumbriculidae) at the expense of eurythermic species. Such a scenario predicts compositional changes leading to clitellate assemblages with a dominance ofgeneralist and semiaquatic species.

Surface coal mining severely affects natural ecosystems, though it might also result in an establishment of biologically unique anthropogenic habitats. We studied spontaneously created post-mining calcareous brooks located at the brown coal spoil heap in the Sokolov coal basin (Czechia). Despite their extreme water conditions, linked most to the ionic mixture of dissolved ions (mainly SO 4 2− , Ca 2+ and Mg 2+ ), and ferric hydroxide precipitations, we recorded unexpectedly species-rich assemblages there (150 species), including several spring fen specialists (31 species) and eight threatened red-listed species. Macroinvertebrate assemblages of post-mining calcareous habitats were compared with those reported from natural brooks draining Western Carpathians calcareous spring fens. The species richness found in the post-mining calcareous brooks was significantly lower than that of the natural calcareous spring brooks. Although we found 29% of species recorded in the two study systems in common (i.e. 80 species), species composition of their assemblages was systematically distinct. This suggests a possible role of environmental filtering in the post-mining brooks and/or dispersal limitation of some species typical for natural calcareous spring brooks (e.g. Trichodrilus strandi , Bythinella austriaca ). In contrast, many macroinvertebrates, particularly those of high dispersal capacities (i.e. Odonata, Coleoptera and Diptera), can recognize post-mining calcareous brooks as surrogate habitats for the natural calcareous spring brooks.

Little is known about macroinvertebrate assemblages inhabiting aquatic-terrestrial transition zones, particularly at groundwater-fed wetlands. We studied diversity and vertical distribution of Dipteran assemblages in 27 spring fens characterised by variable groundwater chemistry ranging from acidic to extremely calcium rich. We sampled semiaquatic habitats of aquatic-terrestrial zones and compared their dipteran assemblages with those of truly aquatic habitats in spring patches. Our study showed that semiaquatic habitats create an important part of spring fens, harbouring about one half of dipteran taxa inhabiting spring fens, with a similar proportion of spring specialists as in aquatic habitats. Dipteran abundance decreased gradually with sediment depth, being the highest in the uppermost layer. However, vertical distribution of Diptera differed among fens of different mineral richness, with the average depth of dipteran counts decreasing from calcareous to mineral-poor Sphagnum fens. Calcium carbonate incrustations in calcareous fens might block migration to deeper horizons and therefore may cause high sensitivity of dipteran assemblages to water level fluctuations induced by various factors, such as climate changes and water abstraction. Semiaquatic habitats contribute significantly to the species richness of dipteran assemblages by providing additional microhabitats in the peripheral parts of spring fens, which are rare habitats of high conservation value.

Recent studies on diversity of stream amphipods proposed that the Western Carpathians have served as an important glacial refugium of freshwater fauna. If this scenario is true, a considerably high molecular diversity can be expected in this biogeographic region also for other taxa. In our project, we aimed to uncover and characterize molecular diversity of benthic macroinvertebrate fauna of spring fens, a well studied and hence convenient model community. Using a DNA metabarcoding approach, we sequenced a fragment of the COI gene of pooled spring fen invertebrate communities from 21 localities in the Western Carpathians. The preliminary analysis of the sequences revealed a substantially higher amount of operational taxonomic units (OTUs), when compared to the number of taxa identified in the same spring fens based on morphological characters. The lack of reference sequences in public databases (Barcoding of Life Database, GenBank) for the majority of the detected OTUs indicates that the Western Carpathian region is not yet sufficiently covered by barcoding efforts, and suggests that there indeed may be a considerable unrecognized diversity of macrozoobenthos. However, most newly uncovered diversity is concentrated in a few taxa such as the dipteran families Tabanidae and Ceratopogonidae, annelid species (complexes) Eiseniella tetraedra and Helobdella stagnalis or the amphipod genus Gammarus. In the future, these findings will be the basis for several levels of research: detailed investigation of seemingly hyperdiverse taxa (phylogeography, phylogeny, reference coverage) and comparison of overall molecular diversity of these communities in the Western Carpathians and neighbouring Bohemian Massif, a region where we expect much lower diversity due to different biogeographic history.

Our understanding of functional roles of aquatic invertebrate taxa is still limited even for common species, although being crucial for explanations of patterns observed in natural communities. As only recently shown, the common native European amphipodGammarus fossarum, traditionally treated as a shredder of leaf litter, shows predatory behaviour which may influence the composition of invertebrate assemblages. However, the evidence for the predation effect ofG. fossarumon natural assemblages at the within-site scale is still lacking. Therefore, we collected 50 quantitative samples of macroinvertebrates along with the important environmental variables within a heterogeneous calcareous spring fen. Using linear regression, we explored the relationships between the abundance ofG. fossarum(separately adult and juvenile) and the abundance and number of taxa for two groups of invertebrates differing in their susceptibility to predation, (a) hard-bodied taxa with protective body structures, such as shells and calcified cuticles, and (b) soft-bodied taxa without those protections. We separated the effect ofG. fossarumfrom that of environmental conditions using variation partitioning. Our results showed that only the abundance of soft-bodied invertebrates was negatively correlated with the abundance of adultG. fossarum. However, the proportion of variation explained purely by predation (5.5%) was much lower than the one explained by the environment (33.8%). BothG. fossarumand soft-bodied invertebrates were positively associated with organic matter. Although hard-bodied invertebrates consisted of only a few taxa, they were more numerous than soft-bodied invertebrates, and only environmental control was confirmed for them. Despite the limitations of the used correlative approach, we conclude thatG. fossarumcan significantly control the abundance of vulnerable taxa in natural assemblages. Its predatory effects, however, may be relatively low and easily confounded by the effect of environmental control.

Climate warming and associated environmental changes lead to compositional shifts and local extinctions in various ecosystems. Species closely associated with rare island-like habitats such as groundwater-dependent spring fens can be severely threatened by these changes due to a limited possibility to disperse. It is, however, largely unknown to what extent mesoclimate affects species composition in spring fens, where microclimate is buffered by groundwater supply. We assembled an original landscape-scale dataset on species composition of the most waterlogged parts of isolated temperate spring fens in the Western Carpathian Mountains along with continuously measured water temperature and hydrological, hydrochemical, and climatic conditions. We explored a set of hypotheses about the effects of mesoclimate air and local spring-water temperature on compositional variation of aquatic (macroinvertebrates), semi-terrestrial (plants) and terrestrial (land snails) components of spring-fen biota, categorized as habitat specialists and other species (i.e. matrix-derived). Water temperature did not show a high level of correlation with mesoclimate. For all components, fractions of compositional variation constrained to temperature were statistically significant and higher for habitat specialists than for other species. The importance of air temperature at the expense of water temperature and its fluctuation clearly increased with terrestriality, i.e. from aquatic macroinvertebrates via vegetation (bryophytes and vascular plants) to land snails, with January air temperature being the most important factor for land snails and plant specialists. Some calcareous-fen specialists with a clear distribution centre in temperate Europe showed a strong affinity to climatically cold sites in our study area and may hence be considered as threatened by climate warming. We conclude that prediction models solely based on air temperature may provide biased estimates of future changes in spring fen communities, because their aquatic and semiterrestrial components are largely affected by water temperature that is modified by local hydrological and landscape settings.

Aquatic invertebrates of groundwater-dependent wetlands can be sensitive to a drop in the groundwater table, which is considered one of the possible impacts of climate change. We investigated whether aquatic clitellate species are able to dwell in waterlogged substrates without surface water, in 27 spring fens studied across the Western Carpathians. A total of 78 clitellate species were recorded in pairs of samples from aquatic and semi-aquatic habitats. Semiaquatic habitats had 27 species in common with aquatic habitats, but algal and fungal feeders were less frequent and abundant, and predatory leeches and Haplotaxis gordioides completely lacking. Results indicate that, during extreme droughts, when aquatic habitats cease to exist, some aquatic clitellates can persist in the waterlogged substrate, while some aquatic specialists may face the risk of local extinction.

Many studies have investigated the vegetation and terrestrial fauna of post-mining spoil heaps, but little is known about aquatic macroinvertebrates in these areas, particularly at spring-fed habitats. We studied nine seepages (i.e. spring-fed habitats) located at two neighbouring spoil heaps in the Sokolov brown-coal basin (Czech Republic), characterised by basic water pH, calcium carbonate precipitation, high heavy metal and sulphate concentrations.

The Socotra Archipelago (Yemen) is remarkable for unique ecosystems and high endemism, for which it is often referred to as the “Galapagos of the Indian Ocean”. Here we describe a new parasitic leech Myxobdella socotrensis sp. nov. from Socotra, the largest island of the archipelago. The new species was found in a freshwater spring attached to the endemic crab Socotrapotamon socotrensis (Hilgendorf, 1883) (Crustacea: Potamidae). Based on its morphology, ecology and a phylogenetic analysis of DNA sequence data (12S, 18S, 28S and COI gene markers), the new leech species is classified into the highly diversified family Praobdellidae (Hirudinida: Arhynchobdellida), distributed in tropical regions of Africa, Asia and Central and South America. The praobdellid leeches are known to infest mammalian mucous membranes, however, some taxa are associated with other hosts, namely crabs, amphibians and birds. By its morphology, the new species fits quite well in the current concept of the genus Myxobdella Oka, 1917. However, the monophyly of Myxobdella was not supported here by molecular data, pointing at the need of a more comprehensive systematic revision of the genus and family. As far as known, Myxobdella socotrensis sp. nov. is endemic to the Socotra Island, but more data are needed to understand its evolutionary origin, biology and distribution.

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Habitat specialists and generalists are known to differ in their width of environmental tolerance and their representation can vary along with the ecological contrast of habitats. In this study we explore factors shaping patterns of species richness and abundance of aquatic macroinvertebrate habitat specialists and generalists at isolated spring fens, separately for spring patch and spring brook mesohabitats at each site. We also examined habitat contrast of these unique island-like communities by the comparison of spring fen specialists and habitat generalists shared between the two spring fen mesohabitats and the nearest stream to each of 13 selects fen sites. Aquatic macroinvertebrates (Clitellata, Ephemeroptera, Plecoptera, Trichoptera, and Diptera) were investigated at 62 isolated spring fens, with 357 taxa identified in more than 172,000 individuals collected. We found that specialists experienced a stronger relation to local environmental conditions (i.e. the amount of dissolved oxygen and water conductivity) at both spring mesohabitats than generalists, primarily responding to fen habitat size. In contrast, responses of species abundances at spring patches and spring brooks differed as the abundances were controlled by the amount of oxygen in spring patches and by habitat size in spring brooks. Based on Trichoptera and Diptera assemblages we found a similar contrast between both spring fen sites and nearby streams. Our results suggest a higher resilience of specialist populations in well oxygenated sites and their competitive advantage over generalists at these sites, which stresses the importance to prevent any significant decrease of oxygenation (e.g., by eutrophication or drainage), especially in spring patches.

Patterns in aquatic Clitellata assemblage composition are known to be driven by several environmental gradients, with water chemistry and substratum characteristics being particularly important. In this study we explored 54 isolated spring fens across the eastern Czech Republic and Slovakia. These fens varied in calcium and magnesium concentrations, forming a sharp and well defined environmental gradient running from calcium-poor acidic fens to extremely calcium-rich tufa-forming fens. We found that the main changes in clitellate species composition were controlled by this gradient, and/or total organic carbon content, over a wide area, including fen sites differing in other environmental conditions and historical development. However, this pattern was weakened in sites with a high organic matter content, which represented a second driver of change in assemblage composition along with water temperature. Three main types of fens were determined using cluster analysis based on clitellate assemblage composition. However, only the first type, which included tufa-forming fens, was found to fit with the previously established spring fen types based on vegetation (i.e. extremely mineral-rich fens with a tufa, brown-moss mineral-rich fens, mineral-rich Sphagnum fens and mineral-poor Sphagnum fens). The second clitellate type included sites with low temperatures and occasional desiccation, while the third type was characterised by high temperatures and trophy. Using eight environmental predictors, we were able to significantly explain changes in the population abundances of all 12 common species (i.e. recorded at 15-plus sites). The results from individual species modelling also suggests that an increase in organic matter content can trigger compositional shifts towards assemblages of common eurytopic tubificid species. Thus, human-induced eutrophication and negative changes in spring fen hydrology, mainly drying up, can represent a serious threat for species-specific assemblages of aquatic clitellates, especially at alkaline sites due to their isolated and spatially limited nature.

Aims The aim was to identify the main drivers of aquatic macroinvertebrate species richness in spring-fen habitats (i.e. groundwater seepage wetlands) because these habitats are among the most threatened temperate biodiversity hotspots. Location Isolated spring fens in the western Carpathian Mountains. Methods Assemblages of Tricladida, Clitellata, Mollusca, Ephemeroptera, Plecoptera, Trichoptera and Diptera were sampled at 48 fens distributed evenly along a gradient of water mineral richness and grouped according to habitat specialization and dispersal mode. Several physicochemical parameters that have been reported to be the main drivers of species distribution were recorded for each site, along with radiocarbon measurements of the absolute age of the sites. The numbers of species in the taxonomic groups analysed were modelled as a function of the predictors via multiple linear regressions. Results We achieved a notably higher sampling efficiency than had been used in previous spring aquatic macroinvertebrate studies. In total, we collected and identified 255 species within 331 taxa from > 235,000 individuals. The number of species in all taxonomic groups increased with water discharge but the highest predictive power was obtained with water redox potential, which explained as much as 55.7% of the specialist species richness variance. We found contrasting and systematic differences in the importance of predictors related mainly to the level of species habitat specialization. Species richness of springfen specialists was strongly determined by the main environmental gradient of change in groundwater chemistry, while generalists primarily reflected habitat stability linked to higher water discharge, habitat size and absolute age. Main conclusion Isolated island-like spring fens can harbour unusually species-rich assemblages of aquatic macroinvertebrates, the species richness of which is shaped by contrasting mechanisms dependent mainly on habitat specialization and also partly on dispersal mode. The richness of habitat specialist species seen at calcareous fens indicates their conservation priority.

This study deals with the habitat preferences of medicinal leech Hirudo medicinalis Linnaeus, 1758 in the Czech Republic, in a highly agriculturally used and fragmented landscape, and provides the detailed information about the ventral coloration of this species. The study was conducted in 2010–2011 at 11 out of total 15 localities of H. medicinalis in the Czech Republic. At each locality a phytocenological sample of littoral and aquatic vegetation was recorded and physicochemical variables were measured. All captured leeches were measured and weighted, and a photo of ventral side was taken. Division of localities based on aquatic vegetation (TWINSPAN) formed groups of localities which corresponded to the population sizes of H. medicinalis. According to the abiotic factors localities with H. medicinalis were rich in carbon, poor in oxygen and situated in an area with warm climate. In this study four different ventral color patterns were described. During the ontogenetic development ventral side becomes darker, as indicated by the significant relationship between the percentage of dark color and leech size.

With 4 figures and 2 tables Abstract: Deep knowledge of the ecology of aquatic invertebrate species has always been essential background for water quality assessment and leeches (Clitellata: Hirudinida), which are at the top of the benthic invertebrate food chain, are hence a group of principal importance. To study the biological and habitat requirements of free- living leeches, 109 sites of running and stagnant water were sampled in the Czech Republic, between 2007 and 2010. The morphological characteristics of the sampling site, chemical parameters of the water and climatic data were available for each site. Leeches were collected by hand, counted and identified. In total, seventeen species of genera Alboglossiphonia, Glossiphonia, Helobdella, Hemiclepsis, Theromyzon, Piscicola, Haemopis, Hirudo, Dina and Erpobdella were recorded. Environmental and species data were used in the analyses. The optima of twelve environmental variables for nine common species were compared using boxplots. The structure of the leech data set was recognised by cluster analysis, where eurytopic species formed a distinct group, well separated from all other species, which was further subdivided according to their ecology. Predictive models designed for seven of the leech species, revealed significant variables, which determined species occurrence and the extent of the effect of these variables. The most frequent significant variables were the type of habitat (lotic or lenitic) and the mean annual temperature.

Mining is a relatively highly monitored industry. While chemical pollutants (toxic ions, radionuclides, etc.) have mostly been eliminated from mining waters, other types of environmental pollution (temperature regime alterations, high concentrations of various anions, etc.) can affect benthic invertebrates. In this study, we focused on the effect of mining water effluent on the diversity and density of aquatic Clitellata. Four sampling sites were selected. Three sites in a natural stream (the Nedvědicka River, Czech Republic), one upstream and two downstream from the mining effluent, and one site on the mining waters were sampled monthly during 2008–2009. Environmental variables were recorded in and samples were collected from two types of habitats — riffles and pools. The response of clitellate assemblages was evaluated using principal component analysis and generalised estimating equations. The results indicated that the mining effluent caused partial species exchange and had negative effects on clitellate taxa richness and abundance. These responses were specific to both the habitat (riffle/pool) and species sampled. In each of the different taxa studied, we observed one of four typical clitellate responses: (a) elimination of stenotherm species; (b) reduction of clitellate species followed by quick recovery; (c) neutral response; or (d) positive influence. We found that aquatic clitellates, which are considered to be eurytopic with broad ecological valences, are also sensitive to even slight environmental pollution.

The relevance of environmental and spatial processes for species distributions varies among environments and types of metacommunities. Here, for the first time, we use modern statistical approaches to test the contribution of these two processes in structuring ecologically unique and threatened biotas of insular spring fens. We applied two species categorisations, common/rare and generalists/specialists, to disentangle the roles of dispersal capacity and habitat specialisation. In accordance with current understanding of headwater ecosystems, we found that environmental processes played a major role in most of the spring fen taxonomic and functional groups. However, we observed significant spatial structure in passive dispersers (Clitellata, a class of annelid worms), common species and habitat specialists. Spatial processes played the leading role in structuring the metacommunity of passively dispersing specialists. In contrast, all analysed insect groups, even those known to be poor dispersers, were able to reach virtually all favourable sites. We conclude that dispersal mode (active versus passive) and, to a lesser extent, habitat specialisation are the main factors determining the mechanism of spring fen metacommunity structuring.

This study provides new information on beta diversity (variation in species composition across space) of three invertebrate groups (Clitellata, Plecoptera, and Chironomidae) on a small, within-site spatial scale. It was conducted at small-sized spring fens where two contrasting mesohabitats, a flowing-water and a standing-water, can be clearly distinguished. Besides flow conditions, these habitats differed in the amounts of inorganic substratum and dissolved oxygen. Factors related to flow conditions (dissolved oxygen and water temperature) influenced the composition of the studied assemblages at both mesohabitats, while substratum features were important at the standing-water habitat. The water chemistry was important for Clitellata at both mesohabitats and for Chironomidae at the flowing-water. Using a new approach of disentangling beta diversity into two components (species replacement and species richness differences), clear difference in beta diversity patterns among the three assemblages were found, despite their roughly equal total beta diversities. Variation in species composition of those assemblages strongly limited by flow conditions (Plecoptera and partly Clitellata) was induced by differences in species richness, while replacement governed the variation in species rich assemblages that were able to utilise a wide range of conditions (Chironomidae and partly Clitellata). These results indicate that the size of species pool and the level of environmental filtering play an important role in forming beta diversity patterns, and caution that the same amount of beta diversity can be promoted by essentially different mechanisms, even at a very fine spatial scale with no involvement of dispersal limitations. (C) 2014 Elsevier GmbH. All rights reserved.

Leeches (Clitellata: Hirudinida) are abundant predators or ecto-parasites inhabiting various freshwater habitats; however many biotic and abiotic drivers of their assemblage patterns have been deduced rather than directly tested. To study species richness and composition changes in leech assemblages, 109 sites of running and stagnant water bodies were sampled in three regions of the Czech Republic in 2007–2010, together with several explanatory variables that are known or expected to be important predictors of leech distribution. In total, 17 species of leeches were recorded, varying between 0–7 and 0–9 species in lotic and lenitic sites, respectively. These differences in species richness of lotic and lenitic sites were highly significant, contrary to the abundances, which varied between 0–283 and 0–295 individuals. The main change in species composition was controlled by water temperature and morphological characteristics (e.g. substrate and cover of macrophytes), mostly reflecting the differences between lotic and lenitic habitats. We found the density of benthos (i.e. prey availability) to be the best predictor of species composition in both lotic and lenitic sites, together with the percentage of canopy cover. However, the other significant predictors (i.e. the substrate and water conductivity found to be significant in lotic sites, and the mean annual temperature and PO 4 3− in lenitic sites), differed between these habitats. Other than mean annual temperature and water temperature, which had different effects on species richness in lotic and lenitic sites, there were no other differences between lotic and lenitic sites in terms of how species richness and abundance responded to all other analyzed predictors. Our results stress the importance of prey availability and canopy for leech distribution patterns. Differences in the significant predictors of leech assemblage patterns between lotic and lenitic sites raise fundamental questions about the underlying mechanisms and ecological constraints to leech distribution in these main types of aquatic systems.

A new clitellate species of Pristininae (Naididae), Pristina armata n. sp., found in the pitcher of the carnivorous plant Nepenthes sp., is reported from East Kalimantan, Indonesia. P. armata n. sp. is a very small clitellate, less than 1 mm long in fixed state, and without proboscis on the prostomium. Signs of reproduction by paratomy were observed, but the generic placement remains preliminary because sexually mature individuals were not found. P. armata n. sp. is characterized by giant hook-like dorsal chaetae at IV. The description of P. armata n. sp. was based on six fixed specimens of different size and stage of development. Noteworthy is the habitat of P. armata n. sp. in Nepenthes pitchers, this being the first clitellate species described from such a habitat. P. armata n. sp. may be a member of the nepenthebionts' community, realizing its life cycle inside the digestive fluid of the Nepenthes pitcher, or it belongs to nepenthephiles, species that commonly occur in this habitat but do not specialize on it.

We examined responses of macroinvertebrate assemblages to environmental and temporal variations along spring source-spring brook transects in two fen habitats, sharply differing in groundwater chemistry, and compared the patterns among individual taxonomical groups. We hypothesised a different importance of environmental heterogeneity and seasonal changes primarily linked to strong tufa precipitation, which causes stronger environmental filtering in the calcareous fen. In concordance, we observed that assemblages of the more homogenous calcareous fen primarily changed over time, due to seasonal shifts in source availability and favourable conditions.

Spring fens are isolated treeless wetlands of a high conservation value. Their environmental conditions are strongly related to their groundwater chemistry, which controls species distribution within various groups of organisms. Clitellates, a dominant group of non-insect aquatic fauna, however, have never been studied in these habitats. It is unclear from previous studies to what extent the distribution of aquatic non-insect taxa reflects water chemistry rather than the substrate structure. We studied 34 spring fens sampled in 17 isolated sites in the Western Carpathian Mountains to determine mainly the effects of water chemistry and substrate structure on variation in species richness and composition of clitellate assemblages as examples of the non-insect fauna. A total of 34 taxa were found, with 3–15 taxa collected per sample. Species richness was negatively correlated with water mineral concentration measured as water electric conductivity (r = −0.57, P < 0.001) and positively with TOC (r = 0.60, P < 0.001). Surprisingly, the lowest number of taxa was found in calcareous fens and richness increased towards Sphagnum-fens. There was a species turnover related to changes in mineral richness and substrate characters. The main change of species composition was promoted by changes in substrate structure. The second gradient of species composition was linked with the amount of nutrients, moisture, and dominance of sphagna, and was associated with an increase of eurytopic species in fens with high nutrient availability. It was difficult to separate the effects of water chemistry and substrate on clitellate species distributions owing to the fact that variation in tufa precipitation and vegetation was driven by water chemistry changes. This study presented the first quantitative data on fen clitellate assemblages, which appear to have an unusual pattern of species richness. In contrast to plants and molluscs, calcareous fens appeared to be a harsh environment for clitellate species. Only few specialized species, mainly Trichodrilus strandi, were able to establish viable populations. The significant effect of water chemistry on clitellate distribution patterns raises questions about the direct influence of water chemistry on non-insect aquatic taxa, which have previously been considered to be mostly determined by substrate characteristics.

Freshwater leeches (Annelida: Clitellata: Hirudinida) of the Czech Republic were studied on the basis of recent literature, information in selected databases, and results of recent surveys conducted by the authors. The objectives of this study were to summarize recent taxonomic information, and to update the check-list of leeches using records collected during an eleven-year study (1998 through 2008). Altogether, twenty-four species representing 12 genera and five families are reported for the Czech Republic, including the first reports of Piscicola cf. haranti Jarry, 1960 and Dina punctata Johansson, 1927 for the country. A detailed description of the distributions of rare species and characterization of localities from which they are reported are presented. Plausible modes of dispersal and propagation of species in Central Europe are discussed. According to recent records, leech species are divided into three groups: indigenous species with stable and strong populations (12 species), indigenous species with weak populations known from a limited number of localities (9 species), and species only recently recorded in the Czech Republic (3 species). For scarce or rare species, a category of threat in the Czech Republic according to the International Union for Conservation of Nature is recommended. Most of threatened species are inhabitants of lowland wetlands and lowland larger rivers—habitats that are negatively impacted, often catastrophically, by human activities throughout Central Europe. The protection of suitable habitats is the most effective way to protect extant populations of endangered leech species. Six species of leeches are recommended for permanent addition to the Red list of threatened species in the Czech Republic.

Combined oligochaete and chironomid data were analyzed to search for main gradients and the separate data sets were analyzed to identify the most important variables determining the structure of the communities. Preferences for particular hydraulic conditions, expressed as Froude number, were calculated for 29 most abundant taxa. The results of Correspondence Analysis (CA) indicated that the main gradient in the data could be explained by hydraulic conditions and, inversely, by the amount of sedimented particulate organic matter (POM). The second CA axis probably reflected the quantity of the available food and space resources. Canonical Correspondence Analysis (CCA) showed the amount of sedimented POM as the most important variable explaining 21 and 24 % of the variance in the oligochaete and chironomid data respectively. Among the other variables, the occurrence of aquatic vegetation, variability of nearbottom current velocity and substrate roughness were the most important.

Populations of Erpobdella octoculata and E. vilnensis were studied monthly over two years (May 1999-April 2001) at four sampling points on the river Rokytna (Czech Republic). The water depth and velocity were measured and the Froude number for each sample was calculated to follow flow conditions above the bottom. Temporal differences in biomass of the two species were studied by comparing their wet weights and evaluated by the time series analysis; differences in their diets were evaluated by gut content analyses. Significantly different hydrodynamic preferences for juvenile and adult stages of E. octoculata and E. vilnensis were recorded. In E. vilnensis only, an annual cycle was recorded with a one-month shift of mean weights compared to E. octoculata. This shift, together with the correlation of the leeches wet weights with their prey sizes and their distinct habitat preferences are suggested as mechanisms that explain their coexistence.

The seasonal dynamics of Bythonomus lemani (Lumbriculidae) were studied for the first time and the knowledge of Bothrioneurum vejdovskyanum (Tubificidae) was extended based on four quantitative samples of oligochaetes taken monthly in the Rokytna River (Czech Republic) during a two-year study (April 1999–April 2001). The influence of water temperature, velocity, depth, discharge, pH, conductivity, dissolved oxygen amount and biochemical oxygen demand (BOD) on their life cycles was evaluated. Habitat preferences of the juvenile and adult stages were recorded. Time series analysis was used to determine the worm densities, seasonality and trends. For Byth. lemani one distinct reproduction cycle per year was found and this was regulated by temperature, while Both. vejdovskyanum showed a one-year cycle not significantly dependent on measured environmental variables. The overall trend was an increase in density for Byth. lemani and a decrease in density for Both. vejdovskyanum. Byth. lemani showed a significant negative correlation between the trend of its density and BOD concentration.

Research was carried out to determine aquatic oligochaete habitat preferences in the Rokytna River (Thaya River basin), a sixth order highland stream in the Czech Republic during the period of April 1999–April 2001. Quantitative samples were collected and current velocity and basic physico-chemical variables were measured monthly in four typical habitats in the Rokytna River. During this study, 28, 842 individuals representing 44 oligochaete species or higher taxa were collected. Temporal variability of proportional occurrence of trophic groups found on selected habitats (gathering collectors and grazers) was analysed. Habitat preferences of oligochaete species were evaluated by Canonical Correspondence Analysis (CANOCO). Biochemical oxygen demand (BOD) and nitrate (NO 3 − ) ion concentration were the most important variables explaining the distribution of Oligochaeta along the first axis. Current velocity (at 40% of the depth) and presence of oligochaetes associated with the habitat where gravel bars never formed were the most important variables along the second axis. Both axes were correlated with the temperature, reflecting the sampling in summer along the first axis and sampling in late spring along the second axis. The amount of organic matter (BOD) and concentrations of NO 3 − ions represented both oligochaete food source and decomposition products contributing to the growth of algae. Current velocity and preferred habitat explained the spatial pattern of oligochaete distributions.

The oligochaete fauna of 57 small streams of the Morava and Odra River basins, Czech Republic, was studied during 1997 and 1998. TWINSPAN and CCA (CANOCO) were used to characterize the relationship between oligochaete species, habitat diversity and environmental variables. Chemical oxygen demand (COD), water hardness, NO3− -N, Ca2+, Mg2+, altitude, and substrate type were found to be the primary factors influencing the distribution of aquatic Oligochaeta.

A new clitellate species of Pristininae (Naididae), Pristina armata n. sp., found in the pitcher of the carnivorous plant Nepenthes sp., is reported from East Kalimantan, Indonesia. P. armata n. sp. is a very small clitellate, less than 1 mm long in fixed state, and without proboscis on the prostomium. Signs of reproduction by paratomy were observed, but the generic placement remains preliminary because sexually mature individuals were not found. P. armata n. sp. is characterized by giant hook-like dorsal chaetae at IV. The description of P. armata n. sp. was based on six fixed specimens of different size and stage of development. Noteworthy is the habitat of P. armata n. sp. in Nepenthes pitchers, this being the first clitellate species described from such a habitat. P. armata n. sp. may be a member of the nepenthebionts' community, realizing its life cycle inside the digestive fluid of the Nepenthes pitcher, or it belongs to nepenthephiles, species that commonly occur in this habitat but do not specialize on it.

This study contributes to the knowledge of central European clitellates by creating a check-list of Oligochaeta (sensu oligochaetous Clitellata; Erseus 2005) of the Czech Republic, exclusive of taxa in the family Enchytraeidae. In total, 95 aquatic oligochaete species representing 43 genera are reported for the Czech Republic. Rare species are highlighted and associated with the categories for threatened species as outlined by the International Union for the Conservation of Nature. The first records of Trichodrilus strandi Hrabě, 1936, Pristina jenkinae (Stephenson, 1931), Pristina osborni (Walton, 1906), Rhyacodrilus subterraneus Hrabě, 1963, Aulodrilus limnobius Bretscher, 1899, and Aulodrilus pigueti Kowalewski, 1914 in the Czech Republic are presented. Their ecology, morphology, and distribution are discussed.