Ancylus Fluviatilis Research Articles

Freshwater Malacofauna and Distribution of Trabzon, Türkiye

In this study, freshwater molluscs and their zoogeographical distributions in Trabzon were investigated. During the period of June-December 2021, samples were collected from 38 freshwater river localities. From the study area, Ancylus fluviatilis from Gastropoda class, Planorbidae family, non-native species Physella acuta from Physidae family, and Dreissena polymorpha from Bivalvia class and Dreissenidae family were identified. While A. fluviatilis specimens were found from all freshwater systems in Trabzon region, the non native P. acuta could be identified from Fol Stream, Yıldızlı Stream, Sera Lake and Manahoz River. Empty shells belonging to the D. polymorpha species were identified from the area where Çatalzeytin Stream joins the sea. P. acuta and D. polymorpha are new records for the freshwater streams of Trabzon region.

Mitigation of impacts of cattle access on stream ecosystems: Efficacy of fencing

AbstractHeadwater streams can constitute up to 80% of river channel length and are vulnerable to anthropogenic pressures due to their high connectivity to adjacent land, large relative catchment size and low dilution capacity. In these environments, unrestricted cattle access is a potentially significant cause of water quality deterioration, resulting from increases in stream bank erosion, riparian damage and sediment deposition among others. Several studies have reported improvements in the physico‐chemical and hydromorphological conditions of streams following the elimination of cattle access; few, however, have focussed on the ecological impacts of such management practices. Here, such impacts are assessed. The study explores the short‐term effects of cattle exclusion by comparing habitat conditions, sediment deposition and instream macroinvertebrate communities upstream and downstream of cattle access points prior to, and 1 year following exclusion via fencing. The long‐term effects are also measured by reassessing a small stream catchment entirely fenced off from cattle access in 2008 under a dedicated management plan. In the short term, cattle exclusion led to a reduction in deposited sediment downstream of cattle access points and a related homogenisation of macroinvertebrate community structure between upstream and downstream of cattle access points. Increased abundances of specific indicator taxa (Ancylus fluviatilis, Glossosomatidae and Elmidae) in the fenced catchment following 9 years of exclusion highlight the long‐term ecological benefits of such mitigation practices. These findings highlight the importance of incentivised agri‐environment measures in reducing the negative impacts of cattle access to vulnerable aquatic ecosystems.

Resource-dependent foraging behaviour of grazers enhances effects of nutrient enrichment on algal biomass

Both the quantity and nutritional quality of food resources can strongly influence the foraging movements of herbivores, which in turn determine the strength of top-down control on primary producer biomass. Nutrient enrichment can alter the biomass and nutritional quality of primary producers, but the consequences for the foraging of herbivores and hence for top-down control are still poorly understood. In this study, we combined a two-factorial experiment (two nutrient levels × grazing by the freshwater gastropod Ancylus fluviatilis) with video analyses tracking grazers’ movements to investigate nutrient enrichment effects on spatial ranges of grazing activity and algal biomass removal. Natural stream biofilms were grown in phosphorus-enriched (P+) and phosphorus-poor flumes (P−) for two weeks before A. fluviatilis were added to the flumes and allowed to graze on biofilm for an additional 2 weeks. Total periphyton biomass was enhanced by P+ and reduced by grazer presence. However, the total grazer effect depended on the nutrient level: at the end of the experiment, on average 95% of algal cover were removed by grazing in the P− flumes versus 26% in the P+ flumes. Fast movements of A. fluviatilis were detected significantly more often in the P− treatment, whereas grazers were detected resting more often in the P+ treatment. Our results demonstrate that nutrient enrichment can increase primary producer biomass both directly and indirectly by limiting the foraging ranges of herbivores. The resulting feedback loop between reduced grazing activity and increased plant biomass might in turn exacerbate eutrophication effects on habitat structure.

Development of transient habitat modeling for stream Macrozoobenthos

AbstractIn addition to the hydromorphological pressure on the ecological conditions of free‐flowing river courses, increasing water temperature is affecting the water bodies, particularly by changing freshwater community compositions. The low discharge of numerous European rivers in the dry and hot hydrological year 2022 proves this relevance. Therefore, ecological assessment tools such as habitat modeling should take these factors into account when assessing the quantity and quality of habitats. In this paper, the habitat modeling tool “Transient River Habitat Modeling for Macrozoobenthos” (TRiMM) is improved by incorporating a fuzzy logic approach and adding water temperature to the set of parameters determining habitat suitability for macrozoobenthos. Habitat‐relevant parameters, including hydromorphological factors (depth, velocity, mineral and organic substrate) and a water quality factor (temperature), are combined in the habitat model so that it can more broadly characterize river physical conditions and their interactions with biological indicators. Habitat modeling employed the mentioned parameters to simulate suitability for the macrozoobenthos in a small river in central Saxony, Germany. Due to its deteriorated condition, this river was selected as a representative for thousands of kilometers of small rivers across the region, which have been restored. The model simulated the status quo of river conditions from spring to summer for three macrozoobenthos species (Ancylus fluviatilis, Ephemera danica and Gammarus fossarum). The results showed that the natural flow resulted in dynamic habitat suitability both spatially and temporally, which differs for each species. Remarkably, the five‐parameter model (depth, velocity, temperature, mineral, and organic substrate) generally performed better compared to a similar model without temperature.

They do not fear the unknown: Ancylus fluviatilis (Mollusca, Planorbidae) shows no predator avoidance behavior towards a novel invasive predator

Biological invasion is a strong threat to native biodiversity, with limnic systems being especially vulnerable due to historical separation and resulting prey naivety. The prey naivety hypothesis states that native species may not be able to recognize novel predators due to a lack of common evolutionary background and, therefore, become easy targets. In a laboratory experiment, we added cues of native European bullhead (Cottus gobio Linnaeus, 1758) and invasive round goby [Neogobius melanostomus (Pallas, 1814)] to Ancylus fluviatilis Müller, 1774 originating from two different populations within the same river (one naive, one experienced towards round goby) and compared their predator avoidance behavior. Individuals from both populations recognized cues from the known predator C. gobio and reduced their locomotive activity. To round goby cues, however, naive individuals did not respond, thereby supporting the prey naivety hypothesis. Experienced individuals, in contrast, reduced their activity, suggesting a learning effect due to the co-occurrence of invasive predator and prey. At fast moving invasion fronts of highly invasive species like N. melanostomus, prey naivety can, hence, enhance their negative impact on ecosystems. Behavioral adaptation of native species resulting in predator avoidance reactions could, therefore, play an important role in ecosystem resilience and temporal invasion dynamics.

Individual small in-stream barriers contribute little to strong local population genetic structure five strictly aquatic macroinvertebrate taxa.

Water flow in river networks is frequently regulated by man‐made in‐stream barriers. These obstacles can hinder dispersal of aquatic organisms and isolate populations leading to the loss of genetic diversity. Although millions of small in‐stream barriers exist worldwide, their impact on dispersal of macroinvertebrates remains unclear. Therefore, we, therefore, assessed the effects of such barriers on the population structure and effective dispersal of five macroinvertebrate species with strictly aquatic life cycles: the amphipod crustacean Gammarus fossarum (clade 11), three snail species of the Ancylus fluviatilis species complex and the flatworm Dugesia gonocephala. We studied populations at nine weirs and eight culverts (3 pipes, 5 tunnels), built 33–109 years ago, mainly in the heavily fragmented catchment of the river Ruhr (Sauerland, Germany). To assess fragmentation and barrier effects, we generated genome‐wide SNP data using ddRAD sequencing and evaluated clustering, differentiation between populations up‐ and downstream of each barrier and effective migration rates among sites and across barriers. Additionally, we applied population genomic simulations to assess expected differentiation patterns under different gene flow scenarios. Our data show that populations of all species are highly isolated at regional and local scales within few kilometers. While the regional population structure likely results from historical processes, the strong local differentiation suggests that contemporary dispersal barriers exist. However, we identified significant barrier effects only for pipes (for A. fluviatilis II and III) and few larger weirs (>1.3 m; for D. gonocephala). Therefore, our data suggest that most small in‐stream barriers can probably be overcome by all studied taxa frequently enough to prevent fragmentation. However, it remains to be tested if the strong local differentiation is a result of a cumulative effect of small barriers, or if larger in‐stream barriers, land use, chemical pollution, urbanization, or a combination of these factors impede gene flow.

Vodní měkkýši přírodní rezervace Maštale (východní Čechy) [Aquatic molluscs of the Maštale Nature Reserve (East Bohemia)

The Maštale Nature Reserve (Eastern Bohemia, Czech Republic) represents a system of rocky sandstone valleys with springs, ponds and several streams. Aquatic molluscs of this area have never been studied, which became a reason for the first inventory conducted in 2019 and 2020. Altogether 19 species were found at 39 sites, from which Radix labiata, Gyraulus albus, Ancylus fluviatilis and Pisidium casertanum belonged among the most often recorded species while Bythinella austriaca, Acroloxus lacustre, Lymnaea stagnalis, Anodonta anatina, Pisidium milium and P. personatum were found at only one or two sites. Majority of recorded molluscs belonged to common and widespread species; only gastropod Bythinella austriaca and pea mussels Pisidium milium and P. obtusale are listed in the Red List of the Czech Republic in the category Near Threatened. The occurrence of hydrobiid B. austriaca in the area where sandstone dominated is noteworthy. Two non-native species Physa acuta and Ferrissia californica were found.

High nutrient availability leads to weaker top‐down control of stream periphyton: Compensatory feeding in Ancylus fluviatilis

Abstract Benthic algal biomass and distribution in freshwater ecosystems are determined by both nutrient availability (bottom‐up control) and grazing activity by herbivores (top‐down control). Fluctuations in algal nutrient ratios may cause grazers to optimise their food intake through behavioural strategies in order to maintain a constant soft body stoichiometry. Such linkages between nutrient availability and grazing control of algal biomass are as yet poorly understood. In this study, we tested whether the stream‐dwelling freshwater gastropod Ancylus fluviatilis would increase its food consumption rate with decreasing periphyton nutrient content, a behaviour known as compensatory feeding. We performed a fully factorial microcosm experiment in which two levels of periphyton phosphorus content (low versus high) were crossed with grazer presence/absence in 12 circular flumes. After 1 week of grazing, food consumption rates were measured by determining the periphyton difference between grazed and ungrazed flumes, and the periphyton biomass variability in every flume was described with a coefficient of variation. The food consumption rate of A. fluviatilis was significantly higher in the low phosphorus compared to the high phosphorus treatment, supporting the compensatory feeding hypothesis. As a result, in the presence of grazers, periphyton biomass was significantly lower under low phosphorus availability, while biomass was not affected by nutrient enrichment in the grazer‐free flumes. Despite the strong difference in periphyton phosphorus content, A. fluviatilis soft body stoichiometry did not differ between the two nutrient treatments, suggesting strong stoichiometric homeostasis. Furthermore, the distribution of algal biomass was significantly more heterogeneous in the grazed phosphorus‐poor than in the phosphorus‐rich periphyton. Our findings suggest that nutrient enrichment may lead to a weaker top‐down control of algal biomass in stream ecosystems and to reduced spatial heterogeneity of periphyton abundance.

Genome-wide single-nucleotide polymorphism data reveal cryptic species within cryptic freshwater snail species-The case of the Ancylus fluviatilis species complex.

DNA barcoding utilizes short standardized DNA sequences to identify species and is increasingly used in biodiversity assessments. The technique has unveiled an unforeseeably high number of morphologically cryptic species. However, if speciation has occurred relatively recently and rapidly, the use of single gene markers, and especially the exclusive use of mitochondrial markers, will presumably fail in delimitating species. Therefore, the true number of biological species might be even higher. One mechanism that can result in rapid speciation is hybridization of different species in combination with polyploidization, that is, allopolyploid speciation. In this study, we analyzed the population genetic structure of the polyploid freshwater snail Ancylus fluviatilis, for which allopolyploidization was postulated as a speciation mechanism. DNA barcoding has already revealed four cryptic species within A. fluviatilis (i.e., A. fluviatilis s. str., Ancylus sp. A–C), but early allozyme data even hint at the presence of additional cryptic lineages in Central Europe. We combined COI sequencing with high‐resolution genome‐wide SNP data (ddRAD data) to analyze the genetic structure of A. fluviatilis populations in a Central German low mountain range (Sauerland). The ddRAD data results indicate the presence of three cryptic species within A. fluviatilis s. str. occurring in sympatry and even syntopy, whereas mitochondrial sequence data only support the existence of one species, with shared haplotypes between species. Our study hence points to the limitations of DNA barcoding when dealing with organismal groups where speciation is assumed to have occurred rapidly, for example, through the process of allopolyploidization. We therefore emphasize that single marker DNA barcoding can underestimate the true species diversity and argue in strong favor of using genome‐wide data for species delimitation in such groups.

Ecotoxicological assessment of the impact of fluoride (F-) and turbidity on the freshwater snail Physella acuta in a polluted river receiving an industrial effluent.

We carried out field studies and laboratory experiments to assess the impact of fluoride (F-) and turbidity on the freshwater snail Physella acuta in a polluted river receiving an industrial effluent (the middle Duraton River, Central Spain). Fluoride concentrations and turbidity levels significantly increased downstream from the industrial effluent (with the highest values being 0.6mg F-/L and 55.2 nephelometric turbidity unit). In addition, higher deposition of fine inorganic matter was evident at polluted sampling sites. Conversely, the abundance of P. acuta significantly declined (until its virtual disappearance) downstream from the industrial effluent. Toxicity bioassays showed that P. acuta is a relatively tolerant invertebrate species to fluoride toxicity, with estimated safe concentrations (expressed as LC0.10 values for infinite hours of exposure) for juvenile and adult snails being 2.4 and 3.7mg F-/L, respectively. Furthermore, juvenile snails (more sensitive than adult snails) did not show significant alterations in their behavior through 15days of exposure to 2.6mg F-/L: mean values of the proportion of test snails located on the water surface habitat, as well as mean values of the sliding movement rate (velocity) of test snails, never showed significant differences when comparing control and treatment glass vessels. It is concluded that instream habitat degradation, derived from increased turbidity levels, might be a major cause for significant reductions in the abundance of P. acuta downstream from the industrial effluent. The presence of the competing gastropod Ancylus fluviatilis could also affect negatively the recovery of P. acuta abundance.

Vodní měkkýši Vysočiny [Freshwater molluscs of Vysočina Region (Czech Republic)

This paper summarizes data about the distribution of freshwater molluscs in the Vysočina Region (6,800 km²). The region is one of the 14 regions of the Czech Republic, situated in its central part. The major part of this region consists of Českomoravská vrchovina (Bohemian-Moravian Highlands) with average elevation about 500 m a. s. l. Data about freshwater molluscs have been obtained by author’s field research since 1993 and from many published and unpublished papers, private collections, and collections in museums dating from 1850. Altogether, data about the occurrence of 49 species of freshwater molluscs (27 gastropods, 22 bivalves) were obtained. This number constitutes 62% of all aquatic mollusc species found in the Czech Republic. Data about the occurrence of individual species were used for the construction of distributional maps of records for three time periods (1851–1950, 1951–2000, 2001–2016). The major part of the data has originated for the last period. This clearly demonstrates a significant increase in the research intensity after 2000. The most common species, i.e. recorded at least in 40 mapping cells out of 72 covering the area to the Vysočina Region, were Galba truncatula, Radix auricularia, R. labiata, Lymnaea stagnalis, Gyraulus albus, Ancylus fluviatilis, Anodonta anatina, Pisidium casertanum, and P. subtruncatum. In contrast, Viviparus viviparus, Potamopyrgus antipodarum, Stagnicola corvus, Radix ampla, R. balthica, Planorbis planorbis, Gyraulus acronicus, Ferrissia fragilis, Unio tumidus, Pseudanodonta complanata, Sinanodonta woodiana, Pisidium amnicum, P. tenuilineatum, and Dreissena polymorpha have been found in less than five mapping cells and belong to rare species of this region. Except 29 common and widespread species, four species (Bythinella austriaca, Physa fontinalis, Pisidium milium, and P. supinum) belonging in the Red List of the Molluscs of the Czech Republic were recorded. Other six species are classified as Vulnerable (Radix ampla, Gyraulus acronicus, Segmentina nitida, Unio tumidus, Anodonta cygnea, and Pisidium hibernicum), three as Endangered (Unio crassus, Pseudanodonta complanata, and Pisidium amnicum), and two as Critically Endangered (Margaritifera margaritifera and Pisidium tenuilineatum).

Estado atual do conhecimento dos ancilídeos na América do Sul (Mollusca: Gastropoda: Pulmonata: Basommatophora)

Ancylids are widespreaded pateliforms basommatophorans in lentic and lotic continental freshwater habitats. This paper shows a list of South American species based on literature revision and personal observations about systematic and morphology as well as some morphological, biological, ecological and paleontological data. Seven genera and at least thirteen good species are found: Anisancylus dutrae (Santos, 1994); Anisancylus obliquus (Broderip & Sowerby, 1832); Burnupia ingae Lanzer, 1991; Burnupia sp.; Ferrissia gentilis Lanzer, 1991; Ferrissia sp.; Gundlachia bakeri Pilsbry, 1913; Gundlachia radiata (Guilding, 1828); Gundlachia ticaga (Marcus & Marcus, 1962); Hebetancylus moricandi (d’Orbigny, 1837); Laevapex sp.; Uncancylus concentricus (d’Orbigny, 1835) and Uncancylus crequii (Bavay, 1904). Gundlachia leucaspis (Ancey, 1901); Gundlachia lutzi Walker, 1925; Gundlachia saulcyana (Bourguignat, 1853); Hebetancylus philippianus (Biese, 1948); Laevapex vazi Santos, 1989; Uncancylus foncki (Philippi, 1866) and Uncancylus patagonicus (Biese, 1948) need to be revised. Anatomical data show that South American ancylids are not closed related to Ancylus fluviatilis Muller, 1774. It is necessary to improve the knowledgement specially about morphology, biology, geographical distribution and genetics in order to assess the true systematic position of the called neotropical genera ( Anisancylus Pilsbry, 1924; Gundlachia Pfeiffer, 1849; Hebetancylus Pilsbry, 1913 and Uncancylus Pilsbry, 1913) and also Burnupia Walker, 1912 and Ferrissia Walker, 1903. Methodological procedures are presented.

Effects of Chaetogaster limnaei limnaei (Oligochaeta, Tubificidae) on freshwater snail communities

From laboratory studies, the relationship between the oligochaete Chaetogaster limnaei limnaei (CL) and its freshwater snail hosts is known to be context-dependent, ranging from mutualistic to parasitic. We monitored snail communities of seven streams in Germany during three seasons of a year and investigated infestation by CL. Some snail species never were infested. In snail species that were infested, size, substratum type, oxygen concentration and species identity were the most important variables explaining the variance in CL infestation. Independent of individual snail size, Bithynia tentaculata, Ancylus fluviatilis and Acroloxus lacustris showed the highest CL abundances. Across species, CL abundances were highest in large individuals on silty substratum at well-oxygenated sites. Reproductive success of snail populations was estimated from proportion of juveniles in populations. This measure of reproductive success of snail populations was inversely related with CL infestation level. These results suggest that CL infestation affects aquatic snails at the population and community level in the field. Differential infestation levels and different impacts of CL infestation between species lead to an asymmetric distribution of positive and negative effects among all snail species present in a habitat. Thus, CL may be an overlooked agent in structuring snail communities.

Cryptic diversity and population structure at small scales: the freshwater snailAncylus(Planorbidae, Pulmonata) in the Montseny mountain range

Anthropogenic impacts like intensified land use and climate change are severe threats to freshwater biodiversity and effective biodiversity monitoring is therefore one of the most urgent tasks. This is, however, often hampered by the lack of knowledge regarding the number and ecology of species. Molecular tools have shown many freshwater taxa to comprise morphologically cryptic species, which often occur in sympatry on a small geographic scale. Here, we studied the freshwater snail Ancylus fluviatilis (Muller, 1774) species complex in the Iberian Montseny Mountains. We hypothesized that (1) several species of A. fluviatilis sensu lato occur in the Montseny and (2) the different species seldom co-occur in syntopy due to different ecological demands or interspecific competition. We barcoded 180 specimens from 36 sites in the Montseny for the cytochrome c oxidase subunit I (COI) barcoding gene and molecularly identified two Ancylus species. These species seldom occurred in syntopy and a species distribution modelling approach showed differing bioclimatic preferences of the species. One species occurs mainly in cooler, higher altitude streams while the second species occurs in lower-altitude areas with higher temperatures. Tests of population structure showed that both species possibly do not disperse well in the study area and that populations within species might be adapted to certain bioclimatic conditions in different regions of the Montseny. Our results highlight the need to incorporate molecular techniques into routine monitoring programmes.

Bioaccumulation and trophic magnification of pharmaceuticals and endocrine disruptors in a Mediterranean river food web

Increasing evidence exists that emerging pollutants such as pharmaceuticals (PhACs) and endocrine-disrupting compounds (EDCs) can be bioaccumulated by aquatic organisms. However, the relative role of trophic transfers in the acquisition of emerging pollutants by aquatic organisms remains largely unexplored. In freshwater ecosystems, wastewater treatment plants are a major source of PhACs and EDCs. Here we studied the entrance of emerging pollutants and their flow through riverine food webs in an effluent-influenced river. To this end we assembled a data set on the composition and concentrations of a broad spectrum of PhACs (25 compounds) and EDCs (12 compounds) in water, biofilm, and three aquatic macroinvertebrate taxa with different trophic positions and feeding strategies (Ancylus fluviatilis, Hydropsyche sp., Phagocata vitta). We tested for similarities in pollutant levels among these compartments, and we compared observed bioaccumulation factors (BAFs) to those predicted by a previously-developed empirical model based on octanol–water distribution coefficients (Dow). Despite a high variation in composition and levels of emerging pollutants across food web compartments, observed BAFs in Hydropsyche and Phagocata matched, on average, those already predicted. Three compounds (the anti-inflammatory drug diclofenac, the lipid regulator gemfibrozil, and the flame retardant TBEP) were detected in water, biofilm and (at least) one macroinvertebrate taxa. TBEP was the only compound present in all taxa and showed magnification across trophic levels. This suggests that prey consumption may be, in some cases, a significant exposure route. This study advances the notion that both waterborne exposure and trophic interactions need to be taken into account when assessing the potential ecological risks of emerging pollutants in aquatic ecosystems.

Utility of environmental DNA for monitoring rare and indicator macroinvertebrate species

AbstractAccurate knowledge of the distribution of rare, indicator, or invasive species is required for conservation and management decisions. However, species monitoring done with conventional methods may have limitations, such as being laborious in terms of cost and time, and often requires invasive sampling of specimens. Environmental DNA (eDNA) has been identified as a molecular tool that could overcome these limitations, particularly in aquatic systems. Detection of rare and invasive amphibians and fish in lake and river systems has been effective, but few studies have targeted macroinvertebrates in aquatic systems. We expanded eDNA techniques to a broad taxonomic array of macroinvertebrate species in river and lake systems. We were able to detect 5 of 6 species (Ancylus fluviatilis, Asellus aquaticus, Baetis buceratus, Crangonyx pseudogracilis, and Gammarus pulex) with an eDNA method in parallel to the conventional kicknet-sampling method commonly applied in aquatic habitats. Our eDNA method showed m...

Macroinvertebrate indicators of ecological status in Mediterranean temporary stream types of the Balearic Islands

In the last years the Water Framework Directive (WFD) has encouraged the development of classification systems to assess the ecological status in permanent rivers and streams, but in temporary streams development has been scarce. Here, we constructed an Invertebrate Multimetric index (INVMIB) to assess the ecological status of temporary streams in Mediterranean Islands based on benthic invertebrates following the WFD guidance. We studied 60 temporary streams in different seasons (n=270 samples), corresponding to three different stream types that were a priori established using topographical and valley information: lowland, canyon and mountain streams. We collected invertebrates with a multihabitat-based macroinvertebrate sampling standardised for a sampling area of 2.5m2, and stream water to analyse most relevant water chemistry variables. The analyses of benthic macroinvertebrate assemblages confirmed our stream typology (ANOSIM, R=0.363, p<0.001). The reference community of lowland streams was defined by taxa belonging to the order Diptera, the gastropod Ancylus fluviatilis, and several beetles and EPT taxa. Canyons showed a high diversity strongly dominated by dipterans and aquatic mites together with mayflies. Finally, the amphipod Echinogammarus sicilianus-monomerus, many dipterans of the Chironomidae family, together with beetles, mayflies, stoneflies and caddisflies were highly represented in the reference communities from mountain streams. The developed INVMIBs consisted of a combination of individual metrics that included diversity, tolerance/sensitivity and composition measures. The metrics and developed type-specific multimetric indices responded significantly to the gradients of pressures obtained from PCAs (i.e., general and organic degradation), as an integrated response to the physico-chemical variables, hydromorphological parameters and land uses. Indeed, the classification system obtained with the INVMIBs reflected the ecological quality of temporary streams of the Balearic Islands. The multimetric indices are considered a valid and accurate tool for the assessment of temporary Mediterranean streams, being currently used by the water authorities of the Balearic Islands.

The impact of an industrial effluent on the water quality, submersed macrophytes and benthic macroinvertebrates in a dammed river of Central Spain

This research was conducted in the middle Duratón River (Central Spain), in the vicinity of Burgomillodo Reservoir. An industrial effluent enters the river 300m downstream from the dam. Fluoride and turbidity levels significantly increased downstream from the effluent, these levels being to some extent affected by differential water releases from the dam. The community of submersed macrophytes exhibited slighter responses and, accordingly, lower discriminatory power than the community of benthic macroinvertebrates, this indicating that metrics and indices based on macroinvertebrates may be more suitable for the biological monitoring of water pollution and habitat degradation in dammed rivers receiving industrial effluents. However, in relation to fluoride bioaccumulation at the organism level, macrophytes (Fontinalis antipyretica and Potamogeton pectinatus) were as suitable bioindicators of fluoride pollution as macroinvertebrates (Ancylus fluviatilis and Pacifastacus leniusculus). Fluoride bioaccumulation in both hard and soft tissues of these aquatic organisms could be used as suitable bioindicator of fluoride pollution (even lower than 1mgF−L−1) in freshwater ecosystems. Echinogammarus calvus exhibited a great sensitivity to the toxicity of fluoride ions, with a 96h LC50 of 7.5mgF−L−1 and an estimated safe concentration of 0.56mgF−L−1. The great capacity of E. calvus to take up and retain fluoride during exposures to fluoride ions would be a major cause of its great sensitivity to fluoride toxicity. It is concluded that the observed fluoride pollution might be partly responsible for the absence of this native amphipod downstream from the industrial effluent.

The study of ontogenetic trajectory reveals the timing of reproductive events in Ancylus fluviatilis (Gastropoda: Planorbidae)

We analysed ontogenetic shape change in the planorbid limpet Ancylus fluviatilis (Müller, 1774) in two rivers in Southern Italy. We developed a new method to discriminate among different cohorts in Ancylus, based on principal component analysis. The method is useful when shape change during growth is allometric, as in our study model. We discovered that bivoltinism occurs in Ancylus in Southern Italy, contrary to previous accounts, which invariably describe A. fluviatilis as a semelparous and univoltine species, although acknowledging difficulty in discriminating among cohorts. The methods presented here may potentially help research in reproductive traits in many other mollusc populations where shape change during ontogeny is demonstrated to be allometric.

Mollusc communities along upstream–downstream gradients in small coastal basins of the south-western Iberian Peninsula

Freshwater mollusc communities readily respond to various human-induced stressors, and thus are appropriate models for studying the effects of such stressors on the structure and dynamics of stream macroinvertebrate communities. This paper examined the distribution of freshwater molluscs in 35 stream reaches of 18 small coastal basins in the south-western Iberian Peninsula. Using several multivariate techniques, I showed that mollusc distribution mainly responded to gradients in drainage area, water availability, pollution and salinity. Upstream and downstream communities were clearly differentiated, with the former dominated by freshwater species (Bithynia tentaculata, Galba truncatula, Radix balthica, Ancylus fluviatilis and Planorbarius metidjensis) and the latter by species typical of brackish waters (Peringia ulvae and Myosotellamyosotis). There was a clear decrease in species richness from upper to lower reaches. The conservation of mollusc communities of these small basins requires a deeper understanding of their ecological requirements, effective control of urban discharges and an analysis of their interaction with invasive species.