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Drought is an increasing risk to the biodiversity within rivers—ecosystems which are already impacted by human activities. However, the long‐term spatially replicated studies needed to generate understanding of how anthropogenic stressors alter ecological responses to drought are lacking.We studied aquatic invertebrate communities in 2500 samples collected from 179 sites on rivers emerging from England's chalk aquifer over three decades. We tested two sets of alternative hypotheses describing responses to and recovery from drought in interaction with human impacts affecting water quality, fine sediment, water temperature, channel morphology, flow and temporal change in land use. We summarized communities using taxa richness, an index indicating tolerance of anthropogenic degradation (average score per taxon, ASPT) and deviation from the average composition.Responses to drought were altered by interactions with human impacts. Poor water quality exacerbated drought‐driven reductions in taxa richness. Drought‐driven deviations from the average community composition were reduced and enhanced at sites impacted by flow augmentation (e.g. effluent releases) and flow reduction (e.g. abstraction), respectively.Human impacts altered post‐drought recovery. Increases in richness were lower at sites impacted by water abstraction and higher at sites with augmented flows, in particular as recovery trajectories extended beyond 3 years. ASPT recovered faster at sites that gained woodland compared to urban land, due to their greater recovery potential, that is, their lower drought‐driven minimum values and higher post‐drought maximum values.Synthesis and applications. We show that communities in river ecosystems exposed to human impacts—in particular poor water quality, altered flow volumes and land use change—are particularly vulnerable to drought. These results provide evidence that management actions taken to enhance water quality, regulate abstraction and restore riparian land use could promote ecological resilience to drought in groundwater‐dominated rivers such as globally rare chalk streams and other rivers of the Anthropocene, as they adapt to a future characterized by increasing climatic extremity. [ABSTRACT FROM AUTHOR]

Sulfate is increasingly found in elevated concentrations in freshwater ecosystems due to anthropogenic activities. Chronic exposure to sulfate has been reported to cause sublethal effects on freshwater invertebrates. Previous sulfate toxicity tests have mostly been conducted in hard or moderately hard waters, and research on species inhabiting soft water is needed, given that freshwater organisms face heightened sensitivity to toxicants in water of lower hardness. In the present study, we examined sulfate sensitivity of two endangered freshwater mussel species, Unio crassus, and Margaritifera margaritifera. Glochidia and juveniles of both species were subjected to acute and/or chronic sulfate exposures in soft water to compare sulfate sensitivity across age groups, and effective concentrations (EC)/lethal concentrations (LC) values were estimated. Mussels were individually exposed to allow relatively larger numbers of replicates per treatment. Chronic sulfate exposure significantly reduced growth, foot movement, and relative water content (RWC) in juvenile mussels of M. margaritifera. Mussels at younger stages were not necessarily more sensitive to sulfate. In the acute tests, LC50 of glochidia of M. margaritifera and U. crassus was 1301 and 857 mg/L, respectively. Chronic LC10 was 843 mg/L for 3-week-old U. crassus juveniles, 1051 mg/L for 7-week-old M. margaritifera juveniles, and 683 mg/L for 2-year-old M. margaritifera juveniles. True chronic Lowest Effective Concentration for 7-week-old M. margaritifera may be within the 95% interval of EC10 based on RWC (EC10 = 446 mg/L, 95%CI = 265–626 mg/L). Our study contributed to the understanding of sulfate toxicity to endangered freshwater mussel species in soft water. [ABSTRACT FROM AUTHOR]

The physical effects of climate warming have been well documented, but the biological responses are far less well known, especially at the ecosystem level and at large (intercontinental) scales. Global warming over the next century is generally predicted to reduce food web complexity, but this is rarely tested empirically due to the dearth of studies isolating the effects of temperature on complex natural food webs. To overcome this obstacle, we used 'natural experiments' across 14 streams in Iceland and Russia, with natural warming of up to 20°C above the coldest stream in each high‐latitude region, where anthropogenic warming is predicted to be especially rapid. Using biomass‐weighted stable isotope data, we found that community isotopic divergence (a universal, taxon‐free measure of trophic diversity) was consistently lower in warmer streams. We also found a clear shift towards greater assimilation of autochthonous carbon, which was driven by increasing dominance of herbivores but without a concomitant increase in algal stocks. Overall, our results support the prediction that higher temperatures will simplify high‐latitude freshwater ecosystems and provide the first mechanistic glimpses of how warming alters energy transfer through food webs at intercontinental scales. [ABSTRACT FROM AUTHOR]

Conservation translocations may be a useful tool for the restoration of declining freshwater invertebrates, but they are poorly represented in the literature. We conducted a before‐after/control‐impact (BACI) experiment to test the efficacy of conservation translocation for re‐establishing abundant populations of the amphipod Gammarus lacustris, a declining species and wildlife food resource in depressional wetlands in the upper Midwest of the United States of America. Each study site (n = 19) contained at least one treatment wetland receiving translocated G. lacustris from a local donor and one control wetland. We selected study wetlands based on a suite of wetland characteristics and randomly assigned recipient versus control treatment. Gammarus lacustris was detected post‐translocation at only 2 of 22 recipient wetlands (1 of 19 sites). Overall, there was a statistical increase in G. lacustris density in recipient wetlands compared to controls; however, the results were of minimal biological significance due to being driven by a single site with low G. lacustris densities. Accordingly, our results suggest that future conservation translocations of amphipods might be successful if limited to recently restored wetlands or informed by a more complex habitat suitability model to differentiate dispersal limitations from habitat limitations. To develop such a model would involve identifying the fewest, most influential physical and biological factors (e.g. wetland size/structure, fish, aquatic vegetation, and water chemistry) from the numerous inter‐related factors that correlate with the abundance of naturally occurring G. lacustris; candidate wetlands to receive amphipods would be those for which the model predicts abundant G. lacustris but in which they do not presently occur. [ABSTRACT FROM AUTHOR]

Aim: Temperature is regarded as an important driver of broad‐scale biodiversity patterns. However, less is known of the role of dispersal in shaping broad‐scale species and trait distributions, particularly given that species had to disperse out of glacial refugia after the Last Glacial Maximum (LGM). Here, we used a unique dataset describing the distributions of freshwater fauna combined with trait information to evaluate biodiversity relationships to distance to glacial refugia and temperature. Location: Twenty‐five biogeographical regions across Europe. Time Period: Data from species occurrence were gathered in 1978. Major Taxa Studied: A total of 2816 freshwater invertebrate species and 230 freshwater fish species. Methods: Using the occurrence of invertebrate and fish species in the biogeographical regions, and publicly available trait information, we analysed patterns in diversity indices (i.e. species richness, trait richness and trait redundancy), trait distribution and species and trait β‐diversity, and their relationship to distance to known glacial refugia and regional temperature. Results: We show that distributions of European invertebrate and fish species and traits are primarily explained by distance to refugia and its covarying effect with temperature (i.e. refugia tend to be warmer). Specifically, species and trait richness were higher in regions proximate to refugia and lower in distant regions. Additionally, communities in colder and distant regions exhibited reduced niche dimensions and slower life histories, suggesting increased vulnerability to environmental change. Main Conclusions: Species more distant from their refugia were characterized by higher dispersal capacities. Accordingly, since the LGM, only a subset of species was able to colonize distant regions, while many species have spatial ranges constrained by their dispersal capacity, increasing their potential for extinction under ongoing climate change. Therefore, additional conservation measures considering species' dispersal capacities are required. [ABSTRACT FROM AUTHOR]

The long‐term impacts of radiocontaminants (and the associated risks) for ecosystems are still subject to vast societal and scientific debate while wildlife is chronically exposed to various sources and levels of either environmental or anthropogenic ionizing radiation from the use of nuclear energy. The present study aimed to assess induced phenotypical responses in both male and female gammarids after short‐term continuous γ‐irradiation, acting as a typical well‐characterized genotoxic stressor that can interact directly with living matter. In particular, we started characterizing the effects using standardized measurements for biological effects on few biological functions for this species, especially feeding inhibition tests, molting, and reproductive ability, which have already been proven for chemical substances and are likely to be disturbed by ionizing radiation. The results show no significant differences in terms of the survival of organisms (males and females), of their short‐term food consumption which is linked to the general health status (males and females), and of the molting cycle (females). In contrast, exposure significantly affected fecundity (number of embryos produced) at the highest dose rates for irradiated females (51 mGy h–1) and males (5 and 51 mGy h–1). These results showed that, in gammarids, reproduction, which is a critical endpoint for population dynamics, is the most radiosensitive phenotypic endpoint, with significant effects recorded on male reproductive capacity, which is more sensitive than in females. Environ Toxicol Chem 2024;43:2071–2079. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Sea level rise threatens ecosystem function in coastal lakes by increasing salinity and altering community composition. As mobile generalists, fish have considerable influence on the stability of a system by impacting trophic network structure. Understanding their diet across abiotic gradients, including salinity, can show key characteristics of their ecological role, and predator diet shifts may serve as warning signs of food web restructuring. Stomach contents analysis was used to look at the diet of Retropinna retropinna (common smelt) across shallow coastal lakes on Rēkohu (Chatham Island). Smelt diets from 10 lakes (seven freshwater; three salt-influenced) were analysed. Comparisons of salt-influenced and freshwater lakes showed shifts in composition. Smelt in freshwater lakes predominantly consumed herbivorous, omnivorous, or predatory insect larvae while diet in salt-influenced lakes was dominanted by crustacean shredders. Population diet varied somewhat less among salt-influenced lakes than among freshwater lakes, suggesting homogenisation of smelt diet with salinity. Differences in composition and heterogeneity did not translate to consistent differences in total niche width or individual specialisation between freshwater and salt-influenced lakes. Further development of knowledge on biological structure across salinity gradients is essential to understand ecosystem function under future climate scenarios. [ABSTRACT FROM AUTHOR]

Rotifers are microscopic metazoans which are generally predominant in freshwater ecosystems both in terms of species richness and species abundance. Despite their small size, they are crucial in maintaining ecological balance. In the present investigation, plankton samples collected during February 2019-January 2021 from two lentic water sources of Jammu region of Jammu & Kashmir revealed 58 species of rotifers belonging to 16 families, among which five species of monogonont rotifers from three genera were recorded to be the first reports from this region. These include three species from family Lecanidae: Lecane arcula, L. inermis, L. (Monostyla) unguitata; one species from family Brachionidae: Anuraeopsis coelata; and species Pompholyx sulcata of family Testudinellidae. Among these five monogonont species, Anuraeopsis coelata shows pantropical distribution, Lecane unguitata is a palaeotropical species, while other three are cosmopolitan in occurrence. Furthermore, comments are made on the diagnosis, seasonality, biogeographical, and ecological distribution of these species. [ABSTRACT FROM AUTHOR]

Assessments of biodiversity and ecosystem status can benefit from DNA metabarcoding as a means to streamline sample processing and specimen identification. Moreover, processing the fixation medium instead of the precious material introduces straightforward protocols that allow subsequent focus on certain organisms detected among the preserved specimens. In this study, we present a proof of concept via the analysis of freshwater invertebrate samples from the Tatra Mountain lakes (Slovakia). Besides highlighting a match between the lake-specific environmental conditions and the results of our fixative DNA metabarcoding, we observed an option to fine-tune the fixation time: to prefer two weeks over a day or a month. This effect emerged from the presence/absence of individual taxa rather than from coarse per-sample records of taxonomic richness, demonstrating that metabarcoding studies—and efforts to optimize their protocols—can use the robust metrics to explore even subtle trends. We also provide evidence that fixative DNA might better capture large freshwater species than terrestrial or meiofauna. [ABSTRACT FROM AUTHOR]

Rotifers are essential invertebrates in freshwater ecosystems. Rotifer community structure reflects the environmental changes. To assess the diversity of rotifers in the Pearl River Delta, we investigated the rotifer community structure in different water bodies types using morphology and DNA metabarcoding. A total of 101 species in 30 genera were recorded. 82 rotifer species were identified by morphology and 31 by OTUs based on DNA metabarcoding. Only 40% (2 orders), 42.9% (9 families), 29.7% (11 genera), and 4% (4 species) were shared by the two identification methods. Primers and imperfect rotifer databases might be responsible for the low annotation of rotifer OTU species. The community structure of rotifer morphospecies and OTUs in the Pearl River Delta changed with seasonal and spatial distribution. Heatmaps showed that different rotifer species responded differently to environmental factors. Our results show that DNA metabarcoding provides complementary rather than identical estimates compared to traditional approaches for rotifers. However, if widely validated and improved, this approach could be a useful alternative for practical applications of rotifers as bioindicators. In the future, environmental DNA metabarcoding is promising for the large-scale study and assessment of rotifer diversity. [ABSTRACT FROM AUTHOR]

The availability of resources varies across a species distributional range, and a low‐productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low‐productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicates that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low‐productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient‐rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient‐poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving the S. salar population in a nutrient‐poor river. [ABSTRACT FROM AUTHOR]

The presence of small pieces of plastic, termed Microplastics (MP), in the environment is a growing ecological concern, especially for the health of organisms that ingest them, but little is known about which MP characteristics influence their likelihood of ingestion. A small freshwater invertebrate, Daphnia magna, was used to determine if the color or odor of MPs influenced feeding preference in this species. We hypothesized that D. magna would have a preference for green MPs that resembled the color and odor of their algal food source. Experiments exposing D. magna to mixtures of different colored MP fibers, or mixtures of pristine and biofouled MP fibers were conducted. The number of ingested fibers in each intestine was quantified under a fluorescence microscope, using the signature autofluorescence of MP colors, to determine if D. magna exhibited a preference for MP based on color or odor. Our results suggest that D. magna do not exhibit a preference for MPs based on color alone. However, in the presence of odorants (biofouled MPs) a significant preference for black MP over green MP is revealed, suggesting that olfactory cues affect feeding behavior. Our results offer insight into the relationship between MP color and odor, and feeding preference, in D. magna. [ABSTRACT FROM AUTHOR]

The subfamily Sphaeriinae is a diverse and ecologically significant group of freshwater invertebrates, playing a keystone role in the energy flow and nutrient cycling in aquatic ecosystems. Despite a long history of its study, the taxonomic structure and species content of this group are a matter of ongoing disputes between malacologists. We clarify the taxonomy, distribution, and evolutionary biogeography of the Sphaeriinae around the world based on the largest dataset of DNA sequences of these clams ever accumulated, which includes the data on specimens collected from various continents and countries around the globe. Our 16S rRNA and two-locus phylogenies reveal that the Sphaeriinae is a monophyletic group, containing at least seven genus-level clades: Sphaerium Scopoli, 1777, Pisidium C. Pfeifffer, 1821 (s.s.), Euglesa Jenyns, 1832, Odhneripisidium Kuiper, 1962, Conventus Pirogov & Starobogatov stat. nov. 1974, 'Pisidium' sterkianum group, and Hindupisidium Vinarski & Bespalaya gen. nov. Our 16S rRNA phylogenetic tree contains 80 well-supported clades corresponding to the putative species-level taxa. Four species new to science are described here: Euglesa kolymensis Bespalaya, Aksenova & Bolotov sp. nov. , Euglesa kyrgyzica Bespalaya, Aksenova, Kondakov & Palatov sp. nov. , Euglesa moroccana Bespalaya, Vinarski, Aksenova, Mabrouki, Kondakov & Palatov sp. nov. , Odhneripisidium caucasus Bespalaya, Vinarski, Aksenova, Kondakov & Palatov sp. nov. Our fossil-calibrated phylogeny and generalized biogeographic model indicate that the most recent common ancestor of the Sphaeriidae could have originated somewhere within a broad area covering China near the Lower Cretaceous boundary. [ABSTRACT FROM AUTHOR]

Metabolic rate, the rate of energy use, underpins key ecological traits of organisms, from development and locomotion to interaction rates between individuals. In a warming world, the temperature-dependence of metabolic rate is anticipated to shift predator-prey dynamics. Yet, there is little real-world evidence on the effects of warming on trophic interactions. We measured the respiration rates of aquatic larvae of three insect species from populations experiencing a natural temperature gradient in a large-scale mesocosm experiment. Using a mechanistic model we predicted the effects of warming on these taxa's predator-prey interaction rates. We found that species-specific differences in metabolic plasticity lead to mismatches in the temperature-dependence of their relative velocities, resulting in altered predator-prey interaction rates. This study underscores the role of metabolic plasticity at the species level in modifying trophic interactions and proposes a mechanistic modelling approach that allows an efficient, high-throughput estimation of climate change threats across species pairs. An empirical study of freshwater invertebrates is coupled with a theoretical model of metabolic ecology to show that metabolic plasticity drives species-specific differences in predator-prey interaction rates under warming. [ABSTRACT FROM AUTHOR]

The traditional taxonomy of freshwater invertebrates is a labor-intensive process requiring extensive knowledge and experience. In addition, this science is largely subjective, which makes its digitalization difficult. However, accurate species attribution is becoming increasingly important for environmental surveys and conservation efforts. In the 21st century, molecular biology methods have proven to be a successful tool for objectively determining biodiversity. Achieving objectivity in identifying the taxa of non-parasitic leeches of the family Erpobdellidae was the main goal of this study. To this end, various bioinformatic approaches to DNA sequence analysis have been tested. As a result, the phylogenetic diversity amounted to 47 species versus 29 morphospecies defined traditionally. The use of molecular species delimitation methods made it possible to identify seven complexes of morphologically hidden (cryptic) species and some morphological misidentifications, as well as to discover a new species from Eastern Siberia (Erpobdella sibirica) with a unique molecular diagnosis (DNA barcode). A pioneering attempt to apply the same approach to higher taxa showed that Erpobdellidae probably consists of seven genera, including the unambiguous elimination of the genus Motobdella. Obtaining quantitative and, therefore, objective data is an advantage of the molecular approach, which has proven to be effective in recognizing species and genera, at least in leeches. [ABSTRACT FROM AUTHOR]

The aim of this study is twofold: i) to determine innovative yet sensitive endpoints for sulfoxaflor and ii) to develop best practices for innovative teaching in ecotoxicology. To this end, a group of 52 MSc students participated in an environmental hackathon, during which they did creative toxicity testing on 5 freshwater invertebrate species: Daphnia magna, Chironomus riparius, Asellus aquaticus, Lymnaea stagnalis, and Anisus vortex. Involving the students in an active learning environment stimulated increased creativity and productivity. In total, 28 endpoints were investigated, including standard endpoints (e.g., mortality) as well as biomechanistic and energy-related endpoints. Despite high variances in the results, likely linked to the limited lab experience of the students and interpersonal differences, a promising set of endpoints was selected for further investigation. A more targeted follow-up experiment focused on the most promising organism and set of endpoints: biomechanistic endpoints of C. riparius larvae. Larvae were exposed to a range of sulfoxaflor concentrations (0.90–67.2 μg/L) for 21 days. Video tracking showed that undulation and swimming were significantly reduced at 11.1 μg sulfoxaflor/L after 9 days of exposure, and an EC50 = 10.6 μg/L for mean velocities of the larvae in the water phase was found. Biomechanistic endpoints proved much more sensitive than mortality, for which an LC50 value of 116 μg/L was found on Day 9. Our results show that performing a hackathon with students has excellent potential to find sensitive endpoints that can subsequently be verified using more targeted and professional follow-up experiments. Furthermore, utilising hackathon events in teaching can increase students' enthusiasm about ecotoxicology, driving better learning experiences. [ABSTRACT FROM AUTHOR]

In many EU countries, a large proportion of domestic effluents is treated in small, decentralized wastewater treatment plants (WWTPs) which often lack appropriate treatment technologies. The low efficiency of these systems and their incorrect maintenance often contribute to environmental deterioration, with a large quantity of inadequately treated sewage dispersed in the soil or discharged into superficial watercourses. In the Abruzzo region (Central Italy), almost all rivers and streams receive wastewater from Imhoff tanks with only primary treatments. The ecological impacts of these effluents have rarely been investigated. This paper aimed to evaluate the response of freshwater invertebrates to Imhoff effluents in receiving watercourses with different ecological status. Our results showed that wastewater from Imhoff plants negatively affected the structure and composition of freshwater communities, with a reduction in the richness and abundance of more sensitive taxa and an increase in the most tolerant ones. These negative effects were more accentuated during low flow periods and in streams with moderate ecological status. To improve the ecological status of rivers and streams and to limit the diffusion of pathogens and micropollutants in freshwater, a more efficient (secondary treatments, possibly with nature-based solutions) and sustainable (water reuse or sewage sludge recycling) approach to wastewater treatment in decentralized WWTPs is urgently needed. [ABSTRACT FROM AUTHOR]

Invasive species represent a significant threat to native biodiversity. The Himalayan Balsam Impatiens glandulifera is an annual plant, which is invasive in Europe and often inhabits the riparian zone. It produces several secondary metabolites causing, for example, growth inhibition of terrestrial plants and invertebrates. One of these metabolites is the quinone 2-methoxy-1,4-naphthoquinone (2-MNQ). The compound gets washed out from the above-ground parts of the plant during precipitation and may then leach into nearby waterbodies. Despite some evidence for the allelopathic effect of plant secondary metabolites on terrestrial invertebrates, little is known about how 2-MNQ affects the survival or development of aquatic dipteran larvae, despite the importance of this functional group in European freshwaters. Here, we investigated the effects of 2-MNQ on larvae of the river keystone species Chironomus riparius in acute and chronic scenarios. The toxicity of 2-MNQ towards the first and the fourth larval stage was determined in a 48-hour acute exposure assay. We show that 2-MNQ has a negative impact on the development, growth and survival of C. riparius. The LC50 of 2-MNQ was 3.19 mg/l for the first instar and 2.09 mg/l for the fourth instar. A ten-day chronic exposure experiment, where the water was spiked with 2-MNQ, revealed that 2-MNQ had a significantly negative impact on larval body size, head capsule size, body weight, development and survival. These results demonstrate the negative impact of the secondary metabolite 2-MNQ from the terrestrial plant I. glandulifera on a crucial macroinvertebrate inhabiting the adjacent stream ecosystem in riverine ecosystems. This may lead to a decline in population size, resulting in cascading effects on the food web. [ABSTRACT FROM AUTHOR]

As climate change accelerates, low summer stream flows are becoming increasingly common in the Colorado Rocky Mountains, USA. The diatom Didymosphenia geminata (Lyngb.) M. Schmidt, typically observed under low-flow and low-P conditions, produces nuisance growth—persistent and extensive proliferation, covering the bottoms of streams in thick algal mats. Nuisance blooms of this diatom physically alter the benthic environment and thereby affect freshwater invertebrates directly and indirectly by altering stream food webs. We compared 9 y of survey data (2013–2021) of D. geminata proliferation with the composition of the macroinvertebrate communities at 8 stream sites near the Rocky Mountain Biological Laboratory in western Colorado. We counted and identified samples of benthic macroinvertebrates and used a glass-bottomed viewing box to estimate D. geminata biovolume at 2 scales: macrohabitat conditions (site level: 2013–2021) and microhabitat conditions (sample level: 2020–2021). At both scales, increases in D. geminata proliferation were associated with shifts in macroinvertebrate community composition that could be explained by altered abundances of focal taxa, specifically declines in Heptageniidae (Ephemeroptera) and increases in Chironomidae (Diptera). Abundances of Baetidae (Ephemeroptera) were unaffected by increased D. geminata biovolume. These changes indicate degradation of stream habitat for some sensitive groups of macroinvertebrates, which may affect higher trophic levels, such as trout, in these mountain stream ecosystems. As climate change trends toward lower summer streamflow, understanding the effects of proliferation of this ecosystem engineer is key to predicting the impact of climate change on stream food webs. [ABSTRACT FROM AUTHOR]

The freshwater amphipod genus Hyalella Smith, 1874 is widely distributed in the Neotropics, with several biogeographically restricted species and a high cryptic diversity throughout South America. Tens of species of Hyalella have been documented from nearby Brazil and Argentina, but no systematic record of the genus exists for Paraguay. Here we describe two new species of Hyalella: H. mboitui sp. nov. and H. julia sp. nov. from the Ñeembucú wetlands of southwestern Paraguay. Hyalella mboitui sp. nov. and H. julia sp. nov. are characterised by a dorsally smooth body, pigmented eyes, uropod 1 endopod with a curved seta, the dorsal margin of uropod 3 ramus without setae, and uropod 3 peduncle longer than wide and with six setae apically. The two species are distinguished by their diagnostic mouthparts, with a median serrated edge on the lacinia mobilis in H. mboitui sp. nov. and two elongated lateral denticles with a serrated edge in H. julia sp. nov., and by the presence of a pronounced cup for the dactylus on gnathopod 2 in H. mboitui sp. nov. In addition, they show differences in the number of articles on antennae 1 and 2, in the relative length of the pereiopods, and in the numbers and types of setae on their gnathopods and uropods 1-3. Hyalella mboitui sp. nov. and H. julia sp. nov. represent the first taxonomically documented occurrence of Paraguayan freshwater amphipods. These new taxa attest to the largely unmapped species richness of freshwater invertebrates in the Humid Chaco of Paraguay. This potential biodiversity hotspot is currently under threat from land conversion, highlighting the need for more systematic studies and effective conservation of the local invertebrate biodiversity. [ABSTRACT FROM AUTHOR]

Seven‐day sublethal toxicity tests were performed with the freshwater invertebrates Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus to determine the effects of per‐ or polyfluorinated alkyl substances (PFAS) of varying chain length within four classes: perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkane sulfonamides, and fluorotelomer sulfonic acids. In general, toxicity increased with increasing chain length, but the slopes of these relationships varied markedly by species and chemical class. The toxicity of individual PFCAs was similar among species. The toxicity of PFSAs was similar to PFCAs for C. dubia and H. azteca, whereas PFSAs were much more toxic to C. dilutus, with median effect concentrations (EC50s) as low as 0.022 mg perfluorooctane sulfonate (PFOS)/L and 0.012 mg perfluorononane sulfonate (PFNS)/L. Despite the high sensitivity to PFOS and PFNS, C. dilutus was not very sensitive to structurally similar fluorotelomer sulfonates (6:2 and 8:2). Perfluoroalkane sulfonamides were the most toxic class tested among all species (e.g., EC50s of 0.011 and 0.017 mg perfluorooctane sulfonamide/L for C. dilutus and H. azteca, respectively). The differences in toxicity among species and chemical classes suggest that mechanisms of PFAS toxicity may differ as a function of both. Environ Toxicol Chem 2024;43:359–373. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The melting cryosphere adds heterogeneity to the abiotic and biotic characteristics of many high latitude and montane rivers. However, climate change threatens the cryosphere's persistence in many regions. While existing research has explored the impacts of cryospheric loss on the diversity and structure of freshwater communities, implications for functional traits of communities, such as production of aquatic invertebrates, remain unresolved. Here, we quantified aquatic invertebrate community structure and secondary production in southeast Alaska (USA) streams that represent a meltwater to non‐meltwater gradient, including streams fed primarily by: (1) glacier‐melt, (2) snowmelt, (3) rainfall, and (4) a combination of these sources. We found alpha diversity was highest in the snow‐fed stream and lowest in the glacier‐fed stream. Annual secondary production was also lowest in the glacier‐fed stream (0.56 g ash‐free dry mass m−2), but 2–5 times higher in the other stream types primarily due to greater production of shared taxa that were found in all streams. However, despite low invertebrate diversity and productivity, the glacier‐fed stream hosted distinct species assemblages associated with unique cycles of stream flow, water temperature, turbidity, and nutrient concentrations, which contributed to higher beta diversity between streams. Our findings suggest that the loss of glacier‐melt contributions to rivers may result in increased freshwater invertebrate production but reduced beta diversity, which could have implications for community stability and the capacity of landscapes to support higher‐level consumers, including fishes. [ABSTRACT FROM AUTHOR]

The wetlands of Marais breton (MB) and Marais poitevin (MP) on the French Atlantic coast are commonly used by several duck species, especially as stopover sites during the prenuptial migration. Understanding the ecological requirements of Anatidae at spring stopover sites is important to define appropriate management actions that might have a carry over effect on the subsequent reproduction success. This study focused on the Northern Shoveler (Spatula clypeata), a species that regularly visits the two marshes during spring and fall migrations and is highly dependent on freshwater invertebrates as the food resource. Fifteen Northern Shovelers were equipped with GPS/GSM tags and monitored during their stopover in both marshes in 2020 and 2021. The aims of the study were to understand the habitat use on stopover sites and relate home range (HR) size with characteristics of the feeding habitats (such as freshwater invertebrates' density and diversity). The HR area of the studied individuals was mainly constituted of ponds in MB (83% of the HR) and wet meadows in MP (71% of the HR). The Northern Shovelers equipped with tag spent more than 72 consecutive hours in 31 wetlands, using them during the day, at night or all day. The diurnal visited sites were deep ponds that were sparsely vegetated and dominated by microcrustaceans, whereas the nocturnal visited sites were wet meadows or ponds with high aquatic vegetation cover and high invertebrate taxonomic diversity. The 31 described sites appeared to be rich in freshwater invertebrates, with no significant difference in invertebrate densities between the diurnal and nocturnal sites. HR sizes were highly homogenous between the two study sites (MB and MP), between sexes or between age classes. In conclusion, according to this study, an appropriate HR for the Northern Shoveler at spring stopover is 8.49 ± 5.95 km² (mean ± standard error). [ABSTRACT FROM AUTHOR]

Trace metal contamination is a widespread issue due to its many natural and anthropogenic sources and known carcinogenic, teratogenic, and reproductive effects. As previous invertebrate trace metal research has primarily focused on model species (Daphnia magna, Chironomidae, etc.), our understanding of effects on non‐model invertebrate species remains relatively poor. As such, this study assessed the exposure effects of cadmium, arsenic, and lead on viability, locomotor behavior, and embryonic development of the Seminole ramshorn snail (Planorbella duryi). Exposure treatments of CdCl2, Na2HAsO4 • 7H2O, or Pb (NO3)2 were prepared at concentrations of 0, 0.01, 0.1, 1, and 10 mg/L and confirmed using inductively coupled plasma optical emission spectroscopy (ICP‐OES). Individual adult P. duryi were exposed for 7 days with viability assessed every 24 h, and locomotor behavior was accessed on Days 1 and 7 using ToxTrac v2.97 automated behavior software. Individual embryos from newly laid (<6 h old) embryonic clutches were exposed for 10 days, during which embryonic development stage was documented every 24 h. Based on our results, an additional follow‐up study for cadmium was conducted using a lower range of 0–0.1 mg/L to allow for the observation of sublethal endpoints. Adult lead and cadmium exposure resulted in significant mortality in the highest treatments (1 and 10 mg/L), dose‐dependent behavioral effects, and delayed embryonic development. Arsenic exposures resulted in little to no impacts for all assessed endpoints. Our results provide new insight into the sublethal impacts of these contaminants and highlight potential for behavior and embryonic development as useful tools for risk assessment. Practitioner Points: The exposure effects of lead, cadmium, and arsenic on the viability, embryonic development, and locomotor behavior of a common freshwater snail species was investigated using environmentally relevant concentrations.The severity of impact differed for each trace metal, with cadmium being the most toxic and arsenic the least toxic at concentrations ranging from 0 to 10 mg/L.Embryonic development appeared to be the most sensitive endpoint of those tested in this study, suggesting that exposure may have prolonged effects that extend to population and community levels.The Seminole ramshorn snail serves as a sensitive alternative model species that can be used to assess the impacts of contaminants on freshwater invertebrates in future studies. [ABSTRACT FROM AUTHOR]

Body size strongly depends on developmental temperature. In more than 80% of the ectotherm species investigated, including bacteria, protists, invertebrates and vertebrates, individuals developing at lower temperatures exhibit protracted growth and achieve larger sizes than individuals developing at higher temperatures (referred to as the 'temperature‐size rule', TSR). One hypothesis to explain the TSR posits that reproduction and/or survival change more steeply with size in cold environments, resulting in larger optimal body sizes and consequently increased selection for growth. However, clearly ascertaining whether size directly affects fitness traits in a temperature‐dependent way is challenging due to the interdependence of size, reproduction and survival.To address this problem, experimental body size manipulation was performed in two male and two female strains of Hydra oligactis, a cold‐adapted temperate freshwater invertebrate. Experimentally enlarged and reduced individuals were followed at two distinct temperatures (8 and 12°C) in the laboratory to record sexual investment and postreproductive senescence. To gain insight into the underlying physiological processes, phenotypic observations were complemented with a large transcriptomic data set obtained from enlarged and reduced individuals from different temperatures.Within male hydra strains, fecundity increased, while survival decreased more steeply with size in cold, compared with warmer temperature. Females showed similar, though less emphasized, trends. Reduced animals in the cold had slower sexual development and were less able to undergo compensatory growth, suggesting temperature‐dependent constraints on physiological performance.Reduced and enlarged males differed dramatically in the expression of reproductive genes at low, but not at higher temperature, while in females, a complex transcriptomic restructuring was seen. In particular, metabolic genes were strongly affected by size manipulation, suggesting resource acquisition and allocation as a central mechanism driving allometric patterns.These results suggest that being large is more beneficial in cold environments, at least in terms of reproduction, while at higher temperature even small individuals can maintain reproductive output. Lower reproduction, however, can be compensated by improved survival in small individuals facing colder environments. The reproductive advantage of large size can provide selection for increased growth at low temperature, thereby explaining the TSR in hydra. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

External nutrient loading can cause large changes in freshwater ecosystems. Many local field and laboratory experiments have investigated ecological responses to nutrient addition. However, these findings are difficult to generalize, as the responses observed may depend on the local context and the resulting nutrient concentrations in the receiving water bodies. In this research, we combined and analysed data from 131 experimental studies containing 3054 treatment‐control abundance ratios to assess the responses of freshwater taxa along a gradient of elevated nutrient concentrations. We carried out a systematic literature search in order to identify studies that report the abundance of invertebrate, macrophyte, and fish taxa in relation to the addition of nitrogen, phosphorus, or both. Next, we established mixed‐effect meta‐regression models to relate the biotic responses to the concentration gradients of both nutrients. We quantified the responses based on various abundance‐based metrics. We found no responses to the mere addition of nutrients, apart from an overall increase of total invertebrate abundance. However, when we considered the gradients of N and P enrichment, we found responses to both nutrients for all abundance metrics. Abundance tended to increase at low levels of N enrichment, yet decreased at the high end of the concentration gradient (1–10 mg/L, depending on the P concentration). Responses to increasing P concentrations were mostly positive. For fish, we found too few data to perform a meaningful analysis. The results of our research highlight the need to consider the level of nutrient enrichment rather than the mere addition of nutrients in order to better understand broad‐scale responses of freshwater biota to eutrophication, as a key step to identify effective conservation strategies for freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Excessive fine sediment (particles <2 mm) deposition in freshwater systems is a pervasive stressor worldwide. However, understanding of ecological response to excess fine sediment in river systems at the global scale is limited. Here, we aim to address whether there is a consistent response to increasing levels of deposited fine sediment by freshwater invertebrates across multiple geographic regions (Australia, Brazil, New Zealand and the UK). Results indicate ecological responses are not globally consistent and are instead dependent on both the region and the facet of invertebrate diversity considered, that is, taxonomic or functional trait structure. Invertebrate communities of Australia were most sensitive to deposited fine sediment, with the greatest rate of change in communities occurring when fine sediment cover was low (below 25% of the reach). Communities in the UK displayed a greater tolerance with most compositional change occurring between 30% and 60% cover. In both New Zealand and Brazil, which included the most heavily sedimented sampled streams, the communities were more tolerant or demonstrated ambiguous responses, likely due to historic environmental filtering of invertebrate communities. We conclude that ecological responses to fine sediment are not generalisable globally and are dependent on landscape filters with regional context and historic land management playing important roles. [ABSTRACT FROM AUTHOR]

Cold acclimation is a biological process that allows animals to survive at low temperatures. The freshwater invertebrate Hydra is subject to broad changes in environmental temperature and does not have the required motility in order to move to warmer environments during the winter. For this reason, Hydra had to develop robust mechanisms to achieve cold acclimation at the onset of winter. How Hydra detects the onset of winter and activates its acclimation mechanism is unknown. Here, we used thermocyclers to induce cold acclimation in Hydra and study its properties. We found that Hydra cultured at room temperature does not survive an abrupt transition from 22 to 4 °C. However, it can be treated to become cold acclimated and survive at 4 °C by exposure to intermediate temperatures such as 12 °C if the treatment duration exceeds more than a week. Once cold acclimated, Hydra is considerably more robust to thermal changes. It survives repeated abrupt transitions from 4 to 22 °C and from 22 to 4 °C. However, acclimation is reversible, and if a cold-acclimated Hydra stays at room temperature for more than a week, it will gradually lose its cold acclimation. We developed a mathematical model representing the dynamics of this process and used it to predict survival according to temperature data recorded in one of their natural habitats. The results of these simulations provide an explanation for how Hydra survives winter under natural conditions. Accordingly, daily fluctuations are too short to cause injury, and seasonal fluctuations, which are long enough to be lethal, allow acclimation to incrementally build up and protect the animal. Cold acclimation in Hydra is therefore an example of a strategy that has adapted during evolution to match the animal's needs for survival. [ABSTRACT FROM AUTHOR]

The present study is the first structured attempt to analyze the species composition and distribution of freshwater invertebrates in the lakes, streams, and rivers of the Shantar Islands and to compare the diversity of the hydrobiont fauna of the archipelago and the continental part of Khabarovsk Krai on the basis of the original and literature data. The research revealed 57 zooplanktonic, 47 meiobenthic, and 142 macrobenthic taxa in the waters of the island and the adjacent continental areas. Different patterns of variability in the species richness, abundance, and the community structure are observed for different groups of hydrobionts along the salinity gradient in the unique, brackish Lake Bolshoe. Zooplankton show no directional variability, reaching a maximum in a frontal zone where riverine and brackish water mix. Meiobenthos show the highest diversity in the most saline zone of the lake, where marine species are abundant. The characteristics of the macrozoobenthos gradually increase with the salinity of the lake, with a dramatic change in the dominance structure at the critical salinity threshold, where amphibiotic insects, dominant in the desalinated water zone, are replaced by amphipods. Latitudinal variability in species richness and biogeographic structure of the fauna are closely related for different groups of freshwater invertebrates. A smooth decline in species richness from southern to northern areas was observed when comparing the faunas of the Shantar water bodies with those located to the south. This trend is shown for amphibiotic insects and microcrustaceans and is most pronounced for mollusks. The fauna of the Shantar Islands is predominantly represented by species with a wide Palaearctic, Holarctic, and cosmopolitan range, with a small proportion of species restricted to the Arctic zone of Eurasia or specific to Eastern Siberia and the Far East. Only three brackish water species have a Beringian type of distribution. The assemblage structures of the zooplankton and meiobenthos communities of continental coastal and island lakes do not greatly differ. On the contrary, brackish communities are clearly distinct from the others. The taxonomic composition of macroinvertebrates differed significantly between the islands and the mainland. [ABSTRACT FROM AUTHOR]

The biotas of old islands formed from continental terranes usually have a more complex biogeographical history than those of young oceanic islands, including taxa which have originated by vicariance and/or colonisation, over a variety of timescales. The Tyrrhenian Islands of Corsica, Sardinia and the Tuscan Archipelago in the Mediterranean have a complex geological history, shaped by interactions between the African and Eurasian plates since the Mesozoic. Our understanding of the historical biogeography of Tyrrhenian endemics remains limited for many groups, including freshwater invertebrates. Here we use a time-calibrated phylogeny, derived from mitochondrial and nuclear DNA sequence data, to explore the evolutionary history of Tyrrhenian endemic Hydraena water beetles, an ecologically important group in the islands' streams. Whilst no endemic Hydraena appear to date from the initial separation of Corsica-Sardinia from the European mainland in the Oligocene, we show that Tyrrhenian species stem from five colonisation events, occurring at different intervals in the last ca. 15 Ma, at least two endemic lineages apparently arising through isolation at the end of the Messinian Salinity Crisis. Hydraena reflexa Rey, 1884, long considered a geographical form or subspecies of the widespread H. pygmaea Waterhouse, 1833, is reinstated as a valid species, endemic to Corsica and Sardinia. H. reflexa can be distinguished from H. pygmaea on external and aedeagal characters, documented here in detail. Specimens of 'H. reflexa' from southern continental Italy are shown to differ from those on Corsica and Sardinia, having identical male genitalia to H. pygmaea from elsewhere in its range. Genetically, this Calabrian form also clusters with H. pygmaea, and may have arisen through past introgression between a reflexa-like ancestor and H. pygmaea following the connection of the Calabrian block with the nascent Apennines in the Pliocene. The degree of genetic divergence seen between H. pygmaea and H. reflexa suggests that they diverged approximately 5.5 Ma in the Miocene, following the isolation of Corsico-Sardinian and mainland populations at the end of the Messinian. [ABSTRACT FROM AUTHOR]

Although ostracods are important components in aquatic ecosystems, little is known about their microbiomes. Here, we analyzed the microbiomes of the putative ancient asexual ostracod species, Darwinula stevensoni, in three natural populations from different freshwater habitats in the UK, Belgium, and Spain. We applied high-throughput amplicon sequencing approaches to analyze the V3–V4 part of the bacterial 16S rRNA region. We tested for host-specific microbiomes by comparing bacterial assemblages of ostracods with those of sediment and water samples from the same locations. Around 2,200 Amplicon Sequence Variants (ASVs) were identified from ostracod samples with universal primers and 1,700 ASVs with endosymbiotic-specific primers, illustrating a high microbiome diversity in D. stevensoni. Most bacterial taxa were unique to the microbiome of D. stevensoni as compared to other freshwater invertebrates and to non-marine ostracods. Alpha diversity of ostracod microbiomes did not differ significantly between the three populations, but PERMANOVA detected significant differences in bacterial compositions. Microbiomes varied highly among ostracod specimens from the same population. Possible factors shaping ostracod microbiomes could be latitude, food, age, and environmental variables. Preliminary functionality analyses showed that Darwinula-specific microbiomes contribute to lipid, carbohydrate, nucleotide, and amino acid metabolic processes and the synthesis of co-factors and vitamins. [ABSTRACT FROM AUTHOR]

The regionally threatened damselfly Sympecma peadisca is one of the few Central European dragonfly species included is considered as Near Threatened in the European Red list. The major threats to this species remain unclear. This species has a unique life history and several adaptations to enabling survival even in semidesert areas, such as overwintering in the adult stage. However, the closely related, more thermophilic species Sympecma fusca has undergone a major range expansion in Europe. Based on data from 129 sites and combining several analytical approaches, I found the following: 1. According to local freshwater conditions, S. paedisca is a typical habitat generalist occupying a wide range of habitats. 2. It requires a wide range of terrestrial habitats to complete its life cycle. 3. An analysis of the land used by both species clearly indicates that both species avoid intensive agricultural areas; however, S. fusca can also occur in suburban areas, where S. paedisca is absent. 4. Projections of the Least Cost Path analysis indicate that the only localities where the species is currently spreading are habitats arising as a consequence of mining activities. The example of S. paedisca is clear evidence of a freshwater species that responds very negatively to the homogenization of the terrestrial environment, even when its natal habitat is not significantly affected. The frequent occurrence of species in postmining areas suggests that species with complex habitat requirements can find suitable secondary habitats where they can prosper in the long term. Implications for insect conservation: Even semi-aquatic groups like damselflies can be very sensitive to gradual changes in surrounding land use. Species with very complex habitat requirements also require comprehensive conservation strategies affecting all habitats utilized by the species. However, the return of some landscape features requires a reduction in the area of production areas in favor of hedgerows and ruderals. Such restoration management requires long-term planning and close cooperation with farmers. [ABSTRACT FROM AUTHOR]

Background: Freshwater ecosystem degradation and biodiversity decline are strongly associated with intensive agricultural practices. Simultaneously occurring agricultural stressors can interact in complex ways, preventing an accurate prediction of their combined effects on aquatic biota. Here, we address the limited mechanistic understanding of multiple stressor effects of two globally important stressors, an insecticide (chlorantraniliprole), and increased fine sediment load and assessed their impact on the transcriptomic profile of two stream macroinvertebrates: the amphipod Gammarus pulex and the caddisfly Lepidostoma basale. Results: We identified mainly antagonistic stressor interactions at the transcriptional level, presumably because the insecticide adsorbed to fine sediment particles. L. basale, which is phylogenetically more closely related to the insecticide's target taxon Lepidoptera, exhibited strong transcriptional changes when the insecticide stressor was applied, whereas no clear response patterns were observed in the amphipod G. pulex. These differences in species vulnerability can presumably be attributed to molecular mechanisms determining the cellular affinity toward a stressor as well as differential exposure patterns resulting from varying ecological requirements between L. basale and G. pulex. Interestingly, the transcriptional response induced by insecticide exposure in L. basale was not associated with a disruption of the calcium homeostasis, which is the described mode of action for chlorantraniliprole. Instead, immune responses and alterations of the developmental program appear to play a more significant role. Conclusions: Our study shows how transcriptomic data can be used to identify multiple stressor effects and to explore the molecular mechanisms underlying stressor-induced physiological responses. As such, stressor effects assessed at the molecular level can inform about modes of action of chemicals and their interplay with non-chemical stressors. We demonstrated that stressor effects vary between different organismic groups and that insecticide effects are not necessarily covered by their described mode of action, which has important implications for environmental risk assessment of insecticides in non-target organisms. [ABSTRACT FROM AUTHOR]

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT‐mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT‐mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT‐mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT‐mag diminished PW toxicity. Therefore, using VMT‐mag to treat PW may be the key to reducing the PW effects on aquatic organisms. Produced water (PW) generated by oil companies is a highly impacting waste. This work aimed to evaluate the treatment with VMT‐mag in reducing PW toxicity to aquatic biota with three aquatic species (Chironomus riparius, Girardia tigrina, and Daphnia magna). The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate. [ABSTRACT FROM AUTHOR]

Diclofenac (DCF), one of the most current and widely used nonsteroidal anti-inflammatory drugs (NSAIDs), has been frequently detected in aquatic environments worldwide. However, the ecotoxicological effects of DCF on freshwater invertebrates remain largely unknown. In the present study, Corbicula fluminea were exposed to environmentally relevant concentrations of DCF (0, 2, 20, and 200 μg/L) for 28 days, and the potential adverse effects of DCF on siphoning behavior, antioxidant responses, and apoptosis were investigated. Our results showed that the siphon efficiencies of clams were significantly suppressed under DCF stress. DCF exerted neurotoxicity via reducing the activity of acetylcholinesterase (AChE) in gills and digestive gland of C. fluminea. Exposure to DCF induced antioxidant stress and increased malondialdehyde (MDA) levels in both gills and digestive gland of C. fluminea. Transcriptional alterations of apoptosis-related genes indicated that DCF might induce apoptosis by triggering mitochondrial apoptotic pathway. These findings can improve our understanding of the ecological risk of DCF in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Simple Summary: The article explains why using free-living invertebrates in biomonitoring aimed at assessing the ecological status of rivers, lakes, streams and ponds can be considered misuse. Invertebrates are excluded from ethical considerations in environmental procedures, resulting in the killing of many more individuals than necessary during such activities. Biomonitoring used as a routine method of environmental protection causes cruel deaths of up to millions of aquatic animals every year. Improperly planned procedures which result in excessive mortality have or may have a negative impact on the environment and biodiversity. The life of aquatic invertebrates, although they should be considered sensitive beings, is reduced to an informative function; they become only data useful for biomonitoring purposes. Some new methods, modifications and improvements of biomonitoring procedures that can significantly reduce freshwater invertebrate mortality are presented in the section "Future Directions". Especially the development of effective, precise and reliable methods of survival, e.g., based on the analysis of DNA taken directly from the environment (eDNA), seems to be not only a breakthrough in biomonitoring, but also an important step towards a significant improvement in the welfare of aquatic invertebrates. The article presents and discusses the issues of the use of free-living invertebrates to assess the ecological status of freshwater environments with different methods of biological monitoring. Invertebrates are excluded from ethical consideration in the procedures of environmental protection, which results in the killing of many more individuals during sampling than necessary. Biomonitoring is used as a routine method for environmental protection that results in the cruel death of even millions of aquatic animals annually. In many cases, the mortality of animals used in such types of activities has been shown as excessive, e.g., because the vast majority die due to unnecessary subsampling procedures. Improperly planned and conducted procedures which result in excessive mortality have or may have a negative impact on the environment and biodiversity. Their existence as sensitive beings is reduced to an information function; they become only data useful for biomonitoring purposes. The main problem when trying to determine the mortality of invertebrates due to biomonitoring activities and its impact on natural populations seems to be the lack of access to raw data presenting how many animals were killed during sampling. [ABSTRACT FROM AUTHOR]

Amphetamine (AMP) is a chiral psychoactive substance that exhibits enantioselectivity in its pharmacological properties. It has been detected in wastewaters and surface waters and can occur as enantiomeric mixtures, but little is known about its environmental risk and potential enantioselective toxicity to aquatic organisms. Our study aimed to target enantioselectivity in AMP toxicity to the freshwater invertebrate Daphnia magna. Daphnids were subchronically exposed to the racemate (rac‐AMP: 0.1, 1.0, and 10 µg/L) and pure enantiomers, (R)‐AMP and (S)‐AMP (0.1, and 1.0 µg/L, respectively), for 8 days. Morphophysiological, swimming behavior, reproductive and biochemical variables were evaluated during critical life stages (juveniles vs. adults). Some responses were context‐dependent and often enantioselective, varying between racemate and enantiomers and across the life stage of the organisms. Overall, rac‐AMP stimulated D. magna growth, decreased heart rate and area, affected behavior, and stimulated reproduction. The effect of enantiomers was totally or partially concordant with rac‐AMP, except for swimming behavior and reproduction. Enantioselectivity was observed for body size, number of eggs/daphnia, and heart rate (steeper decrease caused by (R)‐AMP on day 3). Changes in biochemical parameters were also observed: AMP caused a significant decrease in catalase activity as racemate or pure enantiomers, whereas a decrease in acetylcholinesterase activity was found only for rac‐AMP. Evidence for oxidative stress was contradictory, although both enantiomers caused a significant decrease in reactive oxygen species (unlike rac‐AMP). Overall, these results show that AMP can interfere in an enantioselective way with aquatic organisms at low concentrations (e.g., 0.1 µg/L), demonstrating the relevance of this kind of study to an accurate environmental risk assessment regarding medium‐ to long‐term exposure to this psychoactive drug. Environ Toxicol Chem 2023;42:1743–1754. © 2023 SETAC. [ABSTRACT FROM AUTHOR]

We present the first record of Holocene fossil insect assemblages from Central Yakutia. A stratigraphic sequence in the locality within the Vilyuy River valley is a buried oxbow. The late Holocene water body inherited an impervious stratum from the late Pleistocene. The organic layer preserved rich fossil assemblages of macrofossils including insects and other invertebrates, plants, and charcoal. The ancient flora and fauna include species that are common in Yakutia as well as those that are rare and absent in the region. The most abundant finds are leech cocoons and bogbean seeds. The macrofossils of some insects were found along with remains of their host plants. Despite the absence of intensive human land use in the area, traces of fires were recorded. The oxbow represents the environment of a floodplain wetland that developed separately from the ecosystem of the adjacent sand dunes. [ABSTRACT FROM AUTHOR]

The current paper presents the first effort to organize a comprehensive review of the Invasive Alien Species (IAS) of Greece. For this purpose, a database was developed with fields of information on the taxonomy, origin, ecology and pathways of introduction of terrestrial, freshwater and marine species. Our database includes a) taxa in the Union's list that are present in Greece, b) taxa already present in Greece and considered to be invasive, and c) taxa highly likely to enter Greece in the next 10 years and become invasive. The Database served as the starting point for the compilation of the National List of Alien Invasive Species (HELLAS-ALIENS) in compliance with the EU Regulation 1143/2014. Overall, the HELLAS-ALIENS comprises 126 species, i.e. 32 terrestrial and freshwater plant species, 14 terrestrial invertebrates, 28 terrestrial vertebrates, 30 freshwater fishes and invertebrates and 22 marine species. Terrestrial invertebrates, birds and mammals are mainly of Asiatic origin. Most of the terrestrial plants have their native geographical distribution in the Americas (North and South). Most of the freshwater invertebrates and fishes are of North American origin, while the majority of the marine species are of Indo-Pacific origin. The first records of IAS concern terrestrial plant species, and date back to the 19th century, while those in freshwater and marine ecosystems seem to have been systematically recorded some decades later. Regarding the pathways of introduction, most of the taxa arrived in Greece or are expected to arrive through escape from confinement and unaided. The majority of the terrestrial, freshwater and marine species have been evaluated as of High-risk for the indigenous biodiversity and only 3% of the species listed have been evaluated of Low-risk. Our results provide an important baseline for management and action plans, as required by the priorities set by the European Union through the Biodiversity Strategy for 2030. [ABSTRACT FROM AUTHOR]

Drift is a phenomenon of dispersion of invertebrates in freshwater lotic systems such as rivers and streams resulting from its water currents. The aquatic organisms living in the stream display drift because of their low buoyancy, which causes them to be dragged into the water column downstream. The said study was carried out for two annual cycles i.e. from December 2019 to November 2021 for studying drifting pattern exhibited by aquatic mites from the river Ganga near Deoprayag. The DBD Index was also calculated to derive actual number of drifting mites from the total population in a unit time. [ABSTRACT FROM AUTHOR]

The Northern shoveler, Spatula clypeata, makes several migratory stopovers to reach its breeding site in the best conditions. These stopovers allow the species to replenish their reserves. Therefore, feeding efficiency at such sites is essential. Despite its importance, few studies have been conducted on the spring ecology of the shoveler, particularly on its diet at stopover sites. Therefore, this study focused on the Northern shoveler's feeding habit during its spring migratory stopover in the Marais breton (MB), a wetland situated in Vendée (France, Atlantic coast). The shoveler's plasma and potential food resources were studied using a stable carbon and nitrogen isotope analysis. The study showed that the shoveler feeds primarily on microcrustaceans, especially Cladocera and Copepoda; Chironomidae larvae, Corixidae, Hydrophilidae larvae, and particulate organic matter. This last food source, the POM, had never been highlighted before. [ABSTRACT FROM AUTHOR]

The infamous "master manipulators"—intracellular bacteria of the genus Wolbachia—infect a broad range of phylogenetically diverse invertebrate hosts in terrestrial ecosystems. Wolbachia has an important impact on the ecology and evolution of their host with documented effects including induced parthenogenesis, male killing, feminization, and cytoplasmic incompatibility. Nonetheless, data on Wolbachia infections in non-terrestrial invertebrates are scarce. Sampling bias and methodological limitations are some of the reasons limiting the detection of these bacteria in aquatic organisms. In this study, we present a new metagenetic method for detecting the co-occurrence of different Wolbachia strains in freshwater invertebrates host species, i.e., freshwater Arthropoda (Crustacea), Mollusca (Bivalvia), and water bears (Tardigrada) by applying NGS primers designed by us and a Python script that allows the identification of Wolbachia target sequences from the microbiome communities. We also compare the results obtained using the commonly applied NGS primers and the Sanger sequencing approach. Finally, we describe three supergroups of Wolbachia: (i) a new supergroup V identified in Crustacea and Bivalvia hosts; (ii) supergroup A identified in Crustacea, Bivalvia, and Eutardigrada hosts, and (iii) supergroup E infection in the Crustacea host microbiome community. [ABSTRACT FROM AUTHOR]

Environmental plastic contamination is a global problem, which is driven by the growing demand for plastics. Over time, plastics undergo fragmentation processes and become so-called microplastics, which have been shown to be a threat to the various environments where their presence occurs. The most accepted hypothesis is that, like macroplastics, microplastics have fragmented into smaller and smaller particles, with sub-micrometer sizes. However, little is known about fragmentation rates and which are the most determining factors in this process. The main objective of the present study was to investigate the biofragmentation capacity of microplastics by Daphnia similis, a microcrustacean from inland waters. The organisms were exposed to polystyrene spheres (PS; 24 µm), under two concentrations: 135 and 1350 items/50 mL, for a period of 6 days. The rate of biofragmentation was obtained by analyzing the size of the particles over time (48, 96, and 144 h); ingestion and survival rates were also investigated. At the end of the exposure, the microspheres had their size reduced by 32.8%. From the first 48 h, the organisms ingested particles, and the rate of ingestion was dose dependent. Mortality was shown to increase in the treatment of higher concentration. The results demonstrate the ability of this microcrustacean to induce the reduction of the dimensions of microplastics, evidencing a fragmentation pathway previously neglected. [ABSTRACT FROM AUTHOR]

Meiofauna is a group of heterotrophic organisms smaller than macroinvertebrates but larger than microfauna and characterized by groups such as testate amoebae, ciliates, and nematodes. They are a link between bacteria and resources and macroinvertebrates. However, tropical meiofauna is poorly studied; thus, our goal was to characterize meiofaunal community composition and abundance and assess potential environmental variables controlling these community dynamics. Monthly samplings of meiofauna were conducted for eight months in Quebrada Prieta, El Yunque National Forest, Puerto Rico. Sampling was made in 12 pools, and data on discharge, sediment characteristics, and biotic variables were also collected. A total of 62 meiofaunal morphospecies were identified, with nematodes dominating the community, followed by testate amoebae. Bacterivores and detritivores taxa dominated the community. Meiofaunal abundance was negatively related to discharge and positively to the percentage of coarse sand, nitrate, and macroinvertebrate abundance. The composition of meiofauna in Quebrada Prieta is like the composition reported for temperate streams, at least in major meiofaunal groups present. However, the community in Quebrada Prieta was dominated by testate amoebae. In contrast, temperate streams are often dominated by rotifers and nematodes. Both abiotic and biotic variables are important for meiofaunal communities in the headwater streams in Puerto Rico. [ABSTRACT FROM AUTHOR]

Around the world, researchers are reporting declines in insect fauna. Although uncommonly evaluated in high‐profile studies of insect declines, the community context of population trends can facilitate interpretation of the causes and consequences of such losses. Here, we aimed to explore the shifts in a well‐studied invertebrate community of a blackwater river and identify potential catalysts of such change.We compared the density, biomass and community structure of freshwater invertebrate assemblages separated by more than 30 years in the Ogeechee River, in the southeastern U.S.A., and found biomass declines. We also evaluated long‐term trends in river discharge, water temperature and precipitation.Overall, the biomass in the 2010s was approximately 60% of the total in the 1980s. Community analyses indicated that this decline was associated with reduced densities of large‐bodied, filter‐feeding insects, particularly Hydropsychidae caddisflies (Trichoptera). Conversely, predators and small‐bodied primary consumers increased in density, although their contributions to overall biomass were minimal and their increased density was not sufficient to compensate for biomass declines. Seasonal shifts in both invertebrate populations and environmental parameters were evident, especially when focusing on discharge and dissolved organic carbon.Through a combination of direct analysis and the use of established research on the metabolic dynamics of the study site, we determined that the overall decline of freshwater invertebrate biomass may have been driven by climate‐related changes in flood dynamics: seasonal flooding that facilitates delivery of floodplain carbon to filter‐feeding consumers had decreased over several decades. Water temperature also had increased and was likely to have had effects on the invertebrate assemblages.Whole‐community evaluations such as this one, in contrast to single‐taxon and abundance‐based studies, provide critical information to elucidate the dynamics of freshwater impairment and insect loss in the Anthropocene. [ABSTRACT FROM AUTHOR]

Ionizing radiation and radiation-related oxidative stress are two important factors responsible for the death of actively proliferating cells, thus drastically reducing the regeneration capacity of living organisms. Planarian flatworms are freshwater invertebrates that are rich in stem cells called neoblasts and, therefore, present a well-established model for studies on regeneration and the testing of novel antioxidant and radioprotective substances. In this work, we tested an antiviral and antioxidant drug Tameron (Monosodium α-Luminol or 5-amino-2,3-dihydro-1,4-phthalazinedione sodium salt) for its ability to reduce the harm of X-ray- and chemically induced oxidative stress on a planarian model. Our study has revealed the ability of Tameron to effectively protect planarians from oxidative stress while enhancing their regenerative capacity by modulating the expression of neoblast marker genes and NRF-2-controlled oxidative stress response genes. [ABSTRACT FROM AUTHOR]

In light of the ongoing freshwater biodiversity crisis, detailed knowledge regarding the spatial distribution of freshwater species is urgently required, especially in biodiversity hotspots. Here we present a database of georeferenced occurrence records of four freshwater invertebrate taxa groups across Cuba, namely flatworms (Platyhelminthes: Tricladida), insects (Ephemeroptera, Odonata, Hemiptera, Trichoptera, Coleoptera, Diptera), crabs and shrimps (Crustacea: Decapoda), and mollusks (Mollusca). We collated the geographic occurrence information from scientific literature, unpublished field records, museum collections and online databases. The database, comprising 6292 records of 457 species at 1075 unique localities, is organized in 32 fields that contain the information about the taxonomic classification of each recorded species, the sex and life stage of collected individuals; the geographic coordinates, location, author and date of the record and a reference to the original data source. This database provides an important basis towards an improved understanding of the spatial distribution of freshwater biodiversity in Cuba. [ABSTRACT FROM AUTHOR]

The variety of applications and expected growth in ionic liquid production are raising concerns about the release of these compounds into aquatic systems. Up to date, 103 studies have provided ecotoxicological data regarding the exposure effects of Ionic Liquids towards aquatic microorganisms and invertebrate species: 61 were devoted to freshwater species (n = 28), while marine species (n = 12) were mentioned in 42. The aim of this review, by gathering published studies on ionic liquids and model aquatic organisms, was to present the toxic effects described in distinct species and to understand which are the main factors influencing the toxicity of some ionic liquids. In accordance with the most recognized pattern, freshwater species were featured in a higher number of publications than marine ones. After literature analysis, algal species were the most represented organisms in aquatic toxicity assessments. Among tested compounds, the imidazolium cations in combination with long alkyl-chain anions, showed to be the most toxic one. In analytical terms, it is not straightforward to find the undissociated compound in a natural compartment, as ionic liquids are composed of ionic components, easily subjected to dissociation. Given the aforementioned, the present review paper points out the need of increasing the number of organisms being assessed in ionic liquids toxicity assays, in order to start defining monitoring procedures. Moreover, such would allow a better understanding of ionic liquids contamination status and, also, the opportunity to remark the effectiveness of new in silico methods for the ecotoxicity assessment of this kind of substances. [ABSTRACT FROM AUTHOR]