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Planarian flatworms are best known for their impressive regenerative capacity, yet this trait varies across species. In addition, planarians have other features that share morphology and function with the tissues of many other animals, including an outer mucociliary epithelium that drives planarian locomotion and is very similar to the epithelial linings of the human lung and oviduct. Planarians occupy a broad range of ecological habitats and are known to be sensitive to changes in their environment. Yet, despite their potential to provide valuable insight to many different fields, very few planarian species have been developed as laboratory models for mechanism-based research. Here we describe a previously undocumented planarian isolate, Girardia sp. (Guanajuato). After collecting this isolate from a freshwater habitat in central Mexico, we characterized it at the morphological, cellular, and molecular level. We show that Girardia sp. (Guanajuato) not only shares features with animals in the Girardia genus but also possesses traits that appear unique to this isolate. By thoroughly characterizing this new planarian isolate, our work facilitates future comparisons to other flatworms and further molecular dissection of the unique and physiologically-relevant traits observed in this Girardia sp. (Guanajuato) isolate. [Display omitted] • G. sp (Guanajuato) is a new planarian isolate collected in Mexico. • G. sp (Guanajuato) is largely asexual and highly regenerative. • G. sp (Guanajuato) displays a unique mode of locomotion. • Head regeneration in G. sp (Guanajuato) is less robust than in S.mediterranea. • G. sp (Guanajuato) animals and their piwi-1+ stem cells exhibit increased radiation tolerance compared to S.mediterranea. [ABSTRACT FROM AUTHOR]

[Display omitted] Ancient lakes are a hotspot of biodiversity. Freshwater species often experience spectacular species radiation after colonizing lakes from riverine habitats. Therefore, the relationship between the fauna of the ancient lakes and the surrounding riverine system has a special significance in understanding their origin and evolutionary history. The study of ancient lake species often focused on the lake colonization of riverine species. In contrast, far less attention has been placed on the reverse direction: the riverine colonization of the lake species, despite its importance in disentangling their complex evolutionary history. The freshwater snails in the genus Semisulcospira involve endemic groups that radiated in the ancient Lake Biwa. Using genetics and fossil records, we inferred that the ancestors of these lake-endemic Semisulcospira snails historically colonized the riverine habitats at least three times during the Middle Pleistocene. Each colonization resulted in the formation of a new lineage that was genetically and morphologically distinct from other lineages. Further, one of these colonizations was followed by hybridization with a cosmopolitan riverine species, which potentially facilitated the population persistence of the colonizers in the new environment. Despite their complex histories, all these colonizers were currently grouped within a single species, Semisulcospira kurodai , suggesting cryptic diversity in this species. This study highlights the significance of the riverine colonizations of the lake species to fully understand the diversification history of freshwater fauna in and around the ancient lakes. [ABSTRACT FROM AUTHOR]

The freshwater aquifers of the Indo-Gangetic plains support rich biodiversity which is under the threat of arsenic contamination. The filter feeding bivalve mollusc Lamellidens marginalis is a sessile and sentinel resident of these freshwater habitats. In the present study, the classical cell behaviours of adhesion and aggregation were monitored in the circulating haemocytes of the freshwater bivalve under the exposure of sodium arsenite (NaAsO 2) at sublethal concentrations in controlled laboratory conditions for a maximum time-span of sixteen days. The toxic metalloid significantly inhibited non-self adhesion, inter-haemocyte interactions and haemocyte aggregation in a dose and time dependent manner. The natural occurrence of the filopods on the haemocytes was significantly diminished in the bivalves exposed to the inorganic arsenite. Moreover, a significant fall in the kinetics of phagocytosis index and haemocyte adhesion was observed under the in vitro exposure to NaAsO 2. Compromised non-self adhesion, cell-cell aggregation and phagocytosis of non-self particles by the bivalve haemocytes probably indicate susceptible immunological status of the bivalve. Such vulnerable immunity of the bivalve probably signifies the nature of imminent threat to the freshwater ecosystem as a whole under inorganic arsenite exposure. The findings would be helpful to design bivalve haemocyte based inexpensive biomonitoring tool to assess the health of freshwater ecosystem under potential arsenic threat. • Bivalve Lamellidens marginalis exposed to sublethal concentrations of NaAsO 2. • Haemocyte adhesion and aggregation inhibited dose and time dependently. • Proportion of haemocytes with filopods declined. • Phagocytic index (PI) and haemocyte adhesion inhibited dose dependently (in vitro). • Cell adhesion and PI assays are proposed for biomonitoring of aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Freshwater habitats hold a unique role in the survival of all living organisms and supply water for drinking, irrigation, and life support activities. In recent decades, due to anthropogenic activities, deterioration in the water quality has been a long-lasting problem and challenge to the scientific fraternity. Although, these freshwater bodies have a bearable intrinsic capacity for pollution load however alarming increase in pollution limits the intrinsic capacities and requires additional technological interventions. The release of secondary pollutants from conventional interventions further needs revisiting the existing methodologies and asking for green interventions. Green interventions such as phycoremediation are natural, eco-friendly, economic, and energy-efficient alternatives and provide additional benefits such as nutrient recovery, biofuel production, and valuable secondary metabolites from polluted freshwater bodies. This systemic review in a nut-shell comprises the recent research insights on phycoremediation, technological implications, and influencing factors, and further discusses the associated mechanisms of metal ions biosorption by living and non-living algae, its advantages, and limitations. Besides, the article explores the possibility of future research prospects for applicability at a field scale that will help in the efficient utilization of resources, and improved ecological and health risks. [ABSTRACT FROM AUTHOR]

Food webs consist of numerous connections between consumers and resources that can couple adjacent ecosystems together by the movement of nutrients, prey, and consumers leading to habitat coupling. Habitat coupling and isotopic niche dynamics among mobile consumers at the individual and population-level has been examined extensively in freshwater systems but has received little attention in sub-Arctic estuaries, which act as transition zones between freshwater and marine habitats and resources. The objective of this study was to quantify the diet composition between freshwater-and marine-derived resources and the isotopic niche size of mobile consumers (13 fishes and 2 seal species) within the lower Churchill River, Manitoba, Canada using stable isotopes (δ13C, δ15N and δ34S) in a Bayesian framework. Cisco, lake whitefish, and northern pike represented the habitat couplers in this system and also exhibited the greatest amount of individual variability since most (75%, 56%, 65% of individuals for cisco, lake whitefish, and pike respectively) consumed a mix of both freshwater-and marine-derived resources. The largest isotopic niche sizes were found for lake whitefish and northern pike, whereas the smallest isotopic niche sizes were found for both harbour and ringed seals. The isotopic niche of lake whitefish overlapped with the most species (5 in total), which supports their broader use of both freshwater- and marine-derived resources. Habitat couplers in this system exhibited more variability in their foraging strategy than the other consumers, which aligns with their known life histories and migratory or resident movement strategies. Future changes in the relative availability of freshwater and marine-derived resources due to climate and anthropogenic stressors could pose consequences to these habitat coupling species and overall trophic dynamics of sub-Arctic estuarine systems. • Habitat coupling occurs when consumers integrate resources from different habitats. • Cisco, lake whitefish, and northern pike were the habitat coupling species. • Lake whitefish had the highest niche overlap with many species. • Habitat coupling behaviour aligned with species life histories and movement strategies. • Habitat coupling species are important for the ecosystem structure and function. [ABSTRACT FROM AUTHOR]

• Cichlid visual sensitivities vary by changing cornea and lens transmission, photoreceptor densities, and photoreceptor sensitivities • Cichlid photoreceptor sensitivities shift through changes to chromophore, opsin gene sequence, opsin gene expression and opsin gene loss • Sensitivity differences are linked to differences in ecology including foraging and light environment • Cichlids are a powerful example of how the comparative approach can unravel the proximate and ultimate causes of visual system variation The family Cichlidae contains approximately 2000 species that live in diverse freshwater habitats including murky lakes, turbid rivers, and clear lakes from both the Old and New Worlds. Their visual systems are similarly diverse and have evolved specific sensitivities that differ along several axes of variation. Variation in cornea and lens transmission affect which wavelengths reach the retina. Variation in photoreceptor number and distribution affect brightness sensitivity, spectral sensitivity and resolution. Probably their most dynamic characteristic is the variation in visual pigment peak sensitivities. Visual pigments can be altered through changes in chromophore, opsin sequence and opsin expression. Opsin expression varies by altering which of the seven available cone opsins in their genomes are turned on. These opsins can even be coexpressed to produce seemingly infinitely tunable cone sensitivities. Both chromophore and opsin expression can vary on either rapid (hours or days), slower (seasonal or ontogenetic) or evolutionary timescales. Such visual system shifts have enabled cichlids to adapt to different habitats and foraging styles. Through both short term plasticity and longer evolutionary adaptations, cichlids have proven to be ecologically successful and an excellent model for studying organismal adaptation. [ABSTRACT FROM AUTHOR]

Worldwide, tidal barriers (e.g. barrages, dikes, tide gates) are constructed in the lower reaches and estuaries of rivers to limit saltwater incursion into upstream freshwater reserves, facilitate water diversion and abstraction, limit flooding, reclaim land and generate electricity. While performing these functions, tidal barriers also affect fish through: 1) reduced connectivity; 2) loss of tidal flux; 3) conversion of upstream estuarine habitats to freshwater; and 4) diminished freshwater discharge, which compresses the spatio-temporal salinity regime of downstream estuarine habitats. As such, tidal barriers commonly cause declines of diadromous and estuarine associated fish species, with a subsequent loss of ecosystem services. These impacts will be exacerbated as climate change promotes sea-level rise and alters freshwater flow regimes and will be amplified by increasing demands for freshwater by a growing human population. As a result, more tidal barriers are likely. Nevertheless, in estuaries with tidal barriers, management that promotes connectivity and more natural ecosystem function is increasing but remains complex from ecological, economic and engineering perspectives. We present case studies from the Netherlands, southeastern United States and southern Australia to characterise impacts on fishes in different biogeographical regions and document contemporary approaches to restoring ecosystem function and fish populations in systems with tidal barriers. To meet these goals, we suggest three key considerations for future research and management are provision of fish passage, reinstating tidal flux and delivering environmental flows. • Tidal barriers fragment habitats and alter hydrodynamics to the detriment of fishes. • Global case studies are used to demonstrate impacts on fishes and approaches to remediation. • Key areas for research and remediation are: fish passage, restoration of tidal flux and environmental flows. • Remediation should consider predicted changes to river hydrology and sea level rise. [ABSTRACT FROM AUTHOR]

The Birds and Habitats Directive are the cornerstones of Europe's nature conservation policy and the resulting Natura 2000 (N2k) sites form the largest coordinated network of protected areas in the world. Despite the ambitious targets of these directives and decades of efforts, biodiversity, especially of freshwater-related species, continues to decline in Europe. While multiple stressors at larger spatial scales are known to limit the effect of river restoration projects, the importance of surrounding land use outside the N2k sites for freshwater-related species richness inside N2k sites has rarely been studied. Conditional inference forests were used to assess the importance of land use in the surrounding and upstream of the German N2k sites compared to local habitat conditions inside. Freshwater-related species richness depended on land use in the surrounding besides local habitat conditions. Results indicated that this was especially true for birds in small N2k sites embedded in a wet, diverse, and patchy landscape and for non-birds due to the provision of additional habitats outside the N2k sites. Given that most N2k sites in Europe are rather small, the surrounding habitat conditions and land use potentially influences and affects freshwater-related species in many N2k sites across Europe. The additional conservation and restoration areas to be designated under the EU Biodiversity Strategy and upcoming EU restoration law should either be large enough or surrounded by extensive land use to optimize their effect on freshwater-related species. • Freshwater-related species richness in German Natura 2000 sites was investigated. • Importance of surrounding land use and local habitat conditions were compared. • Species richness strongly depends on surrounding land use providing habitat. • Surrounding landuse is more important for more mobile birds compared to non-birds. • Surrounding landuse is more important in small Natura 2000 sites. [ABSTRACT FROM AUTHOR]

Along with the increasing demand for energy and pressure to reduce carbon emissions, floating photovoltaic (FPV) systems are increasingly built on the surface of water bodies with the aim to produce clean energy. However, little is known about how FPV systems influence freshwater ecosystems, e.g., their zooplankton communities. We investigated how rotifer communities responded to FPV systems in subsidence wetlands created by underground coal mining in the North China Plain. Diversity metrics of the rotifer communities were compared between wetlands with and without FPV systems. The density of rotifers was higher in wetlands without FPV systems. In contrast, rotifer diversity as represented by Shannon-Weiner and Pielou evenness indices was higher in the FPV-covered wetlands, while there was no difference in species richness between the two types of wetlands. Furthermore, community structures differed between the two types of wetlands, in large part reflecting differences in the relative abundance of five dominant species found in both types of wetlands. These differences in rotifer assemblages were in large part explainable from environmental changes caused by the FPV panels, notably reduced light availability and water temperature, leading to reduced phytoplankton production. These findings show that FPV systems cause major changes to rotifer communities in these subsidence wetlands and likely in wetlands more generally, and monitoring of the longer-term effects is recommended given the fundamental role of zooplankton in freshwater ecosystems. [Display omitted] • Floating photovoltaic (FPV) systems are expanding in subsidence wetlands in China. • FPV-covered wetlands had lower density but higher species diversity of rotifers. • Rotifer community structures differed between wetlands with and without FPV systems. • FPV systems affected rotifer community through reducing light and water temperature. [ABSTRACT FROM AUTHOR]

Highlights • The analysis of cortisol in scales could reveal changes in the HPI axis activity. • Scale cortisol deposition may not be affected by long-term environmental pollution. • Transient energetically demanding periods could influence scale cortisol levels. Abstract A significant body of literature suggests that aquatic pollutants can interfere with the physiological function of the fish hypothalamic-pituitary-interrenal (HPI) axis, and eventually impair the ability to cope with subsequent stressors. For this reason, development of accurate techniques to assess fish stress responses have become of growing interest. Fish scales have been recently recognized as a biomaterial that accumulates cortisol, hence it can be potentially used to assess chronic stress in laboratory conditions. We, therefore, aimed to evaluate the applicability of this novel method for cortisol assessment in fish within their natural environment. Catalan chub (Squalius laietanus) were sampled from two sites; a highly polluted and a less polluted (reference) site, in order to examine if habitat quality could potentially influence the cortisol deposition in scales. We also evaluated the seasonal variation in scale cortisol levels by sampling fish at three different time points during spring-summer 2014. In each sampling, blood was collected to complement the information provided by the scales. Our results demonstrated that blood and scale cortisol levels from individuals inhabiting the reference site were significantly correlated, therefore increasing the applicability of the method as a sensitive-individual measure of fish HPI axis activity, at least in non-polluted habitats. Since different environmental conditions could potentially alter the usefulness of the technique, results highlight that further validation is required to better interpret hormone fluctuations in fish scales. Scale cortisol concentrations were unaffected by habitat quality although fish from the polluted environment presented lower circulating cortisol levels. We detected a seasonal increase in scale cortisol values concurring with an energetically costly period for the species, supporting the idea that the analysis of cortisol in scales reveals changes in the HPI axis activity. Taken together, the present study suggests that cortisol levels in scales are more likely to be influenced by mid-term, intense energetically demanding periods rather than by long-term stressors. Measurement of cortisol in fish scales can open the possibility to study novel spatio-temporal contexts of interest, yet further research is required to better understand its biological relevance. [ABSTRACT FROM AUTHOR]

Beetles have colonized freshwater habitats multiple times throughout their evolutionary history. Some of these aquatic lineages are associated exclusively with waterfall–like habitats, often with modified morphologies to cope with their unusual way of life. The historical biogeography of such cascade beetle lineages has been shown to strongly reflect ancient tectonic events. We focus on the pantropical genus Oocyclus of which species dwell in waterfalls and associated habitats. We infer the first molecular phylogeny of Oocyclus using a dataset of seven gene fragments. We recover a well resolved phylogenetic hypothesis, with a monophyletic Oocyclus divided in three genetically well–differentiated subclades which correspond to geography. Comparative dating analyses across Hydrophilidae based on ten fossil calibrations recover a Cretaceous origin for the genus. Based on a comprehensive suite of ancestral range analyses, we suggest a unique pattern with an origin in Southeast Asia followed by the successive colonization of India and the Neotropics via transoceanic stepping–stone dispersal. Diversification rate analyses support a scenario in which old Oocyclus lineages diversified slowly with a homogeneous rate regime. Waterfall beetle radiations are ancient and remarkably track Earth’s paleogeological history, shedding light on intricate patterns of macroevolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The family Achiridae is a monophyletic group. • Achirus and Trinectes were inferred as paraphyletic/polyphyletic genera. • Hypoclinemus mentalis should be taxonomically revisited. • Estuaries are the most likely center of origin for Achiridae. • Hydrogeological historical events have driven the diversification of Achiridae. Even though the monophyletic status of Achiridae has been supported by morphological and molecular data, the interrelationships within the representatives of this family are poorly resolved. In the present study, we carried out the most complete molecular phylogenetic analysis of this group, encompassing all genera and employing both nuclear (Rhodopsin, Recombination activator [Rag 1], Mixed – lineage Leukemia [MLL] and Early Growth Response Protein 3 [EGR3]) and mitochondrial (Cytochrome C Oxidase Subunit I [COI], Cytochrome B [CytB], ATPase 6.8, 16S and 12S RNAr) genes. All topologies based on Maximum Likelihood, Bayesian inferences and Bayesian Inference of the Multispecies Coalescent confirmed the monophyletism of Achiridae, in spite of some incongruences in relation to Achirus mucuri , A. lineatus, Apionichthys finis and Trinectes microphthalmus. In fact, Achirus and Trinectes proved to be non-monophyletic genera while Hypoclinemus mentalis was closely related to A. achirus , suggesting this species should be reevaluated. We provided evidence that Achiridae has first arisen in estuaries (about 23.5 million years ago) and some lineages have evolved independently to either marine or freshwater habitats. Furthermore, we propose a diversification scenario of New World soles involving at least two events of marine incursions during Miocene and Pliocene – Pleistocene associated with natural geographic barriers (Victoria-Trindade chain), the width and exposure of continental shelf and headwater capture along the Amazon basin. Finally, the evolutionary dependence of Achirid soles on estuaries, characterized as highly dynamic environments, has probably driven the recent divergence of many species of Achiridae. [ABSTRACT FROM AUTHOR]

With nearly 6000 named species, water mites (Hydrachnidiae) represent the largest group of arachnids to have invaded and extensively diversified in freshwater habitats. Water mites together with three other lineages (the terrestrial Erythraiae and Trombidiae, and aquatic Stygothrombiae), make up the hyporder Parasitengonina, which is characterized by having parasitic larvae and predatory nymphs and adults. Relationships between the Hydrachnidiae and other members of the Parasitengonina are unclear, as are relationships among the major lineages of water mites. Monophyly of water mites has been asserted, with the possible exception of the morphologically distinctive Hydrovolzioidea. Here we infer the phylogeny of water mites using multiple molecular markers and including representatives of all superfamilies of Hydrachnidiae and of almost all other Parasitengonina. Our results support a monophyletic Parasitengonina including Trombidiae, Stygothrombiae, and Hydrachnidiae. A monophyletic Hydrachnidiae, including Hydrovolzioidea, is strongly supported. Terrestrial Parasitengonina do not form a monophyletic sister group to water mites. Stygothrombiae is close to water mites but is not nested within this clade. Water mites appear to be derived from ancestors close to Stygothrombiae or the erythraoid group Calyptostomatoidea; however, this relationship is not clear because of extremely short branches in this part of the parasitengonine tree. We recovered with strong support all commonly accepted water mite superfamilies except for Hydryphantoidea, which is clearly paraphyletic. Our data support the previously proposed clades Protohydrachnidia (Hydrovolzioidea and Eylaoidea), Euhydrachnidia (all remaining superfamilies), and the euhydrachnid subclade Neohydrachnidia (Lebertioidea, Hydrachnoidea, Hygrobatoidea, and Arrenuroidea). We found that larval leg structure and locomotory behavior are strongly congruent with the molecular phylogeny. Other morphological and behavioral characters, including host choice, are not as strongly correlated with phylogeny. Molecular dating suggests that the Hydrachnidiae arose about 235 MYA, and that Neohydrachnidia began to diversify about 155 MYA. Our results provide a strong framework for classification and for further elaboration at finer taxonomic scales, which will allow testing of ecological and behavioral hypotheses associated with the transition from terrestrial to aquatic life. [ABSTRACT FROM AUTHOR]

Corbicula fluminea arrived in the Miño Estuary in 1989 and, from there, colonized more than 150 km upstream. Our aim was to test the capacity of C. fluminea to cope with osmotic stress conditions previously to invade new freshwater habitats through estuaries. Based on previously collected information, the experiment aims to study the response of the species to marine osmotic stress, evaluated by survival and behaviour. Experiments determined the resistance by the species to various levels of osmotic stress, and recovery time after exposure to high salinity levels, representative of the temporal and spatial salinity variation existing in the estuary. Under osmotic stress the semi-maximum response was reached after 19 days exposure. The species tolerance range, measured by individual maintained activity, was at salinity ∼20 when exposed to winter temperatures, while when animals were exposed to summer ones its tolerance was reduced to salinity lower than 15. C. fluminea show a large physiological flexibility to cope with salinity variations in estuaries. In summer, the temperature increases the metabolic rate thus making the species more vulnerable to osmotic stress exposure. These findings are relevant to preventing new invasions through ship ballast waters ensuring complete mortality if individuals are retained for >26 days. [ABSTRACT FROM AUTHOR]

[Display omitted] • The densest taxonomic coverage to date is employed to infer the phylogeny of mega-diverse Acariformes mites, including 150 families (367 terminals). • Worm-like mites Nematalycidae and Eriophyoidea are unambiguously recovered as a clade. Tenneriffidae was grouped with Eleuthrengona. • Inter-realm land–water transitions were directed, with most transitions occurred from terrestrial to aquatic habitats, but not back. A single possible exception was the freshwater ancestor of the Halacaroidea-Parasitengona clade, leading to a water-to-land transitions in terrestrial Parasitengona. • In many lineages, colonization of the sea occurred via a freshwater ancestor. • Most transitions were not related to mass extiction events, but some were linked to changes in configurations / drying out of ancient seas. Acariform mites are an ancient and megadiverse lineage that may have experienced a complex pattern of invasions into terrestrial and aquatic habitats. These among-realm transitions may relate to periods of turmoil in Earth's history or be simply results of uneven biodiversity patterns across habitats. Here, we inferred a dated, representative acariform phylogeny (five genes, 9,200 bp aligned, 367 terminals belonging to 150 ingroup plus 15 outgroup families, 23 fossil calibration points) which was used to infer transitions between marine/freshwater/terrestrial habitats. We detected four unambiguous transitions from terrestrial to freshwater habitats (Hydrozetes, Naiadacarus, Fusohericia , Afronothrus , Homocaligus); one from freshwater to marine (Pontarachnidae), and four from marine to brackish or freshwater transitions (all among Halacaridae: Acarothrix ; Halacarellus petiti ; Copidognathus sp.; clade Limnohalacarus + Soldanellonyx + Porohalacarus + Porolohmannella). One transition to the sea was inferred ambiguously with respect to the ancestor being either terrestrial or freshwater (Hyadesiidae), and another must be most carefully examined by adding potential related taxa (Selenoribatidae + Fortuyniidae). Finally, we inferred a single, remarkable transition from aquatic to terrestrial habitats involving early evolution of the large and ecologically diverse lineage: the ancestor of the Halacaridae + Parasitengona clade was probably freshwater given our dataset, thus making terrestrial Parasitengona secondarily terrestrial. Overall, our results suggested a strong asymmetry in environmental transitions: the majority occurred from terrestrial to aquatic habitats. This asymmetry is probably linked to mites' biological properties and uneven biodiversity patterns across habitats rather than Earth's geological history. Since the land holds more acariform diversity than water habitats, a shift from the former is more likely than from the latter. We inferred the following relationships: alicid endeostigmatid + eriophyoid (Alycidae, (Nanorchestidae, (Nematalycidae, Eriophyoidea))) being sister group to the remaining Acariformes: (proteonematalycid Endeostigmata, alicorhagiid Endeostigmata, Trombidiformes, Oribatida (including Astigmata)). Trombidiform relationships had several novel rearrangements: (i) traditional Eupodina lacked support for the inclusion of Bdelloidea; (ii) Teneriffidae, traditionally placed among Anystina, was consistently recovered in a clade including Heterostigmata in Eleutherengona; (iii) several lineages, such as Adamystidae, Paratydeidae, Caeculidae and Erythracaridae, were recovered in a large clade along other Anystina and Eleutherengona, suggesting single origins of several fundamental character states, such as the reduction of the cheliceral fixed digit and development of the palpal thumb-claw complex. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thoracotreme crabs invaded terrestrial habitat through direct invasion route during Late Cretaceous. • Secondary invasions into subtidal regions and colonization of freshwater habitats occurred in multiple lineages. • Symbiosis evolved at least two times in Thoracotremata. • Most thoracotreme superfamilies are polyphyletic and a new seven superfamilies classification scheme is proposed. The Thoracotremata is a large and successful group of "true" crabs (Decapoda, Brachyura, Eubrachyura) with a great diversity of lifestyles and well-known intertidal representatives. The group represents the largest brachyuran radiation into terrestrial and semi-terrestrial environments and comprises multiple lineages of obligate symbiotic species. In consequence, they exhibit very diverse physiological and morphological adaptations. Our understanding of their evolution is, however, largely obscured by their confused classification. Here, we resolve interfamilial relationships of Thoracotremata, using 10 molecular markers and exemplars from all nominal families in order to reconstruct the pathways of lifestyle transition and to prepare a new taxonomy corresponding to phylogenetic relationships. The results confirm the polyphyly of three superfamilies as currently defined (Grapsoidea, Ocypodoidea and Pinnotheroidea). At the family level, Dotillidae, Macrophthalmidae, and Varunidae are not monophyletic. Ancestral state reconstruction analyses and divergent time estimations indicate that the common ancestor of thoracotremes already thrived in intertidal environments in the Late Cretaceous and terrestrialization became a major driver of thoracotreme diversification. Multiple semi-terrestrial and terrestrial lineages originated and radiated in the Early Eocene, coinciding with the global warming event at the Paleocene-Eocene Thermal Maximum (PETM). Secondary invasions into subtidal regions and colonizations of freshwater habitats occurred independently through multiple semi-terrestrial and terrestrial lineages. Obligate symbiosis between thoracotremes and other marine macro-invertebrates evolved at least twice. On the basis of the current molecular phylogenetic hypothesis, it will be necessary in the future to revise and recognize seven monophyletic superfamilies and revisit the morphological character states which define them. [ABSTRACT FROM AUTHOR]

Freshwater species and their habitats, and transportation networks are at heightened risk from changing climate and are priorities for adaptation, with the sheer abundance and individuality of road-river structures complicating mitigation efforts. We present a new spatial dataset of road-river structures attributed as culverts, bridges, or fords, and use this along with data on gradient and stream order to estimate structure sensitivity and exposure in and out of special areas of conservation (SAC) and built-up areas to determine vulnerability to damage across river catchments in Wales, UK. We then assess hazard of flooding likelihood at the most vulnerable structures to determine those posing high risk of impact on roads and river-obligate species (fishes and mussels) whose persistence depends on aquatic habitat connectivity. Over 5% (624/11,680) of structures are high vulnerability and located where flooding hazard is highest, posing high risk of impact to roads and river-obligate species. We assess reliability of our approach through an on-ground survey in a river catchment supporting an SAC and more than 40% (n = 255) of high-risk structures, and show that of the subset surveyed >50% had obvious physical degradation, streambank erosion, and scouring. Our findings help us to better understand which structures pose high-risk of impact to river-obligate species and humans with increased flooding likelihood. • A new spatial dataset of road-river structures: bridges, culverts, and fords. • A national-scale screening-level assessment of structure vulnerability and risk. • Structures vulnerable to damage are also high-risk to nature and people under flooding. • Field survey shows that >50% of high-risk structures have physical degradation. [ABSTRACT FROM AUTHOR]

The importance of salinity in regulating CH 4 emissions from coastal tidal wetlands has been widely recognized. However, the different effects of constant versus fluctuating salinity increases on CH 4 emission and methanogens in both tidal freshwater marsh and floodplains are not yet well understood. We constructed mesocosm experiments on both a Cyperus malaccensis marsh and an adjacent non-vegetation-covered tidal floodplain over one year. We examined the effects of constant freshwater (CF), constant salinity (CS), and fluctuating salinity (FS) on porewater geochemistry, CH 4 flux, methanogen abundance, diversity, and community structure in the tidal marsh and floodplain. Compared with CF treatment, methanogen abundance and Chao1 index were significantly lower in the marsh mesocosms under FS and CS treatment, but only in the floodplain mesocosms under CS treatment. CS treatment significantly reduced the proportion of Methanosarcinales but significantly increased the proportion of Methanobacteriales. Porewater SO 4 2− and Cl− concentrations and pH were important factors affecting methanogen abundance and diversity. Both the CS and FS treatments considerably reduced CH 4 fluxes in marsh and floodplain mesocosms; the main factor impacting CH 4 flux was porewater dissolved CH 4 concentration, and both methanogen abundance and Chao1 index were positively correlated with CH 4 flux. Our results suggest that both continuous saltwater intrusion caused by sea-level rise and pulse saltwater intrusion perhaps caused by typhoons could reduce CH 4 flux from subtropical estuarine tidal freshwater wetlands. • Addition of constant and fluctuating saltwater (salinity = 10) significantly reduced CH 4 emissions from tidal freshwater wetlands. • Methanogen abundance, Chao1, and relative abundance of Methanosarcinales significantly decreased with constant saltwater addition. • Porewater dissolved CH 4 concentrations were important indicators of CH 4 fluxes. [ABSTRACT FROM AUTHOR]

[Display omitted] • We used two mitochondrial and one nuclear marker to construct phylogeny of the Genus Cremnoconchus , an endemic genus restricted to waterfalls of the Western Ghats. • The Genus Cremnoconchus , a marine relative in the freshwater is monophyletic and has nine described and 12 undescribed lineages. • There are two distinct clades (Central and Northern), corresponding to the two different regions of the Western Ghats. • Genus Cremnoconchus evolved from marine ancestors around 90.40 mya. • Results help in conservation of this charismatic species in the freshwater habitats which are under severe threat. Snails of the genus Cremnoconchus – the only freshwater members of the gastropod family Littorinidae – are endemic to the spray zones of numerous waterfalls in the Western Ghats of India. Cremnoconchus consists of nine described and possibly numerous undescribed species as many of these appear to be restricted to specific waterfalls. This is the first attempt at resolving the relationships between the various species in this genus and establishing its monophyly in the family. Further, we also undertake species delimitation analysis to characterize cryptic diversity in this group. Phylogenetic analyses based on nuclear and mitochondrial genes support the monophyly of Cremnoconchus within the family. A fossil-calibrated Bayesian time tree suggests that this freshwater lineage diverged from its marine counterparts around 90.40 million years ago. The separation of Cremnoconchus from its marine ancestors might have been facilitated by the break-up of Gondwana or fluctuating sea levels during this period. Species delimitation analysis retrieved 12 potentially undescribed species in this group. These species formed two distinct clades in the phylogeny, one largely confined to the northern Western Ghats and the other to the central Western Ghats. Species belonging to the northern and central Western Ghats seem to have separated around 56.11 mya, i.e. after the northern Western Ghats were formed. Additionally, spatial isolation due to the patchiness of suitable habitats (waterfalls) and low mobility might have facilitated their diversification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyprinodontiformes are a monophyletic group. • Anchored Hybrid Enrichment data support novel sets of relationships among the families. • Strong statistical support for nodes conceals extensive genealogical conflict in the data. • Interrogation of gene tree heterogeneity is an essential step in phylogenetic inference. The Killifishes (Cyprinodontiformes) are a diverse and well-known group of fishes that contains sixteen families inclusive of Anablepidae, Aphaniidae Aplocheilidae, Cubanichthyidae, Cyprinodontidae, Fluviphylacidae, Fundulidae, Goodeidae, Nothobranchiidae, Orestiidae, Pantanodontidae, Poeciliidae, Procatopodidae, Profundulidae, Rivulidae, and Valenciidae and more than 1,200 species that are globally distributed in tropical and temperate, freshwater and estuarine habitats. The evolutionary relationships among the families within the group, based on different molecular and morphological data sets, have remained uncertain. Therefore, the objective of this study was to use a targeted approach, anchored hybrid enrichment, to investigate the phylogenetic relationships among the families within the Cyprindontiformes. This study included more than 100 individuals, representing all sixteen families within the Cyprinodontiformes, including many recently diagnosed families. We recovered an average of 244 loci per individual. These data were submitted to phylogenetic analyses (RaxML and ASTRAL) and although we recovered many of the same relationships as in previous studies of the group, several novel sets of relationships for other families also were recovered. In addition, two well-established clades (Suborders Cyprinodontoidei and Aplocheilodei) were recovered as monophyletic and are in agreement with most previous studies. We also assessed the degree of gene tree discordance in our dataset to evaluate support for alternative topological hypotheses for interfamilial relationships within the Cyprinodontiformes using a variety of different analyses. The results from this study will provide a robust, historical framework needed to investigate a plethora of biogeographic, taxonomic, ecological, and physiological questions for this group of fishes. [ABSTRACT FROM AUTHOR]

In the past several years, all numerical models have forecasted an increase in extreme climatic events linked to global change. Estuarine waters at the interface of marine and freshwater bodies are among the most volatile ecosystems, particularly for aquatic species, and will be strongly influenced by the temperature with extreme flooding events. This study aimed to quantify the acclimation capacity of coastal fish species to estuarine plume modifications. The thicklip mullet ( Chelon labrosus ) and European seabass ( Dicentrarchus labrax ) were selected as representative species of estuarine ecological guilds. These fish were subjected to an experiment mimicking a brief freshwater intrusion (35–5). These experiments were conducted at two different temperatures that these two species would encounter during their incursion from the sea through estuarine waters to freshwater habitats. The experimental results confirmed the high capacity for acclimation of both species to changes in salinity and temperature. Interspecific differences were observed. For example, the salinity has a greater effect on the metabolism of the seabass than on that of the mullets. Meanwhile, the temperature has a greater effect on the mullets. These differences in metabolic responses to fluctuating salinities and temperatures may modify the use of estuarine waters by these species and should be considered when predicting future specific distribution areas in the context of global change. [ABSTRACT FROM AUTHOR]

Decomposing cyanobacterial bloom-induced black blooms been seen as an issue in the management of freshwater ecosystems, but its effect on sulfate-reducing bacteria (SRB) in shallow freshwater lakes is not clear. The objective of this study is to present an in-depth investigation of black bloom effects on the activities and composition of SRB, as well as the interactions between SRB and other bacteria. Water and surface sediments samples were collected from a shallow freshwater lake during black and non-black blooms. Sulfate reduction rates (SRRs) in the water column were determined from the linear regression of sulfate depletion with time. Quantitative real-time polymerase chain reactions (qPCRs), targeting the dsrA gene and Illumina sequencing of 16S rDNA, were used to estimate the SRB population and SRB community structures, respectively. Our data indicate that although a higher abundance of SRB was responsible for the higher SRR in the bottom water (34.09 ± 2.37 nmol mL−1 day−1) than in the surface water (14.57 ± 2.91 nmol mL−1 day−1) during black blooms, cell-specific sulfate reduction rates (csSRRs) in the distinct water layers were not significantly different (P = 0.95), with the value of approximately 0.017 fmol cell−1 day−1. Additionally, Desulfomicrobium and Desulfovibrio were the two main genera of SRB in the water column during black bloom season, while Desulfobulbus , Desulfobacca and Desulfatiglans genera were identified in the sediments of both the black and non-black blooms in genera pools. Each SRB genus preferentially associated with bacteria for specific functions in the bacterial co-occurrence network, regardless of whether black booms occurred or not. These results extend our knowledge on the importance of SRB during black blooms and the adaptation of SRB to environmental changes in freshwater lakes. • Black bloom effects analyzed based on activities of sulfate-reducing bacteria. • Population of sulfate-reducing bacteria determined sulfate reduction rates. • Surface water acted as the main source of dissolved sulfide during black blooms. • Black blooms changed neighboring nodes for sulfate-reducing bacteria in the network. • Different sulfate-reducing bacteria associated with different functional bacteria. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phylogenomic analyses of UCEs reveal that Neaviperla is an invalid genus. • Jump dispersal has influenced the geographic distributions of Suwallia species. • Several Suwallia species appear to exhibit cryptic genetic diversity. • This is first ever reconstructed molecular phylogeny for Suwallia. • Museum specimens are useful for targeted sequencing techniques. Evolutionary biologists have long sought to disentangle phylogenetic relationships among taxa spanning the tree of life, an increasingly important task as anthropogenic influences accelerate population declines and species extinctions, particularly in insects. Phylogenetic analyses are commonly used to identify unique evolutionary lineages, to clarify taxonomic designations of the focal taxa, and to inform conservation decisions. Advances in DNA sequencing techniques have increasingly facilitated the ability of researchers to apply genomic methods to phylogenetic analyses, even for non-model organisms. Stoneflies are non-model insects that are important bioindicators of the quality of freshwater habitats and landscape disturbance as they spend the immature stages of their life cycles in fresh water, and the adult stages in terrestrial environments. Phylogenetic relationships within the stonefly genus Suwallia (Insecta: Plecoptera: Chloroperlidae) are poorly understood, and have never been assessed using molecular data. We used DNA sequence data from genome-wide ultraconserved element loci to generate the first molecular phylogeny for the group and assess its monophyly. We found that Palearctic and Nearctic Suwallia do not form reciprocally monophyletic clades, and that a biogeographic history including dispersal, vicariance, and founder event speciation via jump dispersal best explains the geographic distribution of this group. Our results also strongly suggest that Neaviperla forcipata (Neave, 1929) is nested within Suwallia , and the concept of the genus Suwallia should be revised to include it. Thus, we formally propose a new taxonomic combination wherein Neaviperla forcipata (Neave, 1929) is reclassified as Suwallia forcipata (Neave, 1929). Moreover, some Suwallia species (e.g., S. amoenacolens , S. kerzhneri , S. marginata, S. pallidula, and S. starki) exhibit pronounced cryptic diversity that is worthy of further investigation. These findings provide a first glimpse into the evolutionary history of Suwallia , improve our understanding of stonefly diversity in the tribe Suwallini, and highlight areas where additional research is needed. [ABSTRACT FROM AUTHOR]

Abstract: Linear discriminant analysis (LDA) and habitat discrimination critical value (HDCV) methods are alternatives for evaluating the migratory history, such as the proportion of residence in freshwater (%fwr) and estuarine/marine habitats, of individual American eels (Anguilla rostrata) via the analysis of otolith Sr:Ca data. The LDA process requires Sr:Ca data from both freshwater and estuarine/marine groups while the mean + cSD method requires only a freshwater standard. For the two group (freshwater, estuarine/marine), single predictor variable (Sr:Ca) case, the LDA process defaults to Fisher's linear discriminant where the HDCV equals the average of the group mean Sr:Ca values. The difference between freshwater and estuarine resident eel mean otolith Sr:Ca values, based on 13 published studies and the current study (n = 14), decreased with increasing freshwater group otolith mean (r = 0.80, p < 0.001), reflecting a relatively constant estuarine group mean (r = 0.38, p = 0.17). A process is proposed for estimating a HDCV from freshwater group otolith Sr:Ca mean and SD values based on empirical linear relations between the LDA, HDCV and freshwater mean (n = 14, r = 0.90, p < 0.0001) and c and SD (n = 14, r = −0.89, p < 0.0001) from the equation HDCV = mean + cSD. Variation in the sample sizes of otolith Sr:Ca values used in the discriminant process of estimating a HDCV, while statistically significant, had trivial effect sizes that were likely of little biological consequence. However, larger sample sizes are preferred over smaller sample sizes. Estimates of %fwr increased with increases in the HDCV. Differences in %fwr estimates over a range of HDCVs were highly statistically significant and effect sizes increased with increased HDCV difference. As HDCV levels increased, growth rate estimates increased for a given %fwr value. A HDCV difference of ≤0.5 × 10−3 produced a small effect size. Accurate estimation of a HDCV is fundamental to the assessment of the habitat residence and inter-habitat movement of American eels and perhaps of other diadromous fishes and helps minimize bias in dependent estimates of other useful statistics such as the percentage of freshwater residence (%fwr) and growth rate. [Copyright &y& Elsevier]

Abstract: The ecological model, Daphnia pulex (Cladocera: Daphniidae), is broadly distributed in Holarctic freshwater habitats and has been the subject of multidisciplinary study for over half a century, but never has a natural RNA virus infection been reported in daphnids. Here we report on a group of paleoviruses related to RNA dependent RNA polymerase in the genome of D. pulex. Phylogenetic analysis suggests that these paleoviruses are derived from a viral lineage within the genus Phlebovirus. Comparison of the genomic sequences flanking individual paleoviruses reveal that some are orthologous viral insertions having been present in the common ancestor of the D. pulex species complex, which is millions of years old. Still, we detected some sites that have the signature of purifying selection. In contrast, other paleoviruses in this group seem to be unique to specific host lineages and even contain undisrupted open reading frames, suggesting either more recent acquisition, or selective maintenance. [Copyright &y& Elsevier]

Abstract: Human activities have caused extensive loss of estuarine wetlands, and the restoration of functional habitats remains a challenging task given several physical constraints in strongly embanked estuaries. In the Schelde estuary (Belgium), a new tidal marsh restoration technique, Controlled Reduced Tide system (CRT), is being implemented in the freshwater zone. A polder area of 8.2 ha was equipped with a CRT to test the system functionality. Among different ecological compartments that are studied for assessing the CRT restoration success, avifauna was monitored over three years. The tidal regime generated a habitat gradient typical of tidal freshwater wetlands along which the distributions of bird and ecological groups were studied. 103 bird species were recorded over the three years. In addition to many generalist bird species, several specialist species typical of the North Sea coast were present. Thirty-nine species of local and/or international conservation interest were encountered, emphasising the importance of this habitat for certain species. Species communities and ecological groups were strongly habitat specific and non-randomly organized across habitats. Spatiotemporal analyses highlighted a rapid habitat colonization, and a subsequent stable habitat community structure across seasons in spite of strong seasonal species turnovers. Hence, these findings advocate CRT implementation as a means to effectively compensate for wetland habitat loss. [Copyright &y& Elsevier]

Vessel sound is now globally recognized as a significant and pervasive pollutant to aquatic life. However, compared to marine environments, there is a paucity of data on sound emitted by vessel activity in freshwater habitats. The Upper Mississippi River (UMR) is home to a diverse array of aquatic life as well as being a key route for barge transportation with 29 locks and dams. In this study, passive acoustic monitoring was conducted at Lock and Dam 19 near Keokuk, Iowa, on the UMR between 20 June – August 28, 2019 to coincide with peak navigation use. There was a significant increase in median sound pressure level (SPL; 50–12,000 Hz) recorded during vessel passages (123 dB re. 1μPa for recreational vessels and 137 dB re. 1μPa for commercial vessels) compared to median background levels (111 dB re. 1μPa). Results provide information on the ambient soundscape at a navigation lock, providing a baseline essential for future studies gauging the effect of anthropogenic sound on aquatic life. Lock 19 has also been identified as a potential site for acoustic deterrent deployment to prevent invasive fish movements. The results of this study can help determine the sound level or frequency deterrents would need to emit, to avoid those currently produced during vessel passage. • Passive acoustic monitoring gives data on spatial and temporal patterns of sound. • There is a paucity of data on anthropogenic sound in freshwater habitats. • Recreational vessel passage increased soundscape by 11dB. • Commercial vessel passage increased soundscape by 26dB. • Establishing baseline sound levels is useful for environmental impact assessments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mitogenomes and nuclear rDNA resolve diphyllobothriidean evolutionary relationships. • Host and habitat diversity studied from a phylogenetic perspective. • Freshwater inferred as diphyllobothriidean ancestral habitat. • Confirmed Schistocephalus solidus and S. pungitii as distinct species. • Demonstrated conspecificity of Ligula cf. intestinalis in ringed seal subspecies. Broad tapeworms (Diphyllobothriidea) are parasites whose adults are capable of infecting a wide range of freshwater, marine and terrestrial tetrapods including humans. Previous works examining the evolution of habitat and host use in this group have been hampered by the lack of a well-resolved phylogeny. In order to produce a robust phylogenetic framework for diphyllobothriideans, we sequenced the complete mitochondrial genome of 13 representatives, carefully chosen to cover the major clades, and two outgroup species representing the Spathebothriidea and Haplobothriidea. In addition, complementary data from the nuclear ribosomal operon was sequenced for 10 representative taxa. Mitogenomes and ssrDNA and lsrDNA were used towards elucidating the phylogenetic framework for the Diphyllobothriidea. The Cephalochlamydidae is confirmed as the earliest diverging diphyllobothriidean lineage, and Solenophoridae and Diphyllobothriidae are sister groups. We infer a probable freshwater origin of the diphyllobothriideans. The ancestral condition for life cycle complexity could not be unambiguously resolved. However, we infer exclusive use of a three-host life cycle following the origin of the Solenophoridae + Diphyllobothriidae. Regarding definitive host use, although we infer reptiles as the most likely ancestral condition, this result should be revisited with a more densely sampled phylogeny in future studies. Freshwater habitat is used by the early diverging lineages within the Solenophoridae + Diphyllobothriidae clade. For the latter, habitat use shifts between freshwater and marine environments, and definitive host use includes marine and terrestrial mammals and birds. We use mitochondrial genomes to distinguish Schistocephalus species occurring in different species of sticklebacks and demonstrate conspecificity of Ligula cf. intestinalis specimens collected from two Fennoscandian ringed seal subspecies. [ABSTRACT FROM AUTHOR]

Abstract: Although experiencing strong anthropogenic pressures in many estuaries, the ecology of tidal freshwater areas remains largely undocumented. As part of a restoration project in the freshwater zone of the Schelde estuary (Belgium), a new tidal habitat restoration technique (Controlled Reduced Tide system, CRT) was hypothesised to successfully compensate for the impairment of contemporary habitats. The suitability of this newly-created habitat (CRT) and the estuary was investigated over a period of three years for its macroinvertebrate community development. In both the estuary and the CRT, habitats along a flooding gradient were monitored. Differences between the CRT and reference sites in community functioning were explored according to environmental characteristics and organism biological attributes using the RLQ ordination analysis together with the fourth-corner method. Frequently flooded reference sites exhibited environmental characteristics resulting from a hydrological shear stress. In the CRT, after a rapid removal of the terrestrial fauna at low and mid elevations, the low-energy hydrology led to taxonomic and functional enrichment. The RLQ analysis produced significant environmental filtering of biological attributes mainly related to the terrestrial–aquatic transition and to the environmental stressors. This provides an example of life history modification via estuarine ecosystem management. [Copyright &y& Elsevier]

The performance of three single-station whole stream metabolism models were evaluated within three shaded, seasonally hypoxic, Missouri reference streams using high resolution (15-minute) dissolved oxygen (DO), temperature, and light intensity data collected during the summers (July–September) of 2006–2008. The model incorporating light intensity data consistently achieved a lower root mean square error (median RMSE = 0.20 mg L−1) relative to models assuming sinusoidal light intensity functions (median RMSE = 0.28 mg L−1) and constant diel temperature (median RMSE = 0.53 mg L−1). Incorporation of site-specific light intensity into metabolism models better predicted morning DO concentrations and exposure to hypoxic conditions in shaded study streams. Model choice significantly affected (p < 0.05) rate estimates for daily average photosynthesis. Low reaeration (pooled site mean 1.1 day−1 at 20 °C) coupled with summer temperatures (pooled site mean = 25.8 °C) and low to moderate community respiration (site median 1.0–3.0 g O2 m−2 day−1) yielded diel dissolved oxygen concentrations near or below critical aquatic life thresholds in studied reference streams. Quantifying these process combinations in best-available or least-disturbed (i.e., reference) systems advances our understanding of regional dissolved oxygen expectations and informs environmental management policy. Additional research is warranted to better link landscape processes with distributed sources that contribute to community respiration. [Copyright &y& Elsevier]

Interest in ecosystem services has grown tremendously among a wide range of sectors, including government agencies, NGO’s and the business community. Ecosystem services entailing freshwater (e.g. flood control, the provision of hydropower, and water supply), as well as carbon storage and sequestration, have received the greatest attention in both scientific and on-the-ground applications. Given the newness of the field and the variety of tools for predicting water-based services, it is difficult to know which tools to use for different questions. There are two types of freshwater-related tools – traditional hydrologic tools and newer ecosystem services tools. Here we review two of the most prominent tools of each type and their possible applications. In particular, we compare the data requirements, ease of use, questions addressed, and interpretability of results among the models. We discuss the strengths, challenges and most appropriate applications of the different models. Traditional hydrological tools provide more detail whereas ecosystem services tools tend to be more accessible to non-experts and can provide a good general picture of these ecosystem services. We also suggest gaps in the modeling toolbox that would provide the greatest advances by improving existing tools. [Copyright &y& Elsevier]

Abstract: The Ebro catchment, the largest river basin in Spain, includes various heavily industrialized areas. Among these is the Flix site, where a chemical plant has been operating since the beginning of the 20th century. This extended operational period, together with the construction of a dam next to the factory around 1960, resulted in the accumulation of large amounts of heavily polluted sediments in the adjacent riverbed, many of which are contaminated by mercury. Pollutants from Flix are carried downstream by the Ebro River to its delta. In order to assess the transfer of mercury to the complex river estuary ecosystem, we studied the ecology of the tern community living there as these birds segregate into a range of habitats. For this purpose, first we used stable isotope analysis (SIA) (δ34S, δ13C, δ15N) of eggs to determine the trophic ecology and habitat partitioning of several tern species (Common, Sandwich, Little, Gull-Billed and Whiskered Tern) breeding sympatrically, in order to link their foraging ecology with habitat types. Next we measured mercury concentrations in eggs to monitor the input of this metal into the diverse habitats. With the exception of the Little Tern, the other terns used a restricted habitat range in the Ebro Delta, as shown by C and S isotopes; the Gull-Billed and Whiskered Tern foraged in freshwater habitats, while the Common and Sandwich Tern used marine habitats. This restricted feeding behavior of the Gull-Billed and Common Tern contrasts with previous reports in other breeding sites. The Little Tern, which showed a wide range of isotopic values, was found to be an opportunistic forager but fed mainly in saltpans, a feeding habitat not reported previously for this species in this area. We found that mercury concentrations are related to foraging habitat and diet, and are unexpectedly higher in species feeding on demersal prey in marine habitats and also higher in birds feeding in saltpans than in those feeding in freshwater habitats. The mercury concentrations found in the Little and Common Tern eggs sampled in “Punta de la Banya” may be sufficiently high to endanger breeding success. [Copyright &y& Elsevier]

Abstract: This study measured the relative expression of the genes coding for Na+, K+-ATPase 1α(NAKA), voltage-dependent anion channel (VDAC), cytochrome c oxidase-1 (COX), and NADH dehydrogenase (NDH), in gills of six wild populations of a West African tilapia species, acclimatised to a range of seasonal (rainy or dry) salinities in coastal, estuarine and freshwater sites. Previous laboratory experiments have demonstrated that these genes, involved in active ion transport, oxidative phosphorylation, and intra-cellular ATP transport, are relatively over-expressed in gill tissues of this species acclimated to high salinity. Positive correlations between relative expression and ambient salinity were found for all genes in the wild populations (Spearman rank correlation, p < 0.05), although for some genes these were only significant in either the rainy season or dry season. Most significantly, however, relative expression was positively correlated amongst the four genes, indicating that they are functionally interrelated in adaptation of Sarotherodon melanotheron to salinity variations in its natural environment. In the rainy season, when salinity was unstable and ranged between zero and 37 psu across the sites, overall mean expression of the genes was higher than in the dry season, which may have reflected more variable particularly sudden fluctuations in salinity and poorer overall water quality. In the dry season, when the salinity is more stable but ranged between zero and 100 psu across the sites, NAKA, NDH and VDAC expression revealed U-shaped relationships with lowest relative expression at salinities approaching seawater, between 25 and 45 psu. Although it is not simple to establish direct relationship between gene expression levels and energy requirement for osmoregulation, these results may indicate that costs of adaptation to salinity are lowest in seawater, the natural environment of this species. While S. melanotheron can colonise environments with extremely high salinities, up to 100 psu, this was related to high relative expression for all genes studied, indicating that this imposes increased energy demand for osmotic homeostasis in gill tissues. This study is the first to demonstrate, in fish and in wild populations, that expression of NAKA, VDAC, NDH and COX are interrelated in gill tissues, and are involved in long-term acclimatisation to a salinity range between 0 and 100 psu. [Copyright &y& Elsevier]

Abstract: The genus Craterocephalus is one of the 11 genera within the family Atherinidae. It is the only genus in the family that has undergone an extensive radiation within freshwater habitats. Five species groups are represented within the genus, with 18 species found in Australia, six in New Guinea and one in East Timor. Craterocephalus is the equal fourth most widespread genus in Australian freshwater environments (occurring in 21 out of 31 biogeographic regions), and the most speciose (13 species). This allows identification of broad biogeographic patterns that can later be contrasted with other groups that overlap geographically. Phylogenetic relationships of Craterocephalus were examined using the cytochrome b gene. Results confirmed the monophyly of five species groups, with the marine “new honoriae” group being basal, suggesting a single invasion of freshwater habitats. The “capreoli” group and one species, C. munroi represents reversals back into marine/estuarine conditions. The most striking result from this study is the degree of differentiation between species in the separate freshwater groups within Craterocephalus. Despite often occurring sympatrically in river systems, interspecies and population divergences from “eyresii” and “stramineus” groups were substantially larger than divergences within “stercusmuscarum.” Despite being one of the best freshwater groups characterized morphologically within Australia, it is clear that additional morphological work is required to clarify taxonomic problems within Craterocephalus, as molecular data suggest some species are synonymous, while others appear to represent multiple unrecognized taxa. [Copyright &y& Elsevier]

[Display omitted] • Heptapteridae (three-barbeled catfishes) contains 23 genera, 228 recognized species. • Multi-locus analyses yield first robust, resolved, taxon-rich phylogeny for this family. • We propose new phylogenetic classification of 2 subfamilies, each with 2 tribes. • Tribe Brachyglaniini contains four Guiana Shield specialist genera, many new species. • Brachyglaniini biogeography suggests repeated early dispersals across western Guiana Shield. The catfish family Heptapteridae is ubiquitous across a range of freshwater habitats from southern Mexico to northern Argentina and contains 23 genera and 228 valid species. After a century of mostly morphology-based systematic analyses of these fishes, we provide the first molecular phylogenetic hypothesis spanning most valid Heptapteridae genera (16 of 23). We examined eight of 14 valid genera in the Nemuroglanis -subclade (Heptapterini), all valid genera in the Brachyglanis -subclade (Brachyglaniini) and most valid Brachyglaniini species (11 of 15). Maximum likelihood and Bayesian analyses of a 4156-base alignment of five gene regions (three mitochondrial: COI, Cyt b , and ND2; two nuclear: RAG2, Glyt) yielded thoroughly resolved and statistically robust phylogenies that were largely congruent with each other and with previous morphology-based hypotheses. We propose a revised phylogenetic classification consisting of two subfamilies (Rhamdiinae, Heptapterinae) each with two tribes. Dense taxonomic sampling of Brachyglaniini, including type species of Brachyglanis , Gladioglanis , Leptorhamdia , and Myoglanis , revealed widespread paraphyly. Newly recovered clades within Brachyglaniini are closely associated with either the upper Orinoco or the Essequibo suggesting repeated dispersals and/or range expansions/contractions across the western Guiana Shield highlands and from there to the upper Amazon and Brazilian Shield. These biogeographical processes appear to have been an important driver of allopatric diversification in the clade. [ABSTRACT FROM AUTHOR]

The silverside Odontesthes argentinensis is commonly reported as a euryhaline species, capable of using estuaries as nurseries and/or feeding grounds. However, in Mar Chiquita Coastal Lagoon system (MCH), northern Argentine Sea, substantial genetic differences have been observed between estuarine and adjacent marine populations of this species, despite no geographic barriers separate them. This, in addition to their reproductive isolation, rendered this population a considerable candidate for a marine to freshwater incipient speciation event. Here we combined evidence from fish meristic analysis and parasite ecology to assess if, 1) the structure and composition of parasite assemblages of O. argentinensis are indicators of isolation between populations; 2) a differential use of the lagoon and its freshwater tributaries by O. argentinensis is reflected in their parasite communities, so that it could indicate incipient processes of colonization of freshwater habitats by the estuarine population. Twenty-three species were found parasitizing this host in MCH, whose assemblages evidenced qualitative and quantitative differences regarding those of the neighboring marine waters. Thus, the present study demonstrates the usefulness of parasites as indicators of population differences, revealing the same two evolutionary units previously recognized by more traditional methods (genetics, morphometry, reproductive biology). Consequently, the results support the ongoing speciation process proposed for O. argentinensis in MCH. The homogeneity of the parasite assemblages in these fish from estuarine and freshwater habitatshighlights the capability of this species to colonize new environments. As selective agents of host evolution, parasites can initiate, facilitate and promote adaptive differentiation, triggered by other factors, of certain traits in host populations. Therefore, the high degree of differentiation here observed in the parasite assemblages between marine and estuarine populations of O. argentinensis proves their utility as indicators of host population structure and its ongoing incipient speciation process in MCH at the present. Furthermore, differential parasite faunas in each environment could also play a role in this process in evolutionary time. Image 1 • Parasite tags indicated isolation between estuarine and marine fish populations. • Composition of communities depends on the differential use of habitat by fish hosts. • Parasite indicators supported the hypotheses of incipient speciation in their host. • Parasites can both reveal and reinforce evolutionary processes of their hosts. • Possible co-speciation of some specific parasite species is proposed. [ABSTRACT FROM AUTHOR]

The Vistula Lagoon is an almost closed basin at the southern coast of the Baltic Sea. Its mild salinity gradient provides a unique environment for the coexistence of freshwater and marine bacteria. This study employs catalysed reporter deposition-fluorescence in situ hybridisation (CARD-FISH) to investigate seasonal dynamics of marine (SAR11 clade I/II) and freshwater (SAR11 clade IIIb (LD12), Limnohabitans clades B, C, D, Burkholderiales (former Betaproteobacteria)) bacterial groups. Samples were collected from below the ice in February, and then monthly from April to October 2011 from three stations with different salinity. The abundance of SAR11 clade I/II strongly positively correlated with salinity, with the highest abundance in autumn at time of inflows of saline waters from the Baltic Sea. Two groups (spring-summer and autumn-winter) were distinguished within this clade, based on a scatter chart between SAR11-I/II abundance and salinity. Salinity explained 69% of the variability of the spring-summer group and 77% of the autumn-winter group. This suggests that the presence of marine SAR11-I/II in the Vistula Lagoon was caused by passive inflow with waters from the open Baltic Sea, and this environment is not suitable for its regular existence. The abundance of the freshwater SAR11 clade IIIb was similar to that of SAR11-I/II. However, it depended on temperature, organic and inorganic phosphorous, and not on salinity, suggesting that SAR11-IIIb found a regular niche in the eutrophic Vistula Lagoon. Burkholderiales positively correlated with temperature, chlorophyll-a, organic and inorganic phosphorous, and heterotrophic nanoflagellates, suggesting that their role in the Vistula Lagoon may be similar to that in lakes. Interestingly, Burkholderiales had the highest relative abundance under ice in February. Finally, the abundance of Limnohabitans clades B, C, D positively depended on temperature, chlorophyll-a and negatively on salinity. This together with positive correlation with Cryptophytes and with heterotrophic nanoflagellates emphasis its importance in this ecosystem. These results show that the conditions in the Vistula Lagoon are rather inappropriate for typical marine bacteria, while freshwater bacteria may find their niches despite slightly elevated salinity. • Marine SAR11-I/II was passively brought to the Lagoon with waters inflowing from the Baltic Sea. • Freshwater SAR11-IIIb and Limnohabitans are active members of the bacterial community in the Vistula Lagoon. • Burkholderiales had the highest relative abundance under ice cover in winter. [ABSTRACT FROM AUTHOR]

Tidal barrages on water ways constitute a major threat for diadromous fish species such as the critically endangered European eel (Anguilla anguilla L.). An unobstructed migration route between the spawning area in the Sargasso Sea and the freshwater growth habitats in Europe is crucial for the European eels' long-term survival. Every spring however, millions of glass eels arrive at the European coast to find their inland migration route blocked. Adjusted tidal barrage management (ATBM), i.e. setting the tidal sluice doors ajar during tidal rise, is one of the mitigation measures to enhance glass eel colonisation. Although this management substantially improves the number of incoming glass eels, the fate of these migrants, confronted with abruptly shifting conditions upon sluice passage, remains un-investigated. Glass eel upstream dispersion after sluice passage by means of ATBM was investigated in a drainage canal connecting a small estuary with an adjacent polder area in Belgium. Large numbers of glass eel caught with eel ladders installed at a pumping station about 800 m upstream the tidal barrage indicate that glass eels were well able to switch to an active counter current swimming behaviour to continue upstream dispersion. On the other hand, some glass eels did not initiate active migration but settled in artificial substrates placed in the canal instead. These residents however appeared very successful in using the canal as feeding ground and in time substantially increased their overall fitness. The appearance of both migration strategies (switch to active migration or successful settlement) in this canal shows the potential of ATBM as a valuable tool for the management and restoration of the European eel population and calls for a wide application of this cost-efficient mitigation measure. Image 1 • Glass eel colonisation is enhanced by setting sluice doors ajar during tidal rise. • Glass eels can withstand sharp saltwater/freshwater transitions. • Glass eels can adopt active migration at an early stage and at low temperatures. • Eel ladders are efficient tools to guide glass eels around barriers close to sea. [ABSTRACT FROM AUTHOR]

Anadromous sub-populations of stenohaline freshwater fish are vastly understudied in the estuarine environment. The purpose of the present study was therefore to study the population ecology, growth rate, and physico-chemical environment of an anadromous sub-population of European perch (Perca fluviatilis) from the western Baltic Sea. Fish (301) were marked with external identification tags, and anglers and fishermen reported recaptures in a citizen science set-up over three years. In addition, scale samples were collected for population growth rate determination. Furthermore, water temperature, salinity, and oxygen concentration were monitored in the area. The fish showed a consistent annual migration pattern over the three years residing in a bay during summer while being in a delta during autumn, winter, and spring. The population had a high growth rate, but a meta-analysis showed that growth of European perch is not distinctly different between estuarine and freshwater populations. The average salinity measured in the area was around 10, but increased on multiple occasions to salinity levels known for being physiologically challenging for European perch. We argue that high growth rates of estuarine European perch is more likely due to high food availability and low interspecific competition in this environment, rather than due to physiologically optimal salinities. Furthermore, the European perch in the present study lived on the edge of the species salinity tolerance, and the migration into the delta during winter is likely a combination of avoiding high salinities at low temperatures and a spawning migration. These results are important knowledge for the management of estuaries and coastal areas, especially as climate change is locally altering these environments drastically, and calls for further studies on other anadromous sub-populations of stenohaline freshwater fish. • The fish resided in a bay during summer and overwintered in a delta. • Growth rate of European perch is not different in estuaries and freshwater habitats. • Anadromous European perch temporarily experience and survive salinities up to 22. • High salinity incidents co-occurred with hypoxic conditions. [ABSTRACT FROM AUTHOR]

• Phylogenomics resolves Colponemidia as a sister group to all known alveolates. • The ancestor of all alveolates was a biflagellate predator feeding by phagocytosis. • Colponemids may illuminate the ancestral states of apicomplexans, dinoflagellates, and ciliates. • Colponemids are geographically widespread in freshwater habitats. Alveolates are a major supergroup of eukaryotes encompassing more than ten thousand free-living and parasitic species, including medically, ecologically, and economically important apicomplexans , dinoflagellates, and ciliates. These three groups are among the most widespread eukaryotes on Earth, and their environmental success can be linked to unique innovations that emerged early in each group. Understanding the emergence of these well-studied and diverse groups and their innovations has relied heavily on the discovery and characterization of early-branching relatives, which allow ancestral states to be inferred with much greater confidence. Here we report the phylogenomic analyses of 313 eukaryote protein-coding genes from transcriptomes of three members of one such group, the colponemids (Colponemidia), which support their monophyly and position as the sister lineage to all other known alveolates. Colponemid-related sequences from environmental surveys and our microscopical observations show that colponemids are not common in nature, but they are diverse and widespread in freshwater habitats around the world. Studied colponemids possess two types of extrusive organelles (trichocysts or toxicysts) for active hunting of other unicellular eukaryotes and potentially play an important role in microbial food webs. Colponemids have generally plesiomorphic morphology and illustrate the ancestral state of Alveolata. We further discuss their importance in understanding the evolution of alveolates and the origin of myzocytosis and plastids. [ABSTRACT FROM AUTHOR]

• First molecular phylogeny of a rare (11 species) planarian suborder, Cavernicola. • Confirms monophyly, Maricola sistership and their status as a distinct suborder. • Freshwater and epigean in origin, colonized both epigean and hypogean habitats. • Disjunct distribution may be due to Gondwana origin, and loss of most epigean diversity. • Genetic diversity and new findings foreshadow more species to be discovered. The planarian suborder Cavernicola Sluys, 1990 was originally created to house five species of triclad flatworms with special morphological features and a surprisingly discontinuous and broad geographic distribution. These five species could not be accommodated with any degree of certainty in any of the three taxonomic groups existing at that moment, viz., Paludicola Hallez, 1892, Terricola Hallez, 1892, and Maricola Hallez, 1892. The scarce representation of the group and the peculiarities of the morphological features of the species, including several described more recently, have complicated new tests of the monophyly of the Cavernicola, the assessment of its taxonomic status, as well as the resolution of its internal relationships. Here we present the first molecular study including all genera currently known for the group, excepting one. We analysed newly generated 18S and 28S rDNA data for these species, together with a broad representation of other triclad flatworms. The resulting phylogenetic trees supported the monophyly of the Cavernicola, as well as its sister-group relationship to the Maricola. The sister-group relationship to the Maricola and affinities within the Cavernicola falsify the morphology-based phylogeny of the latter that was proposed previously. The relatively high diversity of some cavernicolan genera suggests that the presumed rarity of the group actually may in part be due to a collecting artefact. Ancestral state reconstruction analyses suggest that the ancestral habitat of the group concerned epigean freshwater conditions. Our results point to an evolutionary scenario in which the Cavernicola (a) originated in a freshwater habitat, (b) as the sister clade of the marine triclads, and (c) subsequently radiated and colonized both epigean and hypogean environments. Competition with other planarians, notably members of the Continenticola, or changes in epigean habitat conditions are two possible explanations -still to be tested- for the loss of most epigean diversity of the Cavernicola, which is currently reflected in their highly disjunct distributions. [ABSTRACT FROM AUTHOR]