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FIGURE 1 in Gastrointestinal nematodes of freshwater fish from Pilcomayo River, Argentina including description of a new species of Procamallanus (Spirocamallanus)

FIGURE 1. Procamallanus (Spirocamallanus) tomsici sp. nov. a: Male, anterior end, lateral view. b: Female, anterior end, lateral view. c: Female, apical view. d: Male, head, lateral view. e: Female, head, lateral view. f: Female, vulva, lateral view. g: Larva. h: Female, tail, lateral view. i: Male, posterior end with spicules, lateral view. j: Male, posterior end with spicules and papillae, ventral view.

FIGURE 6 in A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus

FIGURE 6. Right valve internal views of Popenaias berezai n. sp. Localities correspond to those of Fig. 5. (A) Holotype (CNMO 8037, ex. INHS 90397.5); (B) Paratype (INHS 90397.1); (C) Paratype (INHS 90183.3); (D) Paratype (INHS 90183.1); (E) Paratype (INHS 90175.3); (F) Paratype (INHS 90175.2). Scale bar 1 cm.

FIGURE 3 in A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus

FIGURE 3. Maximum parsimony cladogram for the concatenated mitochondrial and nuclear DNA (cox1, 16S, and ANT) sequence dataset. Bootstrap support values are shown in percent along the branches. The tree is rooted with Quadrula quadrula. Major clades are annotated. Colored box along clades corresponds to the target taxa: blue, Popenaias popeii; green, P. ganina; orange, P. berezai n. sp.

FIGURE 1 in A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus

FIGURE 1. Collection localities for Popenaias species for molecular and morphometric analyses used in this study. Colored symbols represent target species (blue circles, Popenaias popeii; green squares, P. ganina; orange diamonds, P. berezai n. sp.). Shading indicates elevation where darker colors represent higher altitude.

FIGURE 5 in A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus

FIGURE 5. Right valve external views of Popenaias berezai n. sp. (A–F). (A) Holotype (CNMO 8037, ex. INHS 90397.5), 73 mm length, from the Río Valles, Estación Micos, 20 km NW of Ciudad Valles, San Luis Potosí, Mexico; (B) Paratype (INHS 90397.1), 62 mm, from the locality same as A; (C) Paratype (INHS 90183.3), 59 mm, from the Río Tampaón (Río Pánuco) Álvaro Obregón (Pujal), at confluence of the ríos Valles and Tampaón; (D) Paratype (INHS 90183.1), 67 mm length, from the locality same as C; (E) Paratype (INHS 90175.3), 53 mm, from the Río Tancuilin, 0.5 km south of Jalpilla, San Luis Potosí, Mexico; (F) Paratype (INHS 90175.2), 50 mm, from the locality same as E. White bar denotes 1 cm scale.

opencc-zeroNov 2020View details →

Invasion of freshwater ecosystems is promoted by network connectivity to hotspots of human activity

Aim: Hotspots of human activity are focal points for ecosystem disturbance and non-native introduction, from which invading populations disperse and spread. As such, connectivity to locations used by humans may influence the likelihood of invasion. Moreover, connectivity in freshwater ecosystems may follow the hydrological network. Here we tested whether multiple forms of connectivity to human recreational activities promotes biological invasion of freshwater ecosystems. Location: England, UK. Time period: 1990-2018. Major taxa studied: 126 non-native freshwater birds, crustaceans, fish, molluscs and plants. Methods: Machine learning was used to predict spatial gradients in human recreation and two high risk activities for invasion (fishing and water sports). Connectivity indices were developed for each activity, in which human influence decayed from activity hotspots according to Euclidean distance (spatial connectivity) or hydrological network distance (downstream, upstream and along-channel connectivity). Generalised linear mixed models identified the connectivity type most associated to invasive species richness of each group, while controlling for other anthropogenic and environmental drivers. Results: Connectivity to humans generally had stronger positive effects on invasion than all other drivers except recording effort. Recreation had stronger influence than urban land cover, and for most groups high risk activities had stronger effects than general recreation. Downstream human connectivity was most important for invasion by most of the groups, potentially reflecting predominantly hydrological dispersal. An exception was birds, for which spatial connectivity was most important, possibly because of overland dispersal capacity. Main conclusions: These findings support the hypothesis that freshwater invasion is partly determined by an interaction between human activity and species dispersal in the hydrological network. By comparing alternative connectivity types for different human activities, our approach could enable robust inference of specific pathways and spread mechanisms associated with particular taxa. This would provide evidence to support better prioritisation of surveillance and management for invasive non-native species.

opennotspecifiedSep 2019View details →

FIGURE 4 in Areas of endemism for Anablepidae (Teleostei: Cyprinodontiformes): A monophyletic family of freshwater fishes in the Neotropics

FIGURE 4. Consensus areas of endemism (CAs) delimited for Anablepidae by endemicity analysis with grid size of 1.5º.

opencc-zeroAug 2020View details →

Riverscape properties contribute to the origin and structure of a hybrid zone in a Neotropical freshwater fish

Understanding the structure of hybrid zones provides valuable insights about species boundaries and speciation, such as the evolution of barriers to gene flow and the strength of selection. In river networks, studying evolutionary processes in hybrid zones can be especially challenging, given the influence of past and current river properties along with biological species-specific traits. Here, we suggest that a natural hybrid zone between two divergent lineages of the sexually dimorphic Neotropical fish Nematocharax venustus was probably established by secondary contact as a result of a river capture event between the Contas and Pardo river basins. This putative river capture is supported by hydrogeological evidence of elbows of capture, wind gaps, and geological faults. The morphological (color pattern) and genetic (mtDNA and RADseq) variation reveal a clinal transition between parental lineages along the main river, with predominance of F2 hybrids at the centre of the hybrid zone, absence of early generation backcrosses, and different levels of hybridization in the tributaries. We highlight that different sources of information are crucial for understanding how the riverscape spatial history influences the connectivity between and within rivers systems and, consequently, the dynamics of gene flow between freshwater lineages/species.

opencc-by-4.0Aug 2020View details →

Freshwater zooplankton metapopulations and metacommunities respond differently to environmental and spatial variation data files

We used this data to examine how crustacean zooplankton and rotifer species’ metapopulation genetic structure and metacommunities respond to environmental and spatial variation both within and across four regions of boreal Canada (see Martin et al. in press, Freshwater zooplankton metapopulations and metacommunities respond differently to environmental and spatial variation, Ecology). Whole community zooplankton samples were collected from 113 lakes from four environmentally, geologically, and geographically distinct regions of Québec, Canada. Each lake was sampled once, and the bulk zooplankton samples were sequenced using metabarcoding targeting the cytochrome c oxidase subunit I (COI) mitochondrial gene region. Sequences were clustered to species based on 3% OTUs and within species-variation was captured based on ASVs. Read abundances were then normalized using rarefaction to the lowest library to accommodate differences in sequencing depth across sites. In addition 16 environmental variables plus two spatial variables were used to capture abiotic variation between lakes. The data files include the ASV sequences, OTU and taxonomic assignment, and site variables.

opencc-zeroAug 2020View details →

Structure of small tropical islands freshwater fish and crustacean communities: a niche- or dispersal-based process?

Determining the relative importance of niche- and dispersal-based processes in the structuring of animal communities is central in ecology. Freshwater fish and crustacean communities of small tropical islands can bring new insights for understanding these processes as all their species present a pelagic larval stage which gives them important dispersal capacities. Consequently, we hypothesized that dispersal-based process maybe preponderant for structuring these communities from the regional- to the local, i.e. survey site, scales. Gradient forest analyses allowed us to model the effect of 12 environmental variables on freshwater taxa abundances in two southwestern Indian Ocean islands: Mayotte (26 taxa) and Reunion (21). A total of 153 surveys in Mayotte and 266 in Reunion were used for building the models. Despite the strong heterogeneity of environmental conditions between the two islands, the main factors structuring freshwater fish and crustacean communities in both islands were the elevation and the slope of the sites. The observed structure appeared more pronounced for predatory species than for primary consumers and omnivores. As predators generally have limited locomotor capacities, it is concluded that dispersal-based process structures these communities not only at large geographical scales but also at the intra-watershed scale, by limiting the inland penetration (or dispersion) of species in relation to their locomotor capacities. However, more knowledge concerning ecological traits and taxonomic status of many species is needed to confirm this assumption.

opencc-zeroSep 2020View details →

Data from: Cyanophage propagation in the freshwater cyanobacterium Phormidium is constrained by phosphorus limitation and enhanced by elevated pCO2

Intensification of human activities has led to changes in the availabilities of CO2 and nutrients in freshwater ecosystems, which may greatly alter the physiological status of phytoplankton. Viruses require hosts for their reproduction and shifts in phytoplankton host physiology through global environmental change may thus affect viral infections as well. Various studies have investigated the impacts of single environmental factors on phytoplankton virus propagation, yet little is known about the impacts of multiple factors, particularly in freshwater systems. We therefore tested the combined effects of phosphorus limitation and elevated pCO2 on the propagation of a cyanophage infecting a freshwater cyanobacterium. To this end, we cultured Phormidium in P-limited chemostats under ambient (400 µatm) and elevated (800 µatm) pCO2 at growth rates of 0.6, 0.3, and 0.05 d-1. Host C:P ratios generally increased with strengthened P-limitation and with elevated pCO2. Upon host steady state conditions, virus growth characteristics were obtained in separate infection assays where hosts were infected by the double-stranded DNA cyanophage PP. Severe P-limitation (host growth 0.05 d-1) led to a 85% decrease in cyanophage production rate and a 73% decrease in burst size compared to the 0.6 d-1 grown P-limited cultures. Elevated pCO2 induced a 96% increase in cyanophage production rate and a 57% increase in burst size, as well as an 85% shorter latent period as compared to ambient pCO2 at the different host growth rates. In addition, elevated pCO2 caused a decrease in the plaquing efficiency and an increase in the abortion percentage for the 0.05 d-1 P-limited treatment, while the plaquing efficiency increased for the 0.6 d-1 P-limited cultures. Together, our results demonstrate interactive effects of elevated pCO2 and P-limitation on cyanophage propagation, and show that viral propagation is generally constrained by P-limitation but enhanced with elevated pCO2. Our findings indicate that global change will likely have a severe impact on virus growth characteristics and thereby on the control of cyanobacterial hosts in freshwater ecosystems.

opencc-zeroSep 2020View details →

Data from: Spatial and temporal homogenization of freshwater macrofaunal communities in ditches

1. There is a widespread concern that we are witnessing an on-going homogenization of ecological communities. However, in contrast to human impacts on spatial patterns in biodiversity, human impacts on the temporal aspects of β-diversity have received little attention. Moreover, the interplay between spatial and temporal β-diversity is poorly understood. To address this knowledge gap, we assessed dissimilarity within freshwater macrofaunal communities of drainage ditches to determine spatiotemporal β-diversity as well as homogenization in relation to different types of land use. 2. We considered four distinct changes in community composition: spatial turnover, temporal turnover, spatial variation over time and temporal variation in space, as well as the combined effects of space and time on β-diversity. As a metric of dissimilarity, we calculated the taxonomic Hellinger distance between samples from different locations and time points and correlated these with distance in space and in time, as well as with three spatial variables, including land use type, and two temporal variables. We studied the effect of interactions between spatial and temporal variables on dissimilarity by applying a permutational analysis of variance. 3. Our results illustrate the importance of changes in community composition in time with respect to temporal turnover, spatial variation over time and temporal variation in space. While we did not find spatial turnover in community composition, both month and year had a considerable effect. Within a year, β-diversity decreased over the months, yet these assembly patterns differed between years. This suggests major effects of seasonal and year-to-year dynamics on β-diversity. Land use was also observed to be a main driver: ditches in nature conservation areas had higher β-diversity and temporal heterogeneity was lowest in ditches adjacent to the most intensive agricultural land use category, indicating agricultural practices can homogenizes biodiversity in both space and time. 4. By analyzing the spatial and temporal β-diversity patterns in freshwater macrofaunal communities in concert, we have shown that β-diversity is a sensitive and highly informative metric of both spatial and temporal changes in community composition.

opencc-zeroNov 2020View details →

Breaking Free from Thermodynamic Constraints: Thermal Acclimation and Metabolic Compensation in a freshwater zooplankton species

Ectothermic organisms' respiration rates are largely controlled by environment temperatures and the ability to meet metabolic demands at high temperatures sometimes sets their upper thermal limit. Organisms are hypothesized to exhibit acclimatory effects, adjusting their metabolism and physiology by deceleration of metabolic processes including respiration below Arrhenius expectations based in temperature alone. Such deceleration is termed metabolic compensation. We test the hypothesis that either heritable (among genotypes) or plastic (between acclimation regimes) heat tolerance differences can be explained by metabolic compensation in the eurythermal freshwater zooplankton crustacean Daphnia magna. We measured oxygen consumption rates over a range of assay temperatures (5°C - 37°C) in 8 genotypes of Daphnia representing a range of previously reported genotype-specific acute heat tolerance values and, in a narrower range of temperatures (10°C - 35°C) in Daphnia with different acclimation history (either 10°C or 25°C). In a ramp-up experiment we discovered no difference in temperature-specific respiration rates between heat tolerant and heat-sensitive genotypes. In contrast, we observed compensatory differences in respiration rates at both extremes of the temperature range studied. Notably, there was a deceleration of oxygen consumption at higher temperature in the 25°C-acclimated Daphnia relative to their 10°C-acclimated counterparts, observed in active, but not anaesthetized animals, a pattern corroborated by similar changes in filtering rate and, partly, by changes in mitochondrial membrane potential. Daphnia exposed to a sublethal temperature (35°C) with a 24-hour recovery period at a 25°C-acclimation temperature showed no difference in respiration compared to unexposed 25°C-acclimated Daphnia, indicating that the reduction of respiration is not caused by irreversible damage. Response time necessary to acquire the respiratory adjustment to high temperature was much lower than to low temperature, indicating that metabolic compensation at the lower temperatures require slower structural changes.

opencc-zeroDec 2020View details →

Diatoms define a novel freshwater biogeography of the Antarctic

Terrestrial biota in the Antarctic are more globally distinct and highly structured biogeographically than previously believed, but information on biogeographic patterns and endemism in freshwater communities is largely lacking. We studied biogeographic patterns of Antarctic freshwater diatoms based on the analysis of species occurrences in a dataset of 439 lakes spread across the Antarctic realm. Highly distinct diatom floras, both in terms of composition and richness, characterize Continental Antarctica, Maritime Antarctica and the sub-Antarctic islands, with marked biogeographic provincialism in each region. A total of 44% of all species is estimated to be endemic to the Antarctic, and most of them are confined to a single biogeographic region. The level of endemism significantly increases with increasing latitude and geographic isolation. Our results have implications for conservation planning, and suggest that successful dispersal of freshwater diatoms to and within the Antarctic is limited, fostering the evolution of highly endemic diatom floras

opencc-zeroDec 2020View details →

Changes in transcriptomic response to salinity stress induce the brackish water adaptation in a freshwater snail

Studying mechanisms of the establishment of a population in a novel environment allows us to examine the process of local adaptations and subsequent range expansion. In a river system, detecting genetic or phenotypic differences between a freshwater and brackish water population could contribute to our understanding of the initial process of brackish water adaptations. Here, we investigated behavioral and gene expression responses to the saltwater in a freshwater and brackish water population of the freshwater snail, Semisulcospira reiniana. Although the brackish water individuals exhibited significantly higher activity in saltwater than freshwater individuals in the first week, the activity of freshwater individuals increased in subsequent weeks, suggesting that their salinity tolerance was plastic rather than genetic. We found 476 and 1,002 differentially expressed genes across salinity conditions in the freshwater and brackish water populations, respectively. The major biological process involved in the salinity response of the freshwater population was the biosynthesis and metabolic process of nitrogen containing compounds, but that of the brackish water population was influenced by the chitin metabolic process. These results suggest that phenotypic plasticity induces the brackish water adaptation in the freshwater snail by modifying salinity response in the physiological process.

opencc-zeroDec 2020View details →

Quantitative genetics of phosphorus content in the freshwater herbivore, Daphnia pulicaria

1. Phosphorus (P) is essential for growth of all organisms, and P content is correlated with growth in most taxa. Although P content was initially considered to be a trait fixed at the species level, there is growing evidence for considerable intraspecific variation. Selection on such variation can thus alter the rates at which P fluxes through food webs. 2. Nevertheless, prior work describing the sources and extent of intraspecific variation in P content were not genetically explicit, confounded by unknown genetic background and evolutionary history. We constructed an F2 recombinant population of the dominant freshwater grazer, Daphnia pulicaria to mitigate such issues. 3. F2 recombinants exhibited considerable variation in growth rate, P content (0.49% to 1.97%), P use efficiency (PUE; 51 to 208 mg biomass/mg P), and correlated traits such as hatching time of resting eggs, in common garden conditions. 4. These results clearly demonstrate the scope of genetic recombination in generating variation in ecologically-relevant traits. The absence of environmental selection is a likely component driving such variation not observed in natural settings. 5. Although phosphoglucose isomerase (PGI) genotype was significantly associated with variation in hatching time of resting eggs, contrary to prior work with less rigorous designs, allelic variation at the PGI locus did not explain variation in P content and PUE of Daphnia, indicating that such quantitative traits are under polygenic control. 6. Together, these results suggest that although there is considerable genetic scope for variation in key ecologically-relevant traits, such as P content and efficiency of P use, these traits are likely under strong stabilizing selection, most likely due to selection on growth rate and size. Importantly, our observations suggest that anthropogenic alterations to P supply due to eutrophication could alter selection on these traits, thereby rapidly altering the role Daphnia plays in the P cycle of lakes.

FIGURE 10 in Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species

FIGURE 10. Plumatella tanganyikae, Specimen No. 443. (a) Colony shown with a single sessoblast, scale bar = 2 mm; (b) sessoblast valves with frontal valve on the left, scale bar = 100 μm; (c) sessoblast, SEM image, scale bar = 100 μm.

FIGURE 9 in Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species

FIGURE 9. Plumatella ruandensis, Specimen No. 206 (a) Colony on semi-transparent substratum, scale bar = 5 mm; (b) floatoblast valves with dorsal valve on the left, scale bar = 100 μm; (c) floatoblasts, SEM image showing highly convex annular cells, dorsal side on the left, scale bar = 100 μm.

FIGURE 11. Plumatella wiebachi n in Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species

FIGURE 11. Plumatella wiebachi n. sp., Specimen No. 56. (a) Colony surrounded by sessoblasts, scale bar = 3 mm; (b) colony showing greater detail, scale bar = 1 mm; (c) floatoblast valves with dorsal valve on the left, scale bar = 100 μm; (d–g) com-parison of statoblasts in Plumatella javanica and Plumatella wiebachi n. sp. (d) P. javanica floatoblast fenestra showing optical points of light around each tubercle; (e) P. javanica sessoblast from the author's personal collection from Thailand showing relatively large tubercles; (f) P. wiebachi n. sp. floatoblast fenestra showing the absence of such points of light; (g) P. wiebachi n. sp. sessoblast showing relatively small tubercles. Scale bars for figs. 11d–g = 100 μm.

FIGURE 7 in Review of freshwater Bryozoa (Phylactolaemata) of Central Africa with descriptions of two new species

FIGURE 7. Plumatella philippinensis, Specimen No. 440. (a) Colony showing parallel zooecial tubes, scale bar = 2 mm; (b) colony showing zooid detail, scale bar = 1 mm; (c) sessoblast frontal valve, scale bar = 100 μm; (d) floatoblast valves with dorsal valve on the left, scale bar = 100 μm; (e) floatoblast valves of holotype shown for size comparison, scale bar = 100 μm.