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6,771 results for “freshwater”
Data from: Always chew your food: freshwater stingrays use mastication to process tough insect prey
Chewing, characterized by shearing jaw motions and high-crowned molar teeth, is considered an evolutionary innovation that spurred dietary diversification and evolutionary radiation of mammals. Complex prey-processing behaviours have been thought to be lacking in fishes and other vertebrates, despite the fact that many of these animals feed on tough prey, like insects or even grasses. We investigated prey capture and processing in the insect-feeding freshwater stingray Potamotrygon motoro using high-speed videography. We find that Potamotrygon motoro uses asymmetrical motion of the jaws, effectively chewing, to dismantle insect prey. However, CT scanning suggests that this species has simple teeth. These findings suggest that in contrast to mammalian chewing, asymmetrical jaw action is sufficient for mastication in other vertebrates. We also determined that prey capture in these rays occurs through rapid uplift of the pectoral fins, sucking prey beneath the ray's body, thereby dissociating the jaws from a prey capture role. We suggest that the decoupling of prey capture and processing facilitated the evolution of a highly kinetic feeding apparatus in batoid fishes, giving these animals an ability to consume a wide variety of prey, including molluscs, fishes, aquatic insect larvae and crustaceans. We propose Potamotrygon as a model system for understanding evolutionary convergence of prey processing and chewing in vertebrates.
Data from: Climate and local abundance in freshwater fishes
Identifying factors regulating variation in numbers of individuals among populations across a species' distribution is a fundamental goal in ecology. A common prediction, often referred to as the abundant-centre hypothesis, suggests that abundance is highest near the centre of a species' range. However, because of the primary focus on the geographical position of a population, this framework provides little insight into the environmental factors regulating local abundance. While range-wide variation in population abundance associated with environmental conditions has been investigated in terrestrial species, the relationship between climate and local abundance in freshwater taxa across species' distributions is not well understood. We used GIS-based temperature and precipitation data to determine the relationships between climatic conditions and range-wide variation in local abundance for 19 species of North American freshwater fishes. Climate predicted a portion of the variation in local abundance among populations for 18 species. In addition, the relationship between climatic conditions and local abundance varied among species, which is expected as lineages partition the environment across geographical space. The influence of local habitat quality on species persistence is well documented; however, our results also indicate the importance of climate in regulating population sizes across a species geographical range, even in aquatic taxa.
Data from: Do freshwater ecoregions and continental shelf width predict patterns of historical gene flow in the freshwater fish Poecilia butleri?
We examined historical patterns of gene flow in the freshwater fish Poecilia butleri in western Mexico. We tested the hypothesis that the boundaries between four freshwater ecological communities (ecoregions) might have limited the movement of P. butleri because changes in species compositions might restrict establishment between adjacent ecoregions, even in situations where a physical barrier is absent. Hence, we predicted that boundaries between ecoregions should correspond to phylogeographical breaks in P. butleri. We also tested the hypothesis that the width of the continental shelf affected historical gene flow in P. butleri because a broad continental shelf provides a greater opportunity for rivers to coalesce during historical episodes of low sea levels as opposed to a narrow continental shelf that should restrict the potential for gene flow among adjacent rivers. Hence, we predicted greater amounts of historical gene flow among neighbouring river basins in the region of western Mexico where the continental shelf is wider, whereas, in the region where the continental shelf is narrower, we expected to detect limited levels of historical gene flow. We analyzed mitochondrial DNA sequence data (cytochrome b) taken from 264 individuals of P. butleri collected from 34 locations distributed across four different ecoregions in western Mexico. To examine patterns of phylogenetic diversification and historical gene flow in P. butleri, we employed several analytical approaches, including traditional tree-based phylogenetic analyses (likelihood and parsimony), haplotype network reconstruction, analyses of molecular variance, and spatial analysis of molecular variance. We found genetic breaks coinciding with two out of three different ecoregion boundaries, suggesting limited historical gene flow. In addition to different species compositions between these adjacent ecoregions, geological features such as the Trans-Mexican Volcanic Belt and the mountainous topography in south-western Mexico, likely contributed to these observed genetic breaks. By contrast, no genetic break was evident between two other ecoregions, a result that partially rejects our first hypothesis. Several results were consistent with our second hypothesis. Changes in the width of the continental shelf in western Mexico are associated with the observed patterns of historical gene flow. Our results indicate that the interactions among multiple geological and biological factors affect the spatial patterns of genetic diversity of widespread freshwater species.
Data from: Characterizing neutral and adaptive genomic differentiation in a changing climate: the most northerly freshwater fish as a model
Arctic freshwater ecosystems have been profoundly affected by climate change. Given that the Arctic charr (Salvelinus alpinus) is often the only fish species inhabiting these ecosystems, it represents a valuable model for studying the impacts of climate change on species life history diversity and adaptability. Using a genotyping-by-sequencing approach, we identified 5976 neutral single nucleotide polymorphisms (SNPs) and found evidence for reduced gene flow between allopatric morphs from two high Arctic lakes, Linne´vatn (Anadromous, Normal, and Dwarf) and Ellasjøen (Littoral and Pelagic). Within each lake, the degree of genetic differentiation ranged from low (Pelagic vs. Littoral) to moderate (Anadromous and Normal vs. Dwarf). We identified 17 highly diagnostic, putative adaptive SNPs that differentiated the allopatric morphs. Although we found no evidence for adaptive differences between morphs within Ellasjøen, we found evidence for moderate (Anadromous vs. Normal) to high genetic differentiation (Anadromous and Normal vs. Dwarf) among morphs within Linne´vatn based on two adaptive loci. As these freshwater ecosystems become more productive, the frequency of sympatric morphs in Ellasjøen will likely shift based on foraging opportunities, whereas the propensity to migrate may decrease in Linne´vatn, increasing the frequency of the Normal morph. The Dwarf charr was the most genetically distinct group. Identifying the biological basis for small body size should elucidate the potential for increased growth and subsequent interbreeding with sympatric morphs. Overall, neutral and adaptive genomic differentiation between allopatric and some sympatric morphs suggests that the response of Arctic charr to climate change will be variable across freshwater ecosystems.
Data from: Do priority effects outweigh environmental filtering in a guild of dominant freshwater macroinvertebrates?
Abiotic conditions have long been considered essential in structuring freshwater macroinvertebrate communities. Ecological drift, dispersal, and biotic interactions also structure communities, and although these mechanisms are more difficult to detect, they may be of equal importance in natural communities. Here, we hypothesized that in ten naturally-replicated headwater streams in Eastern Switzerland, locally-dominant amphipod species would be associated with differences in environmental conditions. We conducted repeated surveys of amphipods and used a hierarchical joint species distribution model to assess the influence of different drivers on species co-occurrences. The species had unique environmental requirements, but a distinct spatial structure in their distributions was unrelated to habitat. Species co-occurred much less frequently than predicted by the model, which was surprising because laboratory and field evidence suggests they are capable of coexisting in equal densities. We suggest that niche preemption may limit their distribution and that a blocking effect related to the specific linear configuration of streams determines which species colonizes and dominates a given stream catchment, thus suggesting a new solution a long-standing conundrum in freshwater ecology.
Data from: Behavioral diversity is maintained by a conditional strategy in a freshwater zooplankton
Many populations have intraspecific diversity in phenotype and ecological strategy, but the mechanisms maintaining such diversity are not fully understood. Multiple behaviors can be maintained either as a conditional strategy, where fitness depends on an individual's phenotype, or as a mixed strategy where alternative behaviors have similar fitness independent of phenotype. Using high-resolution depth and time sampling, we characterize two distinct diel vertical migration behaviors in a population of freshwater zooplankton (Daphnia pulicaria). Individuals in this population differ in their color phenotype and migratory behavior with red morphs upregulating hemoglobin and undergoing a deep migration, and pale morphs not producing hemoglobin and undergoing a shallow migration. We experimentally manipulated the behavior of each phenotype in the field, and measured population growth in their natural migration behavior as well as population growth in their alternative behaviors. Experimental populations of pale and red morphs under their natural migrations had roughly equal fitness, despite vast differences in environmental conditions. When forced to switch behaviors, pale morphs suffered reduced fitness, whereas red morphs had similar fitness compared to their natural migration. Our results suggest that while behavioral diversity may be promoted by the opportunity for alternative behaviors of equal fitness, the distinct physiological conditions required for survival in alternative behaviors limit the capacity for individual behavioral switching and likely maintain behavioral diversity as a conditional strategy.
Data from: The role of continental shelf width in determining freshwater phylogeographic patterns in southeastern Australian pygmy perches (Teleostei: Percichthyidae)
Biogeographic patterns displayed by obligate freshwater organisms are intimately related to the nature and extent of connectivity between suitable habitats. Two of the more significant barriers to freshwater connections are seawater and major drainage divides. South-eastern Australia provides a contrast between these barriers as it has discrete areas that are likely influenced to a greater or lesser extent by each barrier type. We use continental shelf width as a proxy for the potential degree of river coalescence during low sea levels. Our specific hypothesis is that the degree of phylogeographic divergence between coastal river basins should correspond to the continental shelf width of each region. This predicts that genetic divergences between river basins should be lowest in regions with a wider continental shelf and that regions with similar continental shelf width should have similar genetic divergences. Pygmy perches (Nannoperca australis and Nannoperca 'flindersi') in south-eastern Australia provide an ideal opportunity to test these biogeographic hypotheses. Phylogeographic patterns were examined based on range-wide sampling of 82 populations for cytochrome b and 23 polymorphic allozyme loci. Our results recovered only limited support for our continental shelf width hypothesis, although patterns within Bass clade were largely congruent with reconstructed low sea-level drainage patterns. In addition, we identified several instances of drainage divide crossings, typically associated with low elevational differences. Our results demonstrate high levels of genetic heterogeneity with important conservation implications, especially for declining populations in the Murray–Darling Basin and a highly restricted disjunct population in Ansons River, Tasmania.
FIGURES 1–5. Elachiptera aquila. 1 in A new brachypterous species of Elachiptera Becker (Diptera: Chloropidae) from freshwater wetlands in eastern Canada
FIGURES 1–5. Elachiptera aquila. 1. Wing; 2. Head (dorsal); 3. Antenna (lateral); 4. Male genitalia (lateral); 5. Male genitalia (posterior). Abbreviations: cer — cercus; epd — epandrium; hyp hypandrium; phap — phallapodeme; phal — phallus; pog — postgonite; sur — surstylus. Scale bar = 0.1mm (Figs. 45)
FIGURE 9. AC in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 9. AC. Haplodidymos rubroculatus gen. nov. sp. nov. Reproductive organs. A. ventral view posterior to pharynx. Scale bar = 30 µm. B. Ventral view of fixed holotype. Scale bar = 45 µm. C. Sagital reconstruction of posterior end. Scale bar = 100 µm. BC, bursa copulatrix; CG, caudal glands; CO, copulatory organ; GA, genital atrium; OV, ovary; SR, receptaculum seminis; ST, stylet; TE, testes; UT, uterus; VI, vitellaria; VS, vesicula seminalis.
FIGURE 8 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 8. Haplodidymos rubroculatus gen. nov. sp. nov. Anterior end showing large eyes. Scale bar = 60 µm.
FIGURE 7 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 7. Haplodidymos rubroculatus gen. nov. sp. nov. Slightly squeezed live specimen. Scale bar = 150 µm. AR, adenal rhabdites; BC, bursa copulatrix; EY, eye; OV, ovary; PB, pigment bands; PH, pharynx; RS, receptaculum seminis; TE, testis; UT, uterus; VI, vitellaria.
FIGURE 6. AB in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 6. AB. Austrodalyellia ariena gen. nov. sp. nov. Camera lucida drawings of stylet with different tine layers color coded: dorsal (white), medial (lt. grey), and ventral (dk. grey). The thin membrane that exists between dorsal and medial tine bars is also shaded. A, Squashed stylet from fixed holotype. B, Everted stylet from fixed paratype. Scale bars = 15 µm.
FIGURE 5 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 5. Austrodalyellia ariena gen. nov. sp. nov. Whole mounts of sclerotic stylet. A. DIC micrograph of stylet in genital canal. B, Everted stylet in fixed paratype. C, Stylet from squashed live specimen. D, DIC micrograph of stylet in fixed holotype. Scale bars = 45 µm.
FIGURE 4. AC in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 4. AC. Austrodalyellia ariena gen. nov. sp. nov. A, Frontal section through dorsal body region. Scale bar = 100 µm. B, Frontal section through posterior body region, approximately medial. Scale bar = 80 µm. C, Frontal section through ventral body region. Scale bar = 30 µm. CO, copulatory organ; EG, egg; GL, glands around gonopore; GP, gonopore; GT, gut lumen; PH, pharynx; UT, uterus; VI, vitellaria.
FIGURE 2 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 2. Austrodalyellia ariena gen. nov. sp. nov. Frontal section through anterior end. BR, brain; EY, eye; PH, pharynx. Scale bar = 50 µm.
FIGURE 3 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 3. Austrodalyellia ariena gen. nov. sp. nov. Schematic of the reproductive system. BC, bursa copulatrix; EG, egg; GA, genital atrium; GC, genital canal; GL, glands around gonopore; GP, gonopore; OV, ovary; RS, receptaculum seminis; TE, testes; UT, uterus; VG, vesicula granulorum; VS, vesicula seminalis; VI, vitellaria. Scale bar = 120 µm.
FIGURE 1 in Two new freshwater rhabdocoels, Austrodalyellia gen. nov. and Haplodidymos gen. nov. (Platyhelminthes), from Queensland, Australia
FIGURE 1. Austrodalyellia ariena gen. nov. sp. nov. Slightly squeezed live specimen. BC, bursa copulatrix; BR, brain; CO, copulatory organ; EG, egg; EY, eye; GL, glands around gonopore; OV, ovary; PH, pharynx; RS, receptaculum seminis; TE, testes; UT, uterus; VI, vitellaria. Scale bar = 250 µm.
FIGURE 7 in A new species of Gieysztoria (Platyhelminthes; Rhabdocoela; Dalyelliidae) from a freshwater lake in Queensland, Australia
FIGURE 7. Light microscopical view of the vesicula granulorum (VG) and vesicula seminalis (VS) atop the girdle (G) of the male copulatory organ. Scale bar = 50 m.
FIGURES 36 in A new species of Gieysztoria (Platyhelminthes; Rhabdocoela; Dalyelliidae) from a freshwater lake in Queensland, Australia
FIGURES 36. Male copulatory organ of Gieysztoria queenslandica n. sp. 3, Dorsal view of squashed male organ; 4, Ventral view of squashed male organ; 5, Schematic view of dorsal side of male organ. 6, Schematic view of ventral side of male organ.
FIGURES 12. Gieysztoria queenslandica n in A new species of Gieysztoria (Platyhelminthes; Rhabdocoela; Dalyelliidae) from a freshwater lake in Queensland, Australia
FIGURES 12. Gieysztoria queenslandica n. sp. 1, Features visible in live adult specimens; 2, Schematic of reproductive system. Scale bars = 150 m. BC, bursa copulatrix; DC, ductus communis; GA, genital atrium; GC, genital canal; GP, common gonopore; EG, egg; OV, ovary; RS, receptaculum seminis; T, testis; UT, uterus; V, vitellaria; VG, vesicula granulorum; VS, vesicula seminalis.
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.