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PeerJ 2024Amphibians are experiencing declines globally, with emerging infectious diseases as one of the main causes. Haematological parameters present a useful method for...
Amphibians are experiencing declines globally, with emerging infectious diseases as one of the main causes. Haematological parameters present a useful method for determining the health status of animals and the effects of particular diseases, but the interpretation of differential cell counts relies on knowing the normal ranges for the species and factors that can affect these counts. However, there is very little data on either normal haematological parameters or guides for blood cell types for free-ranging frog species across the world. This study aims to 1) create a visual guide for three different Australian frog species: , , and , 2) determine the proportions of erythrocytes to leukocytes and 3) differential leukocytes within blood smears from these three species and 4) assess the association between parasites and differential counts. We collected blood samples from free-ranging frogs and analysed blood smears. We also looked for ectoparasites and tested for the fungal disease chytridiomycosis. Overall, we found that the differentials of erythrocytes to leukocytes were not affected by species, but the proportions of different leukocytes did vary across species. For example, while lymphocytes were the most common type of leukocyte across the three species, eosinophils were relatively common in but rarely present in the other two species. We noted chytridiomycosis infection as well as ectoparasites present in some individuals but found no effect of parasites on blood parameters. Our results add baseline haematological parameters for three Australian frog species and provide an example of how different frog species can vary in their differential blood cell counts. More information is needed on frog haematological data before these parameters can be used to determine the health status of wild or captive frogs.
Topics: Animals; Anura; Australia; Reference Values; Erythrocytes; Blood Cell Count; Hematologic Tests; Species Specificity; Leukocyte Count; Male
PubMed: 38860213
DOI: 10.7717/peerj.17406 -
Methods in Molecular Biology (Clifton,... 2024Ion channels comprise one of the largest targets for drug development and treatment and have been a subject of enduring fascination since first discovered in the 1950s....
Ion channels comprise one of the largest targets for drug development and treatment and have been a subject of enduring fascination since first discovered in the 1950s. Over the past decades, thousands of publications have explored the cellular biology and molecular physiology of these proteins, and many channel structures have been determined since the late 1990s. Trying to connect the dots between ion channel function and structure, voltage clamp fluorometry (VCF) emerges as a powerful tool because it allows monitoring of the conformational rearrangements underlying the different functional states of the channel. This technique represents an elegant harmonization of molecular biology, electrophysiology, and fluorescence. In the following chapter, we will provide a concise guide to performing VCF on Xenopus laevis oocytes using the two-electrode voltage clamp (TEVC) modality. This is the most widely used configuration on Xenopus oocytes for its relative simplicity and demonstrated success in a number of different ion channels utilizing a variety of attached labels.
Topics: Animals; Patch-Clamp Techniques; Fluorometry; Xenopus laevis; Oocytes; Ion Channels; Ion Channel Gating
PubMed: 38856899
DOI: 10.1007/978-1-0716-3818-7_8 -
Ecology and Evolution Jun 2024We present notable distributional updates for 14 species from western Ecuador (seven amphibians and seven reptiles). Our findings include the northernmost confirmed...
We present notable distributional updates for 14 species from western Ecuador (seven amphibians and seven reptiles). Our findings include the northernmost confirmed sighting of and the southernmost documented record of and . Additionally, we document new records and notes on the distribution range of , , , , , , , , , , and . These observations significantly contribute to filling information gaps in our understanding of these species' distributions. The data, derived from samples collected across diverse forested areas in the western region of Ecuador (provinces of Bolívar, Cañar, Guayas, El Oro, and Los Ríos), provide valuable insights into the ecology and conservation of these species.
PubMed: 38855317
DOI: 10.1002/ece3.11401 -
Journal of Thermal Biology May 2024When amphibians thermoregulate, they face a fundamental trade-off between the ability to maintain activity and an increased rate of dehydration at higher temperatures....
When amphibians thermoregulate, they face a fundamental trade-off between the ability to maintain activity and an increased rate of dehydration at higher temperatures. Canopy coverage affects both the thermal and hydric conditions of the environment and can therefore influence amphibian thermoregulation. Frogs require proper conditions to thermoregulate to successfully grow, survive, and reproduce. But while we know how canopy and environmental variables typically affect operative temperature, less is known about effects on amphibian water loss rates. In this study, we measure the effect of canopy coverage on the conditions available for thermoregulation at a breeding pond of the California red-legged frog, Rana draytonii. We use agar frog models to estimate the thermal and hydric capacities frogs would experience in locations with different canopy coverage and microhabitats. At each site, we deployed models under four microhabitat treatments: wet/sun, wet/shade, dry/sun, and dry/shade. We modeled how environmental variables affected operative temperature and evaporative water loss from agar frogs. We found positive effects of air temperature, the sun treatment, and reduced canopy cover on operative temperature, and negative direct or indirect effects of these variables on evaporative water loss, consistent with the hypothesized trade-off between thermoregulatory behavior to increase temperature and the increased desiccation risk due to higher water loss. Additionally, our results indicate that the availability of wet microhabitats can allow frogs to reduce water loss, potentially mitigating the risk of desiccation when thermoregulating to achieve higher operative temperatures. Our findings suggest, that with access to proper microhabitats, amphibians can mitigate the fundamental trade-off and receive benefits of thermoregulating at high temperatures.
Topics: Animals; Body Temperature Regulation; Ecosystem; Ranidae; Water Loss, Insensible; Temperature; Models, Biological
PubMed: 38852487
DOI: 10.1016/j.jtherbio.2024.103864 -
Developmental Biology Jun 2024The ways in which animals sense the world changes throughout development. For example, young of many species have limited visual capabilities, but still make social...
The ways in which animals sense the world changes throughout development. For example, young of many species have limited visual capabilities, but still make social decisions, likely based on information gathered through other sensory modalities. Poison frog tadpoles display complex social behaviors that have been suggested to rely on vision despite a century of research indicating tadpoles have poorly-developed visual systems relative to adults. Alternatively, other sensory modalities, such as the lateral line system, are functional at hatching in frogs and may guide social decisions while other sensory systems mature. Here, we examined development of the mechanosensory lateral line and visual systems in tadpoles of the mimic poison frog (Ranitomeya imitator) that use vibrational begging displays to stimulate egg feeding from their mothers. We found that tadpoles hatch with a fully developed lateral line system. While begging behavior increases with development, ablating the lateral line system inhibited begging in pre-metamorphic tadpoles, but not in metamorphic tadpoles. We also found that the increase in begging and decrease in reliance on the lateral line co-occurs with increased retinal neural activity and gene expression associated with eye development. Using the neural tracer neurobiotin, we found that axonal innervations from the eye to the brain proliferate during metamorphosis, with few retinotectal connections in recently-hatched tadpoles. We then tested visual function in a phototaxis assay and found tadpoles prefer darker environments. The strength of this preference increased with developmental stage, but eyes were not required for this behavior, possibly indicating a role for the pineal gland. Together, these data suggest that tadpoles rely on different sensory modalities for social interactions across development and that the development of sensory systems in socially complex poison frog tadpoles is similar to that of other frog species.
PubMed: 38851558
DOI: 10.1016/j.ydbio.2024.05.006 -
Environmental Pollution (Barking, Essex... Jun 2024Small plastic debris (0.1 μm-5 mm) or microplastics (MPs) have become major pollutants of aquatic ecosystems worldwide and studies suggest that MPs exposure can pose...
Ingestion of polyethylene terephthalate microplastic water contaminants by Xenopus laevis tadpoles negatively affects their resistance to ranavirus infection and antiviral immunity.
Small plastic debris (0.1 μm-5 mm) or microplastics (MPs) have become major pollutants of aquatic ecosystems worldwide and studies suggest that MPs exposure can pose serious threats to human and wildlife health. However, to date the potential biological impacts of MPs accumulating in low amount in tissues during early life remains unclear. Here, for a more realistic assessment, we have used environmentally representative, mildly weathered, polyethylene terephthalate microplastics (PET MPs), cryomilled (1-100 μm) and fluorescently labelled. We leveraged the amphibian Xenopus laevis tadpoles as an animal model to define the biodistribution of PET MPs and determine whether exposure to PET MPs induce perturbations of antiviral immunity. Exposure to PET MPs for 1-14 days resulted in detectable PET MPs biodistribution in intestine, gills, liver, and kidney as determined by fluorescence microscopy on whole mount tissues. PET MPs accumulation rate in tissues was further evaluated via a novel in situ enzymatic digestion and subsequent filtration using silicon nanomembranes, which shows that PET MPs rapidly accumulate in tadpole intestine, liver and kidneys and persist over a week. Longer exposure (1 month) of tadpoles to relatively low concentration of PET MPs (25 μg/ml) significantly increased susceptibility to viral infection and altered innate antiviral immunity without inducing overt inflammation. This study provides evidence that exposure to MPs negatively impact immune defenses of aquatic vertebrates.
PubMed: 38851377
DOI: 10.1016/j.envpol.2024.124340 -
The Science of the Total Environment Sep 2024Bile acids (BAs) are amphipathic steroid acids whose production and diversity depend on both host and microbial metabolism. Nitrate (NO) is a widespread pollutant in...
Bile acids (BAs) are amphipathic steroid acids whose production and diversity depend on both host and microbial metabolism. Nitrate (NO) is a widespread pollutant in aquatic ecosystems, which can cause rapid changes in microbial community structure and function. However, the effect of gut microbiota reshaped by nitrate‑nitrogen (NO-N) on BAs profiles remains unclarified. To test this, intestinal targeted BAs metabolomics and fecal metagenomic sequencing were performed on Bufo gargarizans tadpoles treated with different concentrations of NO-N. NO-N exposure induced a reduction in the abundance of microbiota with bile acid-inducible enzymes (BAIs) and/or hydroxysteroid dehydrogenases (HSDHs), thus inhibiting the conversion of primary BAs to secondary BAs. Inhibition of BAs biotransformation decreased protective hydrophilic BAs (UDCA) and increased toxic hydrophobic BAs (CA and CDCA), which may contribute to intestinal histopathological damage. Moreover, we found that NO-N treatment increased microbial virulence factors and decreased Glycoside hydrolases, further highlighting the deleterious risk of NO-N. Overall, this study shed light on the complex interactions of NO-N, gut microbiota, and BAs, and emphasized the hazardous effects of NO-N pollution on the health of amphibians.
Topics: Animals; Gastrointestinal Microbiome; Larva; Nitrates; Water Pollutants, Chemical; Bile Acids and Salts; Bufonidae; Intestines
PubMed: 38851338
DOI: 10.1016/j.scitotenv.2024.173795 -
Pigment Cell & Melanoma Research Jun 2024Human pigmentary disorders encompass a broad spectrum of phenotypic changes arising from disruptions in various stages of melanocyte formation, the melanogenesis... (Review)
Review
Human pigmentary disorders encompass a broad spectrum of phenotypic changes arising from disruptions in various stages of melanocyte formation, the melanogenesis process, or the transfer of pigment from melanocytes to keratinocytes. A large number of pigmentation genes associated with pigmentary disorders have been identified, many of them awaiting in vivo confirmation. A more comprehensive understanding of the molecular basis of pigmentary disorders requires a vertebrate animal model where changes in pigmentation are easily observable in vivo and can be combined to genomic modifications and gain/loss-of-function tools. Here we present the amphibian Xenopus with its unique features that fulfill these requirements. Changes in pigmentation are particularly easy to score in Xenopus embryos, allowing whole-organism based phenotypic screening. The development and behavior of Xenopus melanocytes closely mimic those observed in mammals. Interestingly, both Xenopus and mammalian skins exhibit comparable reactions to ultraviolet radiation. This review highlights how Xenopus constitutes an alternative and complementary model to the more commonly used mouse and zebrafish, contributing to the advancement of knowledge in melanocyte cell biology and related diseases.
PubMed: 38849973
DOI: 10.1111/pcmr.13178 -
Heliyon Jun 2024Rapid urbanization and development projects in Korea have posed significant threats to biodiversity; thus, effective mitigation measures are required to preserve natural...
Rapid urbanization and development projects in Korea have posed significant threats to biodiversity; thus, effective mitigation measures are required to preserve natural habitats. Nevertheless, the factors underlying variations in mitigation measure effectiveness according to the disturbance level and surrounding environmental conditions have not been clarified. This study evaluated the effectiveness of mitigation measures implemented in environmental impact assessments (EIAs) of development projects in Korea, with a focus on their effectiveness with respect to the disturbance level and surrounding environmental conditions. A review of 288 EIA reports from selected projects that implemented all 10 mitigation measures classified according to the Wildlife Conservation Comprehensive Plan was conducted. Using the biodiversity tipping point framework, the effects of mitigation measures on biodiversity were categorized into four levels and analyzed. Analysis of variance and redundancy analysis were then performed to discern the variance in mitigation measure effectiveness in terms of the disturbance level, surrounding environment, and species. The results revealed significant variations in the effectiveness of mitigation measures depending on the surrounding environment and disturbance level. Linear projects exhibited a clear impact on various species as the disturbance level increased, whereas area-based projects did not exhibit such pronounced effects. All species demonstrated a negative relationship with development duration, development area, and distance from urban centers. Notably, avian and amphibian species showed a strong negative correlation with the digital elevation model while reptiles and mammals exhibited a strong positive relationship with pre-development biodiversity and distance from protected areas, respectively. Mitigation measures play a key role in alleviating the adverse effects of development projects; therefore, our findings indicate the need for spatially tailored mitigation plans to augment their effectiveness.
PubMed: 38845953
DOI: 10.1016/j.heliyon.2024.e31647 -
Journal of Molecular Evolution Jun 2024Genome size variation in eukaryotes has myriad effects on organismal biology from the genomic to whole-organism level. Large genome size may be associated with lower...
Genome size variation in eukaryotes has myriad effects on organismal biology from the genomic to whole-organism level. Large genome size may be associated with lower selection efficiency because lower effective population sizes allow fixation of deleterious mutations via genetic drift, increasing genome size and decreasing selection efficiency. Because of a hypothesized negative relationship between genome size and recombination rate per base pair, increased genome size could also increase the effect of linked selection in the genome, decreasing the efficiency with which natural selection can fix or remove mutations. We used a transcriptomic dataset of 15 and a subset of six Neotropical salamander species ranging in genome size from 12 to 87 pg to study the relationship between genome size and efficiency of selection. We estimated dN/dS of salamanders with small and large genomes and tested for relaxation of selection in the larger genomes. Contrary to our expectations, we did not find a significant relationship between genome size and selection efficiency or strong evidence for higher dN/dS values in species with larger genomes for either species set. We also found little evidence for relaxation of selection in species with larger genomes. A positive correlation between genome size and range size (a proxy of population size) in this group disagrees with predictions of stronger drift in species with larger genomes. Our results highlight the complex interactions between the many forces shaping genomic variation in organisms with genomic gigantism.
PubMed: 38844681
DOI: 10.1007/s00239-024-10177-w