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Ecology Letters May 2024There is a rich literature highlighting that pathogens are generally better adapted to infect local than novel hosts, and a separate seemingly contradictory literature... (Meta-Analysis)
Meta-Analysis
There is a rich literature highlighting that pathogens are generally better adapted to infect local than novel hosts, and a separate seemingly contradictory literature indicating that novel pathogens pose the greatest threat to biodiversity and public health. Here, using Batrachochytrium dendrobatidis, the fungus associated with worldwide amphibian declines, we test the hypothesis that there is enough variance in "novel" (quantified by geographic and phylogenetic distance) host-pathogen outcomes to pose substantial risk of pathogen introductions despite local adaptation being common. Our continental-scale common garden experiment and global-scale meta-analysis demonstrate that local amphibian-fungal interactions result in higher pathogen prevalence, pathogen growth, and host mortality, but novel interactions led to variable consequences with especially virulent host-pathogen combinations still occurring. Thus, while most pathogen introductions are benign, enough variance exists in novel host-pathogen outcomes that moving organisms around the planet greatly increases the chance of pathogen introductions causing profound harm.
Topics: Animals; Host-Pathogen Interactions; Batrachochytrium; Anura; Amphibians; Mycoses; Adaptation, Physiological; Phylogeny
PubMed: 38712705
DOI: 10.1111/ele.14431 -
Molecular Biology Reports May 2024Thyroid hormones are primarily responsible for the brain development in perinatal mammals. However, this process can be inhibited by external factors such as...
Hydroxylated polychlorinated biphenyls may affect the thyroid hormone-induced brain development during metamorphosis of Xenopus laevis by disturbing the expression of matrix metalloproteinases.
BACKGROUND
Thyroid hormones are primarily responsible for the brain development in perinatal mammals. However, this process can be inhibited by external factors such as environmental chemicals. Perinatal mammals are viviparous, which makes direct fetal examination difficult.
METHODS
We used metamorphic amphibians, which exhibit many similarities to perinatal mammals, as an experimental system. Therefore, using metamorphic amphibians, we characterized the gene expression of matrix metalloproteinases, which play an important role in brain development.
RESULTS
The expression of many matrix metalloproteinases (mmps) was characteristically induced during metamorphosis. We also found that the expression of many mmps was induced by T and markedly inhibited by hydroxylated polychlorinated biphenyls (PCBs).
CONCLUSION
Overall, our findings suggest that hydroxylated PCBs disrupt normal brain development by disturbing the gene expression of mmps.
Topics: Animals; Brain; Xenopus laevis; Matrix Metalloproteinases; Polychlorinated Biphenyls; Metamorphosis, Biological; Thyroid Hormones; Gene Expression Regulation, Developmental; Hydroxylation
PubMed: 38710963
DOI: 10.1007/s11033-024-09555-w -
Environmental Science & Technology Jun 2024Harmful cyanobacterial blooms are frequent and intense worldwide, creating hazards for aquatic biodiversity. The potential estrogen-like effect of Microcystin-LR (MC-LR)...
Harmful cyanobacterial blooms are frequent and intense worldwide, creating hazards for aquatic biodiversity. The potential estrogen-like effect of Microcystin-LR (MC-LR) is a growing concern. In this study, we assessed the estrogenic potency of MC-LR in black-spotted frogs through combined field and laboratory approaches. In 13 bloom areas of Zhejiang province, China, the MC-LR concentrations in water ranged from 0.87 to 8.77 μg/L and were correlated with sex hormone profiles in frogs, suggesting possible estrogenic activity of MC-LR. Tadpoles exposed to 1 μg/L, an environmentally relevant concentration, displayed a female-biased sex ratio relative to controls. Transcriptomic results revealed that MC-LR induces numerous and complex effects on gene expression across multiple endocrine axes. In addition, exposure of male adults significantly increased the estradiol (E2)/testosterone (T) ratio by 3.5-fold relative to controls. Downregulation of genes related to male reproductive endocrine function was also identified. We also showed how MC-LR enhances the expression of specific estrogen receptor (ER) proteins, which induce estrogenic effects by activating the ER pathway and hypothalamic-pituitary-gonadal (HPG) axis. In aggregate, our results reveal multiple lines of evidence demonstrating that, for amphibians, MC-LR is an estrogenic endocrine disruptor at environmentally relevant concentrations. The data presented here support the need for a shift in the MC-LR risk assessment. While hepatoxicity has historically been the focus of MC-LR risk assessments, our data clearly demonstrate that estrogenicity is a major mode of toxicity at environmental levels and that estrogenic effects should be considered for risk assessments on MC-LR going forward.
Topics: Animals; Estrogens; Male; Female; Microcystins; Ranidae; Marine Toxins; Water Pollutants, Chemical
PubMed: 38710655
DOI: 10.1021/acs.est.4c01322 -
Journal of Experimental Zoology. Part... Jul 2024Egg dehydration can kill terrestrial frog embryos, and this threat is increasing with climate change and deforestation. In several lineages that independently evolved...
Egg dehydration can kill terrestrial frog embryos, and this threat is increasing with climate change and deforestation. In several lineages that independently evolved terrestrial eggs, and retained aquatic tadpoles, embryos accelerate hatching to escape from drying eggs, entering the water earlier and less developed. However, the cues that stimulate drying-induced early hatching are unknown. Ammonia is a toxic, water-soluble metabolic waste that accumulates within eggs as embryos develop and concentrates as eggs dehydrate. Thus, increasing ammonia concentration may be a direct threat to embryos in drying eggs. We hypothesized that it could serve as a cue, stimulating embryos to hatch and escape. The embryos of red-eyed treefrogs, Agalychnis callidryas, hatch early to escape from many threats, including dehydration, and are known to use mechanosensory, hypoxia, and light cues. To test if they also use high ammonia as a cue to hatch, we exposed stage-matched pairs of hatching-competent, well-hydrated sibling embryos to ammonia and control solutions in shallow water baths and recorded their behavior. Control embryos remained unhatched while ammonia-exposed embryos showed a rapid, strong hatching response; 95% hatched, on average in under 15 min. This demonstrates that elevated ammonia can serve as a hatching cue for A. callidryas embryos. This finding is a key step in understanding the mechanisms that enable terrestrial frog embryos to escape from egg drying, opening new possibilities for integrative and comparative studies on this growing threat.
Topics: Animals; Ammonia; Anura; Ovum; Cues; Embryo, Nonmammalian; Dehydration; Escape Reaction
PubMed: 38708813
DOI: 10.1002/jez.b.23253 -
Developmental Biology Aug 2024The signals that regulate peripheral blood vessel formation during development are still under investigation. The hormone leptin promotes blood vessel formation, adipose...
The signals that regulate peripheral blood vessel formation during development are still under investigation. The hormone leptin promotes blood vessel formation, adipose tissue establishment and expansion, tumor growth, and wound healing, but the underlying mechanisms for these actions are currently unknown. We investigated whether leptin promotes angiogenesis in the developing tail fin using embryonic transgenic xflk-1:GFP Xenopus laevis, which express a green fluorescent protein on vascular endothelial cells to mark blood vessels. We found that leptin protein is expressed in endothelial cells of developing blood vessels and that leptin treatment via injection increased phosphorylated STAT3 signaling, which is indicative of leptin activation of its receptor, in blood vessels of the larval tail fin. Leptin administration via media increased vessel length, branching, and reconnection with the cardinal vein, while decreased leptin signaling via immunoneutralization had an opposing effect on vessel development. We also observed disorganization of major vessels and microvessels of the tail fin and muscle when leptin signaling was decreased. Reduced leptin signaling lowered mRNA expression of cenpk, gpx1, and mmp9, markers for cell proliferation, antioxidation, and extracellular matrix remodeling/cell migration, respectively, in the developing tail, providing insight into three possible mechanisms underlying leptin's promotion of angiogenesis. Together these results illustrate that leptin levels are correlated with embryonic angiogenesis and that leptin coordinates multiple aspects of blood vessel growth and development, showing that leptin is an important morphogen during embryonic development.
Topics: Animals; Leptin; Tail; Xenopus laevis; Signal Transduction; Neovascularization, Physiologic; Larva; Blood Vessels; Xenopus Proteins; Animals, Genetically Modified; STAT3 Transcription Factor; Embryo, Nonmammalian; Green Fluorescent Proteins; Gene Expression Regulation, Developmental
PubMed: 38705558
DOI: 10.1016/j.ydbio.2024.05.001 -
Journal of Hazardous Materials Jul 2024Diclofenac (DCF) is an environmentally persistent, nonsteroidal anti-inflammatory drug (NSAID) with thyroid disrupting properties. Electrochemical advanced oxidation...
Diclofenac (DCF) is an environmentally persistent, nonsteroidal anti-inflammatory drug (NSAID) with thyroid disrupting properties. Electrochemical advanced oxidation processes (eAOPs) can efficiently remove NSAIDs from wastewater. However, eAOPs can generate transformation products (TPs) with unknown chemical and biological characteristics. In this study, DCF was electrochemically degraded using a boron-doped diamond anode. Ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry was used to analyze the TPs of DCF and elucidate its potential degradation pathways. The biological impact of DCF and its TPs was evaluated using the Xenopus Eleutheroembryo Thyroid Assay, employing a transgenic amphibian model to assess thyroid axis activity. As DCF degradation progressed, in vivo thyroid activity transitioned from anti-thyroid in non-treated samples to pro-thyroid in intermediately treated samples, implying the emergence of thyroid-active TPs with distinct modes of action compared to DCF. Molecular docking analysis revealed that certain TPs bind to the thyroid receptor, potentially triggering thyroid hormone-like responses. Moreover, acute toxicity occurred in intermediately degraded samples, indicating the generation of TPs exhibiting higher toxicity than DCF. Both acute toxicity and thyroid effects were mitigated with a prolonged degradation time. This study highlights the importance of integrating in vivo bioassays in the environmental risk assessment of novel degradation processes.
Topics: Animals; Diclofenac; Water Pollutants, Chemical; Thyroid Gland; Anti-Inflammatory Agents, Non-Steroidal; Risk Assessment; Electrochemical Techniques; Molecular Docking Simulation; Endocrine Disruptors; Xenopus laevis; Diamond; Oxidation-Reduction; Boron
PubMed: 38703679
DOI: 10.1016/j.jhazmat.2024.134458 -
Scientific Reports May 2024Gut microbiota impact host physiology, though simultaneous investigations in ectothermic vertebrates are rare. Particularly, amphibians may exhibit more complex...
Gut microbiota impact host physiology, though simultaneous investigations in ectothermic vertebrates are rare. Particularly, amphibians may exhibit more complex interactions between host physiology and the effects of gut microbiota due to the combination of seasonal changes and complex life histories. In this study, we assessed the relationships among food resources, gut bacterial communities, and host physiology in frogs (Phelophylax nigromaculatus), taking into account seasonal and life history variations. We found that food sources were not correlated with physiological parameters but had some relationships with the gut bacterial community. Variations in gut bacterial community and host physiology were influenced by the combined effects of seasonal differences and life history, though mostly driven by seasonal differences. An increase in Firmicutes was associated with higher fat content, reflecting potential fat storage in frogs during the non-breeding season. The increase in Bacteroidetes resulted in lower fat content in adult frogs and decreased immunity in juvenile frogs during the breeding season, demonstrating a direct link. Our results suggest that the gut microbiome may act as a link between food conditions and physiological status, and that the combined effect of seasons and life history could reinforce the relationship between gut microbiota and physiological status in ectothermic animals. While food sources may influence the gut microbiota of ectotherms, we contend that temperature-correlated seasonal variation, which predominately influences most ectotherms, is a significant factor.
Topics: Animals; Gastrointestinal Microbiome; Seasons; Anura; Bacteria; Bacteroidetes
PubMed: 38698108
DOI: 10.1038/s41598-024-60105-7 -
Analytical Biochemistry Sep 2024Oviductus Ranae is the dried oviduct from Rana dybowskii, a forest frog species with medicinal, tonic, and cosmetic properties. Due to the high price and resource...
Oviductus Ranae is the dried oviduct from Rana dybowskii, a forest frog species with medicinal, tonic, and cosmetic properties. Due to the high price and resource shortage, counterfeit varieties of Oviductus Ranae often appear in the market. However, traditional identification methods cannot accurately differentiate between Oviductus Ranae and its adulterants. In this study, a rapid molecular identification method has been established. The method involves extracting genomic DNA in just 30 s using filter paper purification, species-specific rapid polymerase chain reaction (PCR) amplification, and finally, fluorescence detection of the products. It can accurately identify Oviductus Ranae and its three common adulterants in about 30 min, making the process simple, fast, and highly specific.
Topics: Animals; Ranidae; DNA Primers; Polymerase Chain Reaction; Species Specificity; Female; Oviducts; DNA
PubMed: 38697593
DOI: 10.1016/j.ab.2024.115548 -
PloS One 2024Although behavioural defensive responses have been recorded several times in both laboratory and natural habitats, their neural mechanisms have seldom been investigated....
Although behavioural defensive responses have been recorded several times in both laboratory and natural habitats, their neural mechanisms have seldom been investigated. To explore how chemical, water-borne cues are conveyed to the forebrain and instruct behavioural responses in anuran larvae, we conditioned newly hatched agile frog tadpoles using predator olfactory cues, specifically either native odonate larvae or alien crayfish kairomones. We expected chronic treatments to influence the basal neuronal activity of the tadpoles' mitral cells and alter their sensory neuronal connections, thereby impacting information processing. Subsequently, these neurons were acutely perfused, and their responses were compared with the defensive behaviour of tadpoles previously conditioned and exposed to the same cues. Tadpoles conditioned with odonate cues differed in both passive and active cell properties compared to those exposed to water (controls) or crayfish cues. The observed upregulation of membrane conductance and increase in both the number of active synapses and receptor density at the postsynaptic site are believed to have enhanced their responsiveness to external stimuli. Odonate cues also affected the resting membrane potential and firing rate of mitral cells during electrophysiological patch-clamp recordings, suggesting a rearrangement of the repertoire of voltage-dependent conductances expressed in cell membranes. These recorded neural changes may modulate the induction of an action potential and transmission of information. Furthermore, the recording of neural activity indicated that the lack of defensive responses towards non-native predators is due to the non-recognition of their olfactory cues.
Topics: Animals; Larva; Predatory Behavior; Cues; Anura; Olfactory Receptor Neurons; Astacoidea
PubMed: 38696517
DOI: 10.1371/journal.pone.0302728 -
Environmental Toxicology and Chemistry Jul 2024Persistent organic pollutants pose a great threat to amphibian populations, but information on the bioaccumulation of contaminants in amphibians remains scarce. To...
Persistent organic pollutants pose a great threat to amphibian populations, but information on the bioaccumulation of contaminants in amphibians remains scarce. To examine the tissue distribution and maternal transfer of organic halogenated pollutants (OHPs) in frogs, seven types of tissues from black-spotted frog (muscle, liver, kidney, stomach, intestine, heart, and egg) were collected from an e-waste-polluted area in South China. Among the seven frog tissues, median total OHP concentrations of 2.3 to 9.7 μg/g lipid weight were found (in 31 polychlorinated biphenyl [PCB] individuals and 15 polybrominated diphenyl ether [PBDE], dechlorane plus [syn-DP and anti-DP], bexabromobenzene [HBB], polybrominated biphenyl] PBB153 and -209], and decabromodiphenyl ethane [DBDPE] individuals). Sex-specific differences in contaminant concentration and compound compositions were observed among the frog tissues, and eggs had a significantly higher contaminant burden on the whole body of female frogs. In addition, a significant sex difference in the concentration ratios of other tissues to the liver was observed in most tissues except for muscle. These results suggest that egg production may involve the mobilization of other maternal tissues besides muscle, which resulted in the sex-specific distribution. Different parental tissues had similar maternal transfer mechanisms; factors other than lipophilicity (e.g., molecular size and proteinophilic characteristics) could influence the maternal transfer of OHPs in frogs. Environ Toxicol Chem 2024;43:1557-1568. © 2024 SETAC.
Topics: Animals; Female; Tissue Distribution; Male; Persistent Organic Pollutants; Environmental Monitoring; Halogenated Diphenyl Ethers; Anura; China; Ranidae; Water Pollutants, Chemical
PubMed: 38695729
DOI: 10.1002/etc.5882