Tadpole

BACKGROUND: Anuran metamorphosis, which is driven by thyroid hormone (TH)-mediated processes, orchestrates intricate morphological and functional transformations for the transition from aquatic tadpoles to terrestrial life, providing a valuable model for studying organ functionalization, remodeling, and regression. Larva-specific organ regression is one of the most striking phenomena observed during the anuran metamorphic climax. While previous studies extensively analyzed the regression mechanisms of the tail, the molecular processes governing gill resorption remain elusive...

A critical component of animal conservation in a changing world is an understanding of the physiological resilience of animals to different conditions. In many aquatic animals, hypoxia (low environmental oxygen levels) is a regular occurrence, but the likelihood and severity of hypoxia varies across habitats. Fast-flowing, stream-like habitats are never hypoxic, so long as flow is maintained. Do animals from such habitats retain the capacity to survive hypoxic conditions? We use aquatic frog tadpoles to test the effects of natural habitat on performance in hypoxia in an experimental framework, finding that stream-living tadpoles have reduced performance in hypoxia...

The Xenopus Eleutheroembryonic Thyroid Assay (XETA) was recently published as an OECD Test Guideline for detecting chemicals acting on the thyroid axis. However, the OECD validation did not cover all mechanisms that can potentially be detected by the XETA. This study was therefore initiated to investigate and consolidate the applicability domain of the XETA regarding the following mechanisms: thyroid hormone receptor (THR) agonism, sodium-iodide symporter (NIS) inhibition, thyroperoxidase (TPO) inhibition, deiodinase (DIO) inhibition, glucocorticoid receptor (GR) agonism, and uridine 5'-diphospho-glucuronosyltransferase (UDPGT) induction...

Global warming can either promote or constrain the invasive potential of alien species. In ectotherm invaders that exhibit a complex life cycle, success is inherently dependent on the capacity of each developmental stage to cope with environmental change. This is particularly relevant for invasive anurans, which disperse on land while requiring water for reproduction. However, it remains unknown how the different life stages respond in terms of energy expenditure under different climate change scenarios. We here quantified the oxygen uptake of frogs at rest (a proxy of the standard metabolic rate) in the aquatic phase (at the tadpole and climax, i...

In the present study, using transgenic frogs that express GFP specifically in myeloid cells under the myeloperoxidase enhancer sequence, we found that myeloperoxidase-positive cells are localized in the liver cortex at the late tadpole stages. Immunohistochemical analysis revealed that myelopoiesis in the liver cortex became evident after st. 50 and reached its peak by st. 56. Transplantation experiments indicated that cells with a high density at the liver cortex were derived from the dorso-lateral plate tissue in the neurula embryo...

Frogs of the Allophrynidae are an enigmatic family from South America. To date, published information is lacking regarding this group's reproductive biology and larval morphology. Here, we provide the first detailed description of the reproductive mode, developmental mode, and tadpole morphology for Allophryne ruthveni. We developed a captive breeding and rearing protocol for this species and then conducted a series of observations to describe aspects of its reproductive biology. In captivity, this species exhibits aquatic oviposition, where single eggs are laid ungrouped within a simple jelly capsule and are scattered free in the water column before sinking to develop on benthic substrates...

The bacterial communities of the amphibian skin (i.e., the bacteriome) are critical to the host's innate immune system. However, it is unclear how different drivers can alter this function by modulating the bacteriome's structure. Our aim was to assess the extent to which different host attributes and extrinsic factors influence the structure of the bacterial communities of the skin. Skin bacterial diversity was examined in 148 individuals of the four-eyed frog ( Pleurodema thaul ) from 16 localities spanning almost 1800 km in latitude...

Bullfrog ( Rana catesbeiana ) larvae inhabiting the main island of Japan overwinter as preclimax animals, whereas the larvae that reached climax in summer complete metamorphosis. We analyzed the mRNA expression levels of the adenohypophyseal hormones, hypothalamic hormones, and their receptors that are involved in controlling metamorphosis in tadpoles at various developmental stages available in summer and winter in order to understand the hormonal mechanism regulating metamorphosis progression. Corticotropin-releasing factor (CRF) and thyrotropin β-subunit (TSHβ) mRNA expression was enhanced as they reached the climax stage in metamorphosing summer tadpoles, although type 2 CRF receptor (CRFR2) mRNA levels demonstrated a tendency of elevation, indicating the activation of the hypothalamo-hypophyseal axis for stimulating the release of thyroid hormone in summer...

Emerging evidence suggests a link between alterations in the gut microbiome and adverse health outcomes in the hosts exposed to environmental pollutants. Yet, the causal relationships and underlying mechanisms remain largely undefined. Here we show that exposure to biotoxins can affect gut pathobiome assembly in amphibians, which in turn triggers the toxicity of exogenous pollutants. We used Xenopus laevis as a model in this study. Tadpoles exposed to tropolone demonstrated notable developmental impairments and increased locomotor activity, with a reduction in total length by 4...

Models of toxicity to tadpoles have been developed as single parameters based on special descriptors which are sums of correlation weights, molecular features, and experimental conditions. This information is presented by quasi-SMILES. Fragments of local symmetry (FLS) are involved in the development of the model and the use of FLS correlation weights improves their predictive potential. In addition, the index of ideality correlation ( IIC ) and correlation intensity index ( CII ) are compared. These two potential predictive criteria were tested in models built through Monte Carlo optimization...

BACKGROUND: The tunicates form a group of filter-feeding marine animals closely related to vertebrates. They share with them a number of features such as a notochord and a dorsal neural tube in the tadpole larvae of ascidians, one of the three groups that make tunicates. However, a number of typical chordate characters have been lost in different branches of tunicates, a diverse and fast-evolving phylum. Consequently, the tunic, a sort of exoskeleton made of extracellular material including cellulose secreted by the epidermis, is the unifying character defining the tunicate phylum...

Metal oxide nanomaterials have toxicity towards aquatic organisms, especially microbes and invertebrates, but little is known about their impact on amphibians. We conducted a study on Duttaphrynus melanostictus (D. melanostictus) tadpoles to explore the chronic toxicity effects of iron oxide nanoparticles (IONPs) and the underlying mechanisms of IONPs-induced oxidative stress. IONPs exposure led to increased iron accumulation in the blood, liver, and kidneys of tadpoles, significantly affecting blood parameters and morphology...

Living with a diverse array of predators provides a significant challenge for prey to learn and retain information about each predator they encounter. Consequently, some prey respond to novel predators because they have previous experience with a perceptually similar predator species, a phenomenon known as generalization of predator recognition. However, it remains unknown whether prey can generalize learned responses across ontogenetic stages of predators. Using wood frog tadpole ( Lithobates sylvaticus ) prey, we conducted two experiments to explore the extent of predator generalization of different life stages of two different predators: (1) predacious diving beetles ( Dytiscus sp...

Pathogenic Aeromonas spp. are the etiological agents of Motile Aeromonas Septicemia (MAS). This study aimed to identify the pathogen of diseased tadpoles ( Quasipaa spinosa ) and the antibiotic-resistance characteristics of this bacterium. A Gram-negative bacterium, named strain QST31, was isolated from the ascites of diseased tadpoles and was identified as Aeromonas media based on physiological and biochemical tests, as well as molecular identification. Artificial infection experiments showed that strain QST31 was highly virulent to tadpoles, with an LC50 of 2...

Sparganosis has been a neglected parasitic zoonosis for a long time. The accurate identification of Spirometra tapeworms in clinical practice is poorly understood. A case of breast sparganosis was reported in Henan Province of central China. One plerocercoid approximately 3.5 cm in length was collected from the patient. The clinical isolate was identified as Spirometra mansoni based on the barcoding sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1). Finally, the epidemiology of sparganosis in central China was reviewed...

The aim of this study was to evaluate the acute lethality and chronic sublethal effects of lithium (Li) on Rhinella arenarum tadpoles as model organisms. First a 96 h toxicity assay was performed by exposing tadpoles to Li concentrations from 44.08 to 412.5 mg L-1 to estimate the mortality, and lethal and sublethal effects. Another bioassay was carried out by exposing tadpoles to two environmentally relevant Li concentrations (2.5 and 20 mg L-1 ) for one and two weeks. The sublethal effects of Li on tadpoles were evaluated by analyzing biochemical, genotoxic, and physiological biomarkers...

As part of the US Environmental Protection Agency's perfluoroalkyl and polyfluoroalkyl substances (PFAS) Action Plan, the agency is committed to increasing our understanding of the potential ecological effects of PFAS. The objective of these studies was to examine the developmental toxicity of PFAS using the laboratory model amphibian species Xenopus laevis. We had two primary aims: (1) to understand the developmental toxicity of a structurally diverse set of PFAS compounds in developing embryos and (2) to characterize the potential impacts of perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and hexafluoropropylene oxide-dimer acid (HFPO-DA a...

Thyroid hormones are involved in many biological processes such as neurogenesis, metabolism, and development. However, compounds called endocrine disruptors can alter thyroid hormone signaling and induce unwanted effects on human and ecosystems health. Regulatory tests have been developed to detect these compounds but need to be significantly improved by proposing novel endpoints and key events. The Xenopus Eleutheroembryonic Thyroid Assay (XETA, OECD test guideline no. 248) is one such test. It is based on Xenopus laevis tadpoles, a particularly sensitive model system for studying the physiology and disruption of thyroid hormone signaling: amphibian metamorphosis is a spectacular (thus easy to monitor) life cycle transition governed by thyroid hormones...

BACKROUND: Inflammation characterized by the presence of T and B cells is often observed in prostate cancer, but it is unclear how T- and B-cell levels change during carcinogenesis and whether such changes influence disease progression. METHODS: The study used a retrospective sample of 73 prostate cancer cases (45 whites and 28 African Americans) that underwent surgery as their primary treatment and had a benign prostate biopsy at least 1 year before diagnosis. CD3+, CD4+, and CD20+ lymphocytes were quantified by immunohistochemistry in paired pre- and post-diagnostic benign prostate biopsy and tumor surgical specimens, respectively...

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