Search Results (140)

Anurans, commonly known as frogs and toads, comprise a diverse group of amphibians distributed across all continents except Antarctica. This manuscript provides a detailed overview of the global anuran fauna, emphasizing their biology, remarkable adaptations, and ecological importance. A particular focus is placed on their specialized cutaneous glands, which are crucial for defense, communication, and survival. These glands secrete a diverse array of bioactive compounds, including peptides, alkaloids, and other secondary metabolites, shaped by evolutionary pressures. Among these compounds, toxins with potent antimicrobial properties stand out due to their ability to combat a broad spectrum of microbial pathogens. We explore the chemical diversity of these secretions, analyzing their modes of action and their potential applications in combating antibiotic-resistant bacteria and other pathogens. By integrating knowledge, this study underscores the importance of anurans as both ecological keystones and a valuable resource for biotechnological innovations. Furthermore, it highlights the urgent need to conserve anuran biodiversity for harnessing their potential in the development of novel antimicrobial agents to address global health challenges. Full article

The intestinal microbiota regulates host metabolic homeostasis through production of bioactive microbial metabolites. These microorganisms facilitate digestion, enhance immune function, maintain osmoregulation, and support physiological balance via these bioactive compounds, thereby enhancing environmental adaptation. Our study investigated intestinal microbiota–liver metabolic interactions in Leptobrachium liui using 16S rRNA gene sequencing and non-targeted liquid chromatography–tandem mass spectrometry metabolomics. Key findings include (1) comparable alpha diversity but distinct microbial community structures between the small intestine (SI) and large intestine (LI), with the SI dominated by Enterobacteriaceae (72.14%) and the LI by Chitinophagaceae (55.16%); (2) segment-specific microbe–metabolite correlations, with predominantly positive correlations in the SI and complex patterns in the LI involving fatty acids, amino acids, and energy metabolites; and (3) significant correlations between specific bacterial families (Aeromonadaceae, Enterobacteriaceae, Chitinophagaceae) and hepatic metabolites related to fatty acid metabolism, amino acid synthesis, and energy pathways, indicating potential gut–liver axis associations. These findings provide insights into amphibian intestinal microbiota–hepatic metabolite associations and may inform future studies of host–microbe interactions. Full article

Forest thinning treatments are expanding in scope and scale to counter increasing wildfire risk. Such treatments are being applied in aquatic-adjacent forests that provide a critical habitat for sensitive amphibians, yet little is known about the impact of these treatments. We used a 5-year (2017–2021) before–after–control–impact experiment to investigate the effects of hand-thinning on pond-breeding amphibian activity around an ephemeral lake in the southern Cascade Range of California. We found that hand-thinning had no detectable negative effects on long-toed salamanders (Ambystoma macrodactylum) and western toads (Anaxyrus boreas) and significantly increased adult Sierran chorus frog (Pseudacris sierra) activity (χ² = 4.70, df = 1, p = 0.030) in upland habitats. These results are consistent with pre-treatment habitat associations—chorus frog activity was higher when tree density was lower, and the treatment reduced tree density; adult long-toed salamanders and western toads were positively associated with canopy closure, which was not significantly reduced by the treatment. In addition, late-season surface activity of adult long-toed salamanders and chorus frogs was strongly associated with fall rain events when they tend to cluster very near the lake edge. Hand-thinning in aquatic-adjacent habitat may have minimal negative impacts, and even some positive impacts, on pond-breeding amphibians in coniferous forests, especially if treatments are not implemented during periods of high amphibian activity and do not substantially alter canopy closure. Full article

The intestinal microbiota is vital for host immunity and metabolism, and its changes are associated with the development stage of hosts. However, little is known regarding how growth and development of anurans affect the diversity of their microbiota, which has a complex life cycle. The Tibetan toad (Bufo tibetanus) is a wild population in the high-altitude area of southwest China, which has special adaptability to the environment. Here, the microbial community of the Tibetan toad at six developmental stages (from the tadpole at Gosner stage 18 to the 8-year-old adult) was assessed using high-throughput 16S rRNA sequencing. The alpha diversity index analysis showed that the Chao, Ace, and Shannon indices were highest at Gosner stage 32 and decreased as development progressed, and their alpha diversity remained unchanged over time in adult stages. Beta diversity revealed that the gut microbiota structure differed significantly from Gosner stages 18 to 31, and it became similar to adult toads from Gosner stages 45 to 46 and in juvenile groups. At the phylum level, Firmicutes, Proteobacteria, and Actinobacteria were dominant phyla in tadpoles and adults. The relative abundance of Firmicutes and Proteobacteria in the adult group was significantly higher and lower than that of tadpoles, respectively. The linear discriminant analysis effect size (LEfSe) analysis identified seven phyla exhibiting significant differences during life stages: Verrucomicrobiota, Bacteroidota, and Proteobacteria (Gosner 18 to 31), Cyanobateria and Chloroflexi (Gosner 32 to 41), Actinobacteriota (Gosner 45 to 46), Desulfobacterota (juvenile group), and Firmicutes (adult group). A pathway enrichment analysis revealed that the metabolism and biosynthesis of secondary metabolites were significantly enriched across all developmental stages. This research unveiled variations in the intestinal microbiota composition during development in anurans. Factors such as developmental stage, habitat type and feeding habit jointly affected the gut microbial diversity and community composition in the Tibetan toad. The findings of this study can provide information for understanding the influence of historical developments on the intestinal microbiota and provide protection information for anurans. Full article

The bacterial community in water from the Houston-toad captive assurance colony held at the Houston Zoo, TX, was used for comparison to the native pond bacterial composition by Ilumina-based 16S rRNA V3 amplicon sequencing. We analyzed composite sediment–water samples from native breeding ponds before and after the release of eggstrands, focusing on opportunistic pathogens of the genus Mycobacterium within the phylum Actinobacteria. Proximal native breeding ponds without headstarting were analyzed for comparison. Tank-water samples from holding facilities (NACQ, Rm1, Rm3, Rm4) showed similar bacterial profiles, with sequences identifying Proteobacteria (57.8 ± 6.2% of all reads), Bacteriodetes (28.1 ± 8.9% of all reads), and Firmicutes (4.1 ± 2.0% of all reads) generally accounting for more than 90% of all reads. Actinobacteria were identified in low abundance, accounting for 1.4 ± 1.1% of all reads, with Nocardiaceae being the most prominent group (54 to 75% of reads), followed by Microbacteriaceae (6 to 12%) and Mycobacteriaceae (1 to 3%). In the pond samples, Proteobacteria remained the most prominent phylum, comprising about 30% of all reads, though other phyla such as Acidobacteria, Actinobacteria, Bacteriodetes, Chloroflexi, Cyanobacteria, Firmicutes, Planctomycetes, Verrucomicrobia, and others were also well represented, ranging from 1% to 15%, with individual phyla peaking at specific sampling times. The prevalence of Actinobacteria sequences varied widely among ponds (<1 to 11% of all reads) and over time (10% and 1%). Most mycobacteria sequences retrieved from tank water were not detected in pond water. Thus, the potential introduction of opportunistic mycobacteria pathogens with tank water from holding facilities and eggstrands via headstarting does not seem to lead to the establishment of these bacteria in natal ponds. Full article

The plateau environments are always harsh, with low pressure, low oxygen, and low temperature, which are detrimental to the survival of organisms. The Qinghai toad-headed lizard Phrynocephalus vlangalii has a wide range of altitude adaptation from 2000 to 4600 m. But it is still unclear how organisms maintain tissue function by balancing energy supply and demand changes in high-altitude environments of P. vlangalii. We investigated the plateau metabolic adaptation through transcriptome and metabolome analyses of P. vlangalii from three populations at different altitudes of the Qinghai-Tibet Plateau. The genes related to carbohydrate metabolism were significantly down-regulated at the high altitude. The metabolites alpha-D-glucose 1-phosphate, beta-D-fructose 6-phosphate, D-glycerate 1,3-diphosphate, 3-phosphoglycerate, and phosphoenolpyruvate in glycolysis/gluconeogenesis were down-regulated, too. The lipid metabolic and fatty acid synthase-related genes were up-regulated at a high altitude. In conclusion, the glycogen utilization-related genes and metabolites experienced broad down-regulation, while lipid-related genes and metabolites had a clear trend of up-regulation. Thus, we suggest that P. vlangalii tends to increase lipid utilization and reduce the dependence on glycogen consumption to acclimatize to the high-altitude environment. Full article

Amphibians, as the most threatened group of vertebrates, are the focus of investigation of various agents that could affect their fitness and survival. In this context, we examined the effects of naturally occurring bacteria and their combinations on the embryonic and larval development of common toad tadpoles (Bufo bufo). One egg string that was collected from the wild was disinfected in the lab and divided into short strings, each containing 20 eggs. These strings were exposed to three different control treatments, i.e., a sterile FETAX solution, water collected from the tadpoles’ native habitat, and sterilized habitat water, as well as to three different bacterial cultures isolated from habitat water (Bacillus sp., Mesobacillus sp.). We analyzed several morphometric variables (snout–vent length, total length, and weight), the energy budget by measuring body composition (proteins, carbohydrates, and lipids), and biomarker activity (acetylcholinesterase and lactate dehydrogenase). Our results indicate that the native microbial community had a negative effect on egg and tadpole development, as sterilized habitat water supported their highest development. Additionally, when grown in FETAX, pure bacterial cultures and their combinations decreased acetylcholinesterase activity but positively affected both tadpole size and energy budget. These findings suggest that bacteria can influence the larval development of common toads by modifying physiological traits. Future research should identify which microbes have beneficial or detrimental effects on amphibian development. Full article

Corticosterone (CORT) is a key glucocorticoid hormone that regulates energy balance and physiological responses to environmental stressors, making it a valuable biomarker for assessing how organisms cope with changing conditions. Understanding how amphibians respond to chronic thermal stress is critical in the context of climate change and urbanization. We investigated the effects of a week-long exposure to elevated water temperatures on CORT release rates and growth in Gulf Coast toad (Incilius nebulifer) tadpoles, a species adapted to variable thermal environments. Using a non-invasive water-borne hormone method, we measured CORT at multiple time points (1 h, 2 h, 6 h, 24 h, 48 h, and 5 days) post-treatment to assess how CORT varied with time after exposure to elevated heat vs. the control temperature. We found a significant time-by-treatment response in tadpoles after a week of exposure to 32 °C versus 23 °C (control) temperatures. Both control and treatment individuals showed a marked decrease in CORT release rates 6 h post-return to room temperature, but by 24 h post-experiment, CORT release rates were higher in the tadpoles exposed to 32 °C. Heat-exposed tadpoles also showed significantly faster growth during and after treatment, but a lower survival to 12 days, indicating a potential trade-off between survival and accelerated growth. Overall, our study highlights a trade-off for populations of I. nebulifer when exposed to thermal stress and suggests that amphibian responses to chronic environmental stressors are shaped by adaptive physiological strategies, with implications for understanding and conserving amphibian populations in a rapidly changing world. Full article

Spirocalcaridines A and B are among the most challenging members of the marine invertebrate-derived Leucetta alkaloids. Approaches to the construction and elaboration of the highly compact spirocyclic core are described. The synthesis of tricyclic guanidine via tandem oxidative amination dearomatizing spirocyclization (TOADS) using hypervalent iodine set the stage for total synthesis via the migration of the C4/C8 double bond to the C4/C5 position, followed by oxidation. The undesired but not surprising propensity of the spirocyclic cyclohexadienone to undergo rearrangement to the phenol hindered the desired olefin migration. Furthermore, initial efforts to install the oxidation sequentially, first at C5 and then at C4 in the complete carbon skeleton, were fraught with unforeseen challenges and unusual outcomes. In addition, the scope and limitations of hypervalent iodine-mediated tandem oxidative dearomatizing spirocyclization on various substrates were explored. Urethanes and thiourethanes underwent spirocyclization with an excellent yield, whereas the reaction with allylic substrates and species lacking the p-methoxy substituent did not proceed. Attempts to prepare other guanidine precursors are briefly discussed. Full article

A new species of Asian horned toad, Boulenophrys, is described from Yongzhou City, Hunan Province, China. The species is a phylogenetically sister to B. yunkaiensis, based on 16S rRNA and COI genes. The new species differs from its congeners, possessing the following combination of characters: (1) moderate body size: SVL 37.6–40.2 mm (38.9 ± 1.3, n = 7) in adult males and SVL 41.8–45.9 mm (43.6 ± 2.1, n = 3) in adult females; (2) tympanum boundary clear: TD/ED 0.48–0.57 in males and 0.47–0.57 in females; (3) the presence of a small horn-like tubercle at the edge of the upper eyelid; (4) vomerine ridge present and vomerine teeth absent; (5) margin of tongue rounded, not notched posteriorly; (6) rough dorsal skin: a discontinuous “V”-shaped ridge with two discontinuous dorsolateral ridges on two sides on the back, dense tubercles on the skin of the ventral surface of the dorsal shank and thigh, and spiny tubercles surrounding the cloaca; (7) slender hindlimbs with heels overlapping when the flexed hindlimbs are held at right angles to the body axis; tibio-tarsal articulation reaching forward between anterior margin of tympanum and posterior corner of eye when leg stretched forward; (8) relative finger length IV < II < I < III, with a subarticular tubercle present at the base of each finger; (9) distinct supernumerary tubercles below the base of I and II toes; (10) toes without lateral fringes and with rudimentary webbing (webbing formula: I1 − 1-II1 − 2-III2 − 3IV3- − 2V). Full article

Hibernation is a crucial adaptive strategy for amphibians, facilitating survival in harsh environmental conditions by lowering metabolic rates and reducing energy use. This study employed GC-MS and LC-MS metabolomics to systematically analyze the serum metabolome of Bufo gargarizans during hibernation, aiming to uncover its metabolic adaptation mechanisms. A total of 136 differentially expressed metabolites (DEMs) were identified, of which 115 were downregulated and 21 upregulated, mainly involved in amino acid, carbohydrate, and lipid metabolism. KEGG pathway analysis showed that most metabolic pathways were inhibited in the hibernating group, underscoring a significant reduction in overall metabolic activity. Notably, while amino acid and carbohydrate metabolism were significantly reduced, lipid metabolism exhibited a distinctive adaptive response. Enhanced β-oxidation of fatty acids, including palmitoleic acid, arachidonic acid, and sodium caprylate, suggests a metabolic shift toward lipid-based energy utilization. The reduction in key metabolites like fumaric acid and succinic acid in the TCA cycle further supports the hypothesis of reduced energy requirements. These results enhance our current understanding of amphibian hibernation metabolisms and provide a targeted approach for future mechanistic investigations. Full article

The Kunlun, Arjin, and Qilian mountain ranges mark the northern edge of the Qinghai–Tibet Plateau (QTP), where rapid uplift and Quaternary glacial cycles have shaped a unique cold desert ecosystem and species distribution. Despite sampling challenges, phylogeographic studies are crucial for understanding reptile populations such as the Qinghai toad-headed agama (Phrynocephalus vlangalii), a viviparous lizard with limited dispersal and multiple subspecies in the northeastern QTP. Our fieldwork identified populations of P. vlangalii on the northern slope of the Kunlun–Arjin Mountains, similar to the controversial subspecies P. v. lidskii. We analyzed 130 individuals from the northern slope of the Kunlun–Arjin–Qilian Mountains and 253 individuals from GenBank, using three mitochondrial genes and two nuclear genes to assess intraspecific differentiation and demographic history. We found high haplotype diversity and low nucleotide diversity in P. vlangalii, with phylogenetic analyses revealing six distinct clades. Clade VI, confirmed as P. v. lidskii, and Clade IV, a new genetic lineage, were identified alongside three recognized subspecies. Genetic variation was largely attributed to clade splitting, indicating significant divergence. The Mantel test indicated that geographical and environmental factors drove population differentiation. Bayesian molecular clock analysis suggested that the most recent common ancestor of P. vlangalii lived 2.55 million years ago, influenced by the Qinghai–Tibet Movement and glacial cycles. Demographic history and ecological niche modeling (ENM) indicated no population decline during the Last Glacial Maximum, supporting the glacial maximum expansion model, with ENM predicting future habitat expansion for P. vlangalii. In addition, morphological data from 13 meristic and 15 metric characters confirmed clade differences. Our findings significantly advance our understanding of P. vlangalii diversification, population dynamics and response to geological and climatic changes in the QTP. Full article

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a significant threat to global amphibian populations, leading to widespread declines and extinctions. In the spring of 2023, Bd presence was detected in different amphibian species within two protected areas near Turin, Piedmont, Italy, following an unusual mortality event among the common toad (Bufo bufo). Histological and molecular analyses confirmed Bd infection in a deceased Pelophylax sp. specimen, prompting further investigation. Sampling of 166 individuals across seven amphibian taxa revealed an overall Bd occurrence of 38.6%, with Pelophylax sp. showing the highest detection rate (50.5% of 93 individuals). A marked difference in the positivity rate was observed between the two locations, with La Mandria (67.2% of 58) exhibiting significantly higher rates than Vauda (22.9% of 35). While Bd was identified in the sampled amphibians, the exact cause of the observed mortality remains unclear and may involve other pathogens or multifactorial causes, including but not limited to Bd. These findings represent the first documented case of Bd presence in Piedmont after an 18-year gap, highlighting the potential influence of local environmental factors on infection dynamics. The study emphasises the need for expanded, standardised field sampling and further investigation into the various factors affecting amphibian health to guide conservation efforts for vulnerable amphibian species. Full article

In this brief article, the green toad (Bufotes sitibundus) and the Levant water frog (Pelophylax bedriagae) were compared to better understand the adaptations needed by amphibians, specifically the green toad, to survive in arid regions and to inhabit a wide range of habitats. The information mainly comes from data gathered in Israel, a nation experiencing a shift from Mediterranean to desert ecosystems where both amphibian species can be found. Using these data, a qualitative model is put forward that showcases the differences between these two amphibians and illustrates how the green toad has adapted to arid environments. For instance, green toads travel to breeding and spawning sites during the rainy season. During this journey, they often have to cross roads, which puts them at risk of being hit by vehicles. The main distinction between the green toad and the water frog is that the green toad moves from land environments to water, while the water frog stays in its aquatic habitat for its entire life cycle. Full article

Animal coloration offers a unique opportunity to explore the evolutionary mechanisms underlying phenotypic diversity. Conspicuous coloration caused by pigments plays a crucial role in social signaling across multiple species by conveying information about individual quality, social ranks, or reproductive condition. Nevertheless, most previous studies have focused predominantly on colors produced by the exogenous pigments—carotenoids. Pterins are another prevalent group of conspicuous pigments, which can be produced endogenously and have received comparatively little attention. Whether pterin-based colors represent reliable signals remains elusive. The remarkable red ventrolateral coloration exhibited by males of the Guinan toad-headed lizard (Phrynocephalus guinanensis) in the Mugetan Desert presents an ideal model for investigating pterin-based coloration. Through electron microscopy and metabolomic identification, we discovered three types of pterin pigments within xanthophores. Integrating a series of morphological measurements and behavioral experiments, we found that this red coloration was not correlated with body size, bite force, and testosterone level, nor did females show a preference bias toward it. However, the red intensity predicted male–male competition outcomes, with deeper red males being more likely to emerge as winners. Our results indicated that the pterin-based coloration could convey information about male quality, suggesting its potential role in honest signaling, given the vital importance of pterin metabolism in physiological processes. This study provides a novel case into the understanding of pterin-based colors in animals. Full article