How will warming affect the growth and body size of the largest extant amphibian? More than the temperature-size rule

Diets shape thermal responses in Chinese giant salamanders by altering liver metabolism

Diet can influence the thermal performance of ectotherms, providing potential strategies for biological conservation in the context of global warming. The endangered Andrias davidianus is susceptible to heat stress due to energy deficiency in the liver when fed a worm-based diet rich in carbohydrates. A fish-based diet, rich in protein and lipids, improves their thermal performance, but the underlying physiological mechanisms remain unclear. In this study, we used metabolomics and metagenomics to examine the combined effects of temperature (15, 20, and 25°C) and diet (fish-based and worm-based) on liver metabolism and gut microbiota. Our results show that both temperature and diet shape liver metabolism, with several vital metabolic pathways (e.g., TCA cycle and sulfate metabolism) regulated by their combined effects. Notably, diet-dependent thermal responses in energy metabolism were observed, with fish-fed salamanders exhibiting a marked upregulation of the TCA cycle intermediates under heat stress, a response absent in worm-fed individuals. Given the role of TCA cycle in heat susceptibility of A. davidianus, these findings suggest that the TCA cycle likely mediates the interactive effects of temperature and diet on thermal performance. We then examined whether the gut microbiota is also a target of interactive effects or a mediator of the diet's influence on liver metabolism. While both temperature and diet shape microbiota composition, functional shifts occur only in response to temperature, indicating that the microbiota is not a major link between diet and liver metabolism. However, several bacterial groups (e.g., Thiosulfatimonas and Alcanivorax), jointly regulated by temperature and diet, correlate with liver metabolites, suggesting alternative, function-independent pathways through which dietary-related microbial changes may influence liver metabolism and even thermal tolerance. Overall, this study provides molecular insights into the dietary modulation of thermal performance in A. davidianus and highlight the potential of dietary microbial management strategies for amphibian conservation.

Antioxidant synergistic anti-inflammatory effect in the MAPK/NF-κB pathway of peptide KGEYNK (KK-6) from giant salamander (Andrias davidianus)

BACKGROUND

Giant salamander protein peptide is a peptide with rich functional properties. Giant salamander protein peptide KGEYNK (KK-6) is a peptide with both antioxidant and anti-inflammatory properties. The antioxidant and anti-inflammatory mechanisms of KK-6 are still unclear. When we studied the functional mechanism of KK-6, we found that the antioxidant property of KK-6 has a synergistic and promoting effect on anti-inflammatory properties.

RESULTS

KK-6 enhances cellular resistance to LPS via the MAPK/NF-κB signaling pathway, leading to increased levels of inflammatory factors: interleukin-1β (764.81 ng mL-1), interleukin-6 (1.06 ng mL-1) and tumor necrosis factor-α (4440.45 ng mL-1). KK-6 demonstrates potent antioxidant properties by activating the Nrf2 signaling pathway, resulting in elevated levels of antioxidant enzymes (glutathione peroxidase: 0.03 μg mL-1; superoxide dismutase: 0.589 μg mL-1) and a reduction in the concentration of the oxidative product malondialdehyde (967.05 μg mL-1).

CONCLUSION

Our findings highlight the great potential of KK-6, a peptide extracted from giant salamander protein, as a remedy for intestinal inflammation. Through its dual role as an antioxidant and anti-inflammatory agent, KK-6 offers a promising avenue for alleviating inflammation-related damage and oxidative stress. This study lays the foundation for further exploration of giant salamander products and highlights their importance in health and novel food development. © 2024 Society of Chemical Industry.

Evolution, Diversity, and Conservation of Herpetofauna

Amphibians and reptiles play a critical role in the evolution of Tetrapoda, showcasing significant diversity in terms of their genetics, species, morphology, life history traits, and evolutionary functions [...].

Validation of Salamander Dermal Mucus Swabs as a Novel, Nonlethal Approach for Amphibian Metabolomics and Glutathione Analysis Following Pesticide Exposure

Evaluating biomarkers of stress in amphibians is critical to conservation, yet current techniques are often destructive and/or time-consuming, which limits ease of use. In the present study, we validate the use of dermal swabs in spotted salamanders (Ambystoma maculatum) for biochemical profiling, as well as glutathione (GSH) stress response following pesticide exposure. Thirty-three purchased spotted salamanders were acclimated to laboratory conditions at Washington College (Chestertown, MD, USA) for 4 weeks. Following acclimation, salamanders were randomly sorted into three groups for an 8-h pesticide exposure on soil: control with no pesticide, 2,4-dichlorophenoxyacetic acid (2,4-D), or chlorpyrifos. Before and after exposure, mucus samples were obtained by gently rubbing a polyester-tipped swab 50 times across the ventral and dorsal surfaces. Salamanders were humanely euthanized and dissected to remove the brain for acetylcholinesterase and liver for GSH and hepatic metabolome analyses, and a whole-body tissue homogenate was used for pesticide quantification. Levels of GSH were present in lower quantities on dermal swabs relative to liver tissues for chlorpyrifos, 2,4-D, and control treatments. However, 2,4-D exposures demonstrated a large effect size increase for GSH levels in livers (Cohen's d = 0.925, p = 0.036). Other GSH increases were statistically insignificant, and effect sizes were characterized as small for 2,4-D mucosal swabs (d = 0.36), medium for chlorpyrifos mucosal swabs (d = 0.713), and negligible for chlorpyrifos liver levels (d = 0.012). The metabolomics analyses indicated that the urea cycle, alanine, and glutamate metabolism biological pathways were perturbed by both sets of pesticide exposures. Obtaining mucus samples through dermal swabbing in amphibians is a viable technique for evaluating health in these imperiled taxa. Environ Toxicol Chem 2024;43:1126-1137. © 2024 SETAC.

Genetic insight into a polygenic trait using a novel genome-wide association approach in a wild amphibian population

Body size variation is central in the evolution of life-history traits in amphibians, but the underlying genetic architecture of this complex trait is still largely unknown. Herein, we studied the genetic basis of body size and fecundity of the alternative morphotypes in a wild population of the Greek smooth newt (Lissotriton graecus). By combining a genome-wide association approach with linkage disequilibrium network analysis, we were able to identify clusters of highly correlated loci thus maximizing sequence data for downstream analysis. The putatively associated variants explained 12.8% to 44.5% of the total phenotypic variation in body size and were mapped to genes with functional roles in the regulation of gene expression and cell cycle processes. Our study is the first to provide insights into the genetic basis of complex traits in newts and provides a useful tool to identify loci potentially involved in fitness-related traits in small data sets from natural populations in non-model species.