At a particular aquaculture facility in Zhangjiajie in China, the Chinese giant salamander ( Andrias davidianus ) exhibited analogous clinical manifestations, culminating in sequential mortalities. This study used rigorous aseptic sampling methods to isolate bacteria from the affected liver of salamanders to determine the causative agent behind the decline in amphibians. A bacterial pathogen was isolated from diseased A. davidianus , and the strain was named DN-3. This isolate was subjected to bacterial identification, antibiotic susceptibility assays, reinfection experiments, and biochemical profiling. The isolated bacterial strain was definitively identified as Acinetobacter schindleri using 16S rRNA sequence analysis and biochemical identification. Antibiotic susceptibility testing revealed that this isolate was susceptible to neomycin, macrolides, doxycycline, piperacillin, nitrofurantoin, and carbenicillin. Subsequent reinfection assays, in which varying concentrations of the bacterial inoculum were administered to healthy salamanders, confirmed that the pathogen elicited varying degrees of morbidity or mortality within an eight-day observation period. The median lethal dose (LD50) of A. schindleri DN-3 for A. davidianus was calculated to be 6.25×104 CFU/mL. This result supports the significant pathogenicity of the strain for A. davidianus . The findings of this study provide empirical insights into the clinical management and epidemiological control of diseases affecting A. davidianus .

This study aimed to identify the primary pathogenic bacteria responsible for the mortality of the Chinese giant salamander ( Andriasd davidianus ). A pathogenic bacterium was isolated from a diseased Chinese giant salamander exhibiting typical symptoms under aseptic conditions and then identified by morphological examinations, biochemical analysis, and the sequence analysis of bacterial 16S rRNA. Artificial infection testing was then conducted to determine the pathogenicity of the isolated bacteria strain. Drug susceptibility tests were conducted using the agar diffusion method. The isolated pathogenic bacteria, named DN-2, was successfully identified as Acinetobacter lwoffii . The artificial infection showed that the typical symptoms of the disease could be replicated as the ones originally occurred, and this bacterium exhibited high pathogenicity to the Chinese giant salamander. In the Chinese giant salamander, the median lethal dosage (LD50) of A. lwoffii DN-2 for A. davidianus was determined to be 4.63×104 CFU/g. Drug sensitivity testing showed that these bacteria were highly sensitive to erythromycin, gentamicin, neomycin, streptomycin, midecamycin, ciprofloxacin, piperacillin, florfenicol, doxycycline, carbenicillin, and sulfanilamide. In summary, A. lwoffii was identified as the primary pathogen responsible for the demise of A. davidianus . Our study first presents how these bacteria harm Chinese giant salamanders.

Background: The Chinese giant salamander ( Andrias davidianus ) is a critically endangered living fossil species that is highly sensitive to changes in water temperature. However, systematic studies on the heat shock protein (HSP) gene family and its response mechanisms to environmental stress in this species remain limited. This study utilized transcriptome data from captive-bred salamanders exposed to combined temperature and pathogen stress. Bioinformatics tools were employed to identify the HSP gene family of A. davidianus ( AndHSP ) and to analyze their evolution, structure, and function, thereby revealing their regulatory mechanisms in response to environmental stress. Results: A total of 72 AndHSPs were identified and classified into five subfamilies. Phylogenetic analysis revealed that each subfamily is evolutionarily conserved and functionally related. Gene expression analysis demonstrated that pathogen infection induced the expression of AndHSPs , and elevated temperature significantly intensified this response. Nine key differentially expressed genes were identified, predominantly from the AndHSP70 subfamily, with AndHSP70-18 exhibiting rapid heat-induced expression. Tissue-specific analysis showed high expression of AndHSP60 in the spleen. A qPCR validation confirmed the reliability of the transcriptome expression results. Conclusions: This study presents the first systematic identification of the AndHSP gene family and elucidates its cooperative stress response mechanisms under combined temperature and pathogen stress. These findings provide a molecular basis for understanding the species’ environmental adaptation and have important implications for its conservation and artificial breeding.

Baseline information on terrestrial wildlife communities and their activity patterns is essential for protected-area management, but such information remains limited for Hunan Zhangjiajie Giant Salamander National Nature Reserve, where conservation attention has historically focused on the Chinese giant salamander and associated aquatic ecosystems. From March 2024 to August 2025, we conducted a camera-trap survey in broad-leaved and coniferous forest habitats of the reserve to document terrestrial mammals and ground-dwelling birds, evaluate taxonomic completeness, and describe diel and seasonal activity patterns. Across 43 camera-trap stations and 16,314 effective camera-trap days, we recorded 59 wildlife species, including 18 mammals and 41 ground-dwelling birds. The assemblage included nationally protected, threatened, and Chinese endemic species, indicating that the reserve’s forest habitats support important terrestrial biodiversity in addition to its aquatic conservation target. Taxonomic completeness curves suggested that the current survey captured most camera-detectable mammal and ground-dwelling bird taxa under the present sampling design, although the results should not be interpreted as a complete inventory of the reserve’s total vertebrate diversity. Annual diel activity analysis of 11 focal species showed clear temporal differentiation among ecological groups: small and medium-sized carnivores were mainly nocturnal, ground-dwelling birds, and red-hipped squirrel were primarily diurnal, and ungulates showed mixed or crepuscular-to-nocturnal tendencies. Seasonal analyses based on bioclimatic periods showed interspecific differences in activity-density distributions between the cool-dry and warm-wet seasons. However, peak-shift reliability analysis indicated that most focal species retained broadly similar main activity peaks across seasons; masked palm civet was the only species showing reliable seasonal displacement of its main activity peak. Pairwise temporal overlap analyses described temporal co-occurrence patterns among selected sympatric species but should not be interpreted as evidence of direct interaction or niche differentiation. Overall, this study provides baseline data on camera-detected terrestrial vertebrates in the reserve and supports long-term monitoring, forest habitat management, and disturbance control for terrestrial mammals and ground-dwelling birds.

At a particular aquaculture facility in Zhangjiajie, Hunan Province, the Chinese giant salamander (Andrias davidianus) exhibited analogous clinical manifestations, culminating in sequential mortalities. This study used rigorous aseptic sampling methods to extract bacteria from the affected liver of salamanders to determine the causative agent behind the decline of amphibians. A bacterial pathogen was isolated from the diseased A. davidianus, and the strain was named DN-3. This isolate was subjected to bacterial identification, antibiotic susceptibility assays, reinfection experiments, and biochemical profiling. The isolated bacterial strain was definitively identified as Acinetobacter schindleri using 16S rRNA sequence analysis. Antibiotic susceptibility testing revealed that this isolate was susceptible to neomycin, macrolides, doxycycline, piperacillin, nitrofurantoin, and carbenicillin. Subsequent reinfection assays, wherein varying concentrations of the bacterial inoculum were administered to healthy salamanders, corroborated that the pathogen elicited varying degrees of morbidity or mortality within an eight-day observation period. The median lethal dosage (LD50) of A. schindleri DN-3 for A. davidianus was calculated to be 6.25×10⁴ CFU/mL. This supports the significant pathogenicity of the strain. The findings of this study furnish empirical underpinnings for the clinical management and epidemiological control of diseases affecting the Chinese giant salamander.