Understanding genetic diversity patterns of endangered species is an important premise for biodiversity conservation. The critically endangered salamander Andrias davidianus , endemic to central and southern mainland in China, has suffered from sharp range and population size declines over the past three decades. However, the levels and patterns of genetic diversity of A. davidianus populations in wild remain poorly understood. Herein, we explore the levels and phylogeographic patterns of genetic diversity of wild‐caught A. davidianus using larvae and adult collection with the aid of sequence variation in (a) the mitochondrial DNA (mtDNA) fragments ( n = 320 individuals; 33 localities), (b) 19 whole mtDNA genomes, and (c) nuclear recombinase activating gene 2 ( RAG2 ; n = 88 individuals; 19 localities). Phylogenetic analyses based on mtDNA datasets uncovered seven divergent mitochondrial clades (A–G), which likely originated in association with the uplifting of mountains during the Late Miocene, specific habitat requirements, barriers including mountains and drainages and lower dispersal ability. The distributions of clades were geographic partitioned and confined in neighboring regions. Furthermore, we discovered some mountains, rivers, and provinces harbored more than one clades. RAG2 analyses revealed no obvious geographic patterns among the five alleles detected. Our study depicts a relatively intact distribution map of A. davidianus clades in natural species range and provides important knowledge that can be used to improve monitoring programs and develop a conservation strategy for this critically endangered organism.

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An 8‐week feeding trial was conducted to investigate the influence of dietary replacement of fish meal with crayfish shell meal (red swamp crayfish Procambarus clarkii) on the skin coloration, muscle texture, and amino acid composition of Oujiang color common carp Cyprinus carpio var. color. One‐hundred‐eighty fish with average initial weight of 3.0 ± 0.5 g were fed with two isonitrogenous and isolipidic diets (a control diet and a crayfish shell meal diet with 25% substitution of fish meal protein [CSM25]). At the termination of the feeding trial, there were no significant differences between the two groups in terms of lightness (L*), redness (a*), and yellowness (b*) values. Interestingly, one unexpected finding was the extent to which the highest value for total color difference (ΔE) was observed in caudal skin. The springiness, adhesiveness, cohesiveness, gumminess, and chewiness of the muscle were not affected by the CSM25 diet in this study. Muscle hardness was decreased by dietary supplementation with crayfish shell meal, although this decrease was not significant. Notably, there were significant increases in the levels of threonine, leucine, and lysine in the CSM25 group. The current results indicate that crayfish shell meal can alter some essential amino acid levels in muscle. These findings might help others to better understand the influence of dietary replacement of fish meal with crayfish shell meal on skin coloration, muscle texture, and amino acid composition.

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This study was designed to evaluate the effects of dietary crawfish shell meal (CSM) on the growth performance, digestive enzyme activity and anti-oxidative capacity of Oujiang color common carp. 180 juvenile fish (initial weight 3.0 ± 0.5 g) were assigned to the control group and the CSM25 group (fed with 25% substitution of fish meal by CSM) for 8 weeks. Results showed that significant improvement in the weight gain rate (WGR) in CSM25 group than the control (p < .05), whereas no significant change in feed conversion ratio, specific growth rate and feeding intake between the groups (p > .05). Also, no significant difference was obsevered between the groups in terms of serum biochemical index and muscle composition (p > .05). And liver superoxide dismutase, catalase, glutathione peroxidase (GPx), lysozyme (LYZ) and protease activities in CSM25 group were significantly higher (p < .05). Moreover, histological analysis indicated that width of mucosa and thickness of muscular coat in mid-intestine were significantly changed (p < .05). In conclusion, dietary supplement with CSM25 induced high oxidative stress, promote protease activities and had no negative effects on the growth performance of Oujiang color common carp. Hence, CSM may be a viable alternative protein source to reduce the demand for fish meal. K E Y W O R D Santi-oxidative capacity, crawfish shell meal, Cyprinus carpio var. color, fish meal replacement, growth performance, immune response Highlights• Crawfish shell meal (CSM) supplementation have no negative effects on the growth performance of Cyprinus carpio var. color.• CSM supplementation can improve antioxidant capacity and non-specific immunity of C. carpio var. color.