Legacy and Emerging Per- and Polyfluoroalkyl Substances Surveillance in Bufo gargarizans from Inlet Watersheds of Chaohu Lake, China: Tissue Distribution and Bioaccumulation Potential.

Amphibians are sensitive biomonitors of environmental pollutants but reports regarding per- and polyfluoroalkyl substances (PFAS), a class of synthetic organofluorine substances, are limited. In this study, samples of water and Chinese toads (Bufo gargarizans) were collected in Chaohu Lake, China. Tissue-specific bioaccumulation characteristics of 39 PFAS, including 19 perfluoroalkyl acids (PFAAs), 8 emerging PFAS, and 12 PFAA precursors, were investigated, and the levels of some biochemical indicators were determined. The highest PFAS concentrations were found in the liver [215.97 ng/g dry weight (dw)] of Chinese toads, followed by gonads (135.42 ng/g dw) and intestine (114.08 ng/g dw). A similar tissue distribution profile was found between legacy and emerging PFAS in the toads, and the occurrence of two emerging PFAS, 2,3,3,3-tetrafluoro-2-propanoate (HFPO-DA) and 6:2 hydrogen-substituted polyfluorooctane ether sulfonate (6:2 H-PFESA) in the amphibians were for the first time reported. Field-based bioaccumulation factors of HFPO-DA were higher than perfluorooctanoic acid, indicating the higher bioaccumulation potential of this emerging PFAS than the legacy C8 compound. Males had significantly higher gonad PFAS levels than females while estradiol levels in gonads increased with increasing concentrations of certain PFAS (e.g., 6:2 H-PFESA), implying that PFAS may trigger estrogenic effects in the toads, especially for male toads.

The succession of gut microbiota in the concave-eared torrent frog (Odorrana tormota) throughout developmental history.

The gut microbiota of amphibians plays a crucial role in maintaining health and adapting to various developmental stages. The composition of gut microbial community is influenced by the phylogeny, habitat, diet, and developmental stage of the host. The present study analyzed the microbiota in the intestine of O. tormota at 11 developmental stages (from the tadpole at Gosner stage 24 to the 3-year-old adult) using high-throughput 16S rRNA sequencing. Alpha diversity index analysis of the microbiota revealed that the index decreased from tadpole at Gosner stage 24 to adult frog stage, remained stable during the adult frog stages, but increased significantly at the early metamorphosis and hibernation preparation stages. The gut microbiota structure is similar in adult frogs but differs significantly in other developmental stages. Furthermore, the dominant phyla of gut microbiota in tadpoles were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, whereas those in adult frogs were Proteobacteria, Firmicutes, Bacteroidetes, and Verrucomicrobia. Host and environmental factors jointly affected the gut microbial diversity and community composition of O. tormota, but developmental stage, feeding habit, and habitat type had a more significant influence. The microbial community in the gut varies with the developmental stage of the host and constantly adapts to the survival requirements of the host. These findings advance our understanding of the evolutionary mechanism of amphibian gut microbiota in maintaining health homeostasis and adaptation.

Dynamic transcriptome and histomorphology analysis of developmental traits of hindlimb thigh muscle from Odorrana tormota and its adaptability to different life history stages.

BACKGROUND: Systematic studies on the development and adaptation of hindlimb muscles in anura amphibians are rare. Here, we integrated analysis of transcriptome and histomorphological data for the hindlimb thigh muscle of Odorrana tormota (concave-eared torrent frog) at different developmental stages, to uncover the developmental traits of hindlimb thigh muscle from O. tormota and its adaptability to different life history stages. RESULTS: The development of hindlimb thigh muscle from O. tormota has the following characteristics. Before metamorphosis, myogenous cells proliferate and differentiate into myotubes, and form 11 muscle groups at G41; Primary myofibers and secondary myofibers appeared during metamorphosis; 11 muscle groups differentiated continuously to form myofibers, accompanied by myofibers hypertrophy after metamorphosis; During the growth process of O. tormota from G42 to G46, there were differences between the sexes in the muscle groups that differentiate into muscle fibers, indicating that there was sexual dimorphism in the hindlimb thigh muscles of O. tormota at the metamorphosis stages. Some genes and pathways related to growth, development, and movement ability of O. tormota at different developmental stages were obtained. In addition, some pathways associated with adaptation to metamorphosis and hibernation also were enriched. Furthermore, integrated analysis of the number of myofibers and transcriptome data suggested that myofibers of specific muscle groups in the hindlimbs may be degraded through lysosome and ubiquitin pathways to transform into energy metabolism and other energy-related substances to meet the physiological needs of hibernation. CONCLUSIONS: These results provide further understanding the hindlimb thigh muscle development pattern of frogs and their adaption to life history stages.

Camera trap reveals the co-occurrence patterns of two sympatric muntjac species in southern Anhui Province, China: No spatial segregation.

The competitive relationship and coexistence pattern among close related species have long been one of the hot issues in ecological research. Interspecies interactions can exert important influences on the local distribution of rare species. Black muntjac Muntiacus crinifrons is an endemic species to eastern China, currently restricted to limited regions. In contrast, Chinese muntjac Muntiacus reevesi is the most common and widespread deer in southern China. Both species co-occur in southern Anhui and western Zhejiang Province. Little is known about the interaction of these two sympatric-related species. In this study, to investigate the site use determinants and co-occurrence pattern of the two sympatric muntjac species, we conducted a camera trap survey across about 250 km2 in mountainous area of southern Anhui Province, China. We adopted a multistep approach to incorporate habitat preferences while modeling occupancy and detection. We found that the two species did not separate along elevation gradient (range from 400 m to 1,400 m) as described in previous studies. Results of single-species occupancy models indicated that elevation had positive effects on the site use of both species, while slope had an opposite influence on their site use. Positive effects of elevation on the site use implied that both species try to avoid human interference at low elevations. Significant negative effect of slope on the site use of black muntjac suggested that the species prefer habitat with gentle slope and avoided steep. Co-occurrence models and species interaction factors provided evidence that the two muntjac species had an independent occupancy (ψ BM CM = ψ BM cm, SIF = 1) and exhibited a positive species interaction in detection probability (p BM < r BM CM). Combined with the results of previous studies, we suggested that it was fine differentiation in microhabitats and food resources utilization rather spatial or temporal segregation that allowed the two species co-occurrence. The site use determinants revealed in our study would be useful for the habitat conservation and restoration for the rare black muntjac, and the co-occurrence pattern of the two sympatric muntjac species could provide useful information for deep understanding of the coexistence mechanism among forest-dwelling ungulates.

Integrated analysis of mRNA and miRNA expression profiles reveals muscle growth differences between fast- and slow-growing king ratsnakes (Elaphe carinata).

In some countries, snakes are important protein sources in human diets, and their economic value depends predominantly on their muscle production, including in the king ratsnake (Elaphe carinata). Muscle growth in the king ratsnake clearly differs among individuals. To date, few potential molecular mechanisms underlying these differences in muscle growth and development have been reported. Here, we integrated mRNA and miRNA expression profiles to screen for genes, pathways, and predicted miRNA-mRNA networks associated with muscle growth and development in fast-growing and slow-growing King ratsnakes. Six hundred eight differentially expressed genes (DEGs) were identified, 48 of which were associated with muscle growth. The 37 genes upregulated in fast-growing individuals (FGIs) may be related to the promotion of muscle growth, whereas the 11 upregulated genes in slow-growing individuals (SGIs) may be related to the inhibition of muscle growth. Seven DEGs were enriched in the PI3K-AKT-MTOR signaling pathway, which appears to promote muscle growth in FGIs. Eleven DEGs were enriched in the ubiquitin-proteasome pathway, which appears to inhibit muscle growth in SGIs. It may interpret why muscle growth differences. Furthermore, 698 miRNA were identified, including 125 novel miRNAs. 63 differentially expressed miRNA (DEMs) were screened, and 950 negative miRNA-mRNA interactions with the 63 DEMs and 608 DEGs were predicted. The miRNA-targeted genes were enriched in pathways related to muscle growth, protein synthesis, and protein degradation. Therefore, in addition to the identified DEGs, miRNAs may play important roles in the differential regulation of muscle growth in FGIs and SGIs of the king ratsnake.