Background: The Chinese mitten crab, Eriocheir sinensis, is one of the most studied and economically important crustaceans in China. Its transition from a swimming to a crawling method of movement during early development, anadromous migration during growth, and catadromous migration during breeding have been attractive features for research. However, knowledge of the underlying molecular mechanisms that regulate these processes is still very limited. Findings: A total of 258.8 gigabases (Gb) of raw reads from whole-genome sequencing of the crab were generated by the Illumina HiSeq2000 platform. The final genome assembly (1.12 Gb), about 67.5 % of the estimated genome size (1.66 Gb), is composed of 17,553 scaffolds (>2 kb) with an N50 of 224 kb. We identified 14,436 genes using AUGUSTUS, of which 7,549 were shown to have significant supporting evidence using the GLEAN pipeline. This gene number is much greater than that of the horseshoe crab, and the annotation completeness, as evaluated by CEGMA, reached 66.9 %. Conclusions: We report the first genome sequencing, assembly, and annotation of the Chinese mitten crab. The assembled draft genome will provide a valuable resource for the study of essential developmental processes and genetic determination of important traits of the Chinese mitten crab, and also for investigating crustacean evolution.

Dietary oxidized lipids are key perpetrator to accumulate excessive reactive oxygen species (ROS) that induce oxidative stress for animals. Immoderate oxidative stress dysregulates cell fate, perturbs cellular homeostasis, thereby interrupts metabolism and normal growth. Therefore, a 12-week feeding trial with fish oil (FO, control group), oxidized fish oil (OF), and emodin-supplemented (OF+E) diets was conducted to evaluate the therapeutic mechanism of emodin on metabolic and oxidative resistance in Megalobrama amblycephala liver. Morphologically, emodin remits oxidized fish oil-induced cellular constituents damage, evidenced by lipid droplets enlargement and accumulation, mitochondria rupture, and nucleus aggregation, which were functionally related to oxidative stress, metabolism, and cell fate determination. Consecutively, glucose, lipid, and amino acid metabolism were retained under emodin stimulation. Specifically, fatty acid metabolic genes optimized fatty acid utilization and metabolism, featured as total saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) alternation. Physiologically, inflammation, autophagy, apoptosis, as well as antioxidant capacity were alleviated by emodin. Interactively, fatty acid metabolism was correlated with antioxidant capacity; while the crosstalk and dynamic equilibrium between apoptosis and autophagy determine the cell fate under oxidative stress amelioration. Synergistically, Nrf2 and Notch signaling were active to antioxidant defense. In particular, oxidative stress blocked the crosstalk between Notch and Nrf2 signaling, while emodin rescued Notch-Nrf2 interaction to ameliorate oxidative stress. In conclusion, these results suggest that elevated ROS levels by oxidative stress activates Notch and Nrf2 signaling but intercepts Notch-Nrf2 crosstalk to stimulate cell fate and antioxidant program; dietary emodin alleviates oxidative stress and returns overall ROS levels to a moderate state to maintain homeostatic balance. The crosstalk between Notch and Nrf2 signaling might be the potential therapeutic target for emodin to ameliorate oxidative stress and metabolic disorder in M. amblycephala liver.

As a complementary and symbiotic agro-ecological cycle system, a nature-based integrated rice–fish–duck farming ecosystem was developed in the Honghe Hani Rice Terraces. The main research objective was to evaluate the ecosystem services based on case studies of the Hani integrated rice–fish–duck terraced farming system and determine its potential and its importance as an ecological asset. We developed a valuation model to assess the value of the integrated farming system based on the three aspects of provisioning, regulation and maintenance, and cultural services; we selected eight groups and 10 indictors to evaluate the ecosystem services of the integrated ecosystem in Honghe Hani Rice Terraces was 3.316 billion CNY, of which the provisioning service value was 1.76 billion CNY, the regulation and maintenance service value was 1.32 billion CNY, and the cultural services value was 230.85 million CNY. The evaluation will be useful as a theoretical reference for poverty alleviation policy makers in similar poverty-stricken areas, enabling them to better protect and promote this mode of farming and further promote the protection of the natural environment and cultural heritage alongside the sustainable development of natural resources and human well-being.

Hypothermia-exposure-induced oxidative stress dysregulates cell fate and perturbs cellular homeostasis and function, thereby disturbing fish health. To evaluate the impact of hypothermia on the freshwater drum (Aplodinotus grunniens), an 8-day experiment was conducted at 25 °C (control group, Con), 18 °C (LT18), and 10 °C (LT10) for 0 h, 8 h, 1 d, 2 d, and 8 d. Antioxidant and non-specific immune parameters reveal hypothermia induced oxidative stress and immunosuppression. Liver ultrastructure alterations indicate hypothermia induced mitochondrial enlargement, nucleoli aggregation, and lipid droplet accumulation under hypothermia exposure. With the analysis of the transcriptome, differentially expressed genes (DEGs) induced by hypothermia were mainly involved in metabolism, immunity and inflammation, programmed cell death, and disease. Furthermore, the inflammatory response and apoptosis were evoked by hypothermia exposure in different immune organs. Interactively, apoptosis and inflammation in immune organs were correlated with antioxidation and immunity suppression induced by hypothermia exposure. In conclusion, these results suggest hypothermia-induced inflammation and apoptosis, which might be the adaptive mechanism of antioxidation and immunity in the freshwater drum. These findings contribute to helping us better understand how freshwater drum adjust to hypothermia stress.

Aplodinotus grunniens, known as freshwater drum, is a kind of eurythermal freshwater fish that is widely distributed in North America. In 2019, our research group reached a milestone on its artificial breeding and cultivation and have investigated its physiological adaption to the environment, providing a breakthrough and prospects for aquaculture. However, its adaptability and metabolic homeostasis to hypothermia is not fully understood. In this experiment, cold stress was conducted at 18 °C (LT18) and 10 °C (LT10) with 25 °C as control (Con) for 8 days to explore the effects of short-term hypothermia on the physiology and metabolism of freshwater drum. From the results, the level of free essential amino acids in LT18 and LT10 decreased significantly after 2 days cold stress compared with Con. Furthermore, plasma total triglyceride (TG) content and lipase (LPS) activity were decreased at LT10 for 2d. With RNA-seq in the liver, metabolic-related signaling, especially amino acid synthesis and lipid metabolism, was inhibited by hypothermia. Specifically, the PPAR signaling pathway is correlated with the inhibition of lipid and amino acid metabolism induced by hypothermia. These data confirmed that PPAR signaling maintains lipid and amino acid metabolic homeostasis during cold stress. These results give a theoretical foundation for hypothermia resistance in the area of metabolic homeostasis for freshwater drum.

Lipids are critical nutrients for aquatic animals, and excessive or insufficient lipid intake can lead to physiological disorders, which further affect fish growth and health. In aquatic animals, the gut microbiota has an important regulatory role in lipid metabolism. However, the effects of a high-fat diet on physical health and microbiota diversity in the gut of freshwater drum (Aplodinotus grunniens) are unclear. Therefore, in the present study, a control group (Con, 6%) and a high-fat diet group (HFD, 12%) were established for a 16-week feeding experiment in freshwater drum to explore the physiological changes in the gut and the potential regulatory mechanisms of bacteria. The results indicated that a high-fat diet inhibited antioxidant and immune capacity while increasing inflammation, apoptosis and autophagy in gut cells. Transcriptome analysis revealed significant enrichment in immune-related, apoptosis-related and disease-related pathways. Through 16S rRNA analysis, a total of 31 genus-level differentially abundant bacterial taxa were identified. In addition, a high-fat diet reduced gut microbial diversity and disrupted the ecological balance of the gut microbiota (Ace, Chao, Shannon and Simpson indices). Integrated analysis of the gut microbiota combined with physiological indicators and the transcriptome revealed that gut microbial disorders were associated with intestinal antioxidants, immune and inflammatory responses, cell apoptosis and autophagy. Specifically, genus-level bacterial taxa in Proteobacteria (Plesiomonas, Arenimonas, Erythrobacter and Aquabacteriumb) could serve as potential targets controlling the response to high-fat-diet stimulation.