Amur minnow (Rhynchocypris lagowskii), an economically important freshwater fish, inhabits tributaries of the Heilongjiang River to Yangtze River in China. Thus far, no genome data of this species have been reported. In this study, we constructed chromosome-level genome assembly for R. lagowskii by integration of MGI, PacBio HiFi and Hi-C sequencing technologies. The assembled genome was 1,041.22 Mb in size, with the scaffold N50 of 32.63 Mb, and 99.04% of the sequences (1,007.75 Mb) were anchored to 25 chromosomes. A total of 32,425 protein-coding genes were predicted in the final assembly, of which 91.09% were functionally annotated. The BUSCO score of genome assembly and protein annotation were 96.32% and 97.53%, respectively, indicating a high quality of genome assembly. The high-quality genome serves as a critical resource for in-depth investigations on comparative genomics, population genetics, molecular breeding, and functional exploration of this economically important fish.

Length-weight relationships (LWRs) were reported for ten fish species (Abbottina rivularis, Hemibarbus labeo, Hemibarbus maculatus, Onychostoma macrolepis, Opsariichthys bidens, Rhynchocypris lagowskii, Schizothorax prenanti, Sinibrama macrops, Zacco platypus, and Siniperca scherzeri). Fishes were collected from 62 sampling stations covering an area of ∼7000 km2 in the Qinling Mountains, characterized by unique fauna and distribution pattern, using gillnets and ground cages during June to December 2022. The intercept a ranged from 0.013 for S. prenanti to 0.060 for H. labeo, and the slope b ranged from 2.537 for H. labeo to 3.079 for Z. platypus.

Beneficial effects of indigenous Bacillus spp. on growth, antioxidants, immunity and disease resistance of Rhynchocypris lagowskii

Characterization of Bacillus spp. isolated from the intestines of Rhynchocypris lagowskii as a potential probiotic and their effects on fish pathogens

Probiotics have been widely used in aquaculture. This article aims to study the effect of Bacillus amyloliquefaciens LSG2-8 on the intestinal barrier function of Rhynchocypris lagowskii. B. amyloliquefaciens LSG2-8 were added to R. lagowskii basal diets (CK) as additives at four concentrations: 1.0 × 106 (D-6), 1.0 × 107 (D-7), 1.0 × 108 (D-8) and 1.0 × 109 (D-9) CFU/g by dry weight of basal diet. After a 56 days feeding experiment, the intestinal digestive enzymes and immune enzymes activity of R. lagowski on group D-6, D-7, D-8 and D-9 diet were significantly higher than the control (P < 0.05). In molecular experiments, we found that the levels of TGF-β mRNA, IL-10 mRNA, ZO-1 mRNA and Claudin-3 mRNA in group D-8 R.. lagowskii were significantly higher (P < 0.05) than the control and other groups. Furthermore, the levels of IL-1β and IL-8 mRNA of R. lagowski on group D-6, D-7, D-8 and D-9 diet were significantly lower than the control (P < 0.05). In addition, we found that B. amyloliquefaciens LSG2-8 can regulate the intestinal flora balance and improve the intestinal structure of R. lagowskii. In conclusion, B. amyloliquefaciens LSG2-8 can improve the intestinal barrier function of R. lagowskii,and can be used as a feed additive in aquaculture.

Based on the data of seine surveys (June 2018 and 2019, 57 and 38 catches), species composition and structure of fish communities of the middle and low Amur River were studied. The species richness of fish in the low Amur River is higher compared to the middle Amur River, 37 and 22 species, respectively. Upstream of the Amur River, fish biomass falls. At the beginning of summer, its average value in the low Amur was equal 1,354±0,209 g/m2, in the middle Amur – 0,324±0,058 g/m2. In the middle Amur River, the fish biomass was dominated by Hemiculter spp. (29,1%), Opsariichthys bidens (28,0%), Leuciscus waleckii (22,1%), Squalidus spp. (7,5%) and Tachysurus sinensis (3,9%). In the catches on the low Amur River, the fish biomass was dominated by Hemiculter spp. (26,2%), Leuciscus waleckii (21,0%), Hypomesus olidus (18,1%), Rhynchocypris lagowskii (7,6%), Carassius gibelio (7,2%), Rhodeus sericeus (5,0%) and Xenocypris macrolepis (4,6%). Local maxima of fish abundance were determined by the ecological preferences of most common fish species (in particular, their reopreferendum).

The protective role of vitamin C on intestinal damage induced by high-dose glycinin in juvenile Rhynchocypris lagowskii Dybowski

Long-term ecological restoration can restore aquatic ecosystems to a certain extent and alleviate the crisis of freshwater fish biodiversity. In order to explore the fish community distribution patterns and key factors after ecological restoration and the health status of the watershed, fish and environmental data were collected from 39 sampling points in the Hun River Basin in the spring and autumn of 2021. A total of 51 fish species belonging to 11 families and 37 genera were collected during the survey, and the dominant species were Rhynchocypris lagowskii, Zacco platypus, Carassius auratus and Pseudorasbora parva. Compared with the results of past studies, the number of fish species has increased. The study found that the distribution of fish along the longitudinal gradient of the watershed showed obvious spatial differences and was divided into two groups. The results of canonical correspondence analysis (CCA) showed that agricultural land, urban land and grassland were the key factors for the spatial variation in fish communities in the Hun River Basin. The results of the F-IBI evaluation showed that the health status of the Hun River was fair or above fair, among which healthy, good, fair, poor and bad points accounted for 5.13%, 30.77%, 33.33%, 25.64% and 5.13%, respectively. The upper and middle reaches of the Hun River Basin were in better health, while the lower reaches were in poorer health, which was mainly affected by the intensity of human activities in different regions. This study will help watershed managers to make targeted restoration and protection measures for different regions.

The widely available crop oil is an effective alternative to the increasingly scarce marine fish oil. However, simple alternative strategies have led to declining growth and the edible value of farmed fish. It is worthwhile to explore the effects of micro supplements in diets to improve the tolerance of fish to different dietary lipid sources, which finally optimizes the feeding strategies. This study aimed to investigate the regulation of L-carnitine and dietary oil conditions on nutrient composition, lipid metabolism, and glucose regulation of Rhynchocypris lagowskii. Four diets were prepared according to fish oil, fish oil supplemented with L-carnitine, corn oil, and corn oil supplemented with L-carnitine, and FO, LCFO, CO, and LCCO were labeled, respectively. R. lagowskii was fed experimental diets for 8weeks, and the glucose tolerance test was performed. The CO diet significantly resulted in higher crude lipid content in muscle but a lower level of serum lipid parameters of R. lagowskii than the FO diet. However, dietary L-carnitine supplementation significantly reduced the crude lipid content in the hepatopancreas and muscle of the fish fed with the CO diet yet increased the serum lipid parameters. Additionally, the crude lipid content of muscle was reduced in the fish fed with an FO diet supplemented with L-carnitine. Compared with the FO diet, the CO diet significantly reduced the ratio of n3/n6 polyunsaturated fatty acid in the hepatopancreas and muscle of R.lagowskii. Dietary L-carnitine supplementation significantly reduced the contents of total saturated fatty acids and total monounsaturated fatty acids in hepatopancreas under both dietary lipid sources. The CO diet significantly up-regulated the expression of genes related to lipid uptake and adipogenesis in hepatopancreas, including lipoprotein lipase (lpl), acetyl-coenzyme A carboxylase alpha (accα), and sterol regulatory element binding protein-1 (srebp1), compared with the FO diet. While dietary L-carnitine supplementation significantly down-regulated the expressions of lpl, accα, srebp1, and fatty acid synthase in hepatopancreas and muscle of fish under both dietary lipid sources, along with up-regulated expression of carnitine palmitoyltransferase 1 in hepatopancreas. Moreover, the fish fed with a CO diet significantly increased the expression of glucose uptake and clearance and significantly down-regulated the expressions of glucose regulation-related genes, including glucose transporter 1, glycogen synthase 1, and phosphofructokinase in hepatopancreas and muscle, resulting in slower glucose uptake and clearance than fish fed with FO diet. Nevertheless, dietary L-carnitine supplementation up-regulated the expression of gluconeogenesis-related genes, including glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the hepatopancreas of R. lagowskii under both dietary lipid sources. In conclusion, a higher dietary n6 PUFA resulted in lipid deposition, decreased serum lipid parameters, and limited serum glucose utilization of R. lagowskii. While the regulatory effect of L-carnitine on lipid metabolism and glucose utilization of R. lagowskii varies with dietary lipid sources and tissues.

Between 1975 and 2021 the diversity of fish communities of mountain rivers was studied in seven areas of the river Amur drainage: “Onon”, “Upper Zeya”, “Upper Bureya”, “Upper Amgun”, “Lower Amgun”, “Khingan”, “Lower Amur and Ussuri”. In these areas, various reaches of typical mountain watercourses were surveyed: 1) upper reaches (24), 2) “middle” (17) and 3) “lower” (10); 9 small mountain tributaries of lowland rivers – Amur and Ussuri, 5 mountain lakes and 6 floodplain reservoirs. According to the results of the research, 6 main types of communities were identified, including river ones: 1) upper reaches, 2) “middle” parts, 3) “lower” parts, 4) small mountain tributaries of large lowland rivers. Lake communities are represented by two main types of communities: 5) mountain lakes and 6) floodplain water bodies. In river communities, 30 fish species and one lamprey species were found; river communities are dominated by Barbatula toni, Cottus szanaga, Brachymystax tumensis, species of the genus Thymallus, as well as Rhynchocypris lagowskii and Phoxinus phoxinus. Upper reaches communities include from 4 to 12–13 species. Barbatula toni, Cottus szanaga, Brachymystax tumensis, and species of the Thymallus dominate here. In the communities of the middle parts of the rivers, there are from 7 to 17 species. Up to 23 species and one lamprey species are found in the lower parts. In the upper reaches and middle sections of the rivers, the composition of the community changes during the year as a result of seasonal migrations. In communities of mountain lakes 6 species of fish were found; three species are most common: Barbatula toni, Cottus szanaga, Brachymystax tumensis. 8 species inhabit floodplain water bodies, dominated by Rhynchocypris percnurus, Perccottus glenii, Misgurnus mohoity. The specificity of the region's coenotic diversity is determined by its position in the Amur basin, the presence or absence of mountain and floodplain lakes, as well as geomorphological and paleogeographic features.

This study evaluated the effects of dietary administration of two indigenous Bacillus (A: basal control diet; B: 0.15g/kg of Bacillus subtilis; C: 0.1g/kg of Bacillus subtilis and 0.05g/kg of Bacillus licheniformis; D: 0.05g/kg of Bacillus subtilis and 0.1g/kg of Bacillus licheniformis; E: 0.15g/kg of Bacillus licheniformis) on the digestive enzyme activities, intestinal morphology, intestinal immune and barrier-related genes relative expression levels, and intestinal flora of Rhynchocypris lagowskii. The results showed that the fold height, lamina propria width, and muscle layer thickness of midgut and hindgut in group C were significantly higher than that of group A (P < 0.05). The activities of protease, amylase, and lipase in group C were significantly higher than those of group A (P < 0.05). The relative expression levels of IL-1β and IL-8 in the intestine of group C were significantly downregulated, and the relative expression levels of IL-10 and TGF-β were significantly upregulated (P < 0.05). The relative expression levels of Claudin-2 in group A significantly increased and the relative expression levels of Claudin-4 in group A significantly reduced compared with other groups (P < 0.05). The relative expression levels of ZO-1 in groups C and D were significantly higher than those of other groups (P < 0.05). The Bacillus in the intestine of group C has the highest relative abundance among all groups. Overall, it can generally be concluded that dietary supplementation of indigenous Bacillus subtilis and Bacillus licheniformis (group C) can improve the intestinal morphology, digestion, and absorption enzyme activities, enhance intestinal mucosal immunity and barrier function, and maintain the intestinal microbial balance of R. lagowskii.

Taurine can improve intestinal function and integrity in juvenile Rhynchocypris lagowskii Dybowski fed high-dose glycinin

Alleviative effect of biofloc technology (BFT) on extruded soybean meal (ESBM)-induced growth inhibition and intestinal barrier dysfunction in Rhynchocypris lagowskii

Inhibitory effect of probiotic Bacillus spp. isolated from the digestive tract of Rhynchocypris Lagowskii on the adhesion of common pathogenic bacteria in the intestinal model

The effect of adding Bacillus amyloliquefaciens LSG2-8 in diets on the growth, immune function, antioxidant capacity, and disease resistance of Rhynchocypris lagowskii

A comparative study on the effects of supplemental L-carnitine on fatty acids composition, energy status and related genes expression in Cyprinus carpio var. Jian and Rhynchocypris lagowskii (Dybowski, 1869)

In this study, the phylogeographical pattern of the Amur minnow (Rhynchocypris lagowskii) widely distributed in the cold freshwaters of the Qinling Mountains was examined. A total of 464 specimens from 48 localities were sequenced at a 540‐bp region of the mitochondrial cytochrome b (Cytb) gene, and 69 haplotypes were obtained. The mean ratio of the number of synonymous and nonsynonymous substitutions per site (dN/dS) was 0.028 and indicated purifying selection. Haplotype diversity (h) and nucleotide diversity (π) of natural populations of R. lagowskii varied widely between distinct localities. Phylogenetic trees based on Bayesian inference (BI), maximum likelihood (ML), and maximum parsimony (MP) methods, and network analysis showed five well‐differentiated lineages, but these did not completely correspond to localities and geographic distribution. Meanwhile, analysis of molecular variances (AMOVA) indicated the highest proportion of genetic variation was attributed to the differentiation between populations rather than by our defined lineages. In addition, there was no significant correlation between the pairwise Fst values and geographic distance (p > .05). Based on the molecular clock calibration, the time to the most recent common ancestor (TMRCA) was estimated to have emerged from the Late Miocene to the Early Pleistocene. Finally, the results of demographic history based on the neutrality test, mismatch distribution, and Bayesian skyline plot (BSP) analyses showed that collectively, the populations were stable during the Pleistocene while one lineage (lineage E) probably underwent a slight contraction during the Middle Pleistocene and a rapid expansion from the Middle to the Late Pleistocene. Therefore, the study suggests the current phylogeographical pattern of R. lagowskii was likely shaped by geological events that led to vicariance followed by dispersal and secondary contact, river capture, and climatic oscillation during the Late Miocene to the Early Pleistocene in the Qinling Mountains.

The study was aimed at investigating the effects of Bacillus velezensis LSG2-5 isolated from host’s intestinal tract on growth performance, immune response, antioxidant capacity, and disease resistance of Amur minnow (Rhynchocypris lagowskii Dybowski). 535 fish were divided into 5 groups with 3 replicates per group. Diets containing different doses (0, 106, 107, 108, and 109 CFU/g, respectively) of B. velezensis LSG2-5 were used to feed fish ( 9.95 ± 0.05 g) for 56 days. Results showed that compared with control, weight gain rate and specific growth rate of fish were significantly increased by dietary 107-109 CFU/g B. velezensis ( p &lt; .05 ). While for the feed conversion ratio, all treatment groups were significantly decreased ( p &lt; .05 ). In serum, the contents of lysozyme and immunoglobulin M were significantly increased by dietary 106-109 CFU/g B. velezensis ( p &lt; .05 ); the activities of component 3, component 4, and alkaline phosphatase were significantly increased by dietary 108 CFU/g B. velezensis ( p &lt; .05 ). The activities of catalase, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in hepatopancreas were significantly increased by dietary 108-109 CFU/g B. velezensis ( p &lt; .05 ). The activities of catalase, glutathione, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in the intestinal tract of 108 CFU/g group were significantly increased ( p &lt; .05 ). However, malondialdehyde levels in the hepatopancreas and intestines were significantly decreased by dietary 107-108 CFU/g B. velezensis ( p &lt; .05 ). Dietary 107-109 CFU/g B. velezensis significantly upregulated catalase, glutathione peroxidase, and copper/zinc superoxide dismutase mRNA levels ( p &lt; .05 ). The levels of transforming growth factor β and interleukin-10 mRNA in the hepatopancreas of fish fed with B. velezensis of 108 CFU/g were significantly increased ( p &lt; .05 ), and these in the intestinal tract of 106-109 CFU/g groups were upregulated ( p &lt; .05 ). Feeding dietary 107-108 CFU/g B. velezensis significantly downregulated interleukin-8, interleukin-1β, and tumour necrosis factor α mRNA levels in hepatopancreas and intestines ( p &lt; .05 ). After 56 days of feeding, 225 fish ( 23.20 ± 0.59 g) were challenged with Aeromonas hydrophila (108 CFU/g), and survival rates were recorded for the next 14 days. Meanwhile, the serum immune parameters of fish were determined. Results showed that compared with control, the survival rates of the treatment groups were significantly increased ( p &lt; .05 ). Lysozyme, component 3, component 4, immunoglobulin M, acid phosphatase, and alkaline phosphatase levels in serum by dietary106-109 CFU/g B. velezensis showed significant promoting effects ( p &lt; .05 ). In conclusion, dietary 107-109 CFU/g B. velezensis boosts the growth, immunity, antioxidant capacity, and against A. hydrophila infection of Amur minnow. Regression analysis suggested that the optimal dose of B. velezensis LSG2-5 in the Amur minnow diet was 5.00 × 10 8 CFU/g.

Evaluating the probiotic potential and adhesion characteristics of Bacillus spp. isolated from the intestine of Rhynchocypris lagowskii Dybowski

The effects of L-carnitine (LC) and dietary lipid on the growth and health of farmed fish are still conflicting. This study aimed to explore the effects of LC supplementation and dietary fish oil replacement by corn oil on growth performance, antioxidant, immune function and histomorphology of Rhynchocypris Lagowskii. Six diets were evaluated as follows: dietary fish oil as 50% and 100% replacement by corn oil, and differing in LC supplementation (0 and 400 mg/kg), were tested in R. Lagowskii for 8 weeks. The highest weight gain rate, specific growth rate and feed efficiency were observed in mix oil diets with LC. The diet with LC significantly increased the total antioxidant capacity level, total superoxide dismutase, alkaline phosphatase, lysozyme activities and immunoglobulin M, complement levels in liver and intestine compared with corn oil diet (p < 0.05). Moreover, the diet with LC significantly up-regulated the nuclear factor E2-related factor 2 (p < 0.05), and significantly down-regulated the interleukin-1-beta and tumour necrosis factor-alpha expression in liver and intestine compared with corn oil diet (p < 0.05). In conclusion, LC supplementation improved the weakening of growth performance, antioxidant capacity, immune function and tissue health caused by R. lagowskii intake of corn oil diets.