In China, aquaculture costs have increased because of the increase in fish meal (FM) prices. Plant proteins, such as soybean meal, have the potential to replace FM partially and thus reduce the cost of aquatic feed. In this study, soybean meal (SBM) was fermented using compound microorganisms (lactic acid bacteria, yeast, and Bacillus). Fermented soybean meal (FSBM) replaced FM in the diet. The effect of replacing FM on largemouth bass was comprehensively evaluated at three levels: macro (growth performance), microbial (bacterial diversity and metabolic), and gene (key gene expression) levels. The results showed that FSBM increased the crude protein content by 7.45% and decreased the phytic acid concentration by 48.66% compared with original SBM. Compared with the control, the weight gain rate and feed conversion ratio showed no significant difference (p > 0.05) when the replacement amount of FM was less than 30%. Compared with the 50% FSBM treatment, the 10% and 30% treatments showed more steatosis in the liver slices. Although the replacement of FSBM with less than 30% did not have a significant (p < 0.05) negative impact on body weight, FSBM substitution adversely affected the height and width of the intestinal villi. The expression levels of Hepcidin-1, Hepcidin-2, TGF-β1, and IL-10 in 30% and 50% FSBM treatments were lower than those in the control, whereas the expression levels of SOD1 and SOD2 in 30% FSBM treatment were higher than those in the control group, and the expression level of SOD3a in 30% FSBM treatment was equal to the control. In addition, FSBM substitution could affect the composition of intestinal microorganisms and thus influence metabolic pathways, especially the biosynthesis of amino acids and plant secondary metabolites.

The oriental river prawn (Macrobrachium nipponense) is one of the most popular freshwater prawn in China. In order to study the relationships between morphometric traits and body mass across different geographical locations and provide references of phenotypic traits for the breeding of M. nipponense, we collected wild M. nipponense from three locations (main stream, HH; Suyahu Reservoir, SYH; and Wuyue Reservoir, WY) in the upper reaches of the Huaihe River, China, and measured 26 morphometric traits and body masses. We found that the coefficient of variation of body mass varied from 31.88% to 59.27% across the three populations, exceeding that of morphometric traits within each population. All 26 morphometric traits, except for the fourth abdominals somite length in the WY population, were observed to correlate significantly positively with body mass (p < 0.05). A path analysis indicated that propodus length, body length, ischium length, carapace height, and second abdominals somite length in the HH population; body length, propodus length, abdominal height, sixth abdominals somite length, and telson length in the SYH population; and body length, carapace height, fifth abdominals somite length, and abdominal height in the WY population significantly affected body mass directly (p < 0.05). Comparing the pathway analysis with the grey relation analysis, we can conclude that the trait most correlated with body mass was body length across the three geographical populations. These findings provide references of waiting morphological traits for M. nipponense selective breeding in different geographical populations.

Microcystis, a key genus of bloom-forming cyanobacteria in freshwater ecosystems, has garnered significant research interest due to its species diversity and population dynamics. This study investigated the water profiles and Microcystis populations at six stations in the Nanwan Reservoir (Xinyang, China) throughout 2022 to elucidate the morphological characteristics of Microcystis, analyze its population density patterns, and identify key environmental factors influencing its dynamics. The reservoir was classified as mesotrophic during most of the study period. Seven common Microcystis species were identified, including M. botrys, M. smithii, M. wesenbergii, M. firma, M. novacekii, M. aeruginosa, and a species suspected to be M. flos-aquae. The spatial and temporal distribution analyses revealed a bimodal fluctuation in Microcystis densities, with a monthly occurrence across stations except in August. The highest density, 1.71 × 10⁷ cells/L, was recorded in May, while the lower densities were observed from July to September. The Mantel test results indicated that the nitrogen levels, particularly ${\mathrm{NO}}_3^{-}$-N, were the primary factors influencing the Microcystis density. Additionally, both the reservoir bays and dam areas exhibited a high risk of Microcystis blooms. Effective management of nitrogen inputs, enhanced monitoring, and appropriate gate operations are recommended to mitigate the risk of Microcystis blooms in the Nanwan Reservoir.

Transport stress remains a significant challenge in aquaculture. To optimize sedation protocols, we evaluated MS-222 (tricaine methanesulfonate) for juvenile Xenocypris davidi by combining behavioral dose screening (32–50 mg L⁻¹) with gill transcriptomics and histology analysis. At 10 °C, behavioral screening identified 34 mg L⁻¹ as the minimum dose that induced stage A2 (deep sedation) without prolonging recovery. Following an 8-h simulated transport at this concentration, comparative gill transcriptomics revealed 1,220 differentially expressed genes between MS-222-sedated and unsedated control fish. The MS-222 group exhibited enriched glutathione metabolism and a concurrent reduction in transcripts associated with inflammatory signaling. Additionally, DNA repair and cell cycle pathways were positively enriched, whereas cell death, ion transport, and tight junction modules showed bidirectional modulation, suggesting complex tissue remodeling. Qualitatively, the MS-222 group showed a more regular lamellar arrangement. In conclusion, these behavioral and transcriptomic findings suggest that 34 mg L⁻¹ may serve as a potential sedation protocol for X. davidi transport at 10 °C. Furthermore, the molecular findings identify candidate gill pathways associated with MS-222 sedation, generating novel hypotheses for future unstressed-baseline studies.

Background/Objectives: The monotypic genus Araiocypris is currently classified in Xenocyprididae, yet its familial placement has long been controversial and lacks sufficient molecular phylogenetic support. Mitogenomic resources for the family Tanichthyidae remain limited, and the phylogenetic relationship between Araiocypris and tanichthyid species remains unexplored. This study was conducted to re-evaluate the taxonomic status of Araiocypris and characterize the mitogenomic evolution of Tanichthyidae. Methods: The complete mitochondrial genomes of Tanichthys huidongensis and Araiocypris batodes were sequenced, assembled and annotated. Comparative mitogenomic analyses were performed across seven Tanichthyidae species. A maximum-likelihood phylogenetic tree was reconstructed using concatenated sequences of 13 protein-coding genes and 2 ribosomal RNA genes to clarify the phylogenetic position of Araiocypris. Results: Based on mitochondrial phylogenomic evidence, phylogenetic reconstruction strongly supports the reassignment of A. batodes from Xenocyprididae to Tanichthyidae, as it nests within the Tanichthyidae clade and forms a sister group with the genus Tanichthys. Genetic divergence analysis confirms the validity of Araiocypris as a distinct genus. Tanichthyidae mitogenomes display highly conserved architecture with the typical vertebrate gene order. All protein-coding genes undergo strong purifying selection, with cox1 showing the slowest evolutionary rate. Conserved structural domains including CSB-F, CSB-E, CSB-D and CSB1–3 were identified in the control region. Conclusions: This study provides solid mitogenomic evidence for the familial reclassification of Araiocypris and systematically reveals the evolutionary patterns of Tanichthyidae mitogenomes, offering an important reference for further taxonomic and phylogenetic studies of Cypriniformes.