Jiahui Liu

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.

Background: The oriental river prawn (Macrobrachium nipponense) is an economically important aquaculture species in China. Methods: In this study, the genetic diversity and population structure of 12 populations were investigated using ten microsatellite markers. Among them, the Xiaolong Mountain (XLS) population is a cultured stock, while the Songjiachang Reservoir (SJC) population originates from the Yangtze River as an outgroup. Results: A total of 213 alleles were detected across 342 individuals, with an average of 21.3 alleles per locus. The observed heterozygosity (Ho) ranged from 0.362 to 0.902 (mean = 0.724), and the expected heterozygosity (He) ranged from 0.581 to 0.925 (mean = 0.805). Shannon’s diversity index (I) ranged from 1.224 to 2.810 (mean = 2.130). The polymorphism information content (PIC) varied from 0.532 to 0.920 (mean = 0.787), indicating high informativeness of the markers. Population structure analysis revealed a weak genetic subdivision with a subtle clustering signal (K = 2), but evaluation of LnP(K) indicated that K = 1 could not be confidently rejected. Pairwise Fst values ranged from 0.008 to 0.058, with high gene flow (Nm = 4.060–31.000), denoting low-to-moderate genetic differentiation. AMOVA showed that 98% of genetic variation resided within populations, with only 2% among populations (overall Fst = 0.020, p < 0.01). Nei’s genetic distances ranged from 0.094 to 0.277. Conclusions: Overall, the 12 populations of M. nipponense exhibited high genetic diversity, low-to-moderate genetic differentiation, and a weak population structure with most variation residing within populations. These findings provide valuable molecular markers for selective breeding and offer theoretical guidance for the conservation and sustainable utilization of M. nipponense germplasm resources, although the inferred population structure should be interpreted with caution given the weak differentiation signal.

Biofloc technology (BFT) is an innovative ecological aquaculture approach designed to reduce nitrogen concentrations, provide an in-situ food source, and remove pollutants from culture systems. This is achieved by manipulating the carbon-to-nitrogen (C/N) ratio by adding carbon sources to the aquaculture water. In this study, three C/N ratios were evaluated: 8:1 (group A), 18:1 (group B), and 22:1 (group C). The results showed that group C performed best in terms of end mean weight (78.33 ± 1.79 g) and specific growth rate (1.08 ± 0.08%/d), which were not significantly different from group A but significantly better than group B (P< 0.05). Water quality analysis showed that nitrite nitrogen concentrations were significantly lower (P< 0.05) in groups B and C than in group A. The diversity indices of groups B and C were significantly higher than those of group A (PFlavobacterium and Sphaerotilus were the dominant bacteria in group C. The research shows that adjusting the C/N in the water to 22:1 can optimize the biofloc flora structure and promote the growth of crucian carp.

Dress-out traits, such as abdominal meat weight and abdominal meat percentage, are difficult to improve through direct selection in aquatic species due to the lack of reliable measurement methods. To facilitate the prediction of these traits from morphological characteristics in live prawn, Exopalaemon modestus, a total of 518 individuals were collected in 2025 from Suyahu Reservoir in the upper Huaihe River, China. After excluding individuals with incomplete appendages and egg-bearing females, 301 prawns were randomly selected for model development, and the remaining 60 were used for validation. Based on integrated grey relational analysis and path analysis, body mass was identified as the most effective predictor of abdominal meat weight (p < 0.01), explaining 92.1% of the variation when used as the sole variable in the model. Residual analysis and cross-validation confirmed the adequacy and applicability of the abdominal meat weight model. In contrast, morphological traits exhibited low explanatory power for abdominal meat percentage, with all traits together explaining only 19.2% of the variance, indicating their inability to effectively predict this trait. Therefore, in breeding programs for E. modestus, indirect improvement in abdominal meat weight can be achieved via direct selection for increased body mass. However, abdominal meat percentage is not recommended as a target trait for genetic improvement.

The Siberian prawn Exopalaemon modestus is a commercial freshwater shrimp with high nutritional value in China. To analyze the influence of morphometric traits on the body weight of E. modestus and identify effective indicators for breeding programs of E. modestus , we analyzed the correlations between 12 morphometric traits and body weight using correlation analysis, path analysis, multiple regression analysis, and grey relational analysis. Path analysis showed that body length (BL), carapace height (CH), carapace width (CW), and abdominal width (AW) significantly affect body weight (BW) directly ( P < 0.05). BL had the most significant direct effect (0.721) on body weight. The total determination coefficients of four significant morphometric traits on body weight were 0.906 (>0.85), indicating that substantial morphometric traits explained 90.6% of BW variation. The regression equation was constructed as BW=-1.666+0.049BL+0.045CH+0.035CW+0.021AW ( P < 0.01, R² = 0.906). Grey relational analysis identified that the trait most correlated with BW was BL (relational grade = 0.952), followed by carapace length (CL), abdominal length (AL), and CH. Combined with path analysis and grey relational analysis, BL and CH were the key morphometric traits influencing the body weight of E. modestus . These results provided references for candidate morphometric traits for E. modestus selective breeding programs.

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.

This study aims to investigate the effects of potassium diformate (KDF) and sodium propionate (NaP) on gut digestive and immune functions, intestinal microbiota, and lipid metabolites of Trachinotus ovatus based on multiomics approach. Juvenile T. ovatus (initial weight: 8.65 ± 0.02 g) were subjected to a 56‐day feeding regimen. Three isonitrogenous and isolipidic diets, including the control (CG), an additional 6.6 g/kg of KDF, and an additional 6.0 g/kg of NaP were fed to juvenile fish twice daily. Results showed that KDF and NaP supplementation significantly increased the activities of chymotrypsin (Chy), lipase (Lip), α‐amylase (α‐amy), creatine kinase (CK), Na ⁺ K ⁺ ‐ATPase (Na ⁺ K ⁺ ‐ATP), γ‐glutamyl transferase (γ‐GT), alkaline phosphatase (AKP), glutathione peroxidase (GSH‐Px), total antioxidant capacity (T‐AOC), and superoxide dismutase (SOD) as well as the expression level of Nrf2 ( p < 0.05), while decreased the pH value, malondialdehyde (MDA) content and the mRNA level of Keap1 ( p < 0.05). Dietary KDF and NaP markedly enhanced microbial α‐diversity and induced significant shifts in microbiota composition through selective modulation of bacterial populations, such as Photobacterium , Mycoplasma , and Mycobacterium ( p < 0.05). Besides, KDF and NaP led to notable alterations in the intestinal metabolite lipidome through increasing short‐chain fatty acids (SCFAs) levels, upregulating the abundance of phosphatidylcholine (PC), phosphatidylethanolamine, methyl PC (MePC), lysophosphatidic acid, ceramide (Cer), sitosteryl, monogalactosyldiacylglycerol, coenzyme, and lysophosphatidylethanolamine and downregulating the abundance of sphingomyelin and monoglyceride ( p < 0.05). The assessment of associations revealed inverse relationships of digestive and antioxidative indices with Photobacterium , but positive correlations with Mycoplasma , Mycobacterium , Ruegeria , Synechococcus , Nautella , Turicibacter , and Roseovarius . This study advances our understanding of KDF and NaP on intestinal health.