Housefly maggot larvae (HML) have been identified as a potential alternative animal diet for the fattening process of the Chinese mitten crab (Eriocheir sinensis). However, the feasibility and potential impacts of HML supplementation require further investigation. The present study evaluated the effects of dietary HML on the growth indices, nutrient compositions, antioxidant activity, and texture profiles of edible tissues of E. sinensis. The results showed that dietary HML supplementation effectively improved the hepatic steatosis index of both genders and sweet amino acid content of edible tissues (except for male gonad) (p < 0.05). Additionally, dietary HML significantly increased the total antioxidant capacity in the gonad and female muscle (p < 0.05). For the textural properties, HML feeding significantly improved the adhesiveness in the male muscle, and the cohesiveness, chewiness, and resilience in the female muscle (p < 0.05). Furthermore, HML feeding significantly decreased the levels of the equivalent umami concentration of the male gonad, male muscle, and hepatopancreas (p < 0.05). Conversely, HML feeding significantly increased the sweetness value in the muscle, hepatopancreas, and female gonad (p < 0.05). Our findings indicate that HML could serve as a viable alternative feed for fattening to improve the edible yield and change the flavor characteristics in E. sinensis.

Environmental DNA (eDNA) metabarcoding was utilized to compare the fish species composition, diversity, and their relationships with environmental factors in four medium-sized drinking water reservoirs (Tongjiqiao, Andi, Shafan, and Jinlan) within the Qiantang River Basin during both wet and dry seasons. A total of 44 fish species belonging to 6 orders, 15 families, and 40 genera were detected, with Cyprinidae being identified as the dominant family (68.2%). Silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) were identified as the most abundant species, representing 81.94% and 99.98% of the relative eDNA abundance, respectively. The fish communities were characterized by river-resident species (59.1%), pelagic species (43.2%), and omnivorous (43.2%) and carnivorous (43.2%) feeding habits. Significant influences of seasonal and reservoir-specific variations on physicochemical parameters, species composition, and ecological traits were observed. However, no significant differences in community diversity (Chao1, Pielou_e, Shannon, and Simpson indices) or distribution patterns were detected between wet and dry seasons. In contrast, Jinlan Reservoir was found to exhibit distinct diversity and distribution patterns compared to the other three reservoirs, which was consistent with the relative eDNA abundance of H. molitrix and H. nobilis. Through a Spearman correlation analysis, the relative abundance of H. molitrix was revealed to be negatively correlated with community diversity, while H. nobilis was shown to have positive correlations (except with Chao1). This suggests that the excessive stocking of H. molitrix may lead to reduced diversity, whereas moderate stocking of H. nobilis could promote diversity restoration. Among physicochemical factors, Chao1 richness was found to be negatively correlated with conductivity, pH, phosphate–phosphorus (PO₄-P), and the total nitrogen to total phosphorus ratio (TN/TP), while Shannon and Simpson diversity indices were negatively correlated with nitrate nitrogen (NO₃-N) concentrations. A redundancy analysis (RDA) identified NO₃-N and permanganate index (COD_Mn) as the primary physicochemical drivers of fish community structure, indicating that while physicochemical differences were found to influence species composition and diversity, their effects were considered relatively limited. These findings suggest that the overwhelming dominance of H. molitrix and H. nobilis in the reservoirs may reduce the influence of seasonal variations and cross-reservoir physicochemical disparities on fish community dynamics.

Pearl culture has long been a major global industry. As a significant global producer, China mainly produces pearls from the freshwater mussel (Sinohyriopsis cumingii). S. cumingii with various shell colors can produce pearls of different colors; for example, mussels with a blue-white shell can produce white pearls, while those with a purple shell can produce light-purple pearls. Therefore, investigating the molecular genetics of shell color variation in S. cumingii can advance our understanding of the mechanisms underlying differences in shell and pearl coloration in these mussels. In this study, we selected juvenile S. cumingii with four differently colored inner shells and collected tissue samples for transcriptomic analysis. The results showed that many key genes involved in the regulation of pigment metabolism (such as ADAMTS, TYR, BCDO2, and FTH1), as well as those associated with metabolism and mineral absorption (such as TRPV6, HCP1, HEPH, and Zip4), exhibited significant differences. Furthermore, these DEGs (differentially expressed genes) may influence the synthesis and metabolism of melanin, carotenoids, porphyrins, and heme, thereby affecting shell color variation; they might also be one of the potential reasons why S. cumingii produces pearls of different colors.

Grass carp is a key herbivorous freshwater fish, yet long-term inbreeding reduces growth rates. Current genome-wide association studies (GWAS) primarily focus on a limited range of growth traits, while intestinal morphology is likely to emerge as a promising new proxy for both growth performance and health status. We reared juvenile grass carp from one batch in indoor vs. natural aquatic vegetation groups for 100 days, measuring body weight (BW), length (BL), height (BH), and intestinal length (IL) in 200 individuals (100/group). Phenotypic differences were significant for all traits, with IL most variable. GWAS identified 95 significant SNPs, among which 21 were related to multiple traits. Candidate gene and KEGG pathway analyses linked these SNPs to myogenesis, skeletal development, immunity, calcium signaling, and stress resistance. Twelve SNPs were found to be associated with IL, including 8 multi-trait-related and 4 trait-specific ones. This suggests that IL can serve as a supplementary growth trait. There was no overlap with prior GWAS, but recurrent signals on chromosomes 1, 2, 14 (BW) and 2, 3, 14, 24 (BH) merit further study. Our findings enrich molecular resources for grass carp and highlight IL’s potential for marker-assisted breeding.

Farming models profoundly influence the biological traits of aquatic organisms. This study compared muscle nutrients, muscle transcriptome, and gut microbiota of Pelodiscus sinensis reared under rice-field and pond conditions. Compared with the pond group (Group P), the rice-field group (Group R) exhibited significantly lower linoleic acid (LA) and higher arachidonic acid (ARA), indicating an altered muscle fatty acid profile. Transcriptomic analysis further showed that differentially expressed genes were mainly involved in fatty acid metabolic processes. For gut microbiota, Group R had a higher relative abundance of Firmicutes_C at the phylum level, and Acidaminococcus was uniquely detected at the genus level. These findings reveal that rice-field culture drives distinct muscle fatty acid profiles and gut microbial characteristics in P. sinensis, providing a theoretical basis for understanding the effects of rice-field culture on turtle nutrition and intestinal health.

This study evaluated the effects of partially or completely substituting fishmeal and fish oil with dried housefly (Musca domestica) maggots on the growth, nutritional composition, antioxidant capacity, and immunity of Chinese mitten crab (Eriocheir sinensis). An 8-week feeding trial was conducted using three isonitrogenous and isolipidic diets: T1, a control formulated feed containing 350 g/kg fishmeal and 40 g/kg fish oil; T2, a formulated feed containing 200 g/kg fishmeal and 29 g/kg fish oil, supplemented with 161 g/kg dried housefly maggots; and T3, a formulated feed containing no fishmeal and 15 g/kg fish oil, supplemented with 375 g/kg dried housefly maggots. The results showed that T2 maintained survival and growth comparable to the control while enhancing the HSI, EAA profiles, and n-3/n-6 ratio, along with elevated antioxidant capacities (CAT and GSH-Px) and lysozyme activity. In contrast, T3 increased the EAA, TAA, and EAA-related ratios, while elevating the BAA, atherogenic index and thrombogenic index, but reducing the beneficial PUFA and suppressing immune parameters. Notably, T3 did not induce excessive hepatopancreatic lipid accumulation. A mineral analysis revealed tissue-specific deposition patterns, with muscle accumulating K, Ca, Zn, Cr, and Cu, while the hepatopancreas retained a higher Ca, Fe, and Se. Despite the increased Cr and Cu accumulation with maggot inclusion, all levels remained within safety limits, posing no health risk to crabs. These findings demonstrate that dried housefly maggots represent a viable alternative protein and lipid source for crabs, with 161 g/kg being the preferable inclusion level among the two tested levels. Inclusion at 161 g/kg provides nutritional complementarity with the formulated feed and enhances the immune function, while inclusion at 375 g/kg disrupts the nutritional balance and immunological homeostasis. This study provides a scientific foundation for optimizing maggot-based feeding strategies in sustainable crustacean aquaculture.