Calcium delivery systems based on food‐derived peptides and polysaccharides offer a promising strategy for improving calcium bioavailability while preserving peptide bioactivity. In this study, a fructooligosaccharide‐ Larimichthys crocea peptide (FOS‐LCP) copolymer was fabricated by wet‐heating and evaluated as a multifunctional calcium carrier. FOS‐LCP showed improved calcium‐binding capacity, digestive stability, and resistance to dietary inhibitors, thus increasing Ca ²⁺ uptake and transport in intestinal models in vitro. Bone marrow mesenchymal stem cells isolated from calcium–deficient mice were used to assess bone‐lipid regulation in vitro. In the presence of Ca ²⁺ , FOS‐LCP promoted osteogenic differentiation and osteogenic marker expression, suppressed adipogenic differentiation, activated the Wnt/β‐catenin pathway, inhibited PPARγ/C/EBPα‐driven lipogenesis, reduced adipokine secretion, and enhanced lipolytic gene expression. These findings indicate that FOS‐LCP coordinately enhances calcium absorption and rebalances bone‐lipid metabolism at the cellular level, supporting wet‐heating‐derived peptide‐polysaccharide copolymers as promising functional calcium delivery systems.

Microbial communities associated with fish mucosal tissues play important roles in host health and environmental adaptation. However, the effects of contrasting aquaculture conditions on the microorganisms of the large yellow croaker (Larimichthys crocea, L. crocea) remain poorly understood. In this study, 16S rRNA gene sequencing was used to compare the gut and gill microbiota of L. crocea cultured in a marine system and a saline–alkaline system, together with the corresponding surrounding water samples. The results showed that both host tissue type and rearing environment significantly influenced microbial community structure. Water samples generally exhibited higher alpha diversity than host-associated samples, whereas the gut and gill communities were clearly separated from the surrounding water microbial community. The intestine showed stronger culture system differentiation than the gill, suggesting greater niche selectivity, while the gill retained a closer association with the rearing water. Across multiple taxonomic levels, microbial composition differed markedly among water, gut, and gill samples, and the divergence between the marine culture and saline–alkaline culture system became more pronounced at finer taxonomic resolution. Differentially enriched taxa further revealed clear tissue- and habitat-associated microbial patterns. In addition, several dominant taxa were significantly correlated with environmental variables, especially salinity and nutrient-related factors, indicating that physicochemical heterogeneity contributed substantially to microbial community assembly. Overall, this study shows that host mucosal niche and rearing environment are associated with distinct gut and gill microbiota patterns in L. crocea and provides preliminary ecological information for future microbiome-informed aquaculture management, functional validation of candidate taxa, and the development of land-based culture systems for marine fish.

Gut microbiome development during fish growth involves not only taxonomic turnover but also changes in the persistence and ecological dominance of microbial members. Here, we characterized the gut microbiota of D. maruadsi across three successive growth-associated body-size groups: the early-growth group (BLEGC; 4.98–6.81 g), middle-growth group (BLMG; 16.67–19.63 g), and late-growth group (BLLGC; 27.30–28.66 g). The three groups were successively sampled from the same cohort continuously reared in the same culture system. Fish received the same diet formulation throughout cultivation, with feeding quantity adjusted according to growth stage. At each stage, 15 fish were sampled, and rinsed intestinal tissues from five individuals were pooled to generate one composite sample, yielding three pooled intestinal samples per growth stage. Gut bacterial communities differed significantly among growth stages (ANOSIM: R = 0.2593, p = 0.005), while Pseudomonadota remained the dominant phylum across all groups. Complementary PERMANOVA supported an overall stage-associated difference, although PERMDISP also indicated heterogeneous multivariate dispersion among stages. Growth-associated restructuring became more evident at finer taxonomic levels and was accompanied by a pronounced contraction of stage-specific microbial membership. The number of unique ASVs declined from 361 in BLEGC to 286 in BLMG and 69 in BLLGC, whereas 84 ASVs were shared across all three stages. Forty ASVs met the global persistent criterion of detection in at least eight of the nine pooled samples, and their abundance contribution increased from 58.43 ± 15.08% in BLEGC to 79.54 ± 6.38% in BLMG and 90.14 ± 2.14% in BLLGC. When mean abundance was calculated only among samples in which each ASV was detected, prevalence remained positively associated with conditional mean abundance. Collectively, these results indicate that growth-associated gut microbiome succession in D. maruadsi involves not only taxonomic turnover but also progressive redistribution of community abundance toward highly prevalent and persistent bacterial members.

Estrogen deficiency induces bone loss and is accompanied by lipid metabolic disturbances. This study investigated the protective effects of Larimichthys crocea-derived calcium-chelating peptides (LCP) in a leuprorelin-induced estrogen-deficient mouse model. LCP attenuated tibial trabecular deterioration, increased serum procollagen type I N-terminal propeptide (PINP), osteocalcin (OCN), and bone-specific alkaline phosphatase (BALP), and reduced C-terminal telopeptide of type I collagen (CTX-I). Histological analyses further showed increased trabecular area and OCN expression and reduced marrow adiposity. LCP also attenuated alterations in serum lipid profiles and circulating levels of leptin and adiponectin, while reducing adipogenesis-related gene expression in femoral tissue and white adipose tissue. Exploratory assays using group-pooled cultures of bone marrow mesenchymal stem cells (BMSCs) showed differentiation-related patterns that were directionally consistent with the in vivo findings, but these descriptive observations require confirmation using independent biological replicates. Correlation analysis revealed associations among bone mass, osteogenesis-related indicators, and lipid metabolism-related parameters. Collectively, LCP attenuated estrogen deficiency-induced bone loss together with favorable changes in indicators related to bone formation, adipogenesis, and lipid metabolism. These findings support further investigation of LCP as a food-derived nutritional ingredient for supporting bone health under estrogen-deficient conditions.

Temporary holding water in live aquatic-product markets represents a short-term, animal-associated aquatic microenvironment, but its bacterial community dynamics remain poorly understood. In this study, 16S rRNA gene amplicon sequencing was used to characterize bacterial communities in holding water of Anguilla japonica, Sinonovacula constricta, and Ruditapes philippinarum. Samples were collected in the morning and evening to evaluate taxon-associated differences and short-term temporal shifts. The bacterial communities showed clear differentiation among the six animal–time groups. Anguilla japonica holding water showed distinct bacterial assemblages from the two bivalve-associated systems, whereas S. constricta and R. philippinarum holding water exhibited more pronounced morning-to-evening changes. In particular, R. philippinarum holding water had higher bacterial richness and a larger proportion of group-specific taxa in the morning, suggesting greater initial community heterogeneity. In addition, the occurrence–abundance analysis showed that taxa with broader distributions tended to have higher mean relative abundances, whereas Rud_8 contained a comparatively large proportion of low-occurrence taxa. Overall, this study demonstrates that live aquatic-product holding water harbors taxon-specific and time-responsive bacterial communities. These findings provide preliminary ecological insight into microbial dynamics in market-associated artificial aquatic microenvironments and highlight the need to consider aquatic animal type and sampling time in future water-quality monitoring.

External mucosal microbiota form important interfaces between fish and the aquatic environment, yet their variation during host growth remains poorly understood. We characterized the gill and skin-mucus microbiota of cultured Decapterus maruadsi across three successive body-size stages (4.98–6.81 g, 16.67–19.63 g, and 27.30–28.66 g) using 16S rRNA gene amplicon sequencing. Fish were sampled from the same cohort maintained in the same culture system, and two supplied-seawater samples were included as environmental references. Factorial multivariate analysis indicated significant effects of mucosal tissue, sampling stage, and their interaction on community composition. Broad taxonomic structure remained dominated by Pseudomonadota, whereas extensive differentiation occurred at finer taxonomic resolutions. Skin-mucus richness decreased across successive sampling stages, whereas no corresponding alpha-diversity difference was detected in the gill. Host-wide prevalence analysis revealed contrasting changes in the abundance contribution of recurrent ASVs between the two mucosal compartments; however, tissue-specific sensitivity analyses showed that occurrence categories depended partly on the sample set used to define prevalence. The same dominant Limimaricola ASV occurred at high abundance in one supplied-seawater sample and in middle-stage skin mucus, indicating environmental microbial input as a plausible contributor to the observed composition. Overall, this study provides a descriptive baseline for stage-associated variation in the external mucosal microbiota of one cultured D. maruadsi cohort and highlights distinct responses of gill and skin-mucus communities without attributing these changes solely to host growth.