Serotonin (5-hydroxytryptamine, 5-HT), a pleiotropic biogenic monoamine, modulates immune response through interactions with its distinct receptors (5-HTRs). In this study, thirteen 5-HTRs were identified in the Pacific oyster (Crassostrea gigas) to elucidate their functions in immune response to Vibrio stimulation. Except for the unique ligand-gated cation channels (Cg5-HTR3A-like), the other twelve 5-HTRs (Two Cg5-HTR, Cg5-HTR-like, Cg5-HTR1, Cg5-HTR1A-like, Cg5-HTR1B, Cg5-HTR1B-like, Cg5-HTR2A-like, Cg5-HTR2B, Cg5-HTR4, Cg5-HTR5, and Cg5-HTR6) all belong to G protein-coupled receptor (GPCR) superfamily. Among those twelve 5-HTRs, most are non-canonical members lacking complete seven-transmembrane (7TM) domains; only Cg5-HTR2B and Cg5-HTR6 retain the canonical GPCR architecture. Ten conserved motifs were identified in oyster 5-HTRs, with motif 2 being universal across all receptors and motif 10 unique to Cg5-HTR3A-like, indicating subtype-specific divergence. Molecular docking revealed significant differences in binding affinity and residue interaction among Cg5-HTRs, with Cg5-HTR6 exhibiting the highest binding affinity for 5-HT. Analysis across developmental stages revealed that Cg5-HTR1A-like transcripts were enriched in early gastrula, gastrula and trochophore, Cg5-HTR4, Cg5-HTR1B, and Cg5-HTR-like enriched specifically in the D-shape stage, while Cg5-HTR2B and Cg5-HTR1 transcripts enriched during the pediveliger, spat, and juvenile stages. Furthermore, Cg5-HTR-like and Cg5-HTR1 were primarily expressed in granulocytes, Cg5-HTR1A-like and Cg5-HTR2B in agranulocytes, and Cg5-HTR6 and Cg5-HTR1B in semi-granulocytes. Crucially, following secondary Vibrio splendidus stimulation, the expression levels of Cg5-HTR-like, Cg5-HTR1, Cg5-HTR1A-like, Cg5-HTR1B and Cg5-HTR2B mRNA in hemocytes upregulated significantly, indicating their potential role in immune priming. These findings suggested the potential mechanisms of 5-HTRs in regulating the immune response of hemocytes in C. gigas, which offered insights into the evolutionary conservation and immunoregulation divergence of these receptors in invertebrates.

China has vast areas of saline-alkaline water with significant fishery productivity. pH, as an important physicochemical factor in aquaculture, plays a decisive role in the success of farming. The mud crab (Scylla paramamosain), with its high economic value and strong tolerance, is an ideal species for aquaculture in saline-alkaline waters. However, during the culture process, especially in the middle and late stages, pH increases and causes challenges. Previous studies have focused on the effects of pH stress on S. paramamosain in low-salinity environments, but the impact of pH stress under normal salinity conditions remains unexplored. Therefore, this study was conducted to investigate the histological changes, osmoregulation, immune response, antioxidant capacity, and metabolic function in the gills and hepatopancreas of S. paramamosain under pH stress.The results indicated that with increasing pH, both the gills and hepatopancreas were damaged. Hemocyte aggregation was observed in the gills, while the hepatopancreas was compressed, showing deformation, loss of central stellate lumens, and cytoplasmic leakage. The upregulation of heat shock and apoptosis-related proteins in both tissues confirmed these results. In the gills, the enzyme activities related to osmoregulation, such as Na+/K+-ATPase (NKA) and Ca2+/Mg2+-ATPase (CaMgA), significantly decreased as pH increased, while the activity of carbonic anhydrase (CA), a key enzyme involved in acid-base balance, showed an opposite trend.The levels of inflammatory metabolites such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the hemolymph, as well as malondialdehyde (MDA) in the hepatopancreas, increased with rising pH. In contrast, the activities of immune-related enzymes in the hemolymph (acid phosphatase (ACP) and alkaline phosphatase (AKP)) and antioxidant enzymes in the hepatopancreas, including superoxide dismutase (SOD), total antioxidant capacity (T-AOC), phenoloxidase (PO), glutathione (GSH), and catalase (CAT), significantly decreased, along with the downregulation of related antioxidant genes. These results suggest that pH stress leads to a reduction in the antioxidant capacity of S. paramamosain.Metabolomic analysis of the gills revealed that pH stress significantly inhibited energy metabolism.At pH 8.6, among 125 different metabolites, 83 were downregulated, and 42 were upregulated. AtpH 8.8, 510 different metabolites were detected, with 373 downregulated and 137 upregulated. Thedownregulated metabolites in both groups were mainly amino acids, lipids, and polysaccharides,allinvolved in energy metabolism. Pathway enrichment analysis revealed that at pH 8.6, the metabolism of nicotinate and nicotinamide, which mainly serves a detoxification function, was enriched.AtpH 8.8, the pathways for lysine metabolism, butanoate metabolism, and histidine metabolismwereenriched, all of which are related to energy metabolism.Interestingly, under high salinity conditions, gills at pH 8.6 did not exhibit enrichment of many osmoregulation-related energy metabolism pathways, while at pH 8.8, several energy metabolism pathways were enriched. This indicates that S. paramamosain demonstrates a stronger tolerance to pH stress under high salinity conditions.

Slurry ice is known to extend the shelf life of refrigerated seafood, yet its specific impact on the quality and microbiota of soft-shell mud crabs during storage has not been well characterized. This study examined changes in the K-value, xanthine oxidase (XOD) activity, free amino acids, flavor nucleotides, and bacterial community succession in the muscle of vacuum-packed soft-shell crabs during slurry ice cooling and cold storage. The results showed that the crabs retained acceptable biochemical freshness (K-value < 40%) for up to 7 days. XOD activity increased over time. Gly, L-Arg, L-Ala, and L-Glu were identified as the predominant FAAs, and their marked reduction significantly influenced flavor development. Adenosine monophosphate was the most abundant flavor nucleotide, followed by inosine monophosphate; the decline in both compounds contributed to a reduction in the equivalent umami concentration. Furthermore, while the α-diversity of the muscle bacterial community remained stable, an increase was observed in four families—primarily Comamonadaceae and Shewanellaceae. Notably, the rise in amplicon sequence variant 936 (ASV936, assigned to Shewanella) by day 7 suggested the onset of spoilage. These findings demonstrate that slurry ice cooling combined with cold storage can effectively maintain the edible quality of soft-shell crabs for 7 days, offering a viable method for short-term preservation.

Ultraviolet (UV) disinfection is widely used to enhance water quality in recirculating aquaculture systems (RAS); however, concerns about its potential adverse effects on aquatic animal survival have emerged. The mechanisms underlying UV-induced mortality are poorly understood, complicating the effective health management of aquatic species in RAS. Our study evaluated the impact of UV disinfection on juvenile mud crab survival in RAS, revealing a statistically significant decline from 76.4 % to 48.6 %. To identify contributing factors, we analyzed microbial composition in RAS water, as well as in the gut and carapace of the crabs and the biofilm of moving bed biofilm reactors (MBBRs). Our analysis indicated that UV disinfection compromised the complexity and stability of bacterial communities in the water, which subsequently affected the microbial composition in the gut, carapace, and biofilm. FEAST (fast expectation-maximization for microbial source tracking) analysis revealed an interaction between biofilm and water bacterial communities, with both contributing to the carapace and gut bacterial communities to varying degrees. Metagenomic analysis of the biofilm suggested that changes in microbial dynamics contributed to elevated nitrite levels in the rearing water. Functional analysis of gut and carapace microbial dynamics indicated increased biofilm formation on the carapace, along with strengthened antibiotic biosynthesis and protein export functions in the gut. Structural equation modeling revealed that variation in the carapace bacterial community is correlated with juvenile crab survival. Furthermore, UV disinfection also reduced the relative abundance of ARGs in RAS, thereby reducing the threat to environmental safety posed by aquaculture wastewater. Therefore, it is recommended to adjust the UV dose and disinfection duration, and to avoid prolonged disinfection before the rearing tanks.

A thorough understanding of the reproductive biology of Portunus trituberculatus, a commercially significant crab species prevalent along the temperate western Pacific coast, is required for sustainable aquaculture. The structure and function of the male mating system of P. trituberculatus were systematically studied using gross morphological examination, scanning electron microscopy, and histological analysis. The mating system consists of paired long first gonopods (G1), short second gonopods (G2), and penises, forming a unique mating complex. G1 is slender and tubular with lateral sutures and a needle-like tip, featuring basal insertion ports for the penis and G2. Histological sections revealed striated muscles, mucous glands, and secretory vesicles within the G1 base, complemented by external pinnate setae on the endopodite. G2 displays a bifurcated terminus with basal striated musculature and surface pinnate setae. Pinnate setae may have sensory functions. The penis is supported by the annular muscle layer and contains spongy connective tissue, and its erection mechanism is driven by haemolymph. During mating, the penis and G2 are inserted into the anterior proximal foramen (AF) and posterior distal foramen (PF), respectively. The results of the gonopod regeneration experiments reveal that the regeneration ability of this species is limited, which may be related to the protected position under the pleon. This study clarified the cooperative working mechanism of the male mating system of P. trituberculatus, providing a theoretical basis for its reproductive physiology research.

The swimming crab Portunus trituberculatus is a commercially important species in aquaculture, and its aggressiveness strongly influences productivity, making quantitative assessment a priority. However, such an assessment is hindered by behavioral complexity and a lack of high-throughput approaches. Here, we present a machine learning framework for quantifying aggressive behavior using DeepLabCut-SIMBA (Simple Behavioral Analysis). By converting video data into quantifiable durations of aggression-related events, we established a Time-weighted Aggression Index (TAI) that enables standardized, high-throughput assessment. The TAI showed strong concordance with conventional methods, confirming its validity. To demonstrate its applicability, we examined the correlation between TAI and serotonin levels, revealing distinct physiology-behavior associations. We then stratified crabs into three aggression categories based on TAI and conducted pairwise fighting trials. The frequency of aggressive interactions differed significantly across group combinations, indicating that TAI-based grouping effectively predicts behavioral outcomes. This framework offers a reliable, scalable tool for behavioral phenotyping and practical value for selective breeding programs.

As a commercially valuable crustacean species in mariculture systems, mud crab (Scylla paramamosain) has a broad geographical distribution across intertidal zones of the Indo-Pacific region, particularly in Southeast Asian. Mud crab reovirus (MCRV) is a double-stranded RNA virus that causes severe disease in cultured mud crabs, leading to serious economic loss for the mud crab aquaculture. In this study, the dynamic distribution and tropism of MCRV in the tissues of S. paramamosain was investigated, also, transcriptome differences of hemocytes between MCRV-infected and control group were compared. Results demonstrated a significant reduction of the cumulative survival rate in the MCRV-infected group compared to the PBS-injected control group at 96 h post-infection (45.83 % vs.100.00 %), with the highest mortality at the initial 24 h post-infection (hpi). A remarkable increase of MCRV could be detected in hepatopancreas, hemocytes, muscles and gills, with hemocytes exhibited the highest viral load from 6 to 96 hpi. Transcriptome analysis of hemocytes identified 196 differentially expressed genes (147 up-regulated and 49 down-regulated genes), including eukaryotic elongation factor 1-alpha (EEF1A), interferon gamma inducible protein 30 (IFI30) and myoferlin (MYOF). GO enriched pathways linked to plasma membrane and neural regulation were identified, KEGG pathway analysis indicated that differentially expressed genes were obviously enriched in the pathways related to vascular smooth muscle contraction, which contribute to the molecular mechanisms underlying the response to MCRV infection. These results will be helpful to future research on the pathogenicity of MCRV and the development of effective control strategies against this pathogen in S. paramamosain.

Mud crab (Scylla paramamosain), an economically important euryhaline species, is facing challenges in low-salt saline-alkali water bodies. This study measured the antioxidant capacity and metabolic responses of the posterior gills of mud crabs to explore their adaptation to long-term cultivation in chloride-dominated low-salt saline-alkali water. For mud crabs in low salinity (LS) group, the results showed lower total antioxidant capacity (T-AOC) concentration as well as low superoxide dismutase (SOD) and catalase (CAT) activities in posterior gills, and higher MDA concentration in both posterior gills and serum. Conversely, LS showed higher T-AOC concentration, as well as higher SOD and CAT activities in serum than control group (CK). One hundred and ninety-four (194) metabolites with differential expressions were observed among the 3910 metabolites, while 66 metabolites were up-regulated and 128 metabolites were down-regulated. Nine of the 43 metabolic pathways found by KEGG enrichment analysis were significantly impacted. Glycerophospholipids, organic oxidants, and carboxylic acids and their derivatives were increased in the posterior gills of mud crabs under chloride-type low-salt saline stress, while the amounts of trigonelline, betaine, and organic acids such as phosphoenolpyruvate decreased. Fumaric acid and pantothenic acid levels increased, while the TCA cycle, coenzyme A, and pantothenic acid biosynthesis were also markedly upregulated. According to these results, glycerophospholipid metabolism is essential for preserving posterior gill tissue adaption, while taurine, free amino acids, and betaine are osmotic regulators that help crabs adjust to low-salt saline-alkali stress. Energy metabolism of crabs living in complex chloride-type low-salt saline water depends on the TCA cycle and the differentially-expressed metabolites D-fructose, fumaric acid, and pantothenic acid. This work offers theoretical insights for farming mud crabs in low-salt saline-alkaline waters.

Determining the appropriate dietary arginine (Arg) requirement and elucidating its roles in growth performance and immune defense are essential for the mud crab (Scylla paramamosain). In this study, we evaluated the effects of dietary Arg supplementation on crab growth and resistance to Vibrio. Feeding trials established 1.45

The Litopenaeus vannamei, known for its broad salinity tolerance and strong stress resistance, is an excellent candidate for aquaculture in saline-alkaline water. This experiment aimed to investigate the effects of long-term (60-day) low-salt alkali stress on the antioxidant capacity, apoptosis, inflammatory response, and immune function of the shrimp's hepatopancreas, and to analyze the underlying metabolic mechanisms through metabolomics. The results showed that the activities of SOD, CAT, and GSH-Px enzymes were significantly increased, indicating a notable enhancement in antioxidant capacity. The mRNA expression levels of apoptosis-related genes Caspase3, P53, and BAX were significantly elevated. The activities of ALT and AST enzymes were markedly increased, and the mRNA expression levels of inflammatory factors TNF, JNK, and RAB6A were significantly upregulated, suggesting potential inflammatory damage to the hepatopancreas. Meanwhile, the activities of AKP and ACP enzymes were significantly enhanced, and the mRNA expression levels of immune-related genes TRAF6, Toll, ALF and Crustin were notably increased, indicating that low-salt saline-alkaline stress may enhance immune defense. Metabolomics results indicated that arachidonic acid metabolism was significantly enriched pathway in response to low-salt alkali stress, potentially playing a key regulatory role by generating inflammatory mediators and immune signaling molecules to mediate inflammatory responses and immune activation in the hepatopancreas. Through physiological and biochemical analyses of the hepatopancreas of Pacific white shrimp, this study explores their adaptation to saline-alkaline water, providing important references and practical implications for saline-alkaline aquaculture of this species.

The insulin-like androgenic gland (IAG) gene is considered a crucial factor in the process of sexual differentiation in decapod crustaceans. In this study, we characterized the structural features and ontogenetic expression profile of the IAG gene in the swimming crab P. trituberculatus (Pt-IAG). To further elucidate its biological roles, we performed long-term RNA interference (RNAi) to evaluate the physiological impacts of sustained Pt-IAG suppression. Results showed that the gene structure of Pt-IAG is conserved with the characteristic B-C-A polypeptide arrangement that is representative of decapod IAGs. Transcripts of Pt-IAG were detectable as early as the zygote stage, which may imply its potential role during early-stage development. Although no completesex reversal was observed, continuous knockdown of Pt-IAG resulted in a decrease in body weight and a delay in gonad development in both sexes, underscoring its pleiotropic role in coordinating growth and maturation. Furthermore, the silencing of Pt-IAG led to a significant downregulation of insulin-like growth factor-binding protein (Pt-IGFBP), and a decrease in insulin-receptor (Pt-IR) expression was observed in males. Notably, the Pt-IR gene was not detected in female ovaries. These findings suggest that IAG may modulate male development through an insulin-like signaling axis; however, the absence of ovarian Pt-IR expression implies the potential existence of alternative regulatory pathways in females. Collectively, this study identifies a dual regulatory role of IAG in both growth and reproduction, providing a specific theoretical basis for developing sex-control and growth-optimization strategies in crab aquaculture.

To investigate the growth patterns and sexual differences in pond-cultured mud crabs (Scylla paramamosain), this study measured eight growth patterns in pond-cultured S. paramamosain aged 1 to 5 months, including internal carapace width (ICW), abdomen width (AW), body height (BH), carapace length (CL), propodus length (PL), merus length (ML), first periopod merus length (1PML), and body weight (BW), with measurements taken monthly. The growth patterns for females, males, and a mixed-sex group were fitted using the following three growth curve models: Logistic, Gompertz, and von Bertalanffy. The fitting results indicate that the optimal growth model for male S. paramamosain is the Logistic model, while the optimal growth model for female S. paramamosain is the von Bertalanffy model. The predicted growth inflection points and inflection weight for male S. paramamosain are 3.15 months and 155.00 g, respectively; for female S. paramamosain, the predicted growth inflection point and inflection weight are 4.25 months and 228.71 g, respectively; and for mixed-sex S. paramamosain, the growth inflection point and inflection weight are 3.22 months and 151.80 g, respectively. Males achieve a rapid growth period earlier (at 3-4 months of age) than females, with the weight of male crabs significantly greater than that of females at four months of age (p < 0.05). Males exhibit slow weight gain from the fourth to the fifth month, while females demonstrate a rapid weight gain rate during the same period. These results provided a theoretical basis and reference for the refined pond culture of S. paramamosain.

The effects of seven different light spectra—white (full spectrum), violet (400 nm), blue (425 nm), cyan (510 nm), green (525 nm), yellow (598 nm), and red (638 nm)—on the survival, growth, molting, respiratory metabolism, antioxidant capacity, and stress responses of juvenile swimming crabs were investigated, and to further explore the molecular mechanisms through which light spectra influence these physiological processes, transcriptome analysis was conducted. Results indicate that cyan light enhanced the growth performance of swimming crabs, with greater mean values of specific growth rate (SGR), weight gain rate (WGR), and molting frequency than those of the other groups. Additionally, the oxygen consumption rate (OCR) and ammonia excretion rate (AER) of crabs in yellow group (P<0.05) were significantly increased. Swimming crabs experienced heightened oxidative stress, as antioxidant enzymes were unable to effectively neutralize excessive lipid peroxides under red light. Furthermore, the expression of (retinoid X receptor) rxr and (ecdysone-induced protein 75) e75 genes in juvenile swimming crabs under cyan light were significantly elevated (P<0.05), promoting molting. Our further investigation into the potential molecular mechanisms of these effects revealed the structural molecule activity, cuticle composition, and ribosomal function as potential regulators of molting, and the close ties of DNA replication and base excision repair pathways with oxidative stress responses. Our findings suggest that cyan light is beneficial for enhancing the growth and overall well-being of juvenile swimming crabs.

The distribution of white spots on the shell is one of the remarkable characteristics of the appearance of Portunus trituberculatus, but there have been no reports on its characteristics and genetic analysis. In this study, seven parameters of white spots were extracted based on computer vision, including white spot number (WSN), white spot area (WSA), white spot regional area (WSRA), percentage of white spot area (PWSA), percentage of white spot regional area (PWSRA), white spot number of white spot regional area (WSNRA), and white spot number of carapace area (WSNCA). Using 22 full-sib families, we estimated genetic parameters of these white spot traits and their genetic correlations with growth carapace area (CA). Results demonstrated that these parameters exhibit continuous variation, but the performance of these white spot indicators was not consistent. Based on comprehensive principal component analysis (PCA), they could be categorized into three distinct groups within the full-sib families. The heritability estimated under the animal model ranged from 0.00 to 0.35 for white spot traits and was 0.18 for CA. Most white spot traits showed low to moderate heritability. The genetic correlations among WSN, WSA, WSRA, PWSA, and CA were significantly positive, indicating that selection for one of these traits would result in the improvement of others. This study presents the first estimation of characteristics and genetic parameters of white spot traits of P. trituberculatus, providing valuable information for understanding these traits and facilitating the optimization of breeding strategies for this species.

A 12-week experimental study was conducted to explore the influence of temperature and eyestalk ablation on the spawning rate and ovarian development of mud crab Scylla paramamosain. The study comprised four experimental treatments: 25 °C (coded 25), 25 °C with eyestalk ablation (25EA), 30 °C (30), and 30 °C with eyestalk ablation (30EA). Results indicate that neither temperature nor eyestalk ablation significantly influenced the survival rate, HSI, or GSI (P>0.05). Nevertheless, eyestalk ablation significantly enhanced the spawning rate and oocyte diameter, with the 30EA group showing the greatest increase (P<0.05). Hormonal analysis of the hemolymph showed that eyestalk ablation significantly decreased gonad-inhibiting hormone (GIH) levels while elevating gonad-stimulating hormone (GTH) levels (P<0.05). Under 30 °C with eyestalk ablation, significant elevations in triglyceride (TG) levels were observed in the hemolymph, ovary, and hepatopancreas (P<0.05). Furthermore, eyestalk ablation significantly elevated vitellogenin (VTG) contents in both hepatopancreas and hemolymph. Besides, eyestalk ablation induced a significant upregulation of lipid synthesis (fas, 6pgd) and lipid transport (fatp 4) genes in the hepatopancreas (P<0.05). Similarly, elevated temperature significantly induced the upregulation of lipid synthesis (fas, 6pgd), lipid catabolism (hsl, aco), and lipid transport fatp 4, fabp 3) genes in the ovary (P<0.05). Additionally, eyestalk ablation considerably enhanced the expression of fatp 4 in the ovary (P<0.05). Therefore, eyestalk ablation enhanced lipid accumulation in the ovary by reducing GIH levels, leading to increased oocyte diameter and ultimately enhancing the spawning rate of the crabs. In conclusion, eyestalk ablation significantly improved the spawning rate of S. paramamosain under temperatures of 25–30 °C. These findings provide theoretical support for optimizing artificial breeding strategies and improving seed production efficiency in mud crab aquaculture.

Low-salt saline-alkali water provides great potential for the cultivation of aquatic crustaceans, but the requirements for Ca2+-Mg2+ content and proportion of euryhaline marine crabs such as the mud crab (Scylla paramamosain) are still unclear. In this study, we set different content and proportions of Ca2+-Mg2+ in low-salt saline-alkali water (1.5 parts per thousand), and analyzed the growth indicators (survival rate, molting rate, and specific growth rate), osmotic regulation ability (Na+/K+-ATPase and Ca2+/Mg2+-ATPase) and immune ability (SOD, CAT, AKP, ACP and MDA) of the mud crab. GC/LC-MS was used to explore the metabolic profile changes of gills under low Ca2+-Mg2+ conditions. The results indicated that Ca2+: Mg2+ ratios of 1:2 and 1:3 were generally superior for growth; within these optimal ratios, a total concentration of 600 mg/L produced the best overall performance. At this point, SOD, CAT, and AKP were the highest, while MDA levels were the lowest, indicating that the optimal Ca2+-Mg2+ protect mud crabs from oxidative damage by up-regulating immune enzyme activity. A combination of 150 mg/L Ca2+ and 450 mg/L Mg2+ has been determined to be the optimal Ca2+-Mg2+ content and proportion for the cultivation. Metabolomics analysis of gills revealed 151 up-regulated and 303 down-regulated differential metabolites, with significant up-regulation of metabolic pathways related to fatty acids, including ARA, LA, LNA, and glycerophospholipids. However, metabolic pathways related to amino acid and protein were significantly down-regulated, including arginine, lysine and taurine. This indicates that the energy consumption pattern of mud crab changes, and the thickening of gill membranes with a high proportion of PUFA may also be an important strategy for regulating Ca2+ and Mg2+. This study provides new insights into the ion and osmotic regulation of euryhaline marine crustaceans, and provides theoretical guidance for the low-salt saline-alkali aquaculture of mud crab.

Rhodobacteraceae strains are known to play multiple beneficial roles in shrimp aquaculture. Roseovarius litoreus (RL), a member of this family, has demonstrated probiotic effects in crabs. To explore its potential role in shrimp, this study evaluated the effects of RL on the growth performance, antioxidation, and gut bacterial community of the postlarvae of shrimp Litopenaeus vannamei in an 8-week immersion supplementation experiment. The results revealed that RL significantly increased the weight gain rate (WGR, p < 0.0001) and specific growth rate (SGR, p < 0.0001) while suppressing the mRNA expression of muscle MSTN (p < 0.001), a gene involved in muscle growth regulation. Although RL did not markedly affect superoxide dismutase (SOD) activity, total antioxidant capacity (T-AOC), or malondialdehyde (MAD) levels, it significantly enhanced catalase (CAT) activity. Additionally, RL modulated the gut bacterial community, notably reducing zero-radius operational taxonomic unit (ZOTU) richness and enriching beneficial genera such as Lysobacter, Bacillus, and Ruegeria. Functional profiling indicated that these enriched ZOTUs were associated with enhanced development and regeneration, digestive system function, and immune responses. In summary, this study suggests that RL holds promise as a probiotic candidate for shrimp aquaculture.

The bone morphogenetic protein (BMP) signaling pathway has been established to play a role in growth and development in vertebrates; hence, it was considered that it may have a function in molting and growth in crustacean species such as the swimming crab, Portunus trituberculatus. We investigated the functional involvement of the BMP signaling pathway in P. trituberculatus using LDN-193189 2HCl (LDN) as a pathway inhibitor and SB4 as an activator. The effects of these modulators on molting, growth performance, and gene expression were evaluated. Optimal concentrations of LDN (1 mu mol/L) and SB4 (0.8 mu mol/L) were determined based on survival rate, molting rate, and gene expression profiles. Both the BMP inhibitor and activator significantly reduced molting and growth rates, prolonged the molting cycle, and decreased body weight and size. However, survival rates were not significantly affected. Gene expression analysis revealed that, in the blank group, the expression levels of BMP2, BMPR2, BMPR1B, Smad5, and GDF8 gradually increased throughout the molting cycle. During the pre-molt stages, ecdysteroid receptor (EcR) gene expression was firstly upregulated, and then downregulated following molting, while that of molt-inhibiting hormone (MIH) exhibited the opposite trend. In both the activator and inhibitor groups, BMPR1B, BMPR2, Smad5, Smad4, MIH, and GDF8 were upregulated during the inter-molt stage, while EcR expression was downregulated. The BMP signaling pathway may influence molting and growth in P. trituberculatus by modulating key regulatory gene expression. These findings provide a basis for further investigation into the molecular mechanisms regulating crustacean growth and offer potential applications in aquaculture.

Unilateral eyestalk ablation is commonly employed to induce reproductive maturation in crustacean aquaculture; however, its systemic metabolic, endocrine, and antioxidant effects remain incompletely characterized. This study utilized an integrated metabolomic and biochemical approach to delineate the temporal physiological responses in Scylla paramamosain following ablation across five time points (Day 0, 1, 3, 7, and 14; n = 30). Metabolomic analyses identified an immediate and substantial disruption of ovarian metabolism, with the most pronounced deviation from baseline observed on Day 1, followed by progressive metabolic realignment on Days 3, 7, and 14. Across all time points, 15 core metabolites exhibited consistent differential regulation, primarily linked to lipid mobilization, redox homeostasis, and pathways supporting oocyte development. Endocrine profiling revealed a rapid post-ablation increase in hepatopancreatic methyl farnesoate (MF) and a sustained elevation of plasma vitellogenin (Vg), indicating robust stimulation of vitellogenic processes. Simultaneously, antioxidant assessments demonstrated significant increases in total antioxidant capacity and key antioxidative enzymes, suggesting effective compensation for oxidative stress during the transition from early metabolic disturbance to reproductive activation. Despite increased metabolic turnover, lipid peroxidation (MDA) levels remained stable, indicating successful mitigation of oxidative damage. Collectively, these findings demonstrate a coordinated, time-dependent physiological sequence in which acute metabolic disruption is succeeded by endocrine activation and enhanced antioxidant defence, ultimately facilitating accelerated ovarian maturation. This integrative analysis offers mechanistic insights at the systems level into how mud crabs balance stress adaptation with reproductive investment following eyestalk ablation and identifies potential metabolic and endocrine biomarkers for optimizing broodstock management in aquaculture.

Thiamethoxam (TMX), a widely used neonicotinoid insecticide, poses a potential threat to non-target aquatic organisms. However, systematic toxicity evaluations on economically important crustaceans remain limited. This study comprehensively investigated the toxic effects and possible mechanisms of TMX on the mud crab Scylla paramamosain. Acute toxicity testing revealed a 96-h median lethal concentration (LC50) of 8.78 mg/L, suggesting moderate toxicity. Following a 21-day exposure to sublethal concentrations (8.8, 88, and 880 μg/L), TMX and its metabolite clothianidin accumulated in mud crabs in a tissue- and concentration-dependent manner, with the highest levels detected in the gut. While a two-phase enzyme system appeared to contribute to TMX detoxification, its efficiency may have been suppressed at higher concentrations and over longer durations. Consequently, despite indications of an activated Nrf2-mediated antioxidant response, TMX induced significant oxidative stress and hepatopancreatic damage in a time- and concentration-dependent manner. Notably, neurobehavioral alterations-including limb curling and impaired righting ability-were observed at 880 μg/L TMX. Mechanistic analyses suggested that these deficits may be associated with perturbations in cholinergic signaling and interference in tryptophan metabolism in the thoracic ganglia, potentially leading to neurotransmitter dysregulation. These multiple physiological impacts observed at 880 μg/L TMX collectively corresponded with significant growth inhibition, reflected in reduced survival, molting, and weight gain rates. In contrast, the two environmentally relevant concentrations (8.8 and 88 μg/L) posed relatively low actual ecological risk to mud crabs under the conditions tested. Overall, TMX presents negligible risk at current environmental levels, but projected higher concentrations may cause substantial toxicity.