Search

Simple Summary: The role of fatty acid transport protein 1 (FATP1) in decapod crustaceans is still poorly understood. In this study, we cloned the FATP1 cDNA from the mud crab Scylla paramamosain, identified its sequence features and tissue distribution pattern and analyzed its roles in lipid metabolism in vivo. We found that FATP1 is involved in long-chain polyunsaturated fatty acid metabolism and deposition in crustaceans, which provides new information for understanding the function of FATP1 in invertebrates. In mammals, fatty acid transport protein 1 (FATP1) plays important roles in cellular uptake and activation of long-chain fatty acid (LCFA), especially in processes of transportation, oxidation and triacylglycerol synthesis. However, the role of FATP1 in invertebrates, especially decapod crustaceans, is still poorly understood. In this study, the cDNA of a FATP1 gene from a decapod crustacean, mud crab Scylla paramamosain, was cloned and functionally characterized. The FATP1 gene encoded a polypeptide consisting of 643 amino acids that exhibits all the typical features of the FATP family and shares high homology with the other FATP orthologs of crustaceans. The relative mRNA expression levels of FATP1 were observed to be higher in metabolically active tissues such as hepatopancreas, stomach and gill than in other crab parts. Knockdown of the FATP1 mRNA in vivo significantly reduced triacylglycerols and total lipid levels in the hepatopancreas, accompanied by an increase in the expression of genes related to fatty acid transportation, allocation and hydrolysis, including long-chain acyl-CoA synthetase 3/4 (ACSL3/4) and carnitine palmitoyl transferase 1 (CPT1), and a decrease in the expression of genes related to fatty acid synthesis such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in the hepatopancreas. Furthermore, increased dietary n-3 long-chain polyunsaturated fatty acid (LC-PUFA) levels resulted in the up-regulation of the FATP1 expression in the hepatopancreas, accompanied by an increase in LC-PUFA content, especially eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), in both polar (PLs) and neutral lipids (NLs) in the hepatopancreas and muscles of crabs. These findings suggested that the FATP1 gene identified in S. paramamosain might play important roles in regulating long-chain fatty acid metabolism and deposition in crustaceans. [ABSTRACT FROM AUTHOR]

In this study, we added LDN-193189 2HCL to inhibit the BMP signaling pathway in Scylla paramamosain and then explored the function of this pathway in molting through the changes in the growth performance and molt-related gene expression. The study findings indicated that the expression of ACVR1, BMPRIB, and Smad1 in Scylla paramamosain was suppressed when the LDN-193189 2HCL concentration in the culture water was 2 µm/L. Subsequently, following a 30-day experiment, there was a significant reduction in the molting frequency, growth rate, and body size of the S. paramamosain larvae. An analysis of the BMP pathway gene expression during the molting phase revealed that the BMP2, BMPR2, and Smad1 genes displayed cyclic expression patterns, while ACVR1, BMP7, and BMPRIB maintained consistent expression levels throughout the molting cycle. Additionally, the expression levels of BMP2, BMPR2, and Smad1 in the inhibition group were significantly lower compared to those in the control group. Furthermore, the inhibition of the BMP pathway led to an increase in the expression of MIH during the intermolt period and a decrease in the expression of EcR during the premolt period. These findings demonstrate that the BMP signaling pathway affects the molting of Scylla paramamosain juvenile crabs by influencing the expression of the critical genes MIH and ECR during molting, offering valuable data for functional research on the BMP signaling pathway in crustaceans. [ABSTRACT FROM AUTHOR]

The farming of Scylla paramamosain with specific flavors has a higher commercial value, and the flavors are related to the integrated farming environment and non-volatile flavor substances, while the survival environment is one of the important ways to source gut microorganisms in the organism. In this study, the levels of dominant taxa in the gut flora of S. paramamosain from Mong Cai, Vietnam (VN), Taishan City, Guangdong Province (TS) of China, and Ninghai County, Ningbo City (NB) Zhejiang Province of China converged with those of S. paramamosain from Sanmen County, Ningbo City (CK1, CK2, and CK3) at 28 d of domestication. The top 15 genera with the highest abundance of VN, TS, and NB gut flora were the same as CK1, CK2, and CK3, but with different percentages, and gradually converged to CK1, CK2, and CK3, respectively, at 28 d of domestication. Correlation between intestinal flora and non-volatile flavor substances in the hepatopancreas at the percentage level of relative abundance of bacterial genera found that above 28 d of domestication, Muribaculaceae, Psychrilyobacter, Clostridia_vadinBB60_group, Halarcobacter Carboxylicivirga, Sediminispirochaeta may be the most important genera affecting flavor amino acids of VN. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Psychrilyobacter, and Pseudomonas may be the most important genera affecting flavor amino acids of NB. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Vibrio, and Sphingomonas may be the most important genera affecting flavor amino acids of TS. These results show that the intestinal flora structure of crabs from different areas were domesticated in the same area for at least 28 d before they converged to that of the domesticated crab, and the most important genera affecting the flavor amino acids of TS, VN, and NB were also identified. The results of this study provide a reference and basis for the technique of directional cultivation of the flavor quality of the crab. [ABSTRACT FROM AUTHOR]

Oviposition is induced upon mating in most insects. Spawning is a physiological process that is fundamental for the reproduction of Scylla paramamosain. However, the molecular mechanisms underlying the spawning process in this species are poorly understood. Herein, comprehensive ovary transcriptomic analysis was conducted at the germinal vesicle breakdown stage (GVBD), spawning stage, 0.5 h post‐spawning stage, and 24 h post‐spawning stage of S. paramamosain for gene discovery. A total of 67,230 unigenes were generated, and 27,975 (41.61%) unigenes were annotated. Meanwhile, the differentially expressed genes (DEGs) between the different groups were identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was subsequently conducted. These results suggested that octopamine (OA) and tyramine (TA) could induce oviposition, while dopamine (DA) and serotonin (5‐hydroxytryptamine [5‐HT]) inhibit oviposition. The 20‐hydroxyecdysone (20E) and methyl farnesoate (MF) signal pathways might be positively associated with oviposition. Furthermore, numerous transcripts that encode neuropeptides and their G‐protein‐coupled receptors (GPCRs), such as CNMamide, RYamide, ecdysis‐triggering hormone (ETH), GPA2/GPB5 receptor, and Moody receptor, appear to be differentially expressed during the spawning process. Eleven unigenes were selected for qRT‐PCR and the pattern was found to be consistent with the transcriptome expression pattern. Our work is the first spawning‐related investigation of S. paramamosain focusing on the ovary at the whole transcriptome level. These findings assist in improving our understanding of spawning regulation in S. paramamosain and provide information for oviposition studies in other crustaceans. [ABSTRACT FROM AUTHOR]

Variability in food availability leads to condition-dependent investments in reproduction. This study is aimed at understanding the metabolic response and regulatory mechanism of female Scylla paramamosain in response to starvation in a temporal- and tissue-specific manner. The mud crabs were starved for 7 (control), 14, 28, and 40 days for histological and biochemical analysis in the hepatopancreas, ovary, and serum, as well as for RNA sequencing on the hepatopancreas and ovary. We further highlighted candidate gene modules highly linked to physiological traits. Collectively, our observations suggested that starvation triggered endogenous ovarian maturation at the expense of hepatopancreas mass, with both metabolic adjustments to optimize energy and fatty acid supply from hepatopancreas to ovary in the early phase, followed by the activation of autophagy-related pathways in both organs over prolonged starvation. These specific adaptive responses might be considered efficient strategies to stimulate ovarian maturation of Scylla paramamosain under fasting stress, which improves the nutritional value of female mud crabs and other economically important crustaceans. [ABSTRACT FROM AUTHOR]

The mud crab Scylla paramamosain is a valuable commercial mariculture crab worldwide. During the ebb tide or when transported to market, crabs suffer underlying air exposure stress. Gills tissue is the first tissue to cope with this stress. In this study, the transcriptome of S. paramamosain gills from the control group (CG) and experimental group (EG) were sequenced, assembled, and compared. A total of 7,425,620,293 bp and 6,741,616,977 bp clean data were found in EG and CG, respectively. A total of 38,507 unigenes (42.78%) were annotated successfully. 13,626 differentially expressed genes (DEGs) were up-regulated, and 6,502 DEGs were down-regulated. The DEGs related to immunity, apoptosis, metabolism, and ion exchange were detected. DEGs were enriched significantly into the KEGG pathways related to metabolism and immunity. These results proved that more material and energy were required, and immune defense was enhanced when the crab was under air exposure stress. The present study provides the first-gill transcriptomic analysis challenged with air exposure stress in S. paramamosain under air exposure stress, which will be useful to clarify the molecular mechanisms of air exposure adaptation. [ABSTRACT FROM AUTHOR]

Mud crabs (Scylla genus) are luxury foods in high demand internationally. The efficient techniques for mud crab hatcheries are vital for providing breeds for their aquaculture, which is rapidly growing in many countries. This study aims to investigate the effects of different feeds and stocking densities on mud crabs' growth and survival rates (Scylla paramamosain) in the stage from megalopa to crablet-1 stage. Two separate experiments were conducted indoors in the 60-liter round plastic tanks (containing 50 liters of water at a 28° salinity). Experiment 1 investigated four feeds: frozen Artemia biomass, pureed shrimp meat, Lansy pellet feed (48% protein), and NRD pellet feed (55% protein). Megalopae (mean weight of 5.8 mg) were stocked at a density of 10/L. In experiment 2, the megalopae (mean weight of 5.4 mg) were stocked at densities of 20, 30, and 40/L and were fed the Lansy pellet feed, which was the best one selected from experiment 1. High survival rates were obtained at all four feeds (82.2-87.5%) and three stocking densities (88.4-90.1%). The growth performances in Lansy feed and frozen Artemia biomass were better than those in pureed shrimp meat and NRD pellet feed, which was seen through higher indicators of daily weight gain (DWG) and specific growth rate in weight (SGRw) (p < 0.05). Despite the survival rate showing no significant difference among the feeds, their highest value (87.5%) was observed in the Lansy pellet feed. On the other hand, the growth performances showed a significant decrease at stocking densities = 30/L, as complemented by a significant decrease in DWG and SGRw at these stocking densities (p < 0.05). Both survival rate and metamorphosis durations did not show significant differences among the feeds or stocking densities (p > 0.05). The investigated feeds and stocking densities suit the nursing mud crab (S. paramamosain) megalopa. In contrast, the Lansy pellet feeds had a stocking density of 20/L, resulting in the highest nursing efficiency. [ABSTRACT FROM AUTHOR]

To solve the industrial bottlenecks of the traditional pond aquaculture of the Scylla paramamosain, such as mutual killing,severe losses caused by natural disasters,and the cumbersome operation of the existing factory circulating aquaculture system of “Crab Apartment”,the Scylla paramamosain was cultured in the " Dragon Boat" type factory circulating aquaculture system and the factory circulating aquaculture system of " Crab Apartment" designed in this experiment. The breeding cycle was 30 d. The study aimed compare the survival rate,aquaculture water environment,growth performance and nutritional quality. The results showed as follows:The survival rate of the Scylla paramamosain in the dragon-boat type factory circulating aquaculture system was ( 98. 66 ± 0. 58) %, which was significantly higher than that in the crab apartment factory circulating aquaculture system ( P < 0. 05). In the " Dragon Boat" type industrial recirculating aquaculture system,the ammonia nitrogen content was 0. 062 5-0. 067 1 mg / L,the nitrite nitrogen content was 0. 021 3- 0. 025 3 mg / L,and the active phosphate content was 0. 031 5-0. 034 6 mg / L,all of which were lower than that in the " Crab Apartment" industrial recirculating aquaculture system. The body weight specific growth rate of the " Dragon Boat" type factory recirculating aquaculture system was ( 3. 43 ± 0. 50) % / d, the molting interval time was (20. 4±0. 25) d,and the growth performance was significantly higher than that of the " crab flat" factory recirculating aquaculture system (P<0. 05). The essential amino acid index (E) in muscle of the Scylla paramamosain cultured in the " Dragon Boat" type industrial recirculating aquaculture system was 67. 35,which was higher than that in the " Crab House" industrial recirculating aquaculture system; The fatty acid composition and quality safety of muscle were better than that of " Crab Apartment" industrial circulating aquaculture system. The results showed that the adoption of the " Dragon Boat " type industrial recycle aquaculture system could reduce water pollution,improve the survival rate and growth rate of the crab,improve muscle nutrition and reduce the content of heavy metals in the muscle,which could be used as a new model for the industrial culture of the crab. [ABSTRACT FROM AUTHOR]

The mud crab Scylla paramamosain is a key species in China due to its high nutritional value and great economic worth and has grown in popularity. Myo-inositol can modulate versatile physiological functions in aquatic animals. In the present study, S. paramamosain megalopa were given graded concentrations of myo-inositol (0, 1, 2, 4, and 8 ppm) by water immersion to explore how their metamorphosis would be affected. The results showed that supplementing with myo-inositol remarkably increased transformation and survival rate from megalopa to crablet by at least 1.16 and 1.26 times, respectively. To decipher the molecular mechanism of how myo-inositol increases metamorphosis and survival rate, we further performed transcriptome-based gene expression profiling of both megalopa and crablet treated with myo-inositol. The integrative transcriptome analyses predicted that the differentially expressed genes (DEGs) were significantly enriched in chitinase activity, structural constituent of cuticle, and chitin binding, which are associated with the decomposition and reconstruction of cuticle. qPCR results confirmed that myo-inositol mediated gene expression levels of the above cuticle-related pathways. Considering the importance of the cuticle in exoskeleton formation and molting, it can be concluded that myoinositol-induced changes in the cuticle decomposition and reconstruction might have accelerated the transformation from megalopa to crablet of S. paramamosain. Besides, numerous DEGs were significantly enriched in protein digestion and absorption, amino sugar and nucleotide sugar metabolism. It implies that myo-inositol may improve survival by regulating energy or nutrient absorption. Additionally, the accelerated metamorphosis by myo-inositol may improve survival from megalopa to crablet of S. paramamosain. Overall, this study will provide the first insights into the underlying molecular mechanisms by which myo-inositol increases metamorphosis and survival. [ABSTRACT FROM AUTHOR]

Mesanophrys sp. is reported to be highly pathogenic to marine crustaceans. This study presents the first report of Mesanophrys sp. infection in the mud crab (Scylla paramamosain). In this study, we first recorded the survival rates of an experimentally infected group and a control group; the cumulative survival rate in the infected group was significantly lower compared to the control group after 72 h (73.20% vs. 94.19%), while the highest mortality of S. paramamosain occurred within the first 24 h post-infection. Then, we investigated the dynamic distribution and tissue tropism of the Mesanophrys sp. in the infected S. paramamosain by a quantitative real-time polymerase chain reaction (qPCR). The result showed that a significant increase in the number of Mesanophrys sp. could be detected in all tested tissues (obtained from the eyestalks, gills, heart, nerves, muscles and hepatopancreas) at 3 h post-infection. The numbers of Mesanophrys sp. in the gill, eyestalk and nerve tissues were relatively higher than in the other tissues. The gill tissue showed the highest numbers from 6 to 48 h. Histopathological observation found a severe collapse in the filament structure, which indicated tissue-specific pathogen infection. Furthermore, the antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in three representative tissues (gill, muscle and hepatopancreas) were compared between the infected and control groups, and a significant increase in enzyme activity was observed in all three tested tissues in the infected group, indicating a relatively strong innate immune defense reaction that could have been induced by Mesanophrys sp. infection. These results will be helpful to Mesanophrys sp. pathogenicity-related research and the control of this pathogen in S. Paramamosain in the future. [ABSTRACT FROM AUTHOR]

In the study, a new gene homologous to the known antimicrobial peptide Scygonadin was identified in mud crab Scylla paramamosain and named SCY3. The full-length sequences of cDNA and genomic DNA were determined. Similar to Scygonadin, SCY3 was dominantly expressed in the ejaculatory ducts of male crab and the spermatheca of post-mating females at mating. The mRNA expression was significantly up-regulated after stimulation by Vibrio alginolyticus, but not by Staphylococcus aureus. The recombinant protein rSCY3 had a killing effect on Micrococcus luteus and could improve the survival rate of mud crabs infected with V. alginolyticus. Further analysis showed that rSCY3 interacted with rSCY1 or rSCY2 using Surface Plasmon Resonance (SPR, a technology for detecting interactions between biomolecules using biosensor chips) and Mammalian Two-Hybrid (M2H, a way of detecting interactions between proteins in vivo). Moreover, the rSCY3 could significantly improve the sperm acrosome reaction (AR) of S. paramamosain and the results demonstrated that the binding of rSCY3, rSCY4, and rSCY5 to progesterone was a potential factor affecting the sperm AR by SCYs on. This study lays the foundation for further investigation on the molecular mechanism of SCYs involved in both immunity and physiological effects of S. paramamosain. [ABSTRACT FROM AUTHOR]

The mud crab, Scylla paramamosain, has abundant nutrients in the ovary, where numerous lipids accumulate during ovarian maturation. However, the mechanism behind the accumulation of lipids in the ovary of mud crab during ovarian maturation is largely unknown. This study conducted a comparative transcriptome analysis of the ovaries of mud crabs at various stages of ovarian maturation. A total of 63.69 Gb of clean data was obtained, with a Q30 of 93.34%, and 81,893 unigenes were identified, including 10,996 differentially expressed genes (DEGs). After KEGG enrichment of these DEGs, MAPK signaling pathway was significantly enriched during vitellogenesis. Moreover, the expression levels of genes involved in carbohydrate, amino acid, and lipid metabolism were found to be higher during vitellogenesis. The two genes (Sp-Eip75B and Sp-Eip78C) that are homologous to the vertebrate gene PPARγ in the PPAR signaling pathway, were identified. Additionally, genes in MAPK signaling pathway might regulate lipid metabolism through PPAR signaling pathway based on Protein-Protein Interaction (PPI) network. These findings suggest that MAPK signaling pathway plays a critical role in lipid metabolism in the ovary during vitellogenesis, which provides new insights into the mechanism of lipid accumulation during ovarian maturation in mud crabs. [ABSTRACT FROM AUTHOR]

Biogenic amines (BAs) play an important role in the aggressive behavior of crustaceans. In mammals and birds, 5-HT and its receptor genes (5-HTRs) are characterized as essential regulators involved in neural signaling pathways during aggressive behavior. However, only one 5-HTR transcript has been reported in crabs. In this study, the full-length cDNA of the 5-HTR1 gene, named Sp5-HTR1, was first isolated from the muscle of the mud crab Scylla paramamosain using the reverse-transcription polymerase chain reaction (RT-PCR) and rapid-amplification of cDNA ends (RACE) methods. The transcript encoded a peptide of 587 amino acid residues with a molecular mass of 63.36 kDa. Western blot results indicate that the 5-HTR1 protein was expressed at the highest level in the thoracic ganglion. Furthermore, the results of quantitative real-time PCR show that the expression levels of Sp5-HTR1 in the ganglion at 0.5, 1, 2, and 4 h after 5-HT injection were significantly upregulated compared with the control group (p < 0.05). Meanwhile, the behavioral changes in 5-HT-injected crabs were analyzed with EthoVision. After 0.5 h of injection, the speed and movement distance of the crab, the duration of aggressive behavior, and the intensity of aggressiveness in the low-5-HT-concentration injection group were significantly higher than those in the saline-injection and control groups (p < 0.05). In this study, we found that the Sp5-HTR1 gene plays a role in the regulation of aggressive behavior by BAs, including 5-HT in the mud crab. The results provide reference data for the analysis of the genetic mechanism of aggressive behaviors in crabs. [ABSTRACT FROM AUTHOR]

Mud crab (Scylla paramamosain) fed five different diets with varying concentrations of guava leaf aqueous extract (0 mg·kg-1, 80 mg·kg-1, 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1) for 30 days. Mud crabs in the 320 mg·kg-1 guava-leaf extract groups outperformed the control group in terms of survival rates (SR), weight gain rates (WGR), and specific growth rates (SGR). When compared to the control group, mud crabs in the 320 mg·kg-1 guava-leaf extract groups had significantly higher levels of lipase (LPS), pepsin, lysozyme (LZM), superoxide dismutase (SOD), acid phosphatase (ACP), and glutathione (GSH) (P < 0.05). The amylase (AMS) activity was significantly decreased in all experimental groups (P < 0.05). Malondialdehyde (MDA) content in the hepatopancreas of mud crabs in the 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1 guava-leaf extract groups were significantly reduced compared to the control group (P < 0.05). Additionally, real-time PCR results illustrated that the expression levels of GPx3, CAT, and JNK were all considerably increased in the 80 mg·kg-1 guava-leaf extract groups compared to the control group (P < 0.05). In the 160 mg·kg-1, 320 mg·kg-1, and 320 mg·kg-1 guava-leaf extract groups, the expression levels of SOD genes were considerably greater than the control (P < 0.05), which was consistent with the level of SOD activity. GST and P53 gene expression levels were significantly up-regulated in the 80 mg·kg-1, 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1 guava-leaf extract groups compared to the control group (P < 0.05). Overall, the addition of 160 mg·kg-1-320 mg·kg-1 guava-leaf extract to the feed of Scylla paramamosain promoted growth, enhanced the activities of digestive and antioxidant enzymes, and strengthened immunity. [ABSTRACT FROM AUTHOR]

The function and molecular characterization of the previously reported crab (Scylla paramamosain) vitellogenesis inhibiting hormone SpVIH is still unclear. In this experiment, SpVIH's bioinformatic and functional characterizations were analyzed. Sequence analysis showed SpVIH was clustered with several type II MIH/GIHs of the Brachyura. The expression of SpVIH in the eyestalk was low in the early ovarian developmental stage I and increased with the advancement of ovary maturation. Interestingly, the SpVIH transcript was still at a high level in the ovary of females at the middle to late maturation stage. SpVIH's function was studied according to the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) in the ovary and hepatopancreas after incubation with SpVIH-dsRNA and recombinant SpVIH protein (rSpVIH). In vitro assay results indicated that rSpVIH has a significant stimulative effect on the expression of Vg in the hepatopancreas in the middle stage of vitellogenesis and in the ovary of each vitellogenesis stage. However, SpVIH-dsRNA has no significant effect on the expression of Vg when SpVIH-dsRNA is introduced to the ovary and hepatopancreas at the early, middle, and late stages of vitellogenesis. Furthermore, the co-incubation experiment result indicated that the eyestalk consists of factor(s) that can significantly up-regulate the expression of Vg in the ovary, with a further combination of dsVIH and eyestalk under incubation, the significant increase of Vg-mRNA expression levels were also found in the ovary of four ovarian development stages of S. paramamosain. Contrary to the previous reports, SpVIH does not possess a vitellogenesis-inhibiting function but can promote vitellogenesis in the ovary and hepatopancreas. [ABSTRACT FROM AUTHOR]

The fibroblast growth factor receptor (FGFR) belongs to the tyrosine kinase family consisting of four members (FGFR1-4). This study involved identification and characterization of FGFR1 and FGFR3 from mud crab Scylla paramamosain for the first time. The obtained cDNAs of SpFGFR1 and SpFGFR3 were 2,380 bp and 2,982 bp in length with a 1,503 bp and 2,310 bp open reading frame, respectively. The predicted Sp FGFR1 protein included three immunoglobulin domains and a transmembrane region, while SpFGFR3 protein possessed a typical TyrKc (Tyrosine kinase, catalytic) domain. Real-time PCR analysis showed that SpFGFR1 and SpFGFR3 were highly expressed in the hepatopancreas. Furthermore, the expression levels of SpFGFR1 and SpFGFR3 in the hepatopancreas were enhanced following challenges with Vibro alginolyticus, Staphylococcus aureus , Poly (I:C) and White spot syndrome virus , which shows the involvement of SpFGFR1 and SpFGFR3 in innate immune response to infections from bacteria and virus. There was significant suppression of six antimicrobial peptide genes (SpALF1-5 and SpCrustin) and three NF-κB members (SpDorsal, SpIKK and SpRelish) when SpFGFR1 and SpFGFR3 was interfered in vivo. Also, treatment of the hemocytes with specific inhibitor of Sp FGFR for 24 h consistently down-regulated SpDorsal, SpRelish and AMPs. These results suggested that SpFGFR1 and SpFGFR3 played important roles in regulating the Toll signaling pathway and immune deficiency (IMD) pathway through NF-κB signaling pathway. These findings may provide new insights into the role of FGFR s in the innate immune function of crustaceans. • The SpFGFR1 , SpFGFR3 genes were firstly identified and characterized. • FGFR existed in crab and responded to bacterial and viral infection. • FGFR regulated expressions of antimicrobial peptides genes in S. paramamosain. [ABSTRACT FROM AUTHOR]

Scylla paramamosain is an importantly economical mariculture crab. To figure out the optimized conditions in the culture of juvenile crabs, three experiments were conducted to examine the effects of diet, salinity and light condition on the growth performance (body weight gain, BWG; carapace width gain, CWG; carapace length gain, CLG) and moulting cycle (MC) of crablets from V to VII stages. The growth performances of the crablets from stages V–VII have no significant differences after feeding different diets. However, the MC of crablet V fed Artemia or mixed fish were significantly shorter than that fed artificial diet. The CLG of crablet VI in salinity 25‰ was significantly higher than that in salinity 15‰, while the CWG and CLG of crablet VII in salinity 15‰ were significantly higher than that in salinity 5‰. The MC of the crablets V–VI reared in salinity 25‰ and 15‰ were significantly shorter than that in salinity 5‰, while it was significantly shorter in salinity 25‰ than that in salinity 15‰ from crablets VI–VII. For light conditions, the BWG of crablet VI with full cover was significantly higher than that with half cover. Whereas, the MC of the crablets V and VI with full cover was significantly shorter than that without cover or half cover. These findings indicated that crablet V and VI may prefer to exposing to 25‰ salinity and dark environment and feeding on Artemia for faster growth. Thus, the current findings may serve as a guide for establishing appropriate conditions in the aquaculture of juvenile mud crabs. [ABSTRACT FROM AUTHOR]

Myeloid differentiation protein 2 (MD2), generally functions as a coreceptor of Toll-like receptor 4 (TLR4), facilitating the activation of TLR4 and the recognition of lipopolysaccharides (LPS) in host organisms. While the role of MD2 in immune activation is well-documented across various species, the specific role of the MD2 homolog in Scylla paramamosain (SpMD2) remains unidentified. In this study, we applied RNA interference to reduce SpMD2 expression, aiming to elucidate its role in immune system of mud crabs. Notably, SpMD2 interference leded to decrease in the hemocyte counts and phagocytic activity, along with increase in apoptosis rates and level of reactive oxygen species (ROS). Furthermore, the activities of key enzymes related to immune, such as superoxide dismutase (SOD), catalase (CAT), phenoloxidase (PO), peroxidase (POD), lysozyme (LZM), and acid phosphatase (ACP), were reduced by SpMD2 knockdown. Following infection with Vibrio alginolyticus , increase of SpMD2 expression level was observed. This was accompanied by alterations in the expression levels of genes related to immune in mud crabs. Challenge experiment with Vibrio alginolyticus showed a higher mortality rate after SpMD2 interference. Our study underscore the critical role of SpMD2 in enhancing the innate immunity and disease resistant in S. paramamosain , advancing our understanding of the innate immune regulatory mechanisms in crustaceans. • Total hemocyte counts and hemocyte proliferation were regulated by MD2 in S. paramamosain. • MD2 regulates ROS and apoptosis in S. paramamosain. • MD2 is involved in the immune response of S. paramamosain to bacterial pathogens. [ABSTRACT FROM AUTHOR]

Scylla paramamosain , an economically significant crab, is widely cultivated worldwide. In recent years, S. paramamosain has faced a serious threat from viral diseases due to the expansion of culture scale and increased culture density. Among these, mud crab dicistrovirus-1 (MCDV-1) stands out as highly pathogenic, presenting substantial challenges to the healthy development of mud crab aquaculture. Therefore, a comprehensive understanding of the mud crab immune response to MCDV-1 infection is imperative for devising effective disease prevention strategies. In this study, transcriptomic analyses were conducted on the hepatopancreas of mud crabs infected with MCDV-1. The findings revealed a total of 5139 differentially expressed genes (DEGs) between healthy and MCDV-1 infected mud crabs, including 3327 upregulated and 1812 downregulated DEGs. Further analysis showed that mud crabs resist MCDV-1 infection by activating humoral immune-related pathways, including the MAPK signaling pathway, MAPK signaling pathway-fly, and Toll and Imd signaling pathway. In contrast, MCDV-1 infection triggers host metabolic disorders. Several immune-related vitamin metabolism pathways (ascorbate and aldarate metabolism, retinol metabolism, and nicotinate and nicotinamide metabolism) were significantly inhibited, which may create favorable conditions for the virus's self-replication. Notably, endocytosis emerged as significantly upregulated both in GO terms and KEGG pathways, with several viral endocytosis-related pathways showing significant activation. PPI network analysis identified 9 hub genes associated with viral endocytosis within the endocytosis. Subsequent GeneMANIA analysis confirmed the association of these hub genes with viral endocytosis. Both transcriptome data and qPCR analysis revealed a significant upregulation of these hub genes post MCDV-1 infection, suggesting MCDV-1 may use viral endocytosis to enter cells and facilitate replication. This study represents the first comprehensive report on the transcriptomic profile of mud crab hepatopancreas response to MCDV-1 infection. Future investigations should focus on elucidating the mechanisms through which MCDV-1 enters cells via endocytosis, as this may holds critical implications for the development of vaccine targets. [Display omitted] • First transcriptomic profile of MCDV-1 infection in mud crabs. • Mud crabs fight MCDV-1 infection by activating humoral immunity. • MCDV-1 creates favorable conditions for self-replication by inhibiting vitamin metabolism. • MCDV-1 infection causes metabolic disorders in mud crabs. • MCDV-1 may utilize viral endocytosis to enter and successfully infect cells. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is a widely distributed Gram-negative waterborne pathogen responsible for large-scale outbreaks of hemorrhagic septicemia in fish, causing severe economic losses to the global aquaculture industry. In view of few therapeutic drugs currently available for use in aquaculture and the emergence of multidrug-resistant A. hydrophila , there is an urgent need to develop new antimicrobial agents as an alternative to antibiotics. Antimicrobial peptides (AMPs) have strong antimicrobial effects and unique machanisms of action, and are not easy to induce bacterial resistance, making them an ideal alternative to antibiotics. In this study, we identified a new functional gene from marine crab Scylla paramamosain , named Spasin, which encodes a mature peptide of 240 amino acids and expressed widely in various tissues of crabs. Notably, a truncated peptide Spasin 141 – 165 derived from Spasin, showed potent and broad-spectrum antibacterial and antifungal activity at minimum inhibitory concentrations (MICs) ranged from 0.75 μM–48 μM, which is a novel AMP. It effectively killed S. aureus and A. baumannii within 2 h and 90 min, respectively. Importantly, it is not toxic to HEK-293 T, RAW 264.7, and ZF4 cell lines. Mechanistic studies showed that addition of 8 μg mL−1 lipoteichoic acid or lipopolysaccharides decreased bacterial susceptibility to Spasin 141 – 165. In addition, Spasin 141 – 165 altered the permeability of the inner and outer cell membranes, and resulted in the release of ATP and the accumulation of intracellular reactive oxygen species. Notably, Spasin 141 – 165 significantly increased the survival rate of zebrafish infected with A. hydrophila , redcued the bacterial load in the spleen, and effectively inhibited the expression of inflammation-associated factors (e.g. , IL-1β, TNF-α, etc.). Taken together, Spasin 141 – 165 is a potential antibacterial agent for the treatment of A. hydrophila infections in aquaculture and a promising antibiotic alternative. • Identification of a potent antimicrobial peptide from mud crabs. • Spasin 141 – 165 killed pathogenic microorganisms by disrupting cell membranes. • Spasin 141 – 165 significantly improved the survival of zebrafish infected with Aeromonas hydrophila. • Spasin 141 – 165 remarkably inhibited the inflammatory response in zebrafish after Aeromonas hydrophila infection. [ABSTRACT FROM AUTHOR]

This experiment was conducted to explore the effects of dietary vitamin C supplementation on non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab (Scylla paramamosain). Mud crabs with an initial weight of 14.67 ± 0.13 g were randomly divided into 6 treatments and fed diets with 0.86 (control), 44.79, 98.45, 133.94, 186.36 and 364.28 mg/kg vitamin C, respectively. The experiment consisted of 6 treatments, each treatment was designed with 4 replicates and each replicate was stocked with 8 crabs. After 42 days of feeding experiment, 2 crabs were randomly selected from each replicate, and a total of 8 crabs in each treatment were carried out 72 h low-temperature challenge experiment. The results showed that crabs fed diets with 186.36 and 364.28 mg/kg vitamin C significantly improved the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemolymph and hepatopancreas (P < 0.05). Crabs fed diet with 133.94 mg/kg vitamin C significantly decreased the concentration of nitric oxide (NO) and the activity of nitric oxide synthase (NOS) in hemolymph (P < 0.05). Diet with 133.94 mg/kg vitamin C was improved the activity of polyphenol oxidase (PPO) and the concentration of albumin (ALB) in hemolymph. Crabs fed diet with 133.94 mg/kg vitamin C showed lower concentration of malondialdehyde (MDA) in hemolymph and hepatopancreas than those fed the other diets. Meanwhile, crabs fed diet with 98.45 mg/kg vitamin C showed higher activity of total superoxide dismutase (T-SOD) in hemolymph, and crabs fed diet with 133.94 mg/kg vitamin C showed higher activity of T-SOD in hepatopancreas. Crabs fed diet with 186.36 mg/kg vitamin C significantly decreased the concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GSH-PX) in hepatopancreas (P < 0.05). In normal temperature, crabs fed diets with 133.94 mg/kg vitamin C significantly up-regulated the expression levels of gpx (glutathione peroxidase) and trx (thioredoxin) in hepatopancreas compared with the control treatment (P < 0.05). The highest expression levels of relish , il16 (interleukin 16), caspase 2 (caspase 2), p38 mapk (p38 mitogen-activated protein kinases) and bax (bcl-2 associated x protein) in hepatopancreas were found at crabs fed control diet (P < 0.05). Moreover, crabs fed diet with 133.94 mg/kg vitamin C showed higher expression levels of alf-3 (anti-lipopolysaccharide factor 3) and bcl-2 (B-cell lymphoma 2) in hepatopancreas than those fed the other diets (P < 0.05). Under low-temperature stress, crabs fed diet with 133.94 mg/kg vitamin C significantly improved the expression levels of hsp90 (heat shock protein 90), cat (catalase), gpx , prx (thioredoxin peroxidase) and trx in hepatopancreas (P < 0.05). In addition, dietary with 133.94 vitamin C significantly up-regulated the expression levels of alf-3 and bcl-2 (P < 0.05). Based on two slope broken-line regression analysis of activity of PPO against the dietary vitamin C level, the optimal dietary vitamin C requirement was estimated to be 144.81 mg/kg for juvenile mud crab. In conclusion, dietary 133.94–144.81 mg/kg vitamin C significantly improved the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab. [Display omitted] • Dietary 133.94–144.81 mg/kg vitamin C enhanced the non-specific immune defense of juvenile mud crab. • Dietary 133.94 mg/kg vitamin C improved the antioxidant capacity of juvenile mud crab. • Dietary 133.94 mg/kg vitamin C promoted the resistance to low-temperature stress of juvenile mud crab. • The optimal dietary vitamin C requirement is estimated to be 133.94–144.81 mg/kg for juvenile mud crab. [ABSTRACT FROM AUTHOR]

Sulfate is an important chemical component in seawater, which has a profound influence on the survival, growth, physiology and biochemistry of aquaculture species. The aim of this experiment was to study the effects of sulfate concentration on survival, osmotic regulation, oxidative stress and immune inflammation of mud crab(Scylla paramamosain). The results showed that the 72-h semi-lethal concentration of the crab was 3.373 g/L (1.353–8.589 g/L). After 28 days of cultivation, the contents of Na+-K+-2Cl− cotransporter (NKCC) and Na+-K+ ATPase (NKA) in the gill tissue of the S1 group (0 g/L Na 2 SO 4) were significantly higher than those in the other three groups, and the sulfate content increased and the SOD activity decreased.Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were affected by sulfate content, and the content levels in the S3 group (1 g/L Na 2 SO 4) were significantly lower than those in the other three groups. The activities of ACP and AKP first increased and then decreased with the increase of sulfate content in prepare solution, and the activities of ACP and AKP in the S3 group (1 g/L Na 2 SO 4) were significantly higher than those in the other three groups. The absence of sulfate or high concentration of sulfate will affect the survival rate of mud crabs, and have a stressful effect on the osmotic regulation of mud crabs, inhibit oxidative stress ability, and promote inflammatory response. The purpose of this study was to explore the feasibility of sulfate-type saline-alkali water aquaculture of mud crab by studying the effect of sulfate on the mud crab under low salt conditions, and to provide theoretical basis and technical guidance for the promotion of saline-alkali water aquaculture. • Use Chemical reagents to prepare aquaculture water bodies that could satisfy the survival of euryhaline seafood. • Short-term semi-lethal concentration and safe concentration range of sulfate for mud crabs during culture. • Development and utilization of inland sulfate saline-alkali waters • Sulfate affects the change of water index • Effects of sulfate on survival, antioxidant capacity and immune inflammation of mud crabs [ABSTRACT FROM AUTHOR]

The epidermal growth factor receptor (EGFR) is a pleiotropic glycoprotein which plays a role in regulating cell proliferation, migration and differentiation. However, the genetic diversity of EGFR in crustaceans as well as its function, such as whether it is involved in immune regulation, remains obscure. In this study, two EGFR genes, including EGFR1 and EGFR2 , and three transcripts were identified and characterized in Scylla Paramamosain for the first time. To our knowledge, this is the first time that more than one EGFR gene was identified in a single species. The complete open reading frames (ORFs) of SpEGFR1 , SpEGFR2a and SpEGFR2b were 4377 bp, 4404 bp and 4341 bp encoding deduced proteins of 1458 amino acids (aa), 1467 aa and 1446 aa, respectively. All EGFR had a signal peptide region and two Recep_L_domain region, followed by a transmembrane region and a conserved tyrosine kinase domain (TyrKc), and phylogenetic analysis demonstrated three Sp EGFRs clustered together with invertebrate EGFR branch. Tissue specific expression analysis depicted that all SpEGFR s presented similar transcription patterns. The expression levels of SpEGFR1 and SpEGFR2 s in hepatopancreas and gills were significantly altered after the stimulation of bacterial and viral pathogens including Staphylococcus aureus , Vibrio alginolyticus , White spot syndromre virus and Polycytidylinic acid. The in vivo RNA interference assays demonstrated that expression levels of SpIKK , two members of NF-κB (SpRelish and SpDorsal) and six antimicrobial peptide (AMP) genes (SpCrustin and SpALF1–5) were significantly reduced when SpEGFR1 or SpEGFR2 was silenced, respectively. The transcription patterns of SpIKK , SpRelish , SpDorsal and AMPs exhibited similar down- or up-regulation trend when the primary cultured hemocytes were treated with EGFR antagonist or agonist for 24 h. These results suggested that SpEGFR might play an important role in innate immune responses to bacterial and viral infections by regulating the NF-κB pathway. It also provided a better understanding of the origin or evolution of EGFR in crustaceans and even invertebrates. • Two EGFR genes were firstly identified and characterized in a single species. • The expression patterns of SpEGFR s in hepatopancreas and gill were investigated upon pathogen challenge. • SpEGFR s played an important role in activation of NF-κB Signaling. • SpEGFR s contributed to inflammatory response by inducing the expression of transcription factors and downstream AMPs. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the most suitable kind of feed for the mud crab, Scylla paramamosain , to grow from juvenile to broodstock size and to monitor their monthly size and growth rate, as well as to (1) record them reaching maturity and (2) their subsequent mating frequency. For this research, a Complete Randomized Design was used with three treatments. Each treatment was carried out with 40 individuals. The crabs are usually grown in 90 m3 concrete tanks. The three feeds tested were: (A) trash fish, Leiognathus equula , (B) a combination of that ice trash fish and oyster meat from Crassostrea iredalei , and, (C) that same oyster meat only. The feed was always given at 3-10% of total body weight/day. Newly adult male crabs were selected for mating with a newly adult female crab. The male crabs fed treatments B and C grew faster than male crabs fed treatment A. While the female crabs fed treatment C grew significantly faster than female crabs fed treatment A (p < 0.05), but not significantly than the female crabs fed treatment B (p > 0.05). A total of 30 female crabs were followed in mating from July 2020 to January 2021, and the highest mating intensity was found from September to October 2020. The present study indicates that mud crabs grow fast when they are fed treatment C, i.e., oyster meat only. [ABSTRACT FROM AUTHOR]

The sesquiterpenoid hormone methyl farnesoate (MF) plays a vital role during crustacean development, which is mainly evidenced by its varied titers during different developmental stages. However, the biosynthesis pathways of MF remain obscure to some extent. In this study, we identified the complete MF biosynthesis and related pathway genes in Scylla paramamosain, including three involved in acetyl-CoA metabolism, eight in the mevalonate pathway, five in the sesquiterpenoids synthesis pathway, and five in the methionine cycle pathway. Bioinformatics, genomic structure, and phylogenetic analysis indicated that the JH biosynthesis genes might have experienced evolution after species differentiation. The mRNA tissue distribution analysis revealed that almost all genes involving in or relating to MF syntheses were highly expressed in the mandibular organ (MO), among which juvenile hormone acid methyltransferase was exclusively expressed in the MO, suggesting that most of these genes might mainly function in MF biosynthesis and that the methionine cycle pathway genes might play a crucial regulatory role during MF synthesis. In addition, the phylogenetic and tissue distribution analysis of the cytochrome P450 CYP15-like gene suggested that the epoxidized JHs might exist in crustaceans, but are mainly synthesized in hepatopancreas rather than the MO. Finally, we also found that betaine-homocysteine S-methyltransferase genes were lost in insects while methionine synthase was probably lost in most insects except Folsomia candida, indicating a regulatory discrepancy in the methionine cycle between crustaceans and insects. This study might increase our understanding of synthetic metabolism tailored for sesquiterpenoid hormones in S. paramamosain and other closely related species. [ABSTRACT FROM AUTHOR]

Mud crab reovirus (MCRV) is a serious pathogen that leads to large economic losses in the mud crab farming. However, the molecular mechanism of the immune response after MCRV infection is unclear. In the present study, physiological, transcriptomic, and metabolomic responses after MCRV infection were investigated. The results showed that MCRV infection could increase lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities. MCRV infection decreased antioxidant enzyme activity levels, induced oxidative stress, and caused severe histological damage. Transcriptome analysis identified 416 differentially expressed genes, including 354 up-regulated and 62 down-regulated genes. The detoxification, immune response, and metabolic processes-related genes were found. The results showed that two key pathways including phagocytosis and apoptosis played important roles in response to MCRV infection. The combination of transcriptomic and metabolomic analyses showed that related metabolic pathways, such as glycolysis, citrate cycle, lipid, and amino acid metabolism were also significantly disrupted. Moreover, the biosynthesis of unsaturated fatty acids was activated in response to MCRV infection. This study provided a novel insight into the understanding of cellular mechanisms in crustaceans against viral invasion. • MCRV infection induced oxidative stress, and caused severe histological damage. • Phagocytosis and apoptosis played important roles in response to MCRV infection. • The biosynthesis of unsaturated fatty acids was activated in response to MCRV infection. [ABSTRACT FROM AUTHOR]

As an important pattern recognition receptor (PRR) in the innate immune system, C-type lectin plays an important role in the innate immune process of invertebrates. Two C-type lectins SpCTL-C and SpCTL-D were characterized from mud crab (Scylla paramamosain). The predicted SpCTL-C and SpCTL-D proteins both contain a single carbohydrate-recognition domain (CRD) with key motif Gln-Pro-Ala (QPA) and Met-Pro-Ala (MPA), respectively. SpCTL-C and SpCTL-D transcripts distributed in all examined tissues, and the expression level was the highest in hepatopancreas. As PRR, the purified recombinant proteins rSpCTL-C and rSpCTL-D have high affinity for three kinds of pathogen-associated molecular patterns (PAMPs): β-glucan, lipopolysaccharide, and peptidoglycan. Besides, rSpCTL-D can bind to all nine microorganisms tested, while rSpCTL-C can bind to seven microorganisms except for Staphylococcus aureus and Micrococcus luteus. Both rSpCTL-C and rSpCTL-D showed agglutination activity towards fungi Pichia pastoris and Saccharomyces cerevisiae. However, rSpCTL-C and rSpCTL-D exhibited different antimicrobial activities: rSpCTL-D has a certain inhibitory effect on the growth of Vibrio fluvialis and M. luteus, while rSpCTL-C has no obvious inhibitory activity. The results show that rSpCTL-C and rSpCTL-D had better phagocytosis-promoting effect on M. luteus than the negative control. Meanwhile, both rSpCTL-C and rSpCTL-D had certain encapsulation-promoting activity. Collectively, two C-type lectins with novel key motifs make an important impact as PRR in immune response towards pathogens. At the same time, they play different functions in the innate immunity of mud crab S. paramamosain. [ABSTRACT FROM AUTHOR]

The Dmrt gene family, with conserved functions throughout evolution, contains DM domains that play roles in various physiological processes like sex determination and gonadal differentiation. The mud crab (Scylla paramamosain), a significant marine culture crab in China, exhibits sexual dimorphism and is an important subject for reproduction research. In this study, the ORFs of the SpDmrt-1 and SpDmrt-3 genes from the mud crab gonad transcriptome database were obtained and confirmed by PCR. Both genes were expressed at the highest level in the testis among various tissues and in the T2 stage testis during different gonad developmental stages. In situ hybridization results showed that both genes were expressed during spermatogenesis. Silencing one gene led to a decrease in the expression of the other. Moreover, the expressions of some gonadal development-related genes (dsx , foxl-2 , vasa , Dmrt-like , and IAG) changed significantly. Transcriptomic data indicated that SpDmrt-1 and SpDmrt-3 regulate various signaling pathways, including the Notch signaling pathway, the MAPK signaling pathway, the Hippo signaling pathway, the Calcium signaling pathway, and several other gender-related pathways, showing their involvement in male mud crab development. Furthermore, after long-term interference with SpDmrt-1 in vitro , most cells in the testis of the mud crab were at the spermatid stage, only a small amount of spermatozoa could be observed, and obvious empty plaque-like areas appeared in the tissue. Our findings provided a crucial foundation for understanding the role of the Dmrt in the process of gonadal development in crustaceans. • Two novel Dmrt genes Dmrt-1 and Dmrt-3 were identified from Scylla paramamosain. • SpDmrt-1 and SpDmrt-3 show a sex-biased expression pattern. • SpDmrt-1 and SpDmrt-3 play the functional role in male gonadal development and spermatogenesis. • SpDmrt-3 may be involved in other biological processes besides gonadal development. • Long-term interference with SpDmrt-1 in vitro restricts the formation of spermatozoa. [ABSTRACT FROM AUTHOR]

The world is rich in saline-alkali water resources, and the effective utilization of saline-alkali water resources is of great significance to the promotion of human economic development. This study investigated the effects of carbonate saline water on the immune, antioxidant, osmotic regulatory, and metabolic capacities of S. paramamosain. Bicarbonate stress resulted in damage to the hepatopancreas, as well as significantly upregulating the activities of superoxide dismutase and catalase, indicating that the antioxidant capacity increased under short-term bicarbonate stress, but then decreased. Long-term bicarbonate stress caused further oxidative damage. The activities of alkaline phosphatase and acid phosphatase also significantly increased, indicating an initially enhanced immune response of S. paramamosain to carbonate salinity stress that then declined, suggesting that the ability to mount an immune response decreased following long-term exposure. High bicarbonate levels also significantly inhibited the osmotic regulation ability of S. paramamosain , and negatively impacted metabolic indexes (e.g., glucose, total cholesterol, triglycerides, urea nitrogen, and uric acid). Three groups of metabolites were differentially upregulated and 95 were differentially downregulated, including 'organooxygen compounds', 'carboxylic acids and derivatives', 'fatty acyls', 'glycerophospholipids' and 'keto acids and derivatives'. Thus, long-term bicarbonate stress also decreased energy metabolism in S. paramamosain. Under long-term bicarbonate stress, related products of energy metabolism were significantly downregulated, and bicarbonate stress significantly inhibited energy uptake in S. paramamosain. This study analyzed the stress mechanism of bicarbonate on S. paramamosain , further enriched the culture theory of S. paramamosain , in order to provide a theoretical basis for the improvement of saline-alkaline water culture technology of S. paramamosain. [Display omitted] • Bicarbonate exposure damaged the hepatopancreas of Scylla paramamosain. • Stress of bicarbonate induced oxidative damage, decreased the immune response. • Bicarbonate stress inhibited the osmotic regulation ability of S. paramamosain. • Long-term bicarbonate stress reduced the metabolic level in S. paramamosain. [ABSTRACT FROM AUTHOR]

It is known that the marine euryhaline crab, mud crab (Scylla paramamosain) , is capable of adapting to low salinity conditions through an innate osmoregulatory system. However, the influence of nutritional conditions during low salinity adaptation has not been fully elucidated. In this study, transcriptome analysis was employed to examine whether low salinity affects the AMP-activated protein kinase (Ampk) signaling pathway, and thereby carbohydrate and lipid metabolism. Further analysis revealed that low salinity activated the expression of P-Ampk and promoted glycolysis and lipolysis, which enhances glycogen and lipid utilization. Nutritional deprivation confirmed that nutrients influenced the survival and osmotic pressure regulation of mud crab under to low salinity via the Ampk signaling pathway. During adaptation to low salinity, carbohydrates were the primary energy source in the initial 7 days, followed by lipids. Further investigation showed that pharmacological stimulation of mechanistic targets in the Ampk signaling pathway using metformin could promote the osmotic pressure regulation of mud crab, confirmed the pivotal role of this pathway in low salinity adaptation. Overall, the present study demonstrated that nutrition, metabolism and osmotic pressure regulation interactively contribute to salinity adaptation in mud crab. Specifically, low salinity induced remodeling of nutritional metabolism homeostasis and promoted glycolipid catabolism, thereby providing energy for osmotic pressure regulation in mud crabs. [Display omitted] • Nutrition metabolism is closely involved in low salinity adaptation in mud crabs. • Nutritional deprivation decreased the osmotic pressure regulation ability. • Enhanced utilization of carbohydrate and lipid was key for low salinity adaptation. • The Ampk is involved in the regulation of low salinity adaptation as a fuel sensor. [ABSTRACT FROM AUTHOR]

Soft-shell crabs are highly valued for their commercial significance and culinary appeal. To enhance production of soft-shell crabs, careful attention should be paid to the water calcium concentration in their culture. This study investigated the influences of different levels of calcium concentrations on the molting and growth of mud crab (Scylla paramamosain) within a meticulously controlled recirculating aquaculture system (RAS). We established three distinct water calcium concentration gradients (200, 300, and 450 mg/L) to comprehensively assess feeding habits, molting patterns, growth, and tissue calcium levels of mud crab. Initially, we observed a gradual reduction in water calcium concentrations with increments of crab molting events in RAS. Throughout one molting cycle, the feeding incidence of the crabs remained consistently high from 4 days to 37 days post-molt, irrespective of different calcium concentrations. Nonetheless, high water calcium levels (300 and 450 mg/L) significantly shortened molt intervals and accelerated exoskeletal calcification. Specifically, the molt intervals were 52.30 ± 2.72 d, 41.65 ± 5.24 d, and 37.70 ± 3.02 d, while the carapace hardening durations were 21.51 ± 4.33 h, 17.23 ± 3.38 h, and 13.46 ± 2.76 h at water calcium concentrations of 200, 300, and 450 mg/L, respectively. Moreover, elevated calcium concentrations also significantly enhanced weight gain of the mud crab during molting. Noteworthy, regardless of fluctuations in water calcium concentration, the condition factor of the molting crabs was approximately 63%, which could be an indicator of crab selection in soft-shell crab cultivation. Furthermore, the dynamic changes in calcium concentrations were disparate among different tissues in the post-molt stage. Gill and exoskeleton tissues exhibited an upward trend in calcium concentrations, while hemolymph and hepatopancreas tissues displayed distinct patterns of decrease followed by increase. Gill and exoskeleton tissues were identified as primary sites for calcium absorption and utilization, evidenced by a positive correlation between high calcium concentrations and increased calcium content in these tissues at 6 h and 3 d post-molt. Overall, our findings provide practical evidence for optimizing aquaculture management strategies through adjustments in water calcium concentration, thus to enhance production efficiency and profitability in soft-shell mud crab aquaculture. • Higher water calcium significantly shortened molt intervals, accelerated carapace hardnessduring molting cycles. • The condition factor of crabs at around 63% could be an indicator for crab selection in soft-shell crab cultivation. • Dynamic changes in calcium concentrations varied among different tissues in the post-molt stage. • Gill and exoskeleton tissues were identified as primary sites for calcium absorption and utilization. [ABSTRACT FROM AUTHOR]

A six-week feeding trial was carried out to investigate the impact of dietary ARA and CHOL levels, and their interactions, on the growth, lipid metabolism, and molting response of juvenile mud crabs (Scylla paramamosain) with an initial weight of 17.46 ± 0.04 g. A 3 × 3 two-factor design was adopted for 9 experimental diets with 0%, 0.75% and 1.5% ARA levels and 0%, 0.75% and 1.5% CHOL supplemental levels, respectively. The results showed that ARA and CHOL had significant interaction effects on percent weight gain and specific growth rate. Percent weight gain and specific growth rate of crabs fed 0.75% ARA diet were significantly higher than those of crabs fed 0% ARA diet, but only when dietary CHOL content was 0.75%. ARA and CHOL levels had significant interaction on crude lipid content and percentage of Oil Red O staining area in the hepatopancreas, and when 0.75% ARA was supplemented to 0.75% CHOL diet, the levels of crude lipid and percentage of Oil Red O staining area in hepatopancreas were significantly up-regulated. Moreover, 0.75% CHOL diet that was supplemented with 0.75% ARA significantly up-regulated the levels of DHA, EPA, and ARA in the hepatopancreas. Additionally, significant interactions between ARA and CHOL were found in expression levels of genes related to long-chain polyunsaturated fatty acid anabolism (Δ9 fad , elovl4 , elovl5 and elovl6), fatty acid anabolism and catabolism (aco3 , cpt1 and acc), fatty acid transport (fabp1 , fabp3 and fatp4), and lipid catabolism and anabolism (hsl , srebp1 , lpl and hl) in the hepatopancreas. 1.5% dietary ARA significantly increased the content of serum T-CHO and the activity of hepatopancreatic LCAT. The addition of 1.5% dietary CHOL significantly reduced the concentration of 20E in the serum. Furthermore, both 0.75% and 1.5% dietary ARA reduced concentrations of MIH and CHH in the serum. Significant interactions between dietary ARA and CHOL were observed in the concentrations of 20E and MIH in the serum. Dietary ARA significantly increased the expression levels of dib , e74b , e75 and ftz-f1 in the hepatopancreas. In conclusion, adding 6.02–11.06 mg/kg ARA to 1.21–1.27 mg/kg CHOL diets or adding 6.04 mg/kg ARA to 6.17–7.02 mg/kg CHOL diets both promoted cholesterol metabolism, deposition of essential fatty acids and lipids, and activated ecr -mediated molting response pathway, with these positive benefits likely resulting from a significant increase in PG. • Adding 6.04 mg/kg ARA to 6.17–7.02 mg/kg CHOL diet can promote the growth of mud crabs. • Dietary 11.37–11.60 mg/kg cholesterol reduced 20E synthesis and had a feedback regulation effect on MIH. • Adding 6.04 mg/kg ARA to 6.17–7.02 mg/kg CHOL diet enhanced molting response pathway. • The interaction of ARA and CHOL promoted the deposition of lipids and essential fatty acids. [ABSTRACT FROM AUTHOR]

Laminin receptor (LR), which mediating cell adhesion to the extracellular matrix, plays a crucial role in cell signaling and regulatory functions. In the present study, a laminin receptor gene (SpLR) was cloned and characterized from the mud crab (Scylla paramamosain). The full length of SpLR contained an open reading frame (ORF) of 960 bp encoding 319 amino acids, a 5′ untranslated region (UTR) of 66 bp and a 3′ UTR of 49 bp. The predicted protein comprised two Ribosomal-S2 domains and a 40S-SA-C domain. The mRNA of SpLR was highly expressed in the gill, followed by the hepatopancreas. The expression of SpLR was up-regulated after mud crab dicistrovirus-1(MCDV-1) infection. Knocking down SpLR in vivo by RNA interference significantly down-regulated the expression of the immune genes SpJAK , SpSTAT , SpToll1 , SpALF1 and SpALF5. This study shown that the expression level of SpToll1 and SpCAM in SpLR -interfered group significantly increased after MCDV-1 infection. Moreover, silencing of SpLR in vivo decreased the MCDV-1 replication and increased the survival rate of mud crabs after MCDV-1 infection. These findings collectively suggest a pivotal role for SpLR in the mud crab's response to MCDV-1 infection. By influencing the expression of critical innate immune factors and impacting viral replication dynamics, SpLR emerges as a key player in the intricate host-pathogen interaction, providing valuable insights into the molecular mechanisms underlying MCDV-1 pathogenesis in mud crabs. • Identified a Laminin Receptor gene in mud crab. • Silencing of SpLR in vivo decreased the MCDV-1 replication. • SpLR played a key player in the intricate host-pathogen interaction. [ABSTRACT FROM AUTHOR]

Mud crab (Scylla paramamosain) has become an important mariculture crab along the southeast coast of China due to its strong adaptability, delicious taste, and rich nutrition. Several vertebrate steroid hormones and their synthesis-related genes and receptors have been found in crustaceans, but there are few reports on their synthesis process and mechanism. 3-beta-hydroxysteroid dehydrogenase (HSD3B) is a member of the Short-chain Dehydrogenase/Reductase (SDR) family, and an indispensable protein in vertebrates' steroid hormone synthesis pathway. In this study, the SpHsd3b gene sequence was obtained from the transcriptome data of S. paramamosain , and its full-length open reading frame (ORF) was cloned. The spatial and temporal expression pattern of SpHsd3b was performed by quantitative real-time PCR (qRT-PCR). SpHsd3b dsRNA interference (RNAi) and HSD3B inhibitor (trilostane) were used to analyze the function of Sp HSD3B. The results showed that the SpHsd3b gene has an 1113 bp ORF encoding 370 amino acids with a 3β-HSD domain. Sp HSD3B has lower homology with HSD3B of vertebrates and higher homology with HSD3B of crustaceans. SpHsd3b was expressed in all examined tissues in mature crabs, and its expression was significantly higher in the testes than in the ovaries. SpHsd3b expression level was highest in the middle stage of testicular development, while its expression was higher in the early and middle stages of ovarian development. RNAi experiment and trilostane injection results showed that Sp HSD3B had regulatory effects on several genes related to gonadal development and steroid hormone synthesis. 15-day trilostane suppression could also inhibit ovarian development and progesterone level of hemolymph. According to the above results, crustaceans may have steroid hormone synthesis pathways like vertebrates, and the Hsd3b gene may be involved in the gonadal development of crabs. This study provides further insight into the function of genes involved in steroid hormone synthesis in crustaceans. • Steroid hormone synthesis pathway-related gene— Hsd3b was identified from Scylla paramamosain. • SpHsd3b knockdown can decrease the expression of gonadal development and steroid hormone synthesis-related genes. • Trilostane can inhibit ovarian development and lower progesterone level of hemolymph. • crustaceans may have steroid hormone synthesis pathways like vertebrate. [ABSTRACT FROM AUTHOR]

As a crucial member of pattern-recognition receptors (PRRs), the Tolls/Toll-like receptors (TLRs) gene family has been proven to be involved in innate immunity in crustaceans. In this study, nine members of TLR gene family were identified from the mud crab (Scylla paramamosain) transcriptome, and the structure and phylogeny of different Sp TLRs were analyzed. It was found that different Sp TLRs possessed three conserved structures in the TIR domain. Meanwhile, the expression patterns of different Sptlr genes in examined tissues detected by qRT-PCR had wide differences. Compared with other Sptlr genes, Sptlr-6 gene was significantly highly expressed in the hepatopancreas and less expressed in other tissues. Therefore, the function of Sptlr-6 was further investigated. The expression of the Sptlr-6 gene was up-regulated by Poly I: C, PGN stimulation and Vibrio parahaemolyticus infection. In addition, the silencing of Sptlr-6 in hepatopancreas mediated by RNAi technology resulted in the significant decrease of several conserved genes involved in innate immunity in mud crab after V. parahaemolyticus infection, including relish , myd88 , dorsal , anti-lipopolysaccharide factor (ALF), anti-lipopolysaccharide factor 2 (ALF-2) and glycine-rich antimicrobial peptide (glyamp). This study provided new knowledge for the role of the Sptlr-6 gene in defense against V. parahaemolyticus infection in S. paramamosain. • Nine TLRs were identified from the transcriptome data of mud crab Scylla paramamosain. • The novel Sptlr-6 had a high expression level in the hepatopancreas of S. paramamosain. • PGN, Poly I: C and Vibrio injection induced the expression of Sptlr-6 in the hepatopancreas. • Sptlr-6 played a crucial role via the Dorsal/Relish-AMPs pathway in response to Vibrio challenge. [ABSTRACT FROM AUTHOR]

Phosphofructokinase (PFK), the key enzyme of glycolysis, can catalyze the irreversible transphosphorylation of fructose-6-phosphate forming fructose-1, 6-biphosphate. In the present study, a PFK gene from the mud crab Scylla paramamosain , named SpPFK , was cloned and characterized. The full length of SpPFK contained a 5′untranslated region (UTR) of 249 bp, an open reading frame of 2,859 bp, and a 3′UTR of 1,248 bp. The mRNA of SpPFK was highly expressed in the gill, followed by the hemocytes and muscle. The expression of SpPFK was significantly up-regulated after mud crab dicistrovirus-1 (MCDV-1) infection. Knocking down SpPFK in vivo by RNA interference significantly reduced the expression of lactate dehydrogenase after MCDV-1 infection. Furthermore, silencing of SpPFK in vivo increased the survival rate of mud crabs and decreased the MCDV-1 copies in the gill and hepatopancreas after MCDV-1 infection. All these results suggested that SpPFK could play an important role in the process of MCDV-1 proliferation in mud crab. • The full-length cDNA sequence of SpPFK was first cloned from Scylla paramamosain. • SpPFK might be involved in mud crab response to MCDV-1 infection. • The MCDV-1 proliferation decreased and the survival rate of mud crab increased after SpPFK silencing. [ABSTRACT FROM AUTHOR]

Mud crab, Scylla paramamosain, is an important aquaculture species. In recent decades, with the development of mud crab farming, seed production has become more and more important. Therefore, a precise understanding of embryonic and larval development is required for future study or application. In this study, we described the complete embryonic and larval development of S. paramamosain under the following conditions: temperature 28°C–31°C, salinity 26,000–30,000 mg/L, pH 7.9–8.2, and dissolved oxygen 4–5 mg/L. The embryonic development was divided into five stages: cleavage, blastula, appendage, eyespot‐heartbeat, and prehatching. The entire embryonic period spanned 9–11 days. The larval development consisted of six stages: zoea I (Z1), zoea II (Z2), zoea III (Z3), zoea IV (Z4), zoea V (Z5), and the megalopal stage. The duration of the larval stage was about 22–24 days, and it took about 3 days for each stage of Z1–Z4, about 4–5 days for Z5, and about 5–6 days for the megalopal stage. In general, in this study, we presented a comprehensive description of both embryonic and larval development with massive image information, which would help diagnose different developmental stages and provide an important guidance for future study or application. [ABSTRACT FROM AUTHOR]

Tropomyosin (TM) is an important crustacean (Scylla paramamosain) allergen. This study aimed to assess Maillard-reacted TM (TM-G) induction of allergenic responses with cell and mouse models. We analyzed the difference of sensitization and the ability to induce immune tolerance between TM and TM-G by in vitro and in vivo models, then we compared the relationship between glycation sites of TM-G and epitopes of TM. In the in vitro assay, we discovered that the sensitization of TM-G was lower than TM, and the ability to stimulate mast cell degranulation decreased from 55.07 ± 4.23% to 27.86 ± 3.21%. In the serum of sensitized Balb/c mice, the level of specific IgE produced by TM-G sensitized mice was significantly lower than TM, and the levels of interleukins 4 and interleukins 13 produced by Th2 cells in spleen lymphocytes decreased by 82.35 ± 5.88% and 83.64 ± 9.09%, respectively. In the oral tolerance model, the ratio of Th2/Th1 decreased from 4.05 ± 0.38 to 1.69 ± 0.19. Maillard reaction masked the B cell epitopes of TM and retained some T cell epitopes. Potentially, Maillard reaction products (MRPs) can be used as tolerance inducers for allergen-specific immunotherapy. [ABSTRACT FROM AUTHOR]

p53, the guardian of the genome, is a short-lived protein that is tightly controlled at low levels by constant ubiquitination and proteasomal degradation in higher organisms. p53 stabilization and activation are early crucial events to cope with external stimuli in cells. However, the role of p53 ubiquitination and its relevant molecular mechanisms have not been addressed in invertebrates. In this study, our findings revealed that both HUWE1 (HECT, UBA, and WWE domain-containing E3 ubiquitin-protein ligase 1) and TRAF6 (tumor necrosis factor receptor-associated factor 6) could serve as E3 ubiquitin ligases for p53 in mud crabs (Scylla paramamosain). Moreover, the expression of HUWE1 and TRAF6 was significantly downregulated during white spot syndrome virus (WSSV) infection, and therefore the ubiquitination of p53 was interrupted, leading to the activation of apoptosis and reactive oxygen species (ROS) signals through p53 accumulation, which eventually suppressed viral invasion in the mud crabs. To the best of our knowledge, this is the first study to reveal the p53 ubiquitination simultaneously induced by two E3 ligases in arthropods, which provides a novel molecular mechanism of invertebrates for resistance to viral infection. [ABSTRACT FROM AUTHOR]

Crustacean cardioactive peptide (CCAP) is a pleiotropic neuropeptide, but its immunomodulatory role is not clear. Herein, the mud crab Scylla paramamosain provides a primitive model to study crosstalk between the neuroendocrine and immune systems. In this study, in situ hybridization showed that Sp-CCAP positive signal localized in multiple cells in the nervous tissue, while its conjugate receptor (Sp-CCAPR) positive signal mainly localized in the semigranular cells of hemocytes. The Sp-CCAP mRNA expression level in the thoracic ganglion was significantly up-regulated after lipopolysaccharide (LPS) stimulation, but the Sp-CCAP mRNA expression level was up-regulated firstly and then down-regulated after the stimulation of polyriboinosinic polyribocytidylic acid [Poly (I:C)]. After the injection of Sp- CCAP synthesis peptide, the phagocytosis ability of hemocytes was significantly higher than that of synchronous control group. Simultaneously, the mRNA expression of phagocytosis related gene (Sp-Rab5), nuclear transcription factor NF-κB homologues (Sp-Relish), C-type lectin (Sp-CTL-B), prophenoloxidase (Sp-proPO), pro-inflammatory cytokines factor (Sp-TNFSF , Sp-IL16) and antimicrobial peptides (Sp-ALF1 and Sp-ALF5) in the hemocytes were also significantly up-regulated at different time points after the injection of Sp -CCAP synthetic peptide, but Sp-TNFSF , Sp-ALF1 and Sp-ALF5 were down-regulated significantly at 24h. In addition, RNA interference of Sp - CCAP suppressed the phagocytic activity of hemocytes and inhibited the mRNA expression of Sp-Rab5 , Sp-Relish , Sp-CTL-B , Sp-TNFSF, Sp-IL16 and Sp-ALF5 in the hemocytes, and ultimately weakened the ability of hemolymph bacteria clearance of mud crab. Taken together, these results revealed that CCAP induced innate immune and increased the anti-infection ability in the mud crab. ● Sp - CCAP mRNA in the thoracic ganglion changed during LPS and Poly (I:C) stimulation. ● Sp-CCAP mRNA was localized in various types of cells on the nervous system, while Sp-CCAPR was localized in the semigranular cells of hemocytes. ● Sp -CCAP modulated the phagocytosis and immune effector molecules of hemocytes. ● Sp -CCAP enhanced the resistance of mud crab to bacterial infections. [ABSTRACT FROM AUTHOR]

• Sp TIA-1 is overexpressed during WSSV infection in mud crab. • Sp TIA-1 suppresses WSSV infection via apoptosis promotion. • Sp TIA-1 can activate caspase signaling in mud crab. • Sp TIA-1 can modulate MMP (⊿ψm) by regulating ROS levels. TIA-1 (T cell restricted intracellular antigen-1) is a kind of RNA-binding protein which serves as the downstream of CED-9 (a BCL2 homolog) and induces apoptosis under stress conditions. So far, the function of apoptosis mediated by TIA-1 has been extensively studied in higher animals, and apoptosis happens to be related to biological immune defense. However, the involvement of TIA-1 in the study of immune function during viral infection has not been clearly studied, especially in marine invertebrates. In the study, Sp TIA-1 in mud crab (Scylla paramamosain) was specifically identified. The Open Reading Frame (ORF) of Sp TIA-1 was consisted of 1116 nucleotide bases and encoded 372 amino acids. Besides, the results showed that the expression of Sp TIA-1 was obviously up-regulated during WSSV (White Spot Syndrome Virus) infection in hemocytes of mud crab. Furthermore, through RNAi approach, we found that Sp TIA-1 could activate Caspase-3 signaling and increase ROS levels to reduce mitochondrial membrane potential, resulting in the increase of apoptosis rate in hemocytes, which eventually suppressed WSSV multiplication in mud crab. The current study therefore improves the knowledge of antiviral immunity in mud crab and provides new insights into the innate immunity of marine crustaceans. [ABSTRACT FROM AUTHOR]

Apoptosis plays essential roles in the immune defense mechanism against pathogen infection. Caspase 3 is a family of cysteine proteases involved in apoptosis and the immune response. In this study, the full-length of mud crab (Scylla paramamosain) caspase 3 (designated as Sp-caspase 3) was cloned and characterized. The open reading frame of Sp-caspase 3 was comprised a 1035 bp, which encoded a putative protein of 344 amino acids. Sp-caspase 3 was ubiquitously expressed in various tissues with a high-level expression in hemocytes. Cellular localization analysis revealed that Sp-caspase 3 was located in the cytoplasm and nucleus. Over-expression of Sp-caspase 3 could induce cell apoptosis. In addition, V. Parahaemolyticus infection induced the relative expression of caspase-3 mRNA and increased caspase-3 activity. Knocking down Sp-caspase 3 in vivo significantly reduced cell apoptosis and increased mortality of mud crab after V. parahaemolyticus infection. These results indicated that Sp-caspase 3 played important roles in the immune response and apoptosis against bacterial infection. • Identified a caspase 3 gene in mud crab. • Over-expression of Sp-caspase 3 induced cell apoptosis. • Knocking down Sp-caspase 3 increased mortality of mud crab after V. parahaemolyticus infection. [ABSTRACT FROM AUTHOR]

This study was carried out to analyse the growth performance, feed utilization, and antioxidant capacity of juvenile mud crab (Scylla paramamosain) reared in two conditions. Here, a new indoor polypropylene tank culture system and a traditional outdoor pond cage facility were used to perform feeding experiments on juvenile crabs. After eight weeks, the survival rate, weight gain, moulting rate and feed efficiency of crabs cultured in polypropylene tanks were markedly higher than those cultured in pond cages. Moreover, the activities of serum acid phosphatase (ACP) and alkaline phosphatase (ALP), and the antioxidant indices including glutathione peroxidase (GSH-PX), glutathione transferase (GST), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in hepatopancreas were higher in crabs cultured in the polypropylene tank system than those in pond cages. Based on these results, compared with the traditional pond cages, the polypropylene tank culture system is more suitable for the short-term culture of mud crabs. Résumé: Cette étude avait pour but d'analyser la performance de croissance, l'utilisation de la nourriture et les capacités antioxydantes des juvéniles du crabe de vase (Scylla paramamosain) élevé dans deux conditions. Un nouveau système d'élevage intérieur dans un bassin en polypropylène et la traditionnelle cage dans un étang à l'extérieur ont été utilisés pour les expériences d'alimentation sur les crabes juvéniles. Après 8 semaines, le taux de survie, le gain de poids, le rythme de mues et l'efficacité alimentaire des crabes élevés dans les bassins en polypropylène ont été plus élevés que ceux des crabes élevés dans les cages en étang. De plus les activités sériques de la phosphatase acide (ACP), de la phosphatase alcaline (ALP), les valeurs d'antioxydants dont la glutathion peroxydase (GSH-PX), la glutathion transférase (GST), la superoxyde dismutase (SOD) et les capacités antioxydantes totales (T-AOC) dans l'hépatopancréas étaient plus élevées chez les crabes des bassins en polypropylène que ceux des cages en étang. Sur la base de ces résultats, pour un élevage à court terme des crabes de vase les bassins en polypropylène conviennent mieux que les traditionnelles cages en étang. [ABSTRACT FROM AUTHOR]

The mud crab Scylla paramamosain is one of the economically important aquaculture species in China. The larval development of the mud crab is characterized by two significant morphological changes, from the 5th zoea (Z5) to the megalopa (M) stage and from the M to the first juvenile crab (C1) stage. In this study, we found that methyl farnesoate (MF) could prohibit the Z5 to M metamorphosis in a concentration-dependent manner, and that a concentration of 10 μ M MF could completely prohibit the Z5 metamorphosis. Farnesoic acid (FA) could also prohibit the Z5 metamorphosis, but its effects seemed to be concentration-independent. In addition, MF could delay rather than prohibit the M to C1 metamorphosis, while FA had no effect on the M to C1 metamorphosis at all. To summarize, it is hypothesized that either absence of MF and FA, or at least very low levels of these substances, might be necessary for a successful Z5 to M metamorphosis. Résumé: Le crabe de boue Scylla paramamosain est l'une des espèces d'aquaculture économiquement importante en Chine. Le développement larvaire de ce crabe est caractérisé par deux changements morphologiques significatifs, de la 5ème zoé (Z5) au stade mégalope (M) et de M au premier stade juvénile crabe (C1). Dans cette étude nous avons trouvé que le méthyl-farnésoate (MF) pouvait inhiber la métamorphose de Z5 d'une manière dose-dépendante, et qu'une concentration de 10 μ M de MF pouvait complètement empêcher la métamorphose de la Z5. L'acide farnésoïque (FA) peut aussi inhiber la métamorphose de la Z5, mais ses effets semblent indépendants de la dose. De plus, MF peut retarder plutôt qu'inhiber la métamorphose de M à C1, tandis que FA n'a aucun effet sur la métamorphose de M à C1. En résumé, l'hypothèse est émise que, soit l'absence de MF et FA, soit au moins un faible taux de ces substances, serait nécessaire pour une métamorphose réussie de Z5 à M. [ABSTRACT FROM AUTHOR]

Scylla paramamosain is one of the commercially crucial marine crustaceans belonging to the genus Scylla, which is commonly distributed along the coasts of China. Proteomic data are scarce for the mud crab. Salinity is one of the ecological factors that affect S. paramamosain during overwintering. To understand the energy metabolism mechanism adapted to salinity, we analysed the proteomics of S. paramamosain hepatopancreas in response to two different salinities (4‰ and 25‰). A total of 1283 proteins were detected, of which 426 down‐regulated proteins and 83 up‐regulated proteins were associated with metabolism (p < 0.05). Among these proteins related to metabolic pathways (16 pathways), we identified angiotensin‐converting enzyme, trypsin, glutamate dehydrogenase, aminomethyl transferase, hexokinase, pyruvate kinase, glucose‐6‐phosphate dehydrogenase, L‐lactate dehydrogenase, superoxide dismutase, alkaline phosphatase, catalase and xanthine dehydrogenases. Additionally, real‐time PCR showed mRNA expression of differentially expressed genes correlated positively with their protein levels. Compared with 25‰ salinity group, 4‰ salinity group was involved in amino acid metabolism, carbohydrate metabolism, energy metabolism, lipid metabolism and inorganic ion metabolism by regulating related proteins, which made the metabolism of the overwintering S. paramamosain more vigorous in the low salt environment, and hepatopancreas consumed more energy to maintain life activities. These data are the first to reveal the molecular mechanism of overwintering S. paramamosain in response to different salinities at the protein level. The study provides important information for the aquaculture production of S. paramamosain during indoor overwintering. [ABSTRACT FROM AUTHOR]

Oxidative stress is considered as the toxicity mechanism of environmental stressors on aquatic organisms. This study aims to explore the effects of oxidative stress on physiological responses, DNA damage and transcriptional profiles of the mud crabs Scylla paramamosain. In the present study, mud crabs were injected with 0.1% and 1% hydrogen peroxide (H 2 O 2) for 72 h. The results showed that superoxide dismutase and catalase activities significantly decreased after H 2 O 2 injection. Malondialdehyde content, H 2 O 2 content, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activity significantly increased after H 2 O 2 injection. Moreover, DNA damage occurred after H 2 O 2 injection. Transcriptome analysis showed that 531 and 372 differentially expressed genes (DEGs) were identified after 0.1% and 1% H 2 O 2 injection, respectively. These DEGs were mainly involved in the oxidative stress response and immune functions. All these results indicated that oxidative stress could impair both antioxidant defense systems and immune systems. Transcriptome analysis provided valuable information on gene functions associated with the response to oxidative stress in the mud crab. • First transcriptome of the mud crab response to hydrogen peroxide stress. • H 2 O 2 activated FOXO signaling pathway. • DNA damage response and apoptosis signaling pathways played important roles in response to oxidative stress. [ABSTRACT FROM AUTHOR]

Overwintering is an important part of the conservation of Scylla paramamosain, and salinity is a primary parameter affecting this species' metabolism at this particular time. We compared and analysed gene sequences responsible for the metabolism of S. paramamosain at 4‰ versus 25‰ salinities using transcriptome analysis, in order to find out the optimum salinity for S. paramamosain during overwintering. A total of 5895 genes were detected, of which 105 down‐regulated genes and 131 up‐regulated genes were associated with metabolism (p < 0.05). Among these genes related to metabolic pathways (117 pathways), we identified D‐aspartate oxidase, D‐amino acid oxidase, creatine kinase, sarcosine oxidase, citrate synthase, transferase, glycogen synthase, hexokinase, carbonic anhydrase, glutamine synthetase, V‐type H+‐transporting ATPase, 3′‐phosphoadenosine 5′‐phosphosulphate synthase, fatty acid synthase and others. Additionally, the consistency between qRT‐PCR results and transcriptome data reflected the reliability of transcriptome results in the present study. Compared with the 25‰ salinity group, the 4‰ salinity group promoted energy metabolism, amino acid metabolism, lipid metabolism and carbohydrate metabolism by regulating metabolism‐related genes, which made the overwintering S. paramamosain more active in the low‐salt environment, and hepatopancreas consumed more energy to maintain life activities. These results improve our understanding on molecular mechanisms and metabolic pathways associated with salinity changes in S. paramamosain during overwintering. The data presented in this study are also the first to reveal the molecular mechanisms of S. paramamosain during overwintering in response to different salinities at the gene level. [ABSTRACT FROM AUTHOR]

Overwintering is an important part of the life cycle of Scylla paramamosain. Salinity has a significant effect on the growth and metabolism of overwintering S. paramamosain. 4‰ and 25‰ are typical salinities in different regions where S. paramamosain overwinters. In order to find the optimum salinity for overwintering, the metabolites in overwintering S. paramamosain at salinities of 4‰ and 25‰ were analysed and compared using GC–MS technology. In this study, the weight gain rate of S. paramamosain was 5.51% at 4‰ salinity and 10.69% at 25‰ salinity after overwintering. A total of 1254 valid peaks and 373 metabolites were detected, including 160 significantly different metabolites (16 down‐regulated metabolites and 144 up‐regulated metabolites). In the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, 22 pathways were associated with metabolic changes; they have or identified L‐isoleucine, L‐lysine, urea, D‐ribose‐5‐phosphate, glucose‐6‐phosphate, fumaric acid, L‐lactic acid, docosahexaenoic acid and palmitic acid. Compared with the 25‰ salinity group, 4‰ salinity group promoted amino acid metabolism, carbohydrate metabolism, membrane transport and lipid metabolism through these differential metabolites, so that overwintering S. paramamosain needs to participate in more metabolic activities at 4‰ salinity, and hepatopancreas consumes more energy to maintain life activities, which indicated that 4‰ salinity was not conducive to the overwintering of S. paramamosain. [ABSTRACT FROM AUTHOR]

Scylla paramamosain is a kind of large euryhaline marine crab. As an important physicochemical parameter of seawater, salinity has a great impact on the survival, growth and quality of Scylla paramamosain. This research tested the content of non-volatile flavor substance, lactic acid and taurine on the 0, 1st, 3rd, 7th and 15th day in three salinity gradients (3, 13, 23) with HPLC (High-performance Liquid Chromatography) technology. Results have shown that in low salinity stress, the cumulative amount of free amino acids in muscle of Scylla paramamosain is more than that in hepatopancreas, while the cumulative amount of essential amino acids in hepatopancreas is more than that in muscle. In muscle, contents of three flavor amino acids are ranked as follows: sweet, bitter and delicious amino acid, and in hepatopancreas, it is bitter, sweet and delicious amino acid. The fluctuation rule of free amino acid, essential amino acid and lactic acid in Scylla paramamosain in the low salinity group is similar to that of other salinity control group, while the content of sweet amino acid, bitter amino acid, nucleotide, EUC, taurine is different from that of other salinity control groups. [ABSTRACT FROM AUTHOR]

As a conditionally essential amino acid (CEAA), taurine plays an important role in the growth, development, and physiological metabolism of aquatic animals; however, its demand level in the mud crab Scylla paramamosain is still poorly understood. A 60-day growth trial was conducted to investigate the effects of different taurine levels (0% (T0.0), 0.2% (T0.2), 0.4% (T0.4), 0.8% (T0.8), and 1.6% (T1.6)) added to diet on the survival, growth, body composition, immunity, antioxidant and osmoregulatory capacity of early juvenile S. paramamosain (initial body weight 8.69 ± 0.19 mg). The results showed that dietary taurine levels >0.4% (inclusive) significantly increased the survival of early juvenile mud crabs. The growth performance (final body weight (FBW), weight gain (WG), specific growth rate (SGR)) of early juvenile mud crabs increased significantly with increasing dietary taurine levels, reaching a maximum in the T0.8 group, and the target of rapamycin (tor) gene transcription levels also peaked in the T0.8 group. The body composition of mud crabs was not affected by dietary treatments. Further, dietary taurine significantly increased digestive enzyme (trypsin, lipase, and amylase) activities and transcript levels of appetite-related genes (neuropeptide F1 (npf1) and neuropeptide F2 (npf2)) in early juvenile mud crabs. In addition, dietary taurine increased the expression levels of immune-related genes (prophenoloxidase (proPO), prophenoloxidase activating factor 1 (ppaf1), prophenoloxidase activating factor 2 (ppaf2), crustin antimicrobial peptide (crustin), lysozyme (lzm)) and antioxidant capacity (total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and catalase (CAT) activities) in early juvenile mud crabs. Finally, the results of the acute salinity challenge showed that the early juvenile mud crabs' survival in the T0.8 group was significantly higher than that of the other groups, while significantly higher Na+/K+-ATPase (NKA) activity and Na+/K+-ATPase α-subunit (nka-α) and Na+/K+/2Cl−-cotransporter (nkcc) gene expression levels were also detected in the T0.8 group. Together with growth performance, immunity, antioxidant capacity and osmoregulatory capacity, the present study concluded that the appropriate dietary taurine level for early juvenile mud crabs was 1.08%–1.33%. [Display omitted] • The appropriate dietary taurine level for juvenile mud crabs was 1.08%–1.33%. • Dietary taurine above 0.4% significantly improved the survival of juvenile mud crabs. • Antioxidant capacity of mud crabs was significantly improved by 0.8% dietary taurine. • 0.8% dietary taurine significantly improved osmoregulation in juvenile mud crabs. [ABSTRACT FROM AUTHOR]