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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]

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]

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]

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]

The mud crab (Scylla paramamosain) is among the most economically important seawater crustacean species. Overwintering is one of an important stage for aquatic animals, and light intensity has an important effect on the conservation of Scylla paramamosain during overwintering. Here, S. paramamosain were exposed to three different light intensities (0, 1.43 and 40.31 μmol m−2 s−1) for four months. Then, GC‐MS‐based metabolomic analyses of the hepatopancreas were performed to assess differences in the metabolites produced by S. paramamosain exposed to different light intensities. The weight gain rate (WGR) was also compared among treatment groups. The LL group displayed significantly greater WGRs than the HL group. A total of 117 and 128 significantly different metabolites (SDMs) were identified in LL group and HL group respectively (VIP > 1 and p <.05). The identified SDMs were associated with the amino acid metabolism, the carbohydrate metabolism, the fatty acid metabolism, the nucleotide metabolism and membrane transport. The results suggested that light intensity affected the metabolic pathways in S. paramamosain by influencing the citrate cycle (TCA cycle), the biosynthesis of amino acids and unsaturated fatty acids, ABC transporters, and the purine metabolism. Further integrated analyses of key metabolic pathways showed that the metabolism of S. paramamosain was more vigorous under light conditions. [ABSTRACT FROM AUTHOR]

Overwintering is one of an important stage for aquatic animals, and light intensity has an important effect on the conservation of Scylla paramamosain during overwintering. Three different light intensity levels (0, 1.43 and 40.31 μmol m−2 s−1) were used to explore the effects of light intensity on digestion and immune responses, plasma cortisol and amino acid composition of S. paramamosain. This is the first report that the adult S. paramamosain can be effect by the light intensity. The results showed that S. paramamosain has a strong stress response under high light intensity. Compared with darkness condition, digestive enzyme activity was higher under light condition. S. paramamosain reared under low light conditions had enhanced immunity, and it raised in light conditions exhibited superior qualities to those cultured in dark conditions. The results of this study demonstrated that low light levels are most suitable for breeding and improving the quality of S. paramamosain. [ABSTRACT FROM AUTHOR]

Transformer‐2 (Tra‐2) is an mRNA splicing factor that acts in concert with Tra to regulate the female sexual development in Drosophila melanogaster. In decapods, as no Tra homologues have been identified, the role of Tra‐2 in sexual development is more often discussed accordingly. In the present study, the full‐length cDNA of Tra‐2 of the mud crab Scylla paramamosain (SpTra‐2) was cloned and characterized. The deduced amino acid sequence of SpTra‐2 contained an RNA‐recognition motif (RRM) flanking by two RS‐rich regions, which are the hallmarks of the Tra‐2 proteins. The SpTra‐2 mRNA was highly abundant in the hepatopancreas, muscles and androgenic glands of the male crabs, implying a potential role in male sexual development. The hypothesis was supported by the RNAi experiments, finding that the injection of SpTra‐2 dsRNA in vivo led to a decreased expression of SpIAG, a key gene in crustacean male sexual differentiation. The relationship between SpTra‐2 and SpIAG was further affirmed by eyestalk ablation (ESA) experiments, which caused SpTra‐2 expression earlier than SpIAG expression in both androgenic glands and hepatopancreas. In addition, treatment with SpTra‐2 dsRNA also reduced the mRNA level of SpSxl, but had no effects on SpDmrt expression, suggesting the sex determination system in S. paramamosain is different from that in D. melanogaster. [ABSTRACT FROM AUTHOR]

Three salinities (4‰, 12‰ and 25‰) were selected to determine the effects of different salinities on the growth, survival, nutrition and energy metabolism of Scylla paramamosain during indoor overwintering. Growth performance (survival rate, condition factor, hepatopancreatic index, weight gain rate and specific growth rate), nutrient composition (ash, moisture, crude fat, crude protein and total nitrogen), fatty acids, energy metabolites (glycogen, glucose, triglycerides, cholesterol and lactic acid) and energy metabolic enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase) were measured and calculated. The results showed that S. paramamosain exhibited the best growth and survival at 25‰ and worst at 4‰ after overwintering. In addition to consuming crude fat, excess protein was also broken down to provide energy in the 4‰ and 12‰ groups. The content of unsaturated fatty acids in the 25‰ group was higher after overwintering. Glycogen and glucose consumption and triglycerides, cholesterol and lactic acid production were lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase was highest in the 4‰ group and lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase in the hepatopancreas was higher than in the muscle. In conclusion, S. paramamosain uses less energy, has more unsaturated fatty acids and has a higher survival rate at a salinity of 25‰ after overwintering. The results of this study provide helpful information the indoor overwintering S. paramamosain in aquaculture production systems. [ABSTRACT FROM AUTHOR]

In order to reveal the influence of overwintering behaviour on the flavour of Scylla paramamosain, this study selected crabs of before and after overwintering in SM (Sanmen County, Zhejiang Province), HP (Hepu County, Guangxi Province) and WN (Wanning city, Hainan Province). The contents of flavouring‐related substances in hepatopancreas, muscles and gonads were determined by high‐performance liquid chromatography (HPLC); taste activity value (TAV) and equivalent umami concentration (EUC) were calculated. The results showed that sweetish amino acids were mainly accumulated in muscles, umami amino acids were mainly accumulated in hepatopancreas, free nucleotides were mainly accumulated in gonads, and the EUC value in gonads was the highest. After overwintering, the content of sweetish, umami amino acids and free nucleotides in muscle and hepatopancreas decreased significantly, while the content of flavour‐tasting amino acids in gonads did not change significantly, but the content of umami nucleotides increased significantly. Therefore, overwintering behaviour decreased the flavour of muscle and hepatopancreas, slightly enhanced gonad and the overall flavour of S. paramamosain before overwintering was better than that after overwintering. [ABSTRACT FROM AUTHOR]

An "abnormal" female Scylla paramamosain, named "Butter crab" (B_♀) is more popular than wild‐type mud crab (CK) with people. Histologically, "butter crab" ovaries are partially degraded, with full of yellow oily substances in body. Composition of the essential nutritional components is quite similar in "butter crab" and CK. In a comparison of fatty acids, B_♀ is richer. A comparison of flavour amino acids and nucleotide in muscle showed that sweet amino acids and bitter amino acids in B_♀ is lower than CK_♀, but umami amino acids are significantly higher in B_♀. However, the umami amino acid content in the gonads is significantly less in B_♀ than CK_♀. Moreover, umami nucleotides in B_♀ muscle is significantly higher. From the perspective of EUC evaluation, the umami taste of CK_ ♀ gonads is strongest, followed by B_ ♀ gonads. In the hepatopancreas, the umami taste ranks CK_♀> B_♀ >CK_♂, and there are no significant differences among muscles in the three groups. In conclusion, the characteristics of "butter crab" are more fragrant and nutritious, with sweet and umami taste. The article systematically scientifically analysed the nutritional composition and flavour characteristics of "butter crab", providing a novel insight for development of S. paramamosain industry. [ABSTRACT FROM AUTHOR]

Four iso‐nitrogenous and iso‐lipidic diets were designed to investigate the effects of dietary phospholipids (PL) levels (with 0%, 1%, 2%, and 4% PL supplementation) on growth performance, lipid metabolism, and antioxidant capacity in early juvenile green mud crab (Scylla paramamosain). There were three replicates of 28 crabs (initial body weight from 42.02 to 42.44 mg) for each diet treatment, and growth trial lasted for 8 weeks. At the end of the growth trial, there was no significant difference in survival among all treatments. Crabs fed diet with 2% PL obtained highest weight gain (WG) and specific growth rate than other crabs. The molting frequency was not affected by different dietary PL addition. Besides, the contents of whole body lipid and long chain highly unsaturated fatty acids significantly increased with elevating dietary PL levels. In the hepatopancreas, crabs fed diet with 0% PL had significantly higher malondialdehyde concentration than other crabs. And crabs fed diet with 2% PL obtained significantly higher superoxide dismutase activity than crabs fed diets with 0% and 4% PL. Moreover, the mRNA expression of Na+/K+‐ATPase was significantly down‐regulated with dietary PL supplementation over 2%. Based on the second order polynomial regression analysis of WG, 2.37% dietary PL level was the optimal demand for early juvenile S. paramamosain. Moreover, we found crabs fed diet with 2% PL obtained better antioxidant capacity than other crabs. [ABSTRACT FROM AUTHOR]

Abstract: A 56‐day feeding trial was conducted to investigate the effect of dietary cholesterol (CHOL) levels on growth performance, body composition and gene expression of juvenile mud crab (Scylla paramamosain). Four isonitrogenous and isoenergetic diets were formulated with 0.4%, 0.8%, 1.2% and 1.6% CHOL supplemented, and the final dietary CHOL concentrations were 0.72%, 1.11%, 1.49% and 1.83% respectively. Each dietary treatment was performed with three replicates (28 crabs per replicate, initial body weight 0.04 g). At the termination of the experiment, although the survival had no statistic difference in all treatments, the mud crabs fed the lowest CHOL diet had the lowest survival rate. The weight gain (WG) of mud crab significantly increased with dietary CHOL level up to 1.11% and then significantly decreased with dietary CHOL level further increased. The total‐cholesterol (T‐CHOL) content in whole body had an increasing trend with the dietary CHOL level increased. Besides, dietary CHOL supplement generally increased the hepatic superoxide dismutase (SOD) activity, and the mud crabs fed diets CHOL1.11 and CHOL1.49 showed significantly higher value than those fed other diets. The hepatic aspartate aminotransferase (AST) activity decreased slightly with dietary CHOL level up to 1.11% and then significantly increased with CHOL level further increased. The mRNA expression of ecdysone receptor (EcR) gene in the eyestalk obviously increased with dietary CHOL level up to 1.11% and then significantly decreased with dietary CHOL further increased. These results suggested that about 1.11% dietary CHOL seem fulfil to maintain good growth performance and healthy condition for juvenile S. paramamosain. [ABSTRACT FROM AUTHOR]

Abstract: In crustaceans, chitinases (Chts) play crucial roles in physiological functions such as chitinous food digestion, moulting and stress responses. Chitinases have been identified in both prokaryotes and eukaryotes, but the composition and number of Cht family members vary across species, especially in crustaceans. Seven Cht transcripts, all of which contained the conserved enzyme activity motif, were cloned from Scylla paramamosain for the first time, and SpCht1‐SpCht6 were clearly classified into groups 1–6, respectively, through phylogenetic analysis. Notably, SpCht7, which had two catalytic domains, was identified for the first time in crabs and crustaceans. Although SpCht7 could not be grouped into any known Cht subclasses, it clustered together with insect Cht7 and could be classified into a novel subclass that we named group 7. The tissue distributions of SpChts, as well as their expression profiles during embryonic and larval development, growth‐related moulting, salinity and cadmium stresses, were also investigated. The results suggested that SpChts might have different and varied biological functions. These results would be helpful for understanding and clarifying the roles of chitinases in crab development, moulting and responses to environmental stress. These results also provide new insight into the origin and evolution of the chitinase gene family in crabs and other crustaceans. [ABSTRACT FROM AUTHOR]

This study evaluated the properties of nine Scylla paramamosain microsatellite loci screened by us previously for inclusion in a parentage assignment marker suite. These nine highly polymorphic markers (mean He=0.847 and PIC=0.830) were determined as being suitable for parentage assignment. Simulations based on allele frequency data from 15 known maternal families (165 individuals) demonstrated that at least four loci were required to assign >95% of offspring to maternal parents with 95% confidence. In actual parentage assignments, all progenies were assigned to the maternal parents with six or more loci, which was similar to the simulation predictions. Our results suggest that this set of microsatellites provide a powerful and efficient tool for identifying pedigree information for selective breeding programmes of S. paramamosain. [ABSTRACT FROM AUTHOR]

Calreticulin ( CRT), a well conserved endoplasmic reticulum-resident protein for Ca2+-binding, is widely expressed in multicellular eukaryotes. CRT plays a key role in many cellular processes, including Ca2+ homeostasis. To address the role of CRT underlying the Ca2+ homeostasis alternation during the mineralization cycle of the mud crab ( Scylla paramamosain), we cloned the full-length cDNA of CRT gene ( Sp CRT) from S. paramamosain, and its protein contains all signature domains of CRT. Tissue distribution showed the Sp CRT transcript was far more abundant in hepatopancreas than in others. Meanwhile, seven moult stages of the crab were characterized by observing the third maxilliped under microscope and clear uropod images were presented. During the moult cycle, the total calcium levels in the hepatopancreas were determined using ICP- AES. It decreased significantly at stage A and B ( p < 0.05), and was relatively steady between inter-moult C and early pre-moult D0 ( p > 0.05). It was then gradually increased thereafter by nearly 274.2% until stage E (compared with stage C) ( p < 0.05). Additionally, the expression of Sp CRT in the hepatopancreas was the lowest in the moult stage E and post-moult stage A, and then it maintained at a high level in other stages. Taken together, the relative retard timing of calcium incrument corresponding to the higher expression of Sp CRT may suggest CRT plays a critical role in Ca2+ storage in hepatopancreas during the moult cycle of crustaceans. [ABSTRACT FROM AUTHOR]

Recently, crustacean hyperglycaemic hormone ( CHH) has gained wide attention for its diverse physiological functions. In this study, two cDNA sequences encoding CHH, Sp- CHH1 and Sp- CHH2, were cloned from the eyestalk ganglia of the mud crab, Scylla paramamosain. Each conceptually translated precursor is expected to be processed into the signal peptide, the crustacean hyperglycaemic hormone precursor-related peptide ( CPRP) and the CHH mature peptide. Sp- CHH1 and Sp- CHH2 share an identical sequence for the first 40 residues from the amino-terminus of the peptides, but substantially different from each other in the C-terminus. Quantitative real-time PCR ( qPCR) showed that Sp- CHH transcripts were mainly detected in the eyestalk ganglia and to a much lesser extent in the brain, thoracic ganglia, stomach, hepatopancreas, heart and muscle. RNA in situ hybridization in the eyestalk ganglia indicated that the Sp- CHH was localized in the perikarya of neuroendocrine cells belonging to the X-organ of the medulla terminalis. Moreover, Sp- CHH transcripts were stage-specific changed during the moulting cycle, as it increased significantly from postmoult stage to intermoult stage, then decreased sharply at premoult stage. Sp- CHH expression levels in the eyestalk ganglia were also examined at different ovarian stages (stage I to stage V). It was found that the expression was gradually increased from stage I to stage IV, and then it was decreased at stage V. All the findings together suggested that Sp- CHH should be pleiotropic, which might inhibit the synthesis of ecdysteroids by Y-organs and be involved in promoting vitellogenesis in the mud crab. [ABSTRACT FROM AUTHOR]

A 6-week study was conducted to determine the effects of different lipid sources in pelleted diets on juvenile mud crab Scylla paramamosain. Five isonitrogenous and isolipidic diets containing 8% level of fish oil (FO), lard (LD), safflower oil (SO), perilla seed oil (PO) or mixture oil (MO; VFO:VSO:VPO = 1:1:1), and a live food of marine bivalve Potamocorbula rubromuscula as the control diet (CF), were fed to groups of 25 juvenile crabs (average initial weight 7.4 g, carapace width 3.5 cm) in triplicate. The results showed that crabs fed MO had the highest survival ( P < 0.05). The moisture content was significantly higher in crabs fed LD, SO and PO ( P < 0.05). Crabs fed SO exhibited the lowest crude protein and lipid ( P < 0.05). Ash contents were obviously lower in LD group ( P < 0.05). Highest total lipid in the hepatopancreas and muscle was in LD and FO group respectively. Glucose, total cholesterol and low-density lipoprotein were higher while high-density lipoprotein was lower ( P < 0.05) in LD group. Tissue fatty acid compositions were consistent with those in diets. FO and MO diets had the same depression effect like CF on fatty acid synthase activity and mRNA expression in the hepatopancreas. The results of this study indicated that FO and mixed oil are suitable for preparation of pelleted diets with better effects for juvenile S. paramamosain compared with live food, and the ratio of n-6/n-3 fatty acids in pelleted diets must be <1. [ABSTRACT FROM AUTHOR]

Mud crab is a group of commercially important species that are found throughout the Indo-Pacific region. In this study, the full-length cDNA of molt-inhibiting hormone ( Scp-MIH) was cloned from the green mud crab, Scylla paramamosain. The conceptually translated peptide precursor consists of a 78-residue mature peptide, preceded by a 35-residue signal peptide. The mature peptide shares a high identity with the other known MIHs, and contains six conserved cysteine residues that have been proposed to be functionally critical for MIH activity. Analysis of genomic sequence revealed that Scp-MIH gene was organized in a 3 exons/2 introns manner. Quantitative real-time PCR showed that Scp-MIH transcripts were detected mainly in the eyestalk ganglion and brain. During the molting cycle, Scp-MIH mRNA increased significantly from postmolt stage to intermolt stage, then decreased sharply at premolt stage. It implies that MIH is closely related to ecdysteroid production in S. paramamosain. In the ovarian cycle, Scp-MIH transcripts in some neural tissues (eyestalk ganglion and brain) increased from stage I to stage II, and reached the peak value at stage III, then declined at later stage. It suggests that MIH might be involved in the ovarian maturation in S. paramamosain. [ABSTRACT FROM AUTHOR]

A study which identified TLP, a new trypsin-like serine protease in Scylla paramamosain is presented. Topics covered include the full-length complementary DNA (cDNA) sequence and the gene expression pattern of TLP, and its immune response against bacterial infection using Vibrio alginolyticus marine organism in the challenge experiments.

Two trials, including firstly, diets incorporating individual or combined species of probiotics, Bacillus subtilis E20 and Lactobacillus plantarum 7-40, were fed to the mud crab, Scylla paramamosian, for 28 days to evaluate the growth, immunity and disease resistance, and secondly, the optimal level of B. subtilis E20 in the diet by tracking the growth, immunity and disease resistance after 28 days of feeding were analysed. No significant differences in growth, total haemocyte counts, respiratory bursts, superoxide dismutase, or glutathione peroxidase were found in the two trials. Crabs fed the B. subtilis E20-containing diet (D20) had significantly increased phenoloxidase ( PO) activity, phagocytic activity ( PA) and disease resistance compared with crabs fed the control and the mixed probiotics diet ( MD). The mortality of crabs fed the D20 was significantly lower than that of crabs fed the L. plantarum 7-40-containing diet. L. plantarum 7-40 had a great inhibitory effect on the growth of B. subtilis E20, which may have led to the decreased probiotic effect of the MD. An analysis of the optimal level of B. subtilis E20 in the diet showed that crabs fed the B. subtilis E20-containing diet at a level of 109-10 cfu kg−1 had better immune response of PO and PA, and disease resistance in the second trial. [ABSTRACT FROM AUTHOR]

The present study was conducted to explore the potential to incorporate local plant-based feed ingredients into diets formulated for the mud crab species, Scylla paramamosain, commonly exploited for aquaculture in South-east Asia. Four test ingredients (defatted soybean meal, rice bran, cassava meal and corn flour) were incorporated at 30% or 45% inclusion levels in a fishmeal-based reference diet and used in digestibility trials where apparent digestibility coefficients (ADCs) for experimental diets and test ingredients were determined. Generally, high ADC values were obtained using diets containing 30% soybean meal or rice bran. By contrast, the lowest ADC values were obtained for the diet containing 45% cassava meal [70.9% for dry matter (ADMD); 77.1% for crude protein (ACPD) and 80.2% for gross energy (AGED)]. Similar trends were observed when ADC ingredient (I) digestibilities were compared. Specifically, the highest ADCI values were obtained for soybean meal when used at a 30% inclusion level (87.6% ADMDI; 98.4% ACPDI and 95.6% AGEDI) while the lowest ADCI values were obtained using cassava meal at a 45% inclusion level (53.8% ADMDI; 60.2% ACPDI and 67.3% AGEDI). Based on the current findings, we propose that soybean meal and rice bran could be considered for incorporation into formulated diets for S. paramamosain. [ABSTRACT FROM AUTHOR]

Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post-larval and juvenile stages when the densities of hatchery-reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled-up nursery production in lined-ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m−2 from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m−2 in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds. [ABSTRACT FROM AUTHOR]

The performance of hatchery-reared juveniles either in aquaculture grow-out systems or stock enhancement is likely to be dependent on a range of factors during the hatchery phase of production. With recent progress in the development of hatchery systems for the mud crabs Scylla spp., there is growing interest in evaluation of the quality of hatchery-reared juveniles relative to wild seed crabs as currently used in aquaculture. Hatchery-reared and wild-collected Scylla paramamosain juveniles were stocked either together in ponds or separately. All crabs were tagged with microwire-coded tags, so that origin could be determined in the mixed groups. Preliminary validation demonstrated that tagging did not affect survival or growth, with a tag retention of 94%. After 106 days of culture, there was no significant difference in survival at harvest between the two sources of crabs. The wild juvenile crabs had a significantly higher initial weight:carapace width (CW) ratio compared with those from the hatchery, indicating a difference in condition. However, where crabs were stocked separately, the hatchery-reared animals exhibited significantly faster growth than those collected from the wild, both in terms of specific growth rate and CW increase per month. However, in the mixed ponds, where there was competition with wild crabs, there was no significant difference in growth rate between crabs from the two sources. Overall, the results demonstrate that the growth performance of hatchery-reared S. paramamosain can at least equal that of wild-collected seed crabs in ponds culture. [ABSTRACT FROM AUTHOR]

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab ( Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro-algae ( Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL−1 or maintenance at 1–2 millions cells mL−1), six different types of rearing systems were tried. The combination of a green-water batch system for early stages and a recirculating system with micro-algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L−1) and rotifer (30–60 rotifers mL−1) and Artemia density (10–20 L−1) were observed. A stocking density of 100–150 zoea 1 (Z1) L−1, combined with rotifer of 30–45 mL−1 for early stages and Artemia feeding at 10–15 nauplii mL−1 for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL−1 from Z1 to Z2 and increase the number of Artemia nauplii mL−1 from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%). [ABSTRACT FROM AUTHOR]

Treated with combined bilateral eyestalk ablation and maintenance of water temperature at 22.5±1.5 °C, mud crab Scylla paramamosain females with mature ovaries were induced to produce eggs outside the natural spawning season in subtropical southern China. Newly extruded eggs from a crab were incubated in vitro at 10, 15, 20, 25, 27, 30, 35 °C, respectively, and the embryonic development was closely monitored. Abnormal cell division was observed at temperatures 10 and 35 °C. At 15 °C, development remained at the gastrula stage by day 32 post-spawn, at which time the experiment was terminated. Hatching of in vitro incubated eggs occurred between 20 and 30 °C. An increase in incubation temperature from 20 to 25 °C reduced the incubation duration by 14 days, 2.6 times of that measured for a similar 5 °C increase from 25 to 30 °C. Embryonic development of S. paramamosain was divided into stage 0–10, and the duration of each stage was recorded for each incubation temperature. The information obtained allows accurate prediction of hatching time of female crabs incubated under variable temperatures. Larvae hatched from in vitro incubated eggs were reared to reach first juvenile crab stage and their dry weights were similar to those of larvae hatched naturally. [ABSTRACT FROM AUTHOR]