Dietary lauric acid promoted antioxidant and immune capacity by improving intestinal structure and microbial population of swimming crab (Portunus trituberculatus).

Lauric acid (LA), a saturated fatty acid with 12 carbon atoms, is widely regarded as a healthy fatty acid that plays an important role in disease resistance and improving immune physiological function. The objective of this study was to determine the effects of dietary lauric acid on the growth performance, antioxidant capacity, non-specific immunity and intestinal microbiology, and evaluate the potential of lauric acids an environmentally friendly additive in swimming crab (Portunus trituberculatus) culture. A total of 192 swimming crabs with an initial body weight of 11.68 ± 0.02 g were fed six different dietary lauric acid levels, the analytical values of lauric acid were 0.09, 0.44, 0.80, 1.00, 1.53, 2.91 mg/g, respectively. There were four replicates per treatment and 8 juvenile swimming crabs per replicate. The results indicated that final weight, percent weight gain, specific growth rate, survival and feed intake were not significantly affected by dietary lauric acid levels; however, crabs fed diets with 0.80 and 1.00 mg/g lauric acid showed the lowest feed efficiency among all treatments. Proximate composition in hepatopancreas and muscle were not significantly affected by dietary lauric acid levels. The highest activities of amylase and lipase in hepatopancreas and intestine were found at crabs fed diet with 0.80 mg/g lauric acid (P < 0.05), the activity of carnitine palmityl transferase (CPT) in hepatopancreas and intestine significantly decreased with dietary lauric acid levels increasing from 0.09 to 2.91 mg/g (P < 0.05). The lowest concentration of glucose and total protein and the activity of alkaline phosphatase in hemolymph were observed at crabs fed diets with 0.80 and 1.00 mg/g lauric acid among all treatments. The activity of GSH-Px in hepatopancreas significantly increased with dietary lauric acid increasing from 0.09 to 1.53 mg/g, MDA in hepatopancreas and hemolymph was not significantly influenced by dietary lauric acid levels. The highest expression of cat and gpx in hepatopancreas were exhibited in crabs fed diet with 1.00 mg/g lauric acid, however, the expression of genes related to the inflammatory signaling pathway (relish, myd88, traf6, nf-κB) were up-regulated in the hepatopancreas with dietary lauric acid levels increasing from 0.09 to 1.00 mg/g, moreover, the expression of genes related to intestinal inflammatory, immune and antioxidant were significantly affected by dietary lauric acid levels (P < 0.05). Crabs fed diet without lauric acid supplementation exhibited higher lipid drop area in hepatopancreas than those fed the other diets (P < 0.05). The expression of genes related to lipid catabolism was up-regulated, however, and the expression of genes related to lipid synthesis was down-regulated in the hepatopancreas of crabs fed with 0.80 mg/g lauric acid. Lauric acid improved hepatic tubular integrity, and enhanced intestinal barrier function by increasing peritrophic membrane (PM) thickness and upregulating the expression of structural factors (per44, zo-1) and intestinal immunity-related genes. In addition, dietary 1.00 mg/g lauric acid significantly improved the microbiota composition of the intestinal, increased the abundance of Actinobacteria and Rhodobacteraceae, and decreased the abundance of Vibrio, thus maintaining the microbiota balance of the intestine. The correlation analysis showed that there was a relationship between intestinal microbiota and immune-antioxidant function. In conclusion, the dietary 1.00 mg/g lauric acid is beneficial to improve the antioxidant capacity and intestinal health of swimming crab.

Dietary Astaxanthin Can Promote the Growth and Motivate Lipid Metabolism by Improving Antioxidant Properties for Swimming Crab, Portunus trituberculatus.

This study aimed to assess the influence of varying dietary levels of astaxanthin (AST) on the growth, antioxidant capacity and lipid metabolism of juvenile swimming crabs. Six diets were formulated to contain different AST levels, and the analyzed concentration of AST in experimental diets were 0, 24.2, 45.8, 72.4, 94.2 and 195.0 mg kg-1, respectively. Juvenile swimming crabs (initial weight 8.20 ± 0.01 g) were fed these experimental diets for 56 days. The findings indicated that the color of the live crab shells and the cooked crab shells gradually became red with the increase of dietary AST levels. Dietary 24.2 mg kg-1 astaxanthin significantly improved the growth performance of swimming crab. the lowest activities of glutathione (GSH), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and peroxidase (POD) were found in crabs fed without AST supplementation diet. Crabs fed diet without AST supplementation showed lower lipid content and the activity of fatty acid synthetase (FAS) in hepatopancreas than those fed diets with AST supplementation, however, lipid content in muscle and the activity of carnitine palmitoyl transferase (CPT) in hepatopancreas were not significantly affected by dietary AST levels. And it can be found in oil red O staining that dietary 24.2 and 45.8 mg kg-1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas. Crabs fed diet with 195.0 mg kg-1 AST exhibited lower expression of ampk, foxo, pi3k, akt and nadph in hepatopancreas than those fed the other diets, however, the expression of genes related to antioxidant such as cMn-sod, gsh-px, cat, trx and gst in hepatopancreas significantly down-regulated with the increase of dietary AST levels. In conclusion, dietary 24.2 and 45.8 mg kg-1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas and im-proved the antioxidant and immune capacity of hemolymph.

High dietary lipid level promotes low salinity adaptation in the marine euryhaline crab (Scylla paramamosain).

The physiological processes involved in adaptation to osmotic pressure in euryhaline crustaceans are highly energy demanding, but the effects of dietary lipids (fat) on low salinity adaptations have not been well evaluated. In the present study, a total of 120 mud crabs (Scylla paramamosain, BW = 17.87 ± 1.49 g) were fed control and high-fat (HF) diets, at both medium salinity (23‰) and low salinity (4‰) for 6 wk, and each treatment had 3 replicates with each replicate containing 10 crabs. The results indicated that a HF diet significantly mitigated the reduction in survival rate, percent weight gain and feed efficiency induced by low salinity (P < 0.05). Low salinity lowered lipogenesis and activated lipolysis resulting in lipid depletion in the hepatopancreas of mud crabs (P < 0.05). Thus, HF diets enhanced the process of lipolysis to supply more energy. In the gills, low salinity and the HF diet increased the levels of mitochondrial biogenesis markers, the activity of mitochondrial complexes, and the expression levels of genes related to energy metabolism (P < 0.05). Consequently, the positive effects of the HF diet on energy metabolism in mud crabs at low salinity promoted osmotic pressure regulation. Specifically, significantly higher haemolymph osmotic pressure and inorganic ion content, as well as higher osmotic pressure regulatory enzyme activity in gills, and gene and protein expression levels of NaK-ATPase were observed in crabs fed the HF diet at low salinity (P < 0.05). In summary, high dietary lipid levels improved energy provision to facilitate mitochondrial biogenesis, which increased ATP provision for osmotic pressure regulation of mud crabs. This study also illustrates the importance of dietary lipid nutrition supplementation for low salinity adaptations in mud crabs.

Dietary Corn Starch Levels Regulated Insulin-Mediated Glycemic Responses and Glucose Homeostasis in Swimming Crab (Portunus trituberculatus).

Carbohydrate is the cheapest source of energy among the three major nutrient groups, an appropriate amount of carbohydrates can reduce feed cost and improve growth performance, but carnivorous aquatic animals cannot effectively utilize carbohydrates. The objectives of the present study are aimed at exploring the effects of dietary corn starch levels on glucose loading capacity, insulin-mediated glycemic responses, and glucose homeostasis for Portunus trituberculatus. After two weeks of feeding trial, swimming crabs were starved and sampled at 0, 1, 2, 3, 4, 5, 6, 12, and 24 hours, respectively. The results indicated that crabs fed diet with 0% corn starch exhibited lower glucose concentration in hemolymph than those fed with the other diets, and glucose concentration in hemolymph remained low with the extension of sampling time. The glucose concentration in hemolymph of crabs fed with 6% and 12% corn starch diets reached the peak after 2 hours of feeding; however, the glucose concentration in hemolymph of crabs fed with 24% corn starch attained the highest value after 3 hours of feeding, and the hyperglycemia lasted for 3 hours and decreased rapidly after 6 hours of feeding. Enzyme activities in hemolymph related to glucose metabolism such as pyruvate kinase (PK), glucokinase (GK), and phosphoenolpyruvate carboxykinase (PEPCK) were significantly influenced by dietary corn starch levels and sampling time. Glycogen content in hepatopancreas of crabs fed with 6% and 12% corn starch first increased and then decreased; however, the glycogen content in hepatopancreas of crabs fed with 24% corn starch significantly increased with the prolongation of feeding time. In the 24% corn starch diet, insulin-like peptide (ILP) in hemolymph reached a peak after 1 hour of feeding and then significantly decreased, whereas crustacean hyperglycemia hormone (CHH) was not significantly influenced by dietary corn starch levels and sampling time. ATP content in hepatopancreas peaked at 1 h after feeding and then decreased significantly in different corn starch feeding groups, while the opposite trend was observed in NADH. The activities of mitochondrial respiratory chain complexes I, II, III, and V of crabs fed with different corn starch diets significantly increased first and then decreased. In addition, relative expressions of genes related to glycolysis, gluconeogenesis, glucose transport, glycogen synthesis, insulin signaling pathway, and energy metabolism were significantly affected by dietary corn starch levels and sampling time. In conclusion, the results of the present study reveal glucose metabolic responses were regulated by different corn starch levels at different time points and play an important role in clearing glucose through increased activity of insulin, glycolysis, and glycogenesis, along with gluconeogenesis suppression.

Evaluation of Krill Meal in Commercial Diets for Juvenile Swimming Crab (Portunus trituberculatus).

An 8-week feeding trial was carried out to assess the effect of dietary krill meal on growth performance and expression of genes related to TOR pathway and antioxidation of swimming crab (Portunus trituberculatus). Four experimental diets (45% crude protein and 9% crude lipid) were formulated to obtain different replacements of fish meal (FM) with krill meal (KM); FM was replaced with KM at 0% (KM0), 10% (KM10), 20% (KM20), and 30% (KM30); fluorine concentration in diets were analyzed to be 27.16, 94.06, 153.81, and 265.30 mg kg-1, respectively. Each diet was randomly divided into 3 replicates; ten swimming crabs were stocked in each replicate (initial weight, 5.62 ± 0.19 g). The results indicated that crabs fed with the KM10 diet had the highest final weight, percent weight gain (PWG), and specific growth rate (SGR) among all treatments (P < 0.05). Crabs fed with the KM0 diet had the lowest activities of total antioxidant capacity (T-AOC), total superoxide dismutase (SOD), glutathione (GSH), and hydroxyl radical scavenging activity and had the highest concentration of malondialdehyde (MDA) in the hemolymph and the hepatopancreas (P < 0.05). In the hepatopancreas, the highest content of 20:5n-3 (EPA) and the lowest content of 22:6n-3 (DHA) were shown in crabs fed with the KM30 diet among all treatments (P < 0.05). With the substitution level of FM with KM gradually increasing from 0% to 30%, the color of the hepatopancreas changed from pale white to red. Expression of tor, akt, s6k1, and s6 in the hepatopancreas was significantly upregulated, while 4e-bp1, eif4e1a, eif4e2, and eif4e3 were downregulated with dietary replacement of FM with KM increasing from 0% to 30% (P < 0.05). Crabs fed with the KM20 diet had notably higher expression of cat, gpx, cMnsod, and prx than those fed with the KM0 diet (P < 0.05). Results demonstrated that 10% replacement of FM with KM can promote growth performance and antioxidant capacity and notably upregulate the mRNA levels of genes related to TOR pathway and antioxidant of swimming crab.

A Method to Determine BeiDou GEO/IGSO Orbital Maneuver Time Periods.

Because there are different types of BeiDou constellations with participating geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites, the maneuvering frequency of BeiDou satellites is higher than that of other navigation systems. The satellite orbital maneuvers lead to orbital parameter failure for several hours from broadcast ephemeris. Due to the missing initial orbit, the maneuvering thrust, and the period of orbital maneuvering, the orbit products of maneuvering satellites cannot be provided by the International Global Navigation Satellite System (GNSS) Service (IGS) and International GNSS Monitoring and Assessment System (iGMAS). In addition, the period of unhealthy status and the orbital parameters of maneuvering satellites in broadcast ephemeris are unreliable, making the detection of orbital maneuver periods more difficult. Here, we develop a method to detect orbital maneuver periods involving two key steps. The first step is orbit prediction of maneuvering satellites based on precise orbit products. The second step is time period detection of orbit maneuvering. The start time detection factor is calculated by backward prediction orbit and pseudo-range observations, and the end time detection factor is calculated by forward prediction orbit and pseudo-range observations. Data of stations from the Multi-GNSS Experiment (MGEX) and iGMAS were analyzed. The results show that the period of orbit maneuvering could be detected accurately for BeiDou GEO and IGSO satellites. In addition, the orbital maneuver period of other GNSS medium Earth orbit (MEO) satellites could also be determined by this method. The results of period detection for orbit maneuvering provide important reference information for precision orbit and clock offset determination during satellite maneuvers.

Structure, luminescence and temperature sensing in rare earth doped glass ceramics containing NaY(WO4)2 nanocrystals.

Novel rare earth doped glass ceramics containing NaY(WO4)2 nanocrystals were fabricated for the first time. The appearance of sharp diffraction peaks and well-resolved lattice fringes certifies the precipitation of NaY(WO4)2 nanocrystals with high crystallinity. After the crystallization process, significant changes in the photoluminescence emission spectra and fluorescence lifetime of Sm3+ ions are observed, which are ascribable to the enrichment of Sm3+ ions in the highly disordered NaY(WO4)2 nanocrystals. Under 980 nm excitation, characteristic green and red upconversion emission signals were detected and the enhanced upconversion luminescence of Er3+ ions in the glass ceramics was attributable to the incorporation into the low energy phonon NaY(WO4)2 nanocrystals. Based on the dependence of upconversion intensity on the excitation power, the upconversion mechanism of Er3+-Yb3+ ions was proposed. The temperature-dependent fluorescence intensity ratio (FIR) of the thermally-coupled 2H11/2 and 4S3/2 energy levels was determined at a low power density of 0.4125 W cm-2. The maximum temperature sensitivity is 146 × 10-4 K-1 at 523 K, which is mainly attributed to the highly disordered structure of NaY(WO4)2 nanocrystals and exhibits promising potential for optical temperature sensors.

Ultrastructure of underutilized tuber starches and its relation to physicochemical properties.

Starches from five underutilized tubers (canna, potato, Chinese yam, water chestnut, and taro) were extracted to investigate quantitative structure-property relationships (QSPR) in each starch using a combination of X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS). Structural parameters of the tuber starches were determined using the paracrystalline model. Swelling power (SP), water solubility index (WSI), amylose leaching (AML), and thermal properties were also measured. The XRD results indicated that starches from Chinese yam, water chestnut, and taro are C-type starches with relatively high crystallinity (29.23-35.02%). In contrast, canna and potato starches are B-type starches exhibiting lower crystallinity and higher amylose content. The paracrystalline model provided a better fit for the C-type starches than for the B-type starches because the former was highly compressible (indicated by a higher "ß" value). B-type starches, on the other hand, tend to be more rigid along the lamellar repeat direction, requiring the layers to bend to accommodate internal stress. The QSPR analysis showed that three structural parameters, "Ø", "ß", and "Δρu", correlate well with the SP and WSI, and thus can be used to predict certain physicochemical properties.