Latest Accepted Articles
The change of intracellular calcium (Ca2+) concentration is an important factor in oocyte maturation. As a member of the P-type ATPase family and a crucial regulator of intracellular calcium transport, sarco/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) is a key enzyme. To investigate the function of SERCA in the development of the oocytes of Sipunculus nudus, we obtained the full length of S. nudus SERCA (Sn-SERCA) cDNA by using RACE technique, and determined the Sn-SERCA relative expression level at different periods of oocyte development by using real-time fluorescence quantitative PCR (qRT-PCR). The results indicate that the overall length of the Sn-SERCA was 3 840 bp, the 5'UTR was 196 bp, the 3'UTR was 581 bp, and the open reading frame was 3 060 bp, encoding 1 020 amino acids. Sn-SERCA had TGES and DKTGT which were the P-type ATPase family's two conserved motifs and were necessary for catalytic reactions. According to multiple sequence alignment, motif analysis, and predictions of tertiary structures, the SERCA homologous proteins exhibited great conservatism. The phylogenetic tree analysis shows that the Sn-SERCA formed a broad branch with homologous protein sequences from invertebrates such as Lumbricus rubellus and Lingula anatine. The result of qRT-PCR demonstrates that the Sn-SERCA was significantly expressed in the late yolk vigorous synthesis period and had the maximum value during coelomic fluid development. When the oocytes moved to the nephridioduct, the Sn-SERCA expression was considerably higher than that at other time (P<0.05). The variable expression of Sn-SERCA in different periods of oocyte development suggests that Sn-SERCA is crucial in the development and germinal vesicle breakdown in S. nudus oocytes.
In order to study the basic blood indexes of artificially bred yellowfin tuna (Thunnus albacares), we determined the concentrations or activities of albumin, triglyceride, total cholesterol, transaminase, lysozyme and phosphatase in its serum (W1: 400−900 g; W2: 900−1 400 g; W3: 1 400−1 900 g) with different body mass. The results show that there were significant differences among the albumin, triglyceride and aspertate aminotransferase groups (P<0.05). The glutamic pyruvic transaminase activity and total cholesterol concentration in W2 group were significantly lower than those in the other two groups (P<0.05). The ascending order of the concentrations of albumin, triglyceride and total cholesterol was W3>W1>W2. There was no significant difference in the alkaline phosphatase activity among the groups (P>0.05). The acid phosphatase activity in W1 group was significantly higher than that in the other two groups (P<0.05), and the lysozyme concentration in W1 group was not significantly different from that in the other two groups (P>0.05). The results reveal that there were differences in the blood indexes among the three groups of different mass; the difference between W2 group and the other two groups was greater, and the difference between W1 group and W3 group was smaller.
Semicarbazide (SEM) is a toxic substance, which is a marker residue to determine whether Nitrofurazone is used illegally or not. To explore the detection of SEM in Crustacean aquatic products, we detected the SEM content of M. rosenbergii by High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). The results show that SEM was detected in different parts of M. rosenbergii, higher in the cephalothorax and shrimp shell [Average: (32.02±3.75) and (26.85±13.90) μg·kg−1], but lower in the muscle and liver [Average: (1.35±0.67) and (5.56±0.87) μg·kg−1], and all exceeded the residue limit standards in China (1 μg·kg−1). The SEM content in the shrimp shell and shrimp meat increased with the prolongation of storage time, but that in the shrimp shell was higher than 1.0 μg·kg−1. Different storage temperatures had a little effect on the SEM content of M. rosenbergii. Therefore, when taking SEM as a marker for Nitrofurazone residue detection of M. rosenbergii, the detection time and background content factors should be considered so as to avoid false judgment; and in order to ensure the authenticity and accuracy of the test results, the crushed shell should be avoided in preparing samples.
To find out whether the tilapia (Oreochromis spp.) skin collagen peptides can effectively inhibit melanin production, we used three kinds of proteases to hydrolyze the tilapia skin, and filtered the tilapia skin tyrosinase (TYR) inhibitory peptides (TSTIP) with the highest inhibitory activity. Then we studied the relevance between TYR inhibitory activity and Cu2+ binding activity. The results show that the product of tilapia skin hydrolyzed by alcalase for 4 h exhibited both the highest TYR inhibitory activity and Cu2+ binding activity, which were significantly positively correlated (R=0.856). When TSTIP was bound to Cu2+ or tyrosinase, the intrinsic fluorescence absorption had a consistent decreasing trend, but the UV absorption increased and the maximum absorption wavelength had a red shift. For FTIR results, TYR and Cu2+ bound to TSTIP mainly by carbonyl and amino groups. Circular dichroism shows that the β-turn and random curl contents of the two conjugates decreased relatively, while the β-fold content increased relatively, which was more obvious for TSTIP-Cu2+. In conclusion, the structural change of TSTIP-TYR is similar with that of TSTIP-Cu2+, which indicates that TSTIP can inhibit TYR's activity by binding to its Cu2+ active site.
To provide references for the application of two anesthetics in Litopenaeus vannamei, we studied the anesthetic effects of eugenol (20, 30, 40, 60, 80, 100, 120, 140, 160 mg·L−1) and MS-222 (800, 900, 1 000, 1 100, 1 200, 1 300, 1 400, 1 500, 1 600 mg·L−1) on L. vannamei with body mass of (14±3) g. Besides, we tested the secondary stress injury on the physiological functions and pathomorphologic changes by the two anesthetics. The results show that: 1) Eugenol of 80 mg·L−1and MS-222 of 1 400 mg·L−1 induced L. vannamei to enter the stage of deep anesthetic within 3 min, and return to the normal stage within 5 min. 2) The gills and hepatopancreas of L. vannamei were injured by the two anesthetics, and the antioxidant indexes of gills in the eugenol group reached the maximum value earlier than the MS-222 group. The Caspase-3 activity in the eugenol group decreased significantly after anesthesia recovery of 6 h, while that in the MS-222 group increased significantly (P<0.05). The Na+/K+-ATPase activity in both the groups decreased significantly (P<0.05). Pathomorphologic analysis shows that the two anesthetics could cause deformation or lysis of gills and hepatopancreas, and the eugenol group could recover after anesthesia recovery of 6 h. In conclusion, eugenol and MS-222 have anesthetic effects on L. vannamei, but the concentration of MS-222 is higher and the secondary stress damage to the body is more serious.
To determine the application effect of Euphausia superba powder (PE) in shrimp culture, we designed five groups [S0 group (No PE supplementation), S5 group, S10 group, S15 group, and S20 group (5%, 10%, 15% and 20% PE supplemented to the feed, respectively)] for a 35-day experiment on Litopenaeus vannamei [Body mass of (7.27 ± 0.88) g]. The effect of dietary supplementation with PE on the growth performance, body composition and color of L. vannamei were evaluated. The results show that: 1) PE supplementation improved the survival rate (SR) of L. vannamei significantly (P<0.05), and the final body mass (FBW), weight gain rate (WGR) and specific growth rate (SGR) of L. vannamei in S15 group were significantly higher compared with the other groups (P<0.05). 2) With the increase of PE supplementation, the crude fat content of L. vannamei increased gradually, and those in S10 group, S15 group and S20 group were significantly higher than that in S0 group (P<0.05). Additionally, the brightness (L*) of the cephalothorax and the yellowness (b*) of the carapace of L. vannamei decreased gradually, which were significantly lower than those in S0 group (P<0.05). 3) PE supplementation to the feed increased the astaxanthin content in the hepatopancreas and crustacean of L. vannamei significantly (P<0.05), and the effect was positively associated with PE supplementation. The expression level of the LVPBP75 related to body color was also positively correlated with PE supplementation. The results indicate that dietary supplementation with PE, especially with 15% PE, can improve the growth, astaxanthin content, body color as well as expression level of LVPBP75 of L. vannamei.
The ingestion of seagrass by herbivorous fish will affect the transfer process of metal elements in seagrass beds, and the accumulation of heavy metals will cause human ingestion risks. Taking two typical fish species (Siganus guttatus and S. fuscessens) eating seagrasses in two tropical seagrass beds as main research objects, we determined the enrichment of heavy metals and their contamination, and assessed the dietary exposure risk in seagrass bed environment and fishes. Then we further explored the transfer characteristics of heavy metals in seagrass bed ecosystems. The results show that the contents of Cu, Cd, Zn and Pb in fish muscles were at a low level. There are significant positive correlations between Cu and Pb, and between Zn and CD. The enrichment effects of Zn and Cu were greater than those of Cd and Pb, but only Zn showed an potential enrichment effect in these two fish muscles. The Zn contents in these two fishes showed a serious pollution risk, while Pb contents showed slight pollution, but the contents of Cu and Cd were at a normal risk level. Eating these two fishes has little health risk. Due to the different growth rate and food sources, the content, pollution and enrichment of heavy metals in S. fuscessens are slightly higher than those in S. guttatus. The contents and enrichment of heavy metals in seagrass beds are generally higher than those in fishes. The accumulation of heavy metals mainly occurs in seagrass, and the heavy metal content in fish decreases with higher trophic levels.
To investigate the genetic diversity and genetic differentiation of natural resources of Gymnocypris przewalskii, and provide references for its conservation measures, we collected 72 individuals of G. przewalskii from six natural populations in Qinghai Lake to analyze the genomic SNP and genetic characteristics by using simplified genome sequencing. Altogher 1 600 061 SNP markers were obtained, and 45 266 high-quality SNP loci were screened for genetic analysis after filtering. The average Pi diversity index was 0.317 0–0.327 4. The average observed heterozygosity (Ho) and expected heterozygosity (He) were 0.459 4–0.482 3 and 0.336 7–0.344 4, respectively. The genetic distance (D) was 0.018 4–0.023 3 and the genetic differentiation index (Fst) were not significant (P>0.05). AMOVA analysis shows that the genetic variation was 102.37% within populations. Further more, both population structure and phylogenetic tree analysis show that the six G. przewalskii populations clustered into one glade with similar genetic structure. In contrast, the genetic structure obtained from DAPC analysis was relatively clearer, showing that the Haergai, Heima and Shaliu River populations cross-clustered with each other, while the remaining three populations clustered into three other branches. In conclusion, the observed heterozygosity of the six geographic populations was higher than the expected value, with a homogeneous population structure.
To investigate the effects of global climate change on the habitat pattern of Scomber japonicus in the East China Sea and to slow down the adverse effects of climate change on the fishing ground of S. japonicus, based on the water temperature data of 2.5 m (Temp_2.5 m), 25 m (Temp_25 m) and 50 m (Temp_50 m) output by CMIP6 climate model, we analyzed the spatio-temporal changes of the habitat in the East China Sea under three future climate conditions (SSP126, SSP370 and SSP585). The results show that for SSP126, Temp_2.5 m, Temp_25 m and Temp_50 m showed relatively minor changes. For SSP370 and SSP585, Temp_2.5 m, Temp_25 m and Temp_50 m showed an overall upward trend. The three factors also changed in the spatial distribution during 2015−2020, 2055−2060 and 2095−2100. The habitat suitability index (HSI) on the fishing ground and proportion of suitable habitat of S. japonicus in the East China Sea from 2015 to 2100 showed a similar downward trend under SSP126, SSP370 and SSP585 conditions. However, the proportion of unsuitable habitat area from 2015 to 2100 increased under SSP126, SSP370 and SSP585 conditions. The suitable habitats of S. japonicus were mainly distributed in the waters of 122°E−126°E and 28°N−30°N during 2015−2020, 2055−2060 and 2095−2100, while the unsuitable habitat was mainly distributed in the middle of fishing ground. In addition, the gravity center of suitable habitat of S. japonicus tended to move northward. The results suggest that the global warming is unfavorable for the formation of suitable habitat of S. japonicus in the East China Sea.
In order to explore the water ecological health status of Cyprinus carpio and Leiocassis longirostris national aquatic germplasm resources reserve in Huaihe River, according to the survey results of phytoplankton community structure in 2020 and combined with the morphological functional group classification, we constructed the ecological health evaluation system of the reserve based on the biological integrity index of phytoplankton. Besides, we carried out the Mann-Whitney non-parametric test and correlation analysis of the candidate parameters to determine the final evaluation parameters, and used the ratio method to determine the grading evaluation standard for the evaluation of the health status of the reserve water. The results show that the evolution trend of dominant functional groups of phytoplankton was III+IV+V (Spring)→III+IV+V+VI (Summer)→V+VI (Autumn)→IV+V+VI (Winter). Except that the dominant functional groups in the core area were III+ IV+V+VI, the dominant functional groups of the experimental area, the Guo river and the Huaihe River were III+IV+V+VI. 68.06% of the sampling sites in the reserve were evaluated as "average" or above, indicating that the overall water ecological health status was good. Specifically, the temporal pattern of winter was better than autumn, followed by summer, and the worst was in spring; the spatial pattern of Huaihe River mainstream was better than Guohe River, and the experimental area was better than the core area.
To establish an assay of reverse transcription droplet digital PCR (RT-ddPCR) for Tilapia Lake Virus (TiLV), we designed a pair of specific primers and probe based on the conserved region of TiLV segment 3 and evaluated the specificity, sensitivity and repeatability of this method. The structured standard curve was evaluated by using TiLV-cDNA as a template. Finally, the samples were tested. When the concentrations of primers and probes were 500 and 300 nmol·L−1 and the annealing temperature was 54.2 ℃, the established TiLV RT-ddPCR amplification reaction efficiency was the highest, the distribution boundary of the positive and negative droplets was the most obvious, and the average copy number was higher. The RT-ddPCR of TiLV had a lower limit of detection with 2 copies·μL−1 and showed a good linear relationship between 1–90 000 copies·μL−1 (Correlation coefficient R2=0.995 8). There was no amplification reaction to other viruses in aquatic animals. The CV of ddPCR for TiLV-cDNA was 4.86%. There was no cross reaction with the positive samples of other five common aquatic animal disease viruses [Carp edema virus (CEV), Koi herpesvirus (KHV), Grass carp reovirus (GCV), Cyprinid herpesvirus 2 (CyHV-2), Red sea bream iridovirus (RSIV)]. Among the 53 detected samples, 48 were negative, three of five proficiency testing samples were positive, consistent with satisfactory previous proficiency testing results. Thus, a more sensitive, specific, repeated molecular biological detection method for TiLV was established, which can be used for early rapid diagnosis and provided a technical support for the differential diagnosis of TiLV disease. The method provides references for TiLV infection.
In order to explore whether Bacillus can replace antibiotics in the culture of Babylonia areolata, during the growth and development of B. areolata from early veliger larva to juvenile, we used Bacillus (Bacillus coagulans, B. licheniformis) and antibiotics (sulfamethoxazole) for artificial regulation to study their effects on the growth, survival, immune and digestive enzyme activities of B. areolata. The results show that Bacillus and sulfamethoxazole promoted the growth of each trait index of B. areolata, and the difference among them was not significant (P>0.05). The survival rate of the Bacillus group was significantly higher than that of the control group and the sulfamethoxazole group in the later veliger larva stage (P<0.05). The activities of AKP, ACP, CAT, POD, MDA, GSH-Px, TAOC, SOD, LPS and AMS in Bacillus group were higher than those in the control group and the sulfamethoxazole group. The results show that appropriate use of Bacillus (B. coagulans and B. licheniformis) during the seedling breeding of B. areolata can improve the immunity and disease resistance of the body, increase the activity of digestive enzymes, promote the growth of larvae and improve the survival rate, and the effect is better than that of sulfamethoxazole.
In order to study the early developmental characteristics of red saddleback clownfish (Amphiprion ephippium), and provide a theoretical reference for its breeding we had continuously observed and analyzed the morphological and growth characteristics of larvae, juveniles and young individuals. The body of 0 dah (Days after hatching) individuals (Total length 4.472‒6.152 mm) was translucent with obvious fin membrane, only a small part of yolk sac remaining, and feeding had been started. For 7 dah individuals (Total length 5.213‒12.985 mm), the fin membrane disappeared, and the development of each fin basically completed and the bands began to appear on the head, entering into juvenile stage. Then bands began to appear in the middle of the body and fully formed on the head. For 23 dah individuals (Total length>7.652 mm), the whole body was covered by scales, and the bands in the middle of the body extended to the abdomen, with yellow fins, and the trunk was mainly red pigment and yellow pigment, entering young fish stage. For 28 dah individuals, the middle band fully formed, then the bands gradually disappeared from the middle. For 130 dah individuals, the middle band disappeared completely, while the head band disappeared completely until about 160 dah. At this time, the shape and body color of young fish were the same with that of adult fish. In general, the growth of larval, juvenile and young of A. ephippium showed a trend of slow-rapid-slow trend with the increase of age. The formation and disappearance of white band on the head and middle part of the body were the most obvious features during the early development stage of A. ephippium.
In order to improve the efficiency of the determination of total phosphorus (TP) in the mariculture tailwater, we determined the TP content by microplate reader instead of spectrophotometer in mariculture tailwater, and optimized the digestion method of TP, the type of microwell plate and the amount of sample. The results show that there was no significant difference between 60 min of digestion using a temperature-controlled heating plate and 30 min of digestion using an autoclave (P>0.05). The sensitivity of the assay was better than those of the other experimental groups (200 µL for 96-well plate, 200 µL for 96-well quartz plate, 200 and 500 µL for 48-well plate, 500 µL and 1 mL for 24-well plate) when using a 48-well plate with 1 mL of sample. The linear correlation between phosphate concentration and absorbance was the best (R2=0.999 9) for the 48-well plate with 1 mL and the 96-well plate spiked with 200 µL. The accuracy and precision validation of TP determination in mariculture tailwater showed that the relative error (RE) and relative standard deviation (RSD) of the 48-well plate spiked with 1 mL were higher than those of the other experimental groups (96-well plate 200 µL, 96-well quartz plate 200 µL, 48-well plate 200 µL and 500 µL, 24-well plate 500 µL and 1 mL). The recoveries of disodium glycerophosphate (β-GLP) and sodium hexametaphosphate (SHMP) were 98.2%−99.6% and 93.4%−97.1%, respectively, and the limit of quantification (LOQ) of TP were 0.25 µmol·L−1; the RE and RSD of 96-well ELISA plate spiked with 200 µL were −14.03%−0.21% and 2.63%−14.23%, respectively, and the recoveries for β-GLP and SHM were 94.7%−99.0% and 88.9%−97.3%, respectively, and the LOQ of TP was 0.55 µmol·L−1. At TP concentration of 0.55−6.4 µmol·L−1, the accuracy and precision of the two optimized methods meet the determination requirements and can be used for the determination of TP in mariculture tailwater.
To explore the accumulation of tissue fat and its contribution to reproductive energy during gonadal development of Illex argentinus has important theoretical value for understanding its reproductive investment strategy, as well as the sustainable development and utilization of resources. By using tissue energy density measurement technology and fat extraction technology, we measured and analyzed the energy density of mantle soma, digestive gland, ovary and oviduct eggs of female I. argentinus before and after degreasing, as well as the fat content per unit mass, fat energy and proportion of each tissue. Results indicate that the energy density of all tissues decreased significantly after lipid extraction. During the maturation, female I. argentinus maintained a relative stable level of the lipid content and percentage of lipid energy in mantle soma and oviduct eggs. However, there was a significant decreasing trend in the lipid content and percentage of lipid energy in the digestive gland but an increasing trend in the ovary (Maximum in Phase IV) along with maturation. Furthermore, Pearson's r analysis indicates that there was a significantly negative relationship in the lipid content, lipid energy and percentage of lipid energy between gonadal tissues (Combination of ovary and oviduct eggs) and digestive gland, but without a significant relationship between gonadal tissues and mantle soma. In summary, female I. argentinus exhibits tissue-specific lipid content and lipid energy accumulation. The lipid content has a significant contribution to the reproductive energy, and lipids in the gonadal tissues are apparently derived from concurrent food intake, which further supports the argument that energy allocation to reproduction in I. argentinus mainly depends on the income resources.
Exploring the habitat suitability of Coilia mystus, a migratory fish in the Pearl River estuary, can provide scientific basis for the protection and utilization of fishery resources of C. mystus. Based on the date collected by bottom-trawl in the Pearl River Estuary during winter in 2019 and summer in 2020, we constructed the habitat suitability index (HSI) model of C. mystus, taking the water depth, bottom salinity, bottom temperature, as well as bottom dissolved oxygen as indicator environment indicators. The analytic hierarchy process (AHP) was used to calculate the weight of the indicators. The arithmetic mean (AMM) and the geometric mean (GMM) were used to build a model. Then a suitability curve was developed and the HSI of C. mystus was calculated. Results show that the optimal bottom salinities for C. mystus in the Pearl River Estuary in winter and summer were 21.03−30.55 and 20.25−25.82, respectively; the mass concentrations of suitable dissolved oxygen were 6.79–7.28 and 3.85–4.01 mg·L−1, respectively; the suitable water depths were 11.69–20.10 and 7.80–9.23 m, respectively; the suitable bottom temperatures were 19.84–19.95 and 28.36–9.44 ℃, respectively. The sites with HSI value greater than 0.5 accounted for 17.39% of the total survey sites. The study shows that the suitability of C. mystus was low, and its suitable habitats in the Pearl River Estuary are mainly located in the Sousa chinensis Nature Reserve in the Neilingding sea area.
Illumination is an important factor in aquaculture. Exploring the changes in the plasma physiology and biochemistry of Euthynnus affinis can provide references for the regulation of its optimal environmental factors. We designed four sampling time to investigate the light intensities on sunny days [2.7 lx (6:00), 1 116 lx (12:00), 913 lx (18:00) and 1 lx (24:00)] and those on cloudy days [1.9 lx (6: 00), 698 lx (12:00), 192 lx (18:00) and 1.4 lx (24:00)], so as to study the changes in the plasma cortisol, total cholesterol, triglyceride, malondialdehyde content, myeloperoxidase activity, lysozyme activity and immunoglobulin M concentration. The results show that there was no significant difference in the cortisol, malondialdehyde concentration and lysozyme activity among the four groups on sunny days, but all reached the maximum at 18:00 on cloudy days. Besides, the concentraions of cortisol and malondialdehyde were significantly higher than those at 18:00 on sunny days (P<0.05), while the lysozyme activity was significantly lower than that at 18:00 on sunny days (P<0.05). The total cholesterol content reached the maximum at 12:00 on sunny day and 18:00 on cloudy day, with no significant difference on sunny day and cloudy day at 12:00. However, it was significantly higher at 18:00 on cloudy days than on sunny days. The triglyceride content and myeloperoxidase activity reached the maximum both on sunny and cloudy days at 6:00, without significant difference. The immunoglobulin M concentration reached the maximum at 24:00 both on sunny and cloudy days, and it was significantly lower on sunny days than on cloudy days at 24:00 (P<0.05). The results show that the E. affinis is more suitable for surviving on sunny days, but it can adapt to the changes of light intensity in different weather by its active physiological adjustment, thereby reducing the damage of environmental factors to its physiological and immune functions.
The regulation of bacterioplankton is the core content of the environmental control strategy in shrimp agriculture. Exploring the general rules of the construction of bacterioplankton community can further promote the research on water quality regulation for shrimp ponds. Using 16s rRNA high-throughput sequencing technology, 12 weekly surveys were conducted in Litopenaeus vannamei desalinated ponds.The results indicate that a total of 2 854 OTUs (97% similarity) were obtained from 48 samples (Archaea belonged to 2 phyla, 1 class, 1 family and 1 genus and bacteria belonged to 30 phyla, 59 classes, 98 orders, 199 families and 433 genera, among which 25 genera were dominant flora). The dominant flora had high similarity in the composition, but with great differences in the distribution and relative abundance in each pond. The total average phylogenetic diversity index was 77.57, ranging from 24.39 to 111.65; the total average Shannon diversity index was 3.96, ranging from 2.64 to 5.06; the total average species richness index was 716, ranging from 229 to 1 054. NMDS analysis shows that the community structure of bacterioplankton in each pond varied greatly at the early stage of aquaculture, but not so greatly at the middle and late stages. The results of redundancy analysis shows that the labile phosphorus, total alkalinity, dissolved oxygen and sulfide were the main environmental factors affecting the distribution characteristics of community structure of bacterioplankton.
In order to improve the application performance of agar/sodium alginate composite membrane, we used agar and sodium alginate as film-forming base material, glycerol as plasticizer, ferulic acid, tannin acid, citric acid and succinic acid as crosslinking agents to prepare the agar/sodium alginate composite films by solution casting method. Then we studied the effects of four crosslinking agents on the properties of the composite films based on the mechanical properties, water resistance, moisture resistance, opacity, fourier transform infrared spectroscopy (FT-IR) and microstructure of the composite films. The results show that the four crosslinking agents improved the tensile strength, water resistance and moisture resistance of the composite films significantly (P<0.05), but reduced the transparency significantly (P<0.05). The crosslinking agents had the best improvement effect on the composite films with additions of ferulic acid and tannin acid of 5%, citric acid and succinic acid of 10%. Among the four crosslinking agents, citric acid cross-linked film had the best performance, and when the addition of citric acid was 10%, each index reached the optimal values [The tensile strength was 46.98 Mpa; the elongation at break was 17.87%; the water solubility was 24.17%; the swelling ratio was 38%; the water vapor permeability (WVP) was 0.51 g·mm·(m2·h·KPa)−1]. FT-IR analysis shows that citric acid and succinic acid improved the properties of the composite films by esterifying with −OH of agar and sodium alginate, and ferulic acid or tannin acid achieved crosslinking by forming intermolecular hydrogen bonds with agar and sodium alginate. Scanning electron microscopy (SEM) analysis shows that agar and sodium alginate had good compatibility, and the cross section of composite film became denser and smoother with the addition of crosslinking agents. Therefore, moderate addition of crosslinking agent to agar/sodium alginate composite films can improve the physical and chemical properties of composite films at different degrees, which provides scientific references for the preparation and application of packaging films.
Sander lucioperca is extremely sensitive to hypoxia, and is prone to hypoxia stress and death during intensive breeding and seedling transportation. In order to investigate the regulating effect of heme oxygenase 1 (HO1) in the response to hypoxia of S. lucioperca, we cloned the full-length cDNA sequence of ho1 gene by RACE (Rapid amplification of cDNA ends) technology. The results indicate that the cDNA length was 1 256 bp (840 bp ORF, 162 bp 5'-UTR and 254 bp 3'-UTR), encoding 279 amino acids. The multiple sequence alignment shows that the similarity of Ho1 with Siniperca chuatsi, Dicentrarchus labrax and Micropterus salmoides was 91.84%, 88.69% and 88.11%, respectively. Real-time quantitative PCR discloses that ho1 was expressed in all the tested tissues, with the highest concentration in the brain, followed by the kidney, liver and gills. During the first 3-hour hypoxic stimulation of Pikeperch, ho1 primarily responded in the skin and gills. But after 3 h of hypoxic stress, ho1 mainly played transcriptional regulatory roles in the heart, liver and kidney. At 12th hour of reoxygenation, the expression levels of ho1 in all the tissues except the liver returned to a normal level, and hypoxia stress had an enormous effect on the expression of ho1 in the liver. The study reveals that ho1 gene is involved in the molecular regulation mechanisms of S. lucioperca in response to hypoxia and plays an important biological role, which provides theoretical references for the understanding of the genetic mechanism of hypoxic stress.
To evaluate the application effect of spray-dried egg product in the diet of Procambarus clarkii, we formulated five isonitrogenous and isoenergetic diets containing 0% (Control group), 2.0%, 4.0%, 6.0% and 8.0% spray-dried egg product, which replaced 0% (CON), 25% (R1), 50% (R2), 75% (R3) and 100% (R4) fishmeal, respectively, to feed the shrimps [Initial body mass (9.02±0.12) g] for six weeks. The results show that there were no significant differences in the specific growth rate, feed conversion ratio, feeding rate, survival rate and hepatosomatic index among all the groups (P>0.05). The weight gain rate in R4 group decreased significantly compared with the CON group (P<0.05). The contents of crude protein, essential amino acid and total amino acid in abdominal muscle in R4 group increased significantly compared with the CON group (P<0.05). The contents of crude fat and ash in muscle in R2, R3 and R4 groups were significantly higher than those in the CON group (P<0.05). There were no significant differences in the contents of 17 hydrolyzed amino acids in muscle among all the groups (P>0.05). Compared with the CON group, the intestinal protease activities increased significantly but the amylase activities decreased significantly in egg product supplementation groups, and the intestinal lipase activity increased significantly in R3 and R4 groups (P<0.05). The serum alkaline phosphatase activity and total protein content in R2, R3 and R4 groups increased significantly than those in the CON group (P<0.05). The bacterial abundances of Clostridium sensu stricto and Lysobacter in R3 group were significantly higher than those of the other groups, while the bacterial abundance of Streptococcus in R4 group was significantly higher than that of the other groups (P<0.05). In conclusion, when the diet of P. clarkii contains 6% fishmeal, the spray-dried egg product can replace 75% fishmeal.
To develop a new type of aquatic feed additive for promoting growth and enhancing immune function, we cultured Epinephelus fuscoguttatus with body mass of (44.48±2.06) g for 56 d by adding fermented Astragalus membranaceus with proportions of 0% (Control group), 0.25%, 0.5%, 1%, 2% and 4% (L0, L1, L2, L3, L4 and L5 groups), and then conducted an ammonia nitrogen stress test. Taking growth, digestion and immune function as the indicators, we evaluated the physiological, biochemical and stress-resistant effects of fermented A. membranaceus on E. fuscoguttatus, and determined the optimal ratio. The results show that: 1) Compared with the control group, the addition of fermented A. membranaceus increased the weight gain rate (WGR) and specific growth rate (SGR), as well as the activities of digestive enzymes in gastrointestinal tract significantly (P<0.05), but reduced the feed conversion ratio (FCR) of E. fuscoguttatus in L3 and L4 groups significantly (P<0.05). 2) Before the ammonia nitrogen stress, fermented A. membranaceus increased the liver antioxidant performance significantly (Except L5 group, P<0.05), but decreased the liver malondialdehyde (MDA) content and serum glutamic-oxalacetic transaminase (GOT) activity significantly (P<0.05). The serum glutamic-pyruvic transaminase (GPT) activity, glucose (GLU) concentration and serum triglyceride (TG) concentration in L3, L4 and L5 groups were significantly lower than those in the control group (P<0.05). 3) After the ammonia nitrogen stress, fermented A. membranaceus did not improve the antioxidant performance of liver, but reduced the MDA content in liver (Except L5 group), the activities of GOT and GPT as well as the GLU concentration in serum (Except L4 and L5 groups) significantly (P<0.05). In conclusion, the recommended feed additive proportion of fermented A. membranaceus is 1%–2%.
In order to understand the genetic resources of Mastacembelus armatus populations in southern China, and provide important scientific basis for the management and protection of the genetic resources of M. armatus, we collected 140 individuals from 16 geographical populations from seven independent river systems in southern China and sequenced two mitochondrial genes (COI and Cytb) via PCR amplification and Sanger sequencing, and finally revealed the genetic structure and demographic history of M. armatus populations by phylogenetic analysis, haplotype network, population genetic analysis and Bayesian skyline plot. The results show that M. armatus populations consisted of three lineages (I, II and III) and split between 0.596 and 0.676 million years ago (Ma). Haplotype network shows that there was a common domain distribution among different lineages, and suggests that there might be two diffusion routes between Hainan Island population and mainland population. Population genetic analysis finds significant genetic differentiation (FST=0.676, P<0.001) and isolation by distance pattern (R=0.463, P=0.001) among M. armatus populations, implying that spatial distance was an important factor for genetic differentiation of M. armatus. Demographic analysis shows that M. armatus populations experienced population expansion at 0.025 Ma.
In order to investigate the effects of single and combined stress of nitrite and microplastics on the physiological functions of gill tissues of Litopenaeus vannamei. We designed the control group, 20 mg·L−1 nitrite stress group (NIT), 10 μg·L−1 microplastic stress group (MP), 20 mg·L−1 nitrite and 10 μg·L−1 microplastic composite stress group (NM), and then measured the changes of immune and osmotic regulation in gills of shrimps on the 14th day. The results show that: 1) The oxidative stress indicators such as the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) changed in different degrees after the stress. 2) The detoxification metabolic indicators such as the relative expression levels of cytochrome P450 (CYP450), glutathione S-transferase (GST) and apoptosis factor (CASP-3) were disturbed in different degrees after the stress. 3) The relative gene expression levels of the osmoregulation indexes such as ion transporters (VATP, NHE, NKA-α, NKA-β and CA) and channel proteins (TIP4, CCP, CLC and AQP) occurred in different degrees of disorder after the stress. 4) The apoptosis index sucha as the relative expression level of apoptosis factor (CASP-3) gene decreased significantly in the three groups (P<0.05). Thus, it is inferred that nitrite and microplastic stress can induce the changes of immune, detoxification metabolism and osmotic regulation in the gills of L. vannamei, affecting its normal physiological functions.
Water flow is one of the important ecological factors that affect the physiology and growth of fish. Studying the stress level changes of Plectropomus leopardus under flow velocity stress, and clarifying the maximum flow velocity that the fish can tolerate, can provide a theoretical basis for the cage culture site selection, intensive flow culture and deep-sea industrial boat culture. Taking P. leopardus [Body length (11.38±1.48) cm, body mass (34.71±11.57) g] as the research object, we designed a hydrostatic control group (0 cm·s−1 or 0 BL·s−1, body length·s−1) and three experimental groups (11.4, 22.8 and 34.2 cm·s−1 corresponding to 1, 2 and 3 BL·s−1) by a self-made fish swimming experimental device, so as to explore the effect of 40-min water flow stimulation on its tail swing frequency change, blood glucose, lactic acid and cortisol content in blood. The results show that there was a linear correlation between the tail beat frequency and water velocity. The blood glucose and cortisol levels increased linearly with the number of tail beat, but the lactate increased non-linearly with the number of tail beat. The flow rate over 2 BL·s−1 resulted in a significant increase in cortisol in the blood of P. leopardus (P<0.05). When the flow rate reached 3 BL·s−1, the blood lactate and blood glucose levels increased significantly (P<0.05). In conclusion, the upper limit of tolerance to flow velocity of P. leopardus was 2 BL·s−1. When the flow velocity of cultured water was higher than 2 BL·s−1, the stress level and metabolic load increased significantly and the stress effect appeared (P<0.05). The results provide references for the farming workboat system of swinging and the site selection of net tank culture waters.
Aiming at the current low level of automation in the fishing of Antarctic krill (Euphausia superba) in China, and the error in determining the fishing depth by manually observing the fish detector image, a dynamic truss trajectory planning method based on the metadata of Antarctic krill sonar equipment is proposed. First, we analyzed the data sent back by the underwater acoustic instrument EK80 scientific echo sounder, obtained the target intensity of krill at different depths, and used statistical methods to determine the resource of krill at this depth, so as to get the densest depth (Y) of krill corresponding to each horizontal distance (X). Then we used cubic B-spline curve and Dynamic Window Algorithm to carry out the global path planning and local path planning. The planned route passed through the densest depth of these krill. The results show that the total length of the planned path was 1 054 m, and the total time was 614 s. The maximum deviation distance tracked by the Dynamic Window Algorithm was only 3.3 m, which was less than the expected maximum deviation distance of 5 m. The proposed method can: 1) Avoid the impact of artificial judgment of resource depth on the fishing volume effectively, and improve the fishing efficiency. 2) Realize the automatic planning of the truss forward route with the best fishing efficiency.
To understand the potential impact of La Niña events on fish community structure in Beibu Gulf, based on the bottom trawl survey data of fishery resources in July 2006 and July 2008, we analyzed the variation in the fish community structure before and after La Niña event in the Beibu Gulf. The results show that the dominant species were Acropoma japonicum and Trachurus japonicus in the summer of 2006, and T. japonicus, Decapterus maruadsi, A. japonicum and Evynnis cardinalis in the summer of 2008. T. japonicus and A. japonicum were the common dominant species in the two years. The diversity index (H') and evenness index (E1 and E2) did not differ significantly between years, but the richness index (D') differed significantly. After the La Niña event, the density of warm-water fish resources, such as A. japonicum, decreased, while that of warm-water fish resources, such as T. japonicus and D. maruadsi, increased. Besides, T. japonicus and D. maruadsi moved in the direction of the coast of the Beibu Gulf. The diversity index of the Beibu Gulf coastal sites (C1–C22) was significantly different before and after the La Niña event (P<0.05). The results of cluster analysis and non-metric multidimensional scale ranking show that the fish community spatial distribution was more stable, the main difference was in the western coast of Hainan Island. The La Niña event resulted in a decrease in water temperature and an increase in primary productivity in the Beibu Gulf, causing an increase of the density in small pelagic fish stocks such as T. japonicus and D. maruadsi. In conclusion, when the fishing pressure is relatively stable, the significant variation in the fish community structure in the Beibu Gulf is closely related to the La Niña event.
Albacore tuna (Thunnus alalunga) is the main target species of longline fishery, accounting for 1/3 of the annual catch of tuna. Since the fishery resources of T. alalunga are rich in South Pacific, to explore the spatial pattern characteristics of its fishery resources in that sea area, and to analyze whether there are differences in the spatial scale are important for the rational utilization and protection of its fishery resources in South Pacific. We aggregated the longline fishing logs of the Chinese mainland from 2015 to 2019 at three spatial scales (1°, 2° and 5°) by season, and calculated their spatial pattern characteristics based on the 5°grid data from Western and Central Pacific Fisheries Commission (WCPFC). The results show that: 1) The spatial pattern of T. alalunga resources in the South Pacific was characterized by large ellipticity, and there was a significant east-west distribution in the direction of the spatial pattern at all scales. The spatial pattern characteristics of resources (Distribution range, flatness, azimuth, etc.) had similar and obvious seasonal fluctuation characteristics. 2) The spatial pattern of resources obtained from three different scales of the same origin had a small difference, while that from different sources had a great difference. 3) In the same scale of 5°grid data, the resource center of the spatial pattern in China was more southeast and about 10°east in longitude than that of the data from the WCPFC. 4) The aggregation degree of resource spatial pattern obtained from large-scale data was stronger than that from small-scale aggregation data. Besides, the hot spots of spatial pattern obtained from different scale data of same origin were different to some extent.