Different thermal processing methods have great influence on the quality of Litopenaeus vannamei. In this paper, microwave-infrared combined heating technology was used to treat L. vannamei. The effect of combined heating conditions on the quality of L. vannamei. was discussed, which laid a theoretical foundation for the development of shrimp products. Firstly, the change of center temperature of shrimp during microwave-infrared heating was clarified, and then the weight loss rate, color, texture and other quality changes of shrimp meat under different heating conditions were discussed. The results showed that at the same microwave power and different infrared temperatures, the weight loss rate of L. vannamei was the highest at 75 °C, and the lowest at 179 °C. Comparing the texture characteristics of the shrimp, the elastic fluctuation range of the shrimp was not large about 3.0 mm. The chewiness of shrimp was not significantly different under different heating conditions, but positively correlated with its corresponding hardness, cohesiveness and elasticity; the hardness, cohesiveness and cohesiveness of shrimp meat changed regularly under different combined heating conditions; in terms of color difference, L*, a*, b* and E were negatively correlated with infrared temperature. These results lay a foundation for the application of combined heating technology in shrimp processing.
In order to study the function of serum amyloid A (SAA) in the immune defense of Macrobrachium nipponense, the full-length cDNA sequence of the SAA gene in M.nipponense, named MnSAA, was cloned using rapid amplification of cDNA ends (RACE) method. The expression level of MnSAA in different tissues and different development stages of M. nipponense, and the expression profile of MnSAA in hemocytes and hepatopancreas of M. nipponense after Micrococcus lysoleikticus, Aeromonas hydrophila and white spot syndrome virus (WSSV) infections were also examined by quantitative real-time PCR (QPCR). At the same time, the expression changes of activator protein-1 (AP-1) and class B scavenger receptor (CD36) genes in hepatopancreas and cumulative mortality of prawn after MnSAA gene silencing plus A. hydrophila infection were further investigated using RNA interference (RNAi) technology. The results showed that the full-length cDNA of MnSAA was 649 bp, including a 21 bp 5′-untranslated region (UTR), a 232 bp 3′UTR, and a 369 bp open reading frame (ORF) encoding a deduced protein with 131 amino acids. Sequence and phylogenic analyses revealed that MnSAA belongs to acute-serum amyloid A (A-SAA) and had a close relationship with the invertebrate Crassostrea hongkongensis. mRNA expression analysis revealed that MnSAA gene was ubiquitously expressed in various tissues and growth stages of M. nipponense, and abundantly expressed in the hepatopancreas and adult prawn stage. Pathogen infection experiment showed that the expressions of MnSAA in hemocytes and hepatopancreas were all significantly increased compared with the control group after M. lysoleikticus, A. hydrophilahe and WSSV infections for 12-72 h. The RNAi experiment showed that after MnSAA silencing, AP-1 and CD36 gene expressions in hepatopancreas of M. nipponense were all significantly decreased compared with the control group after 12-72 h and 6-72 h, respectively, of A. hydrophila infection, and the cumulative mortality of prawn was increased compared with the control group after A. hydrophila infection. These results suggested that MnSAA is involved in the activity of anti-pathogen infection in M. nipponense and plays an important role in the immune defense system of M. nipponense.
Hybridization is the most widely used and effective way of artificial breeding in aquaculture. This study use Epinephelus lanceolatus as female parent, E. moara as male parent by artificial insemination technology has carried on the interspecific cross experiment, and developmental sequence of fertilized egg, growth of larvae, juvenile and young fish was observed and studied, and then with the parent and the hybrid F1 generation " yunlong grouper” (E. moara ♀× E. lanceolatus) contrasted the phenotypic traits. Results showed that the embryos as oval, transparent, floating, the fertilized eggs size (0.787±0.013)mm, each egg has one oil globule in the center. In sea-water temperature of 24 °C, salinity 30, pH 7.8, embryos can develop normally, according to the data, six period including 25 stages of embryos were recorded,which were fertilized egg, cleavage, blastula, gastrula, organogenesis and hatching period, the length of newly hatched larvae(1.595±0.015)mm and shows the feasibility of the cross;3 days after hatching, the yolk membranes disappeared and became the late larva, with a total length of (2.530±0.023)mm. 52 days After hatching, entering the juvenile stage, the total length(17.500±1.915)mm, the length of the second dorsal fin spine (5.795±0.049) mm, and the length of the first pelvic fin (2.992±0.911) mm. When the dorsal fin spine contracted to the minimum value (4.460±0.600) mm, scales began to appear and body color began to darken. The second dorsal fin spine and the first pelvic fin spine completely degenerated. The body shape was similar to that of the adult fish. The whole body was covered with scales. The growth comparison results showed that the growth rate of the positive and negative cross F1 generation was between that of the parents, which was faster than that of the E. moara, which was slower than that of the E. lanceolatus, and the growth rate of the reverse cross F1 generation was slower than that of the orthogonal F1 generation. The results provide a basis for the formation of hybrid dominant traits and genetic analysis of grouper.
A 56-d feeding trial with 480 yellow catfish (Pelteobagrus fulvidraco) juveniles [(1.67±0.01) g initial body weight] was carried out to estimate the effect of replacing fish meal with defatted black soldier fly larvae meal (DBSFLM) on growth performance, nutrient retention, serum biochemical parameters and digestive enzymes activity of juvenile P. fulvidraco. Fish were randomly allocated into four isolipidic and isoprotein dietary treatments which were formulated by replacing 0 (T0), 20% (T20), 40% (T40) and 60% (T60) of fish meal (FM) protein with DBSFLM. Each treatment was randomly assigned to triplicate groups of 40 fish per aquarium. Fish were fed twice daily to apparent satiation. With increasing content of DBSFLM, the final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) of yellow catfish was increased at first and then decreased. Gowth performance of FBW, WGR and SGR in T20 were highest and higher than T60, whereas the feed conversion rate was the lowest. The feed intake in T20 and T60 was higher than that in control and T40 groups. With the increasing content of DBSFLM, the intraperitoneal fat index (IFI) was declining with T60 group was lower than control, ash, calcium retention declining with T40 and T60 group lower than control.There was no difference of condition factor, viscera index, hepatosomatic index, intestine index and gastric index among treatments. Nutrient retention such as protein,lipid and phosphorus, moisture, crude protein, lipid and ash in whole body were not affected by dietary treatments. Compared with control, the serum cholesterol and triglyceride were reduced and the high density/low density lipoprotein cholesterol were increased in T20, T40 and T60 groups and pepsase and intestinal trypsin increase in T40 group. Results suggested that the growth performance and body composition of yellow catfish juveniles was not affected by dietary DBSFLM and the optimal alternative ratio was 20%,which was better than control. The replacement of fish meal with DBSFLM may reduce IFI, serum triglyceride, cholesterol and ash, calcium retention and increase protease.
In order to explain the influence of temperature and light intensity on the growth process of Saccharina japonica sporophyte and explore the physiological response mechanism of the temperature and light environment from the perspective of physiological ecology. In this study, based on the growth parameters of Saccharina japonica sporophyte, set up four water temperature gradient (6 °C, 10 °C and 14 °C and 18 °C) of the Saccharina japonica sporophyte in a laboratory experiment, and determined the chlorophyll fluorescence parameters at night under 9 photochemical light gradients (0, 25, 70, 133, 230, 317, 421, 582, 786 μmol·photons/(m2·s)). Results showed that ① under the condition of 6 °C, Saccharina japonica sporophyte fluorescence parameters (Fv/Fm)and(Fv/F0)value maximum, 0.71 and 2.40 respectively; When water temperature 18 °C, its (Fv/Fm)and(Fv/F0)minimum value of 0.65 and 1.85 respectively.② The maximum values of photochemical quenching and non-photochemical quenching of Saccharina japonica sporophyte occur at 18 °C (0.92 and 3.29, respectively). ③ The light response curve of kelp first increased and then decreased with the enhancement of PAR. ④ The maximum leaf length growth rate, leaf width growth rate and dry weight growth rate of Saccharina japonica sporophyte were 1.34 cm/d, 0.33 cm/d and 1.01 g/d, respectively. These results indicated that the change of dry weight growth rate was consistent with the change of light response curve under different water temperature conditions, and high temperature inhibited the photosynthetic efficiency of Saccharina japonica sporophyte. When the ambient photosynthetic effective radiation was larger than the light saturation point (Em), the relative electron transfer rate of kelp decreased and photosynthesis was inhibited.
The study aimed to reveal the trends and research hotspots of fisheries science in major fisheries countries in the world. Based on the data collected in Incites and Web of science Core Collection database from 2000 to 2018 and we used the method of bibliometrics analysis to review documents related to the study on fisheries science. We firstly created descriptive statistics of the number of articles published annually and the journal frequency distribution. Then, the methods of author, institution cooperation network and keyword based knowledge mapping were used to explore the research hotspots of fisheries science in the world. Descriptive statistics suggested that the number of documents in USA have maintained at a high level and showed a dynamic fluctuation, with a slight downtrend in recent years. The documents number in China Mainland have basically increased exponentially, showing a steady upward trend, approaching the documents number in the USA by 2018. The other countries have shown a relatively stable dynamic fluctuation. Research in all countries are increasingly focusing on cooperation among countries, institutions and authors. The journals distribution is consistent with the law of literature dispersion proposed by Bradford. Most of the top 20 journals in major fisheries countries in the world are top journals, which have great academic influence. Marine and freshwater biology, veterinary medicine, oceanography, zoology, immunology, limnology, biochemistry and molecular biology are the dominant disciplines of fisheries science in the world, but the key research areas of each country is different. The research hotspots are: 1) fishery management and protection research based on biological reference points; 2) fishery resource evaluation and management strategy research; 3) basic biology research of fishery resource; 4) management measures and policy objectives research based on ecosystem. And all the research hotspots are highly integrated and promote the development of comprehensive interdisciplinary.
This study aimed to investigate the effect of soybean meal on the growth, intestinal microbiota composition and metabolic enzymatic activities of microbial amino acid of Channa argus. Four isonitrogenous and isoenergetic diets were formulated with soybean meal by replacing 0, 25%, 50% and 75% fish meal (G1, G2, G3 and G4, respectively). The fish of (8.65±0.25)g was hand-fed daily to satiation twice in cylindrical fiberglass tanks for 21 days. Results showed that no significant difference in survival rate was found among four groups. The growth performance of C. argus in G4 was significantly lower than those in G1 and G2, while the difference was not statistically significant between G3 and other three groups. The proportion of Firmicutes in the intestine of fish in G1 and G2 was significantly higher than that in G3, and the lowest was found in G4. The proportion of Proteobacteria in G1 and G2 was significantly lower than those in G3 and G4. The proportion of Lactococcus, Bacillus, Pseudomonas, Streptococcus, Laseczka and Acinetobacter in G4 was significantly lower than those in the other three groups. Additionally, the activities of glutamic-pyruvic transaminase and adenosine deaminase were highest in G4, while the activity of lactic dehydrogenase was highest in G1. All results indicated that, except for the effect on the growth of C. argus, dietary soybean meal significantly induced the changes in the intestinal microbiota composition and the activity of the microbial amino acid metabolic enzymes, which may provide theoretical basis for further considering the application of soybean meal in the formulated diets of C. argus.
The growth and maximum photon quantum yield of photosystem II (Fv/Fm) of the blades of two high-temperature resistant strains (YZ-4 and TM-18) and one wild-type strain (WT, used as control group) in Pyropia yezoensis were analyzed under high-temperatures or low-salinities, in order to screen out strains resistant to the two abiotic stresses. The results showed that YZ-4 and TM-18 blades grew faster than those of WT between 50-85 d under the optimal culture condition (18 °C and salinity of 26). The ratios of Fv/Fm and contents of photosynthetic pigments were also higher than those of WT. The absolute growth rate and Fv/Fm of every strain showed high positive correlations. In addition, WT blades began to form spermatangia around 70 d, their absolute growth rate and Fv/Fm decreased significantly. When cultured under high-temperatures, Fv/Fm and absolute growth rates of the blades of every strain decreased. The higher the temperature or the longer the stress lasted, the greater the decline would be. Fv/Fm of WT, YZ-4 and TM-18 decreased by 56.7%, 43.2% and 28.7%, respectively, after 35 d of high-temperature stress at 24 °C. The growth of WT was completely stagnated after 15 d of high-temperature stress at 25 °C. Meantime, growth rates of YZ-4 and TM-18 were 0.51 and 0.84 cm/d, respectively, indicating that they were veritable high-temperature resistant strains. The effects of low-salinity stress on the blades were similar to that of high-temperature stress. After 35 d of low-salinity stress at salinity of 9, Fv/Fm of WT, YZ-4 and TM-18 decreased by 46.2%, 42.0% and 32.0%, respectively. The absolute growth rates of WT, YZ-4 and TM-18 were 0.12, 0.10 and 0.90 cm/d, respectively. Besides, growth of the blades of WT and YZ-4 cultured under salinity of 5 was greatly affected, in that the blades were deepened in color, curled and rotted after 15 d under stress, while TM-18 did not rot at the same salinity of 5 for 25 d. These results indicated that TM-18 was more tolerant to high-temperature and low-salinity stress than WT and YZ-4, the internal reason was that the decrease of Fv/Fm of TM-18 blades was small. It was indicated indirectly that Fv/Fm could be used as a new index for breeding of stress-resistant strains in P. yezoensis.
In order to compare and evaluate the differences in nutritional and physiological functions of fiber sources in fish feed, compared the effects of dietary fiber sources on the growth, plasma biochemical, intestinal antioxidant capacity and histology of M.salmoides. Fish [initial weight of (21.59±0.12) g] were fed four isonitrogenous and isolipid experimental diets containing same fiber content soybean dregs fiber (SF), fermented soybean dregs fiber (FF), carboxymethyl cellulose (CF) and microcrystalline cellulose (MF) for 8 weeks. The results indicated that the CF group showed significantly lower final body weight (FBW), specific growth rate (SGR) and protein efficiency ratio (PER) compared with other groups, while feed conversion ratio (FCR), heparsomatic index (HSI) and liver lipid content was significantly higher than other groups. The activities of alanine amiotransferase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP) and the content of triglyceride (TG) in plasma of CF group were significantly higher than other groups. At the same time, the activities of superoxide dismutase (SOD) and Na+, K+-ATP enzyme of CF group were significantly lower than other groups, while the content of malondialdehyde (MDA) was significantly higher than other groups. The content of nitric oxide (NO) was highest in FF group. Compared with the other groups, the liver appearance become white and liver cells were vacuolated seriously and aggravation of mechanical damage of the hindgut villi in CF group. The results showed that dietary fiber source can significantly affect the liver and intestinal health and then affect growth performance of M.salmoides, and the feasibility of carboxymethyl cellulose as an adhesive should be re-evaluated.
The ectopic biofloc reactor was used to compare the simulated carbon sources (NaHCO3) concentration of 0.0 g/L (control group), 0.5 g/L, 1.0 g/L and 1.5 g/L of simulated aquaculture wastewater which effect the nitrogen reduction and sedimentation performance of the bioflocs in two stages: organic carbon source exist (stage I for 21 d) and organic carbon source loss (stage II for 21 d). The results showed that the effluent ammonia nitrogen concentration in the first-stage control group was significantly higher than that in the other treatment groups (P < 0.05), but generally decreased first and then stabilized. The nitrite nitrogen and nitrate nitrogen in each group accumulated a small amount; the biofloc biomass and sedimentation rate of the control group were significantly lower than the treatment groups (P < 0.05), and the difference between the treatment groups was not significant. There was no significant difference in the concentration of ammonia nitrogen and nitrite nitrogen in the effluent of each group in stage II (P > 0.05). The concentration of nitrate nitrogen in the control group was higher than that in treatment groups, and the concentration of ammonia nitrogen decreased rapidly. At this stage, the biomass and sedimentation rate of the bioflocs decreased, and the 1.0 g/L NaHCO3 treatment group showed better sedimentation effect; the particle size distribution also tends to be uniform. During the whole experimental period, the removal efficiency of ammonia nitrogen reached 97.8% and the nitrite nitrogen did not accumulate significantly under different concentrations of inorganic carbon source. The sedimentation rate and biomass of bioflocs in the treatment groups were significantly higher than those in the control group (P < 0.05). The results show that the addition of inorganic carbon source can improve the nitrogen reduction performance of bioflocs and enhance its sedimentation rate. After removing the organic carbon source, the biofloc reactor can maintain the ammonia nitrogen removal capacity, but caused nitrate nitrogen accumulation, biofloc organisms. The amount is reduced when the organic carbon source was missing, the inorganic carbon source (≥0.5 g/L) helps the biofloc reactor to maintain its ammonia nitrogen removal capacity.
Using magnetic-bead enrichment and PCR screening method, we obtained 19 pairs of microsatellite primers from Tridacna crocea. Comparison between Qilianyu and yongxing island wild population with these markers shows: the mean allele number and the effective allele number were 11.105, 11.895 and 6.274, 6.173 respectively; the values of average expected heterozygosity were 0.776and 0.788; the mean PIC was 0.730 and 0.744; High-genetic diversity was maintained in those wild population. Four loci significantly deviated from Hardy-Weinberg equilibrium after Bonferroni correction in each population. In addition, the transferability of all polymorphic short sequence repeats (SSRs) was assessed in five closely-related species.the test resulted in 7 loci amplifying and 6 loci polymorphisming in T.squamos; 3 loci amplifying and 1 loci polymorphisming in T.derasa; 5 loci amplifying and 5 loci polymorphisming in T.noae; 9loci amplifying and 8 loci polymorphisming in T.maxima; 2 loci amplifying and 2 loci polymorphisming in H.hippopus.
The previous studies found that KK-42 treatment can significantly shorten the duration of molting cycle in juvenile prawn Macrobrachium nipponense, and increase the thickness of the carapace endocuticle in late premolt (D3 stage). In order to further investigate the effect of KK-42 on cuticle structure, the juvenile prawns in postmolt stage during which the formation of exocuticle gradually ends but that of endocuticle starts, were employed to study the structures of carapace exocuticle and endocuticle using the observation of paraffin section by scanning electron microscopy (SEM). Healthy intermolt juvenile prawns with body length of 3.5±0.1 cm were randomly divided into two groups. The prawns were soaked for 1 min in KK-42 solution at a concentration of 1.95×10−4 mol/L (treatment group) or 0 mol /L (control group), respectively. The carapaces of juvenile prawns at 1.5, 3, 6 and 12 h after molting were obtained to be used for ultrastructural observation. To observe directly the surface structure of endocuticle, the carapace obtained at 6 h after molting was scraped gently with an anatomical knife to remove tissues on the inner surface of carapace, and then examined using SEM. The results showed that the carapace was only composed of the epicuticle and exocuticle at 1.5 and 3 h after molting. The number of exocuticle lamellae derived from KK-42 treatment group rised significantly at 1.5 and 3 h after molting, and the thickness of exocuticle increased by 72.07% and 38.67%, respectively, compared with the corresponding control group. At 6 and 12 h after molting, the loose lamellaes in exocuticle tended to be dense, and there was no significant difference in thickness to be found between two groups. The number of endocuticle lamellar with a loose structure, being only one at 6 h, separately increased to two in control group and three in treatment group at 12 h after molting. In addition, pore canals within the endocuticle presented different sizes and head-tail orientation. No significant structural change was observed in the endocuticle after KK-42 treatment. The results reveal that KK-42 treatment has a significant effect on the carapace ultrastructure of juvenile M. nipponense during postmolt, and accelerate the formation rate of the exocuticle as well as endocuticle.
In order to complement the basic biological information of Oratosquilla oratoria and provide managers with scientific guidance and theoretical basis, based on the size composition data of O. oratoria obtained from fishery independent surveys from 2016 to 2017 in coastal waters of Shandong Peninsula, this study estimated the growth and mortality parameters of O. oratoria. A length-structure yield per recruitment model was used to assess the population dynamics and management strategy of the species. A total of 5 028 individuals were caught, from which the length-weight relationship was derived W=0.014 5L2.88, showing a negative allometric growth pattern. Asymptotic body length and growth coefficient estimated by ELEFAN were L∞=19.87 cm and K=0.62 a−1, respectively. The growth rate of O. oratoria showed remarkable seasonal oscillation, the highest in October and the lowest in April, and the amplitude of the seasonal oscillation (C) was 0.76. The total mortality (Z) estimated by length-converted catch curve was 3.24 a−1, and the natural mortality (M) estimated by several estimators ranged from 0.75 to 1.27 a−1. Accordingly, the fishing mortality (F) ranged from 1.96 to 2.49 a−1, and the mean exploitation rate was 0.67. Results of YPR model showed that with the F increasing, YPR tended to increase at first then decrease. Biological reference points F0.1 and Fmax were 0.92 a−1 and 1.88 a−1, respectively. This study shows that the O. oratoria stock is over-exploited. In order to maintain stock and fishery of O. oratoria, fishing pressure needs to be reduced and length at first capture should be increased.
Aiming at the low survival rate of marine medaka (Oryzias melastigma), the experiment was carried out to understand the feeding behavior development of O. melastigma in early stage, which provided a theoretical basis for breeding. The growth characteristic and feeding behavior of O. melastigma had been observed and analyzed feeding with Artemia nauplii durying the first 90 days after hatching, by using a single camera a waterproof-mirror and fish behavior analyze system. The results were as followed: its average growth rate in body length was 2.579%/d, and the relationship between body length and day-old age was y=3.132+0.383x−0.004x2+0.000 03x3, R2=0.98. Its larvae period could be divided into 3 stages (larvae stage was 0~10 d, juvenile stage was 11~30 d and young stage was 30-65 d) and 6 phases (pre-larvae was 0~4 d, post-larvae was 5-10 d, pre-juvenile was 11-18 d, mid-juvenile was 18-24 d, post-juvenile was 24-30 d, and young was 31-65 d) according to several indicators of the different feeding behavior. At the 4th day after hatching (DAH), O. melastigma were fed with Artemia nauplii that hatched within 12 hours. And all larvae can feed Artemia nauplii at 10th day after hatched (DAH). There was high mortality rate in larvae stage but the feeding ability was improved steadily. By the end of the period, the feeding success rate increased to 45%-55%, and the feeding efficiency reached 0.5-0.6 ind./min. At the juvenile stage (26-30 d), all indicators of feeding behavior had been greatly improved, such as the response time to Artemia was shortened and the distance was elongated, the feeding rate increased, and food intake also increased. At the same time, the success rate of feeding had been raised to a high level, up to 90%-95%. At the young stage, all indicators of feeding behavior were very close to the adult fish. The feeding efficiency reached more than 9 ind./min. Its feeding behavior development was mature, and feeding function tends to prefect at this stage. Experiments show that the O. melastigma had a low feeding ability with a shot response distance to Artemia nauplii, and the feeding success rate and feeding efficiency still at a low level. The feeding success rate and feeding efficiency were gradually increased with its own development and feeding ability improving, and the survival rate tended stable. It may be an effective way to increase the survival rate of breeding when paying closed attention to the changes in feeding behavior of O. melastigma through changing the feeding quantity and frequency that making more larvae fish transition to the juvenile period.
An 8-week feeding trail was carried out to investigate the effect of dietary vitamin A (178.2, 2 058.9, 18 436.2 IU/kg) on growth performance, serum biochemical index and hepatic glucose and lipid metabolism key enzyme activities and gene expression levels of juvenile black carp (Mylopharyngodon piceus). Using a one-factor experiment design, three isonitrogenous and isoenergetic purified experimental diets (diet 1, diet 2 and diet 3) containing 0, 2 200 and 20 000 IU/kg VA diets were formulated. Total vitamin A contents in the diets were measured by HPLC (Agilent-1100, Agilent, USA), actual content of vitamin A in each diet were 178.2, 2 058.9 and 18 436.2 IU/kg, respectly. Casein (vitamin free) and gelatin were used as protein sources, rapseed oil was used as lipid source, dextrin was used as carbohydrate source. Total 360 juvenile black carp with initial weight (6.10 ± 0.10) g were randomly divided into 3 groups with 3 replicates per group and 40 black carp per replicate. The results showed as follows: weight gain rate (WGR) and specific growth rate (SGR) were significantly reduced for fish fed diet with 178.2 IU/kg VA. When VA is deficient, concentrations of serum glucose (GLU), triglycerides and Low-density lipoprotein (LDL) were decreased, but total cholesterol (TCH) concentration was increased. The activities of hexokinase (HK), phosphofructokinase (PFK) and pyruvate (PK) increased for fish fed diet with 2 058.9 IU/kg VA. Gene expression of liver Glucose transporter-2 (GLUT-2), HK, GK, PFK and G6Pase were increased in fish fed diet with 2 058.9 IU/kg VA. However, there were no significant difference on the gene expression of fatty acid transporter protein-1 (FATP-1) for fish fed diet with 2 058.9 IU/kg VA. But the gene expression of Carnitine O-palmitoyltransferase-1 (CPT-1) and Carnitine O-palmitoyltransferase-2 (CPT-2) were significantly influenced. The gene expression of CPT-1 and CPT-2 were inhibited for fish fed VA deficient diet. When fish fed diet with 18 436.2 IU/kg VA, the expression of acetyl-CoA carboxylase-2 (ACC-2) and lipoprotein lipase (LPL) genes were inhibited. Besides, the gene expression of Peroxisome proliferator-activated receptor-γ (PPARγ) decreased when the VA content was 18436.2 IU/kg in feed. Overall, fish fed diet with 2058.9 IU/kg VA could improve growth performance and ability of liver cells to transport glucose of juvenile black carps. Diet with 2058.9 IU/kg VA could keep a balance between glycolysis and gluconeogenesis, it also could promote fatty acids synthesis and transport.
In order to determine the dietary protein requirement of juvenile giant salamander, 6 isolipidic diets were formulated to contain graded levels of D1(43.7%), D2(47.1%), D3(51.3%), D4(55.7%), D5(59.9%) and D6(64.4%) crude protein(dry matter) to feed juvenile giant salamander initially weight (20.99±0.15)g for 92 days. The results show that: 1) Dietary protein levels had significant effects on weight gain rate of giant salamander, it reached the highest in the D4 group, which is 276.37% higher than group D1, and the whole body protein deposition rate and muscle RNA, RNA/DNA ratio, pepsin, H+-K+- ATPase in stomach, trypsin, lipase and Na+-K+- ATPase in intestine, liver superoxide dismutase (SOD) reached the best in the group D4, and the malondialdehyde (MDA) in liver and intestine were both lowest in group D4. 2) The content of muscle crude protein linearly with the increase of dietary protein level, while the fat content in giant salamanders declined linearly, and there was no significant difference in moisture and crude ash of whole body between different groups, whole body crude protein increased first and then tended to be stable, reached the highest in the group D4. 3) The skin collagen content in group D4 reached the highest, increasing by 27.83% compared with D1. With weight gain rate, muscle RNA/DNA ratio, protein deposition rate, and skin collagen content as evaluation indexes, the optimum dietary protein level of the giant salamander was 55.9%~58.3%(based on dry mater), this dietary protein level can significantly improve gastric acid secretion, the digestion and absorption, and antioxidant capacity, and increase the nutrient deposition, thus promote growth and feed conversion; While low protein level diet significantly inhibited the growth of A. davidianus.
In this study, We obtained the full length of the spcactus gene by RACE technology from Scylla paramamosain(SpCactus). And we analyzed the biological information of the SpCactus and its immune response under pathogen stimulation. The full length of SpCactus mRNA contains a 5′ untranslated region (UTR) of 228 bp, an open reading frame of 1 311 bp and a 3′ UTR of 496 bp. The SpCactus protein contains five characteristic ANK homology domains and showed 62% identity (73% similarity), 24% identity (36% similarity), and 9% identity (18% similarity) to the Litopenaeus vannamei Cactus (LvCactus) protein, the Drosophila melanogaster Cactus (DmCactus), and the Homo sapiens IκB protein, respectively. Prediction of the protein physicochemical properties of SpCactus revealed that it is a hydrophilic protein. The physical and chemical properties analysis, SpCactus was a hydrophilic protein. And its isoelectric point (pI) is 4.91. The mRNA of SpCactus showed high expression in the muscle, Eyestalk and Heart, but low expression in the hepatopancreas. Moreover, the expression of SpCactus were significantly upregulated by stimulation with Staphylococcus aureus and lipopolysaccharide. In this study, SpCactus gene was successfully cloned and characterized for the first time, and its bioinformatics analysis, physical and chemical properties were predicted. The biological functions of SpCactus gene were preliminarily explored, providing a basis for further study of its biological functions in immune response.
In order to study the infection characteristics of TiLV in the cultured tilapia species and susceptible cells, Oreochromis niloticus(GIFT strain) and E-11 cells were chosen as models. For present study, first of all, the whole nucleotide sequences of the fourth genome segment of TiLV from the experimental infected Oreochromis niloticus(GIFT strain) were determined. The length of the cDNA of the fourth genome segment was 1 250 bp containing an open reading frame of 1 065 bp, encoding a protein with 354 amino acids. The sequences and phylogenetic tree analysis showed that the fourth genome segment encoded TiLV Hemagglutinin-esterase-fusion (HEF) protein. Subsequently, GST fusion HEF was expressed in Escherichia coli and purified, and it was used to immunize New Zealand white rabbits according to the conventional method to prepare rabbit anti-HEF polyclonal antibody. The results showed that the antiserum titer obtained by ELISA was higher than 1:51200, and the serum could specifically recognize the HEF protein from the spleen of TiLV infected Oreochromis niloticus(GIFT strain). Through artificial infection experiments, it was found that TiLV infected juvenile Oreochromis niloticus(GIFT strain) severely and caused surface ulceration, systemic bleeding and ocular lens opacity. Furthermore, hematoxylin and eosin (HE) stain showed the syncytium in liver, hemosiderin and vacuolar degeneration in spleen, necrosis in head kidney lymphocytes, protein precipitation and glomerulus necrosis in trunk kidney. Western blot and immunohistochemistry results showed that the virus was distributed in all the tissues with the higher abundance in the spleen, head kidney and gill than that in the liver, trunk kidney and brain tissues. Through indirect immunohistochemistry assay, it was found that HEF protein mainly distributed in the cytoplasm in E-11 cells infected with TiLV. Our results demonstrate that TiLV infection could cause disease by targeting liver, spleen, kidney, gill and brain tissue of Oreochromis niloticus(GIFT strain).
In order to create a new strain with deep-cupped shell of Crassostrea hongkongensis and better growth traits, a breeding program of truncation selection was initiated based on the 2-year-old culture population of wild Crassostrea hongkongensis collected naturally from Taishan Town Bay, Guangdong Province. The index of shell depth was used as an indicator, with 10% retention rate and 1.755 selection strength. The genetic parameters including selection reaction, genetic gain and realized heritability in larval stage, intermediate cultivation stage and later grow-out stage were estimated. The results showed that the shell height and index of shell depth in selected group were higher than that in control group, and the genetic parameters increased with the growth of individuals, showing a favorable genetic improvement potential. The average selective reaction, genetic gain and realized heritability of shell height at larval stage is 0.363±0.167, (1.678±0.416)% and 0.207±0.095, respectively; at intermediate cultivation stage is 0.639±0.115, (7.618±2.666)%, and 0.364±0.065, respectively; and later grow-out stage is 0.668±0.179, (8.861±3.072)% and 0.381±0.102, respectively. At the later grow-out stage, the average selective reaction, genetic gain and realized heritability of index of shell depth is 0.748±0.066, (9.090±0.565)%, and 0.426±0.038, respectively. The research provided a useful data for the creation of a new strain with deep-cupped shell and good growth traits in Crassostrea hongkongensis.
In this study, the growth and physiological parameters were compared between tilapia (GIFT Oreochromis niloticus) cultured in a traditional pond and in an in-pond raceway system (IPRS) for 120 days. For the traditional way, 5 tails/m2 (Stocking Densities 1, SD1) were reared, while 180 tails/m2 (SD2) and 270 tails/m2 (SD3) were cultured in an IPRS. The main objective of this study was to find the appropriate density of tilapia to be cultured in an IPRS. The results showed that after 120 days of culture, the body weight, specific growth rate and absolute growth rate of the SD2 fish were significantly higher than those of the SD1 and SD3 fish. The survival rate, coefficient of variation of weight and feed coefficient rate of SD2 and SD3 tilapia were lower than those of the SD1 tilapia. Compared with SD1 fish at 30 days, the relative expressions of serum cortisol, serum alanine aminotransferase, lysozymal aspartate aminotransferase and hepatic hsp70 mRNA were significantly increased in the SD2 fish. After The levels of serum cortisol and glucose in the SD3 fish were significantly higher after 120 days of culture than those in the SD1 fish. Compared with SD1, the levels of SAA, LAA and hepatic Hsp70 mRNA expressions of the SD2 fish were significantly higher after 60 and 90 days, while the level of triglyceride was significantly lower during the whole experimental period. The results implied that tilapia in the SD2 were stressed in the early stage of cultivation but gradually acclimated to the environment, while tilapia in the SD3 were stressed for a relatively longer time. Taken together, this study demonstrated that the appropriate stocking density of tilapia cultured in the IPRS might be 180tails /m2 or less in order for a better growth performance than in the traditional culturing mode.
Takifugu rubripes were instant killed, bled and gutted, two treatments for 6 days storage are designed including storage in ice and ambient temperature, respectively. During storage, the progression of rigor mortis and body temperature were recorded. Sampling and assay were carried out at both different rigor stages and every storage day. Rigor index, ATP and related compounds, glycogen, pH and phosphoprotein were selected as indicators as postmortem biochemical changes. The results showed that the onset of rigor mortis for iced treatment start at around 7th hours after slaughtered, and its maximum rigor index was up to 89% with 20-24 hours duration in stiff, the fish body maintained at rigor with rigor index as 9-16% after 4 days icing storage. However, the maximum rigor index of 71% was observed fleetingly in the control treatment with higher temperature under ambient, and the whole rigor progression or stages were undefined. Glycogen degraded sharply at the initial post-mortem period for all treatments. Comparing with the trace amounts was still detected in 5 days storage for the iced treatment, glycogen was almost depleted after 3 days storage in the control treatment. The pH decreasing patterns of two treatments reflected the differences glycogen consumption rates between the two storage treatments. ATP was rapidly depleted in all treatments with accumulation of IMP exclusively. Maximum of IMP reached to 9.5 μmol/g on the 3rd day and remained at about 7.5 μmol/g on the 6th day of the iced treatment. As to the control treatment, IMP was degraded rapidly after the maximum as 9.2 μmol/g on the 1st storage day with higher temperature. Comparing to the iced treatment with a trace Hx amounts, the control treatment present a significant accumulation of Hx. Muscle protein phosphorylation indicated that the rigor mortis progression of T. rubripes was also related to the properties of muscle protein components. Notably, the protein components relating to glycolytic enzymes have a significant difference in phosphorylation between the iced and ambient treatment. The ambient treatment present higher phosphorylation level, which is consistent with the glycolysis properties observed in ambient treatment. In conclusion, T. rubripes had advanced in icing stability and high accumulation of IMP after slaughtered, and the association between protein phosphorylation level and the process of rigor mortis is worth exploring further.
Vibrio which are widely distributed in marine environments, have ability to form biofilms for the purpose of adaption to harsh environmental conditions. Biofilms formed by Vibrio have been known to promote larval and plantigrade settlement of the mussel Mytilus coruscus, how the dynamics succession of these biofilm during the formation impact mussel settlement remains unknown. In this study, V. cyclitrophicus, V. chagasii and Vibrio sp. 22 with different settlement-inducing activities on plantigrades of the mussel M. coruscus were used to observe the changes of biofilm characteristics such as bacterial density, biofilm thickness and extracellular polymeric substances during the dynamic succession, and to explore subsequent effects of biofilm characteristics on mussel plantigrade settlement. The results showed that during the dynamic evolution of three Vibrio species, the bacteria on the biofilm were aggregated over time. The bacterial density and thickness of the Vibrio biofilms firstly increased with time and finally decreased. Except for Vibrio sp. 22, the bacterial density and biofilm thickness of V. cyclitrophicus and V. chagasii were correlated to the settlement of plantigrades. During the dynamic succession of Vibrio biofilms, the extracellular polysaccharides increased first with time and then began to decrease. In contrast, there were no change in the proteins and lipids on biofilms. The change trend of extracellular polysaccharide was similar to the settlement-inducing activity of biofilms, suggesting that extracellular polysaccharides play important role in succession of biofilms regulating mussel settlement. Thus, the present finding is important to understand the interaction between substrata and marine invertebrate settlement, and to clarify settlement mechanism of micro- and macro-organisms on artificial reefs.
An outbreak of an infectious disease occurred amongst farmed Oncorhynchus mykiss at PenZhou city, Sichuan Province, in October 2017 with heavy mortality of 85%. Major symptoms of the diseased fish included darkening of the body, yellow mucoid fluid fecal casts on anal. Internally, the symptoms were hemorrhage in the swim bladder and peritoneum, gastric distention, enteritis and hydropericardium. Bacteriologic test was negative. Histopathologically, the spleen showed typical coagulative necrosis with marked degeneration and necrosis in the haematopoietic tissue. Hepatocytes showed degeneration and necrosis and edema in some areas. After filtration treatment, the tissue suspension was injected intraperitoneally into 60 O. mykiss. The O. mykiss displayed similar clinical symptoms as fish that were naturally infected. The O. mykiss died acutely in the trial group (cumulative mortality rate of 85%), while there was no abnormal fish in the control group. After filtration treatment, the spleen tissue suspension was inoculated to the Fathead minnow cells (FHM). The typical cytopathic effects were observed after three blind passages in FHM. RT-PCR assay of tissue filtrates from the fish natural infected, the fish artificial infected and diseased cells were IHNV-positive. The amplification products shared 98.2% identity to that of IHNV nucleoprotein gene at nucleotide level. Phylogenetic analysis based on the G gene showed that the viral isolate was classified into Asian isolates, belonged to the JRt genotype.
Oreochromis spp. are important cultured fish species worldwide. Recently, tilapia lake virus (TiLV) has been epidemic in many countries and posed a serious threat to Oreochromis spp. aquaculture industry. China has contributed the most amount of cultured Oreochromis spp in the world. Up to date, there is no report of the TiLV epidemic in Oreochromis spp. in the mainland of China. However, since O. niloticus (GIFT strain) is one of the most cultured Oreochromis spp species in the mainland, therefore it is necessary to characterize the features of the GIFT strain infected with TiLV. Taking the advantage of the TiLV was kindly gifted by Dr. Sven Bergmann from Institute of Infectology, Friedrich Loffler Institute, we performed the infection of TiLV in the GIFT strain. The whole nucleotide sequences of the sixth genomic segment of TiLV from the experimental infected O. niloticus were determined. The length of the cDNA of the sixth genomic segment was1 044 bp containing an open reading frame of 954 bp encoding a protein with 317 amino acids with predicted molecular weight of 36.38 ku. There is 5′ end non-coding region of 19 bp and 3′end non-coding region of 972 bp. The sequences and phylogenetic tree analysis showed that the sixth genomic segment encoded TiLV nucleoprotein (NP). Subsequently, GST fusion NP was expressed in Escherichia coli and purified, and it was used to immunize New Zealand white rabbit (Albus lepus) according to the conventional method to prepare rabbit anti-NP polyclonal antibody. The results showed that the antibody titer obtained by ELISA was higher than 1:51 200, and the antibody could specifically recognize the NP protein from the tissues of O. niloticus infected with TiLV. Hematoxylin-eosin staining (H.E) was performed on different tissues of O. niloticus. The results showed that there were apparent pathological changes in the observed tissues, including hepatic necrosis and syncytium; vacuolization, necrosis and increased amount of hemosiderin in the spleen; necrosis and inclusion body in the head kidney; dissociation and shedding of the epithelial cells of the gill filament, small pieces adhered to each other; vacuoles of nerve cells in the brain tissue. Western blot and immunohistochemistry (IHC) were used to detect the expression of the NP protein in different tissues of O. niloticus infected with TiLV. The results showed that the highest amount of NP protein was expressed in the liver, followed by in the brain, trunk kidney and head kidney. In order to elucidate the immune responses of O. niloticus to the TiLV infection, real-time quantitative PCR (qRT-PCR) was used to measure the mRNA expressions of TNF-α and TGF-β in the spleen and head kidney which are the two major immune tissues of fish. The results showed that during the early period of the infection (12-24 h post of the infection), the expression of both TNF-α and TGF-β was significantly inhibited by the viral infection, indicating that TiLV might inhibit these cytokines so as to facilitate its early replication in the host. The current study will shed a new light on the pathogenesis of TiLV infection and will pave a new way on the development of effective prevention and control strategy against the epidemic of TiLV in O. niloticus.
The emergence of novel variety " All-male NO.1” dramatically promoted the development of the yellow catfish industry, of which the cultivation of YY super-male was a critical step. Recently, YY super-male yellow catfish with intersexual gonad emerged largely, which hindered the development of yellow catfish industry. We only found the problem of gonad development in YY super-male breeding with tubificidae by checking the production and breeding records for nearly 10 years. Therefore, four different baits including Artemia salina, Zooplankton, Chironomus plumosus, Tubificidae were used to treat YY super-male for 20 days (11 to 30 days post hatching). The survival rate, body length, and body weight of each group were measured at 60 dph (day post-hatching). Tubificidae treatments significantly increased the body length and weight compared with other baits, and the survival rate of fish fed with Artemia salina was significantly lower than fish fed with the other three baits. In addition, we performed histology analysis on gonadal structure at 60 dph and 1 year old and statistics of fertilization rate at 1 year old. As a result, the fish group fed with Tubificidae displayed 75% intersexual gonad and 25% testis without seminiferous lobule, and the fertilization rate was only 36.70%±4.05%, which was significantly lower than the other groups. In order to study the reasons for the feminization of YY yellow catfish, we measured the estradiol content and found that the estradiol content was low in all four different animal baits. It is speculated that the feminization of YY super-male yellow catfish may be caused by the environmental endocrine disruptors (EDCS) enriched by Tubificidae. Therefore, zooplankton or Chironomus plumosus could be fed in the early stage of large-scale breeding of YY-supermale yellow catfish, whereas Tubificidae should not be fed.
Abalone is not only precious seafood in China, but also important mariculture shellfish. In recent years, the genetic breeding research of abalone has made rapid progress, but the research data of cytogenetic analysis is still in lack. Therefore, this study used the fluorescence in situ hybridization (FISH) to compare the distribution of 45S rDNA clusters in Haliotis discus hannai, H. gigantea, H. fulgens, and H. diversicolor. In H. discus hannai, 83% of the metaphase had 2 pairs of 45S rDNA sites, locating at terminal of the long arm ends of chromosomes 13th and 16th, respectively. In H. gigantea, about 75% of the metaphase had 3 pairs of 45S rDNA sites, locating at the terminal of the short arm of chromosome 6th, and at the terminal of the long arm of chromosomes 14th and 17th, respectively. In H. fulgens, about 85% of the metaphase cells detected three pairs of 45S rDNA sites located at the terminal of the long arms of chromosomes 4th, 6th, and 8th. In H. diversicolor, about 65% of the metaphase had 3 pairs of 45S rDNA sites, locating at the terminal of the short arms of chromosomes 3th, 4th, and 12th. In addition to the main mode, there were other low-frequency modes in all the 4 species of abalone, suggesting that these abalone may have several unstable 45S rDNA sites besides the unambiguous sites. The number and the location of 45S rDNA loci in abalone showed a high level of intraspecific variation in general. These findings enrich the cytogenetic research data of abalone and provide basic data for the further studies of genetic breeding in abalone.
It’s helpful to know the formation of fishing grounds by the center of gravity of fish resource density and temporal and spatial heterogeneity. The traditional economic fish resources are declining owing to the impact of over fishing, environmental change and other factors. Priacanthus spp., the main catches in bottom trawls in the South China Sea, are important in ecological. But few studies of their spatial-temporal patterns of distribution are available, and spatial autocorrelation of data is often lacking in the studies. Analysis of temporal and spatial heterogeneity in the distribution of Priacanthus spp. in the northern South China Sea has significance for sustainable development and rational management of the fishery. To study this, we used the data of bottom trawl fishery in the northern South China Sea by a fishery information network from 2009 to 2014, for spatial analysis of center of gravity and semivariogram plots to investigate temporal and spatial distribution of Priacanthus spp. resource density. The results showed that the resource density of Priacanthus spp. was a gradually decreasing trend and the differences were extremely significant (P<0.01) from 2009 to 2014. The maximum value of resource density was (26.69±7.34) g/h/kW/nets in 2012. The center of gravity of the resource density distributed between the 50-m and 100-m isobath in the middle part of the survey area, and the differences were not significant (P>0.05). The spatial distribution of Priacanthus spp. in the survey area displayed a well-organized structure, with strong spatial autocorrelation in 70–90 km. Spatial heterogeneity in resource density of Priacanthus spp. appeared to be caused less by randomness than by structural variations. The spatial distribution of Priacanthus spp. displayed weak spatial autocorrelation when the distance exceeded 90 km.
In order to elucidate the development of gill and swim bladder of Lateolabrax maculatus, in this study, histological section technique and morphological observation were used to systematically study the occurrence and development of gill and swim bladder of L. maculatus from 1 to 45 days. The results showed that the post-embryonic development of the gill of L. maculatus juvenile can be divided into four stages, including the appearance period of gills primordium (0-3 d), the differentiation period of filaments (4-14 d), the differentiation stage of lamella (15-25 d) and the completed period of gills (26-45 d). At the water temperature of 15-18 °C, the primordial filament was observed at 1 d, and the lamella structures formed from the pseudobranch were firstly observed at 15 d. After 25 d, the lamella structures were widely distributed in each juvenile gill arch. After 45 d, a well-developed gill structure of juvenile fish was clearly detected and identical to adult fish. According to the observation results, the development stages of the swim bladder organ of L. maculatus were divided into four stages: formation, expansion, aeration and degeneration. The appearance of swim bladder primordium was not observed on the newly hatched larvae, but after hatched for 1 day. After 5 d, the swim bladder cavity of larvae becomes larger and longer. The inflation of the larvae swim bladder was completed at 11 d. Finally, the degeneration of swim bladder of larvae began to occur after 13 d.
Haloalkane dehalogenase (HLD) is a kind of enzyme that can degrade halogenated aliphatic compounds. In order to provide information on the possible use of the algal HLD for the degradation of halogen compounds in the environment, we used bioinformatics, quantitative real-time PCR and pET28a system to study the characteristics and prokaryotic expression of HLD in the macroalga Gracilariopsis lemaneiformis (Rhodophyta). The open reading frame of HLD in G. lemaneiformis (recorded as GlHLD) is 969 bp, and its theoretical molecular weight and isoelectric point is approximately 36.33 ku and 5.53, respectively. The GlHLD amino acid sequence is identical to an HLD sequence of G. chorda (PXF45553.1), and is close to G. chorda and Chondrus crispus in the phylogenetic tree. The high temperature, substrate 1,2-dichloroethane and phytohormone salicylic acid all promoted the expression of GlHLD gene with an increment fold of 3.64, 2.64 and 2.43 times, respectively. Finally, the recombinant vector of pET28a-GlHLD was transformed into E. coli BL21 (DE3), and the recombinant protein displayed a dehalogenase activity. The optimal induction conditions were 16 °C and 0.1 mmol/L IPTG treatment for 12 h. And then, the HLD protein was preliminarily purified by nickel column. This study will lay the foundation for further understanding of the algal HLD family and the acquisition of high purity HLD enzyme.
Beak is an important hard tissue of Cephalopoda which is usually used in the study of fisheries biology such as population identification, growth and stock assessment and so on. Based on the 860 samples of Sthenoteuthis oualaniensis collected by light falling-net fishery during May to August in the year of 2017 in the Xisha Islands waters of the South China Sea, the morphologic growth of beak impacted by gonad maturity and individual size was analyzed. The result of principal component analysis of twelve morphologic indices indicated that the upper hood length (UHL), upper crest length (UCL), upper rostrum width (URW), upper lateral wall length (ULWL), lower hood length (LHL), lower crest length (LCL),lower rostrum length (LRL) and the lower lateral wall length (LLWL) could be used to describe the length growth features of beak, and the HL/CL, URW/UCL, LRL/LCL, LWL/CL and WL/CL could be used as the indicators of entire growth of beak. The analysis of variance (ANOVA) and the least-significant difference (LSD) indicated that there were significant differences in the morphologic growth between sexes, gonad maturity and different mantle length, however the values of HL/CL, URW/UCL, LRL/LCL, LWL/CL and WL/CL were nearly constant with the change of sex, gonad maturity and mantle length. This study suggested that there are significant effects of gonad maturity and individual size on beak morphology and the mantle length of 121mm to 150 mm, the gonad maturity of Ⅲ seemed to be the inflection points of the morphologic growth beak of S. oualaniensis.
Extant cephalopod species are characterized by the lag of sexual maturation, when compared to their body growth. And they have evolved a range of flexible reproductive strategies, which are associated with different characteristics of body growth and reproductive investment, and the latter is vital important to understand their reproduction. In this study, the specimens of Dosidicus gigas, collected from equatorial waters of eastern Pacific Ocean during a jigging fishery period from February to April 2017, were used to explore their body condition and reproductive investment, by applying methodologies of morphometric measurement and residual index analyses. Both female and male individuals were found isometric growth, according to weight-length relationship analysis. Female D. gigas attained maturation from mantle length (ML) of 270 mm and body weight (BW) of 766 g; whereas, males were found maturity from 270 mm ML and 479 g BW. Both female and male individuals had the lowest rate of zero stomach fullness degree (FD), with the majority being found at FD of 1-2. Along with the sampled months, D. gigas showed a better body condition, but which was the worst during the sexual maturation period. The gonadosomatic index (GSI) was measured a mean value of 2.26%±1.33% for sexual mature females, and nidamental index was estimated 34.34%±18.62%. Mature males had a mean GSI of 1.31%±0.35%. The body condition indices, measured as the standardized residuals of body weight and mantle length relationship, and reproductive investment indices, measured as the standardized residuals of reproductive system weight and mantle length relationship, showed a decreasing trend with sexual maturation. When corresponding to stomach fullness degree, the body condition index showed a decreasing trend, whereas the reproductive investment index increased with higher stomach fullness degree. However, there was a significantly positive relationship between indices of body condition and reproductive investment. Therefore, these evidences indicated that D. gigas continue feeding during sexual maturation, and the energy sourcing for reproduction is mostly from food intake. Meanwhile, energy reserve in the muscle tissues might be mobilized to meet the high energy demand during gonadal development.
The Pacific oyster Crassostrea gigas is cultured worldwide due to the advantages of rapid growth and good adaptability, and has become one of the most commercially important bivalve species. In our successively selective breeding, three strains of C. gigas with black, white and gold shell color traits have been developed. Tyrosinase (Tyr) is known as one of the most important enzymes in the regulation and production of melanin in animals. In this study, exons in the C. gigas TYR gene (CgTyr1) were sequenced. Mutations of the CgTyr1 gene and its association with shell color were analyzed in the three shell color strains of C. gigas. A total of 23 single nucleotide polymorphisms (SNP) were detected using single-strand conformation polymorphism (SSCP) and sequencing analysis, of which 11 SNP loci had highly significant differences between the three shell-color strains. In the SNP loci with significant difference, mutation c.591C/T, c.632G/A and c.1155T/C are non-synonymous which lead to amino acid changes Ala122Val, Gly136Ser and Phe310Ser. For further analysis, 11 SNP loci with a highly significant difference were selected for haplotype construction. One specific haplotype for every shell color strain was constructed and confirmed in the validating group. The mutations and haplotypes that are strongly associated with the shell color phenotypes in this study could be useful in understanding the molecular mechanism of pigmentation, and potentially applied to marker-assisted selection breeding programs for C. gigas.
In order to understand the quality change and shelf life of high quality cultured grouper(♀Epinephelus fuscoguttatus×♂E. lanceolatue) after the treatment of unfrozen liquid in the normal temperature direct-sale logistics course, in this paper, the fresh grouper was treated with unfrozen liquid, and its muscle microstructure, the change of temperature curve, sensory evaluation, total volatile basic nitrogen (TVB-N), the total number of colonies and K value were determined, and compared with the results of air freezing treatment and control group. The results showed that the treatment of fresh grouper with unfrozen liquid not only can maintain the quality of fresh fish, but also can extend the shelf life of normal temperature logistics, and the logistics time can reach 80 h. At this time, its TVB-N reached 26.88 mg/100 g. The K value was 47.965%, the colony number was 5.88 lg (CFU/g), the fish muscle fiber structure was intact, close to fresh fish meat, and the sensory evaluation was good, which was 10 hours longer than the still air freezing group and 30 hours longer than control group. This research can provide new fresh-keeping, fidelity and quality assurance technology for high-quality groupers, and also provide technical support for the current grouper’s normal temperature logistics demand from the direct production of the grouper to the consumer's home.
Spotted mackerel (Scomber australasicus) is an important economic species in northwest Pacific. The paper evaluates the Pacific stock biomass by aged-structure virtual population analysis (VPA) and Yield per recruit model, and analyses the utilization of stock biomass by using the mackerel catch and CPUE data of the Pacific group which is supplied by Japan’s central fisheries research institute from 1995 to 2015. The results show that the biomass of spotted mackerel remains at a high level. The stock biomass is about 650000 tons in 2015, the average fishing mortality shows a trend of falling volatility and fishing mortality of 2015 is 0.15, the current fishing mortality (Fcur) is 0.33, the spawning potential ratio (SPR) remains 36.5%. There is no growth overfishing and recruitment overfishing. It is also discussed that the fluctuations of natural mortality caused by water temperature change and different fishing age affect the resources of spotted mackerel. The study suggests that the fishery is currently utilized in the sustainable way and has great potential for development. It also suggests that the fishery resource could be developed and utilized by using the management reference point F0.1.
The present trial was conducted to investigate the dietary vitamin B6 requirement of sea cucumber Apostichopus japonicas Selenka juveniles. The experimental diets were formulated with graded levels of vitamin B6 (1.23, 5.29, 9.35, 17.47, 33.71, 66.17 mg/kg), and named D1, D2, D3, D4, D5 and D6 group. Each diet was randomly assigned with triplicate sea cucumber juvenile with initial body weight (12.23±0.11) g for 12 weeks. The results showed that weight gain rate and specific growth rate presented an increasing firstly and then decreasing afterwards, and got maximum in D5 group (33.73 mg/kg). Crude protein of body wall was increased firstly by dietary vitamin B6 and then decreased, and crude protein of D6 group was significantly lower than other groups; Crude lipid of D1 group was significantly lower than other groups. All of activities of glucose 6-phosphatede hydrogenase, isocitrate dehydrogenase, acetyl coA carboxylase, and nitric oxide synthesis were increased firstly and then decreased afterwards, activity of D6 group was significantly lower than other groups. With the increasing of dietary vitamin B6, both protease and amylase were increased, and cellulase was decreased by dietary vitamin B6, while the height of villus; MC and the thickness of muscularis were increased significantly. With the weight gain rate as the evaluation indictor, regression analysis showed that the optimum dietary vitamin B6 for sea cucumber juveniles were 45 mg/kg.
A serious disease occurred in black seabream, Acanthopagrus schlegelii, cultivated in runway fish culture pond of mariculture farm in Taizhou, Zhejiang province, in April, 2017. The diseased fish showed sluggish swimming, anorexia and ulceration on surface. Moribund fish were dissected with symptom of massive ascites and swelling on liver, spleen and kidney, with white granulomatous nodules, especially in spleen. The bacteria were isolated with tryptone soybean agar, and all the fish with typical symptoms showed the pure culture of grayish white colony with Gram negative rods. The bacterial strain AS15, from the spleen of fish with most serious granulomatous, was choose for challenging test to healthy black seabream by injection intraperitoneally. Mortality was recorded with similar symptom with native infected seabream, with the median death dose of 6.5×104 CFU/ind. AS15 was identified as Edwardsiella tarda with API 20E biochemical bacteria identification system as well as 16S rDNA sequences blasted on NCBI, with 99% similarity to reference strains. With phylogenetic analysis for 16S rDNA, AS15 belonged to the same cluster with ETT883、LADL05-105, E. piscicida according to new classification for genus E.dsiella, and same cluster to LADL05-105 and NCIM2056, E. piscicida-like, the new recommended species of the genus, with 100% similarity on gyrB phylogenetic tree. The species-specific primers for genus E. dsiella were used for PCR test, and AS15 showed positive to EPL, the species primer for E. piscicida-like, and PCR negative to all other three primers of E. tarda, E. piscicida and E. ictalur. Ten pathogenic gene, including four fimbrial genes, and sodB, citC, esrB, mukF, katB, the related virulence gene were analyzed by PCR. The strain AS15 showed positive to all four fimbrial genes and other virulence gene except gene gadB. It could be considered that AS15, E. piscicida-like bacteria, the first pathogenic strain isolated and reported from marine cultivated seabream, was the pathogen of serious outbreak case of visceral granulomatous disease in black seabream in runway pond culture system.
The four experimental groups were carried out to test the response of Carassius auratus and Ctenopharyngodon idella to ammonia toxicity and taurine within 96 h. Group 1 was injected with NaCl, group 2 was injected with ammonium acetate (C. auratus 7 mmol/g; C. idella 9 mmol/g), group 3 was injected with ammonium acetate and taurine (100 μg/g), and group 4 was injected with taurine. C. auratus in group 2 had lower mRNA expression of SOD, CuZnSOD and CAT in liver than those of tested fish in groups 1 and 3; tested fish in groups 2 and 3 had lower mRNA expression of GPX in liver than that in group 1; the highest mRNA expression of SOD, CuZnSOD, CAT and GPX in brain were found in group 1; C. idella in groups 2 had higher mRNA expression of SOD, CuZnSOD, CAT and GPX in liver; fish in groups 2 and 4 had lower mRNA expression of SOD and CuZnSOD in brain than those which in groups 1 and 3; fish in group 3 had the highest mRNA expression of CAT and GPX in brain. C. auratus and C. idella in group 2 had the highest mRNA expression of TNF and IL in the brain and liver. This study indicates that defensive strategies are more effective on C. idella in dealing with the ammonia challenge compared with C. auratus; the taurine could more effective mitigate the adverse effect of oxidative stress on C. auratus and C. idella, but the inflammatory response in hyperammonemia C. auratus and C. idella were not affected by taurine.lic> were not affected by taurine.
To obtain single nucleotide polymorphism (SNP) markers of heat shock protein 70 (ScHsc70) gene related to heat tolerance traits in Sinonovacula constricta, the full-length sequence of ScHsc70 gene was cloned by direct sequencing. The results showed that the ScHsc 70 gene was 4 048 bp, including 6 introns and 7 exons, and the coding region was 1 950 bp. The high temperature resistance group and control group from a new variety of razor clam were established six potential SNPs Rs1 (g.588 C > T), Rs2 (g.840 C > T), Rs3 (g.885 T > A), Rs4 (g.1233 A > G), Rs5 (g.1467 T > G), Rs6 (g.1482 T > C) were screened from the exon region of ScHSc70 gene by PCR product direct sequencing. SNPs genotyping was performed on the high temperature tolerant population and the control population of the new variety " Shenzhe No.1” by Sanger sequencing. The results of genetic diversity analysis showed that the polymorphism information content (PIC) of the two populations was between 0.111 2 and 0.371 8, and the average polymorphism information content of the control population was 0.267 0, which is higher than that of the high temperature resistant populations (0.236 5). Association analysis results showed that the genotype frequency and allele frequency of Rs1, Rs3 and Rs4 were significantly different between control group and high temperature tolerant group. Haploid linkage disequilibrium analysis showed that SNPs markers of ScHsc70 gene could form 2 haploid blocks and 7 haplotypes, among which CCT haplotypes were significantly correlated with high temperature tolerance traits. It was found that Rs2 and Rs3 were in a linkage state (r2 = 0.86, LOD = 25.56, Dx = 1.0), and could be used as SNP markers for the Genetic breeding of S. constricta for high temperature tolerance. In summary, Rs1, Rs3, Rs4 and haplotype CCT can be used as candidate auxiliary molecular markers for high temperature tolerance breeding of razor clam, which lays a theoretical foundation for the subsequent functional verification of resistance-related SNPs.
Insect research suggests that autophagy plays an important role in virus infection and proliferation, while shrimp autophagy research reports are rare. Understanding the autophagy of shrimp cells will open up new ideas for shrimp disease immunity research. Autophagy related protein LC3 is a marker protein of autophagy, existing in the membrane of autophagosome during the whole autophagy process. Our bioinformatics analysis found that Cherax quadricarinatus LC3 (CqLC3) and α-tubulin (Cqα-tubulin) has the interaction relations. To further reveal transport way of autophagosome during autophagy process, in this study, recombinant plasmids pET-HIS-CqLC3 and pET-GST-Cqα-tubulin were constructed and induced for protein expression in vitro. Then HIS and GST tagged fusion proteins HIS-CqLC3 and GST-Cqα-tubulin were purified by using affinity chromatography respectively. Recombinant proteins HIS-CqLC3 and GST-Cqα-tubulin were found binding each other by the GST pull-down assay. In order to further reveal the role of microtubules for autophagosome transport, C. quadricarinatus cell microtubules were depolymerized by vincristine which was one microtubule inhibitor, then the autophagosomes were detected by MDC staining. The results showed that autophagic reaction was incomplete, and autophagosomes increased after microtubule depolymerization. Therefore, the autophagosomes in C. quadricarinatus cells can interact with microtubules through CqLC3, and microtubules play an important role in autophagosome transport during autophagy process. This paper firstly revealed the transport pathway of autophagosomes in shrimp autophagy, and the results laid the foundation for the study of autophagy in shrimp cells.
The diversity of species makes the research on cell level of Chinese perch extremely limited. Establishing a simple and feasible method for primary culture of brain neurons from Chinese perch (Siniperca chuatsi) in vitro is beneficial to further study on fish nervous system. Our laboratory combined with the usual method of cell culture, Chinese perch brain neruons (born 3 months) were isolated by collagenase digestion and mechanical blow. L15+20%FBS suspended brain neruons were inoculated on the cell culture vessels, in 28 °C without CO2 incubator. The medium was replaced after 3 days. Subculture was carried out after the cells covered with the bottom of the cell culture vessels. The morphological changes of the neurons were observed under inverted phase-contrast microscope; Immunofluorescence staining for NeuN or β-tubulin was performed to identify the purity of neurons. The results showed that the cells began to adhere to the culture bottle and develop small neurites and form network gradually after Primary culture for 2 days. Up to the 5th day, many neurites extended to form dense network and Soma of neurons became well. Fluorescence staining with NeuN or β-tubulin showed that the purity of neurons can reach above 95%. The present protocol is a simple and efficient method for culturing brain neurons of Chinese perch with high purity, Which is of great significance for the fine study of fish growth and development, expression regulation of various receptors and proteins, cell apoptosis and cell signal transduction.
A plenty of non-coding RNAs (ncRNAs) have been identified through the application of high-throughput analysis of the transcriptome, and this has led to an intensive search for possible biological functions attributable to these transcripts. In this study, the gonad tissue of the two-year-age Crassostrea gigas of same family cultured in Rizhao Huanghai area were used to identify a large number of miRNA, lncRNA and circRNA by small RNA-seq and RNA-seq, and their biological characteristics were analyzed. The results showed that, with Danio rerio as a reference, 25-30 known miRNA matures and 51-63 known miRNA hairpin was obtained, 53-71 new miRNA matures and 53-77 new miRNA hairpin were predicted. The length of miRNA in C. gigas ranged from 18-26 nt, where the largest number was in the 20-22 nt and the first nucleotide position was tent to U. 2302-2349 known lncRNA transcripts were obtained, and 20083-24114 new lncRNA were predicted. Among them, the percentage of the intergenic lncRNA, intronic lncRNA and antisense lncRNA was 29.0%, 62.1%, and 8.9%, respectively. The data showed that genomic characteristics of lncRNA in C. gigas were similar to those of other eukaryotes. Compared with mRNA, the transcript and open reading frame of lncRNA was much shorter at length and much lower at expression level. 383 circRNA transcripts were obtained, among which the average percentage of 88.54% came from exon, 4.51% came from intronic and 6.95% came from intergenic. The data showed that the endogenous circRNA have a lot miRNA target sites. This study showed that the basic biological characteristics of miRNA, lncRNA and circRNA in C. gigas. The results set the foundation for the subsequent research on the expression and biological function of regulatory non-coding RNA in C. gigas.
Competitive behavior exists widely in animal and plant groups. When groups or individuals have the same needs for the limited resources, competition will occur in intra-species or inter-species. The existence of competitive behavior can significantly affect the growth performance of individuals. There is strong competitive behavior in the breeding of Fenneropenaeus chinensis, and we has proved that the competitive behavior among individuals of F. chinensis has a significant effect on individual growth traits, and this effect can be inherited. However, little information was available for the molecular mechanism of competition behavior in shrimp. Candidate genes involved in competitive behavior of F. chinensis have been identified by comparative transcriptome analysis in our previous study, among which there is a calcineurin (CN) B gene. CN is a highly conserved Ca2+/calmodulin (CaM)-dependent serine/threonine phosphatase, which composes of a catalytic subunit (CNA) and a regulatory subunit (CNB). Previous studies reported that CN-B played an important role in the central nervous system mediated by Ca2+/CaM. In order to further prove the role of CN-B gene in the competitive behavior, in the present study, the full-length cDNA of CN-B of F. chinensis (FcCN-B) was cloned by RACE technology, and its expression in different tissues (nervous, heart, stomach, hepatopancreas, and intestine) between high competitive group (HCG) and low competitive group (LCG) was analyzed by Real-time PCR. The results show that the full-length cDNA of FcCN-B is 2867 bp, containing 95 bp of 5′ untranslated regions (UTR), 540 bp of open reading frame (ORF), and 2232 bp of 3′ UTR. There are four conserved EF-hand Ca2+ binding domains in the ORF of FcCN-B. Protein homology analysis indicated that the amino acid sequence of FcCN-B has high homology with other species (78.8%-93.8%), among which FcCN-B has the highest homology with Eriocheir sinensis (93.8%) and then with Drosophila. melanogaster (90.5%). The phylogenetic relationship analysis showed that vertebrates and invertebrates were independently clustered into two branches. Furthermore, F. chinensis was clustered with E. sinensis into an independent branches, and then it was clustered to D. melanogaster, which suggesting that FcCN-B might have similar functions as it did in D. melanogaster. The results of Real-time PCR showed that the expression of FcCN-B in the nerve ganglion was significantly higher in HCG than in LCG, but its expression in heat was significantly lower in HCG than in LCG. This study preliminarily proved that the calcineurin B may play a certain role in the competition behavior of F. chinensis, and will lay an important foundation for investigating the molecular mechanism of the competition behavior of F. chinensis.
In order to determine the pathogen, which can cause the death of cultured Paralichthys olivaceus from ascites disease in Beidaihe area, Hebei Province, three dominant bacteria were isolated from P.olivaceus infected with ascites. The biological status of the isolates was determined by physiological and biochemical identification and 16S rRNA sequence alignment. The pathological characteristics of the isolates were further identified by virulence genes (toxR, vhhA, vhhB) and histopathological analysis. The results showed that the three isolates were Vibrio harveyi and the virulence genes of the three isolates were all positive. Pathological sections showed that the isolates could be used to treat multiple organs (intestine, kidney, spleen and liver) of P.olivaceus. The LD50 of strain BDHYPFS-Y1G to P.olivaceus was 5.88×106 CFU/g, which was lower than the toxicity of natural state. Drug susceptibility test indicated that all three isolates were highly sensitive to the nitrofurantoin. This study confirmed the pathogen of this ascites disease, and preliminarily studied the pathogenicity and drug sensitivity of the pathogen, which can provide scientific basis for the prevention and control of the disease in industrial culture of flounder.
In April 2018, a large number of largemouth bass (Micropterus salmoides) were infected with lethal sarcoidosis in a farm in Qionglai, Sichuan Province. In order to define the potential pathogens, a bacterial strain named HSY-NS02 was isolated from skin ulcers, effusions from fish swimming bladder’s cavity and liver of the diseased Micropterus salmoides by traditional pathogen isolation methods. The strain HSY-NS02 was identified as Nocardia seriolea by means of morphologic structure and dyeing observation, PCR amplification and sequence analysis of 16S rRNA gene and specific primer, constructing phylogenetic tree, physiological and biochemical test. Furthermore, the pathogenicity of the strain HSY-NS02 was confirmed by the infection experiment in healthy largemouth bass,which’s results showed that the strain HSY-NS02 was cofirmed to be pathogenic to healthy largemouth bass and the same bacterium could be recovered from these infected largemouth bass. Histopathological observation and analysis of diseased largemouth bass showed that there were different degrees of chronic granulomatous lesions in skin ulcers, heart, liver, spleen, kidney and gill, of which spleen lesions were the most serious. the antibiotic susceptibility of the strain HSY-NS02 was carried out to guide the clinically choosing medicine, and the results showed that the strain was sensitive to gentamicin, neomycin and nystatin, but resistant to other 18 kinds of antibiotics, which implied the strain HSY-NS02 was resistant to multiple antibiotics.
The changes in the marine environment and overfishing have caused imbalances in the ecological environment, making the various diseases of shellfish increasingly prominent, and the diseases caused by pathogenic Vibrio have become more common. In this context, the number of wild resources of Scapharca broughtonii has been sharply reduced, and its breeding industry is in urgent need of improved germplasm. In order to effectively prevent the damage of bacteria and other pathogenic microorganisms on S. broughtonii, we observed the response process of the lysozyme activity in different tissues of S. broughtonii infected by Vibrio anguillarum, and explored the immune function of the lysozyme in the body of S. broughtonii. In this experiment, 20-month-old S. broughtonii. individuals were infected by injecting live bacteria, and 16 individuals were randomly selected. And 1 mL (about 1×109) V. anguillarum suspension was injected into the axe of each individual as the infection group. 16 randomly selected individuals were not injected with V. anguillarum as the control group. The two groups were cultivated in clean seawater for 4、12、24 and 48 h. Each group randomly selected 4 S. broughtonii individuals who were dissected the blood, mantle, gill, axe foot, hepatopancrea and adductor muscle tissues. The concentration of lysozyme was determined by ELISA kit. The results showed that for the invasion of V. anguillarum, the lysozyme content in the blood of the S. broughtonii rapidly increased from the normal low value and maintained a high level, indicating that the blood is one of the main immune tissues of the S. broughtonii body defense pathogen.In the case of no infection, the S. broughtonii mantle always maintained a high lysozyme concentration to prevent the interference of the external water environment. The concentration of lysozyme in infected gills and axe foot are significantly higher than the normal values after the injection about 24 hours, indicating that the mantle, gills and axe foot were the first barrier as the S. broughtonii body to contact with the outside world can also respond to the invasion of pathogenic bacteria, but the response was delayed compared with the blood. The lysozyme content of hepatopancrea and adductor muscle did not change significantly. And it was speculated that hepatopancrea and adductor muscle were not important immune tissues or organs of S. broughtonii. The results of this study can provide relevant parameters for the study of disease resistance and immune mechanism of S. broughtonii.
Shell matrix proteins control the nuleation、size and crystal phase of calcium carbonate during the biomineralization of pearl, and they are related to pearl quality. In order to study more about the molecular mechanism of nacre formation, we cloned a novel shell matrix protein silkmaxin (accession No. MK188932) from freshwater mussel Hyriopsis cumingii. With the gene expression detected by RT-PCR and in situ hybridization, silkmaxin specially expressed in the pallial epithelial cells of mantle outer fold, which indicated that silkmaxin is a nacreous layer matrix protein. The amino acid sequence of silkmaxin featured high proportion of Gly (33.0%) and Ser (10.4%) residues, and the second structure is mainly composed of β-folds. The high structure prediction indicated that silkmaxin is a silk-like protein. In addition, the expression of silkmaxin was detected in the early stage of pearl formation by real-time quantitative PCR. The results indicated that silkmaxin play important roles in the transition of the calcium carbonate disordered deposition to ordered deposition in the early stage of pearl formation. The study of shell by silkmaxin RNAi treatment indicates that silkmaxin is essential for the correct growth of aragonite tablets, including the size and shape of the newly formed calcium carbonate crystals.
In order to study the effect of adding Bacillus in the pond on the physicochemical factors and bacterial community structure, high throughput sequencing technology was used to analyze the bacterial community structure in water and sediment of the experimental group (adding Bacillus in pond) and the control group (without adding in pond). At the same time, the physicochemical parameters in water and sediment of the two groups were collected. The results indicated that the contents of TN,
Chub mackerel (Scomber japonicus) is an important pelagic fishes in the Northwest Pacific Ocean. It is necessary for us to find the relationship between the abundance and influence factors, which are beneficial to exploit and utilize this resource. In this study, based on the recruitment data and the spawning stock biomass (SSB) data of the Pacific-cohort of S.japonicus during 1980−2016 obtained from Japan fisheries institution, the normality test of natural logarithm of recruitment was finished and the time period passed the normality test was during 1980−1999, as well as the environmental data of spawning ground, we analyzed the relationship between the sea surface height (SSH), sea surface salinity (SSS), sea surface temperature (SST) and the natural logarithm of SSB (ln(SSB)) and the recruitment during 1980−1999 with generalized linear model (GLM) and generalized additive model (GAM). The GLM results revealed the importance of variables ranked by decreasing magnitude are ln(SSB) ×Year, ln(SSB), SSS ×Year and SSS, which were significant (P<0.05) and considered the combined effects of factors. Considering the single factor in GLM models affected on the recruitment, the importance of variables ranked by decreasing magnitude are SST, SSS, Year, ln(SSB) and SSS. The GAM results indicated that the model which contained Year, SST and SSH was the optimal model based on Akaike’s Information Criterion (AIC), the importance ranked by decreasing magnitude are Year, SST and SSH. However, considering the single factor in GAM models affected on the recruitment, the importance of variables ranked by decreasing magnitude are Year, SSS, ln(SSB), SST and SSH. The suitable range of SSH was 62−65 cm, the suitable range of SSS were 34.72−34.74 psu and 34.78−34.83 psu and the suitable range of SST was 20.2−20.6 °C. When ln(SSB)>6.0, the recruitment was at a high level, based on GAM analysis.
Exosomes are nano-scale vesicles with a phospholipid bimolecular membrane, which can participate in many physiological processes. The aim of this study was to investigate the isolation and identification methods of extracellular exosomes from grass carp hepatocyte and preliminary study on the effects of exosomes secreted from fatty hepatocyte on the expression of miRNAs and immune-related genes in grass carp hepatocytes. In this study, The exosomes of grass carp hepatocytes L8824 were extracted by ultracentrifugation. The morphology of exosomes were observed by Electron Microscopy, the parcicle size and quantity of exosomes were determined by Nano-particle Tracking Analysis. Meanwhile, we analyzed the expression of the specific protein CD63 using Western blot. Then, we used exosomes,which secreted from normal hepatocytes and fatty hepatocyte induced by oleic acid to incubate grass carp hepatocytes, and the effects of two different exosomes on the transcription levels of miR-122/33 and immune-related genes, which are TNF-α, NF-κB, IL-1β, IL-6 and IL-10 were detected by real-time qPCR. Our results indicate that the exosomes secretion of grass carp hepatocytes culture medium are uneven vesicles of 30-150 nm, which was round or oval, and had a complete membrane structure. The expression of exosomes marker protein CD63 was positive, and the NTA results showed that the exosome vesicles accounted for more than 50 % of all the vesicles. Additionally, the exosomes of fatty liver cells significantly increased the expression of miR-122 and the immunogenic genes (TNF-α, IL-1β and IL-6) in hepatocytes (P<0.05). These results suggest that the exosomes of grass carp hepatocytes can be isolated successfully by ultracentrifugation. Moreover, exosomes may play an key role in the regulation of immunity of grass carp hepatocytes.
In order to research the genetic diversity of different populations of Paramisgurnus dabryanus, four populations from Liaoning, Henan, Hubei and Taiwan were analyzed by sequencing the mitochondrial cytochrome oxidase subunit Ⅰ(COI) genes. The results showed that 642 base pair(bp)fragment was consisted of A, T, C and G base with 23.5%, 30.6%, 26.7% and 19.2%, respectively, indicating a preference for A and T base. A total of 44 mutations of nucleotide and 23 haplotypes were identified in 4 populations. The haplotype diversity index ranged from 0.424~0.855, and the nucleotide diversity ranged from 0.000 84~0.016 59, the results indicated that Paramisgurnus dabryanus from Taiwan population had a higher genetic diversity than Liaoning, Henan and Hubei population. The genetic differentiation index (Fst) and genetic distance showed that genetic differentiation among Taiwan and other populations was represents extremely significant difference (P<0.01), also had a further genetic distance with other populations. In general, the results showed that there was a certain genetic difference between the different geographical groups, AMOVA analysis revealed that 52.11% of genetic variations derived among populations and 47.89% of genetic variations occured within populations. In terms of the negatively selective neutrality test, the results indicated that a population expansion occurred in the populations of Liaoning, Henan and Hubei population. Which provides a reference for protection of the genetic diversity and breeding work of Paramisgurnus dabryanus.
In order to understand the behavioral characteristics of large yellow croaker (Larimichthys crocea), the ultrasound pinger system has been used to track 4 tails test fish for 24 hours to access the fish movement data by implanted methods on Aug. 27th and 28th, 2018. The results show that: ① the vertical movement depths of the text fish is 0.89±0.51 m (18:00—24:00), 0.73±0.50 m (0:00—6:00), 1.04±0.50 m (6:00—12:00), 1.00±0.45 m (12:00—18:00), and keep in 0.5—1.25 m; ②the horizontal movement of test fish appear on the inside of tank about 159±9.50 times, and 27% in total data, and about 489±12.50 times appear around tank, 73% in total data, it means that the fish are assembling inside the tank and do the random motion, occasionally appear motion around the tank wall. This experiment is the first time to study the behavioral characteristics in tank-farming by ultrasound pinger system, it is aims to provide a scientific theoretical basis and data support for the fishing management for production and behavior monitor of L. crocea.
Knowledge of target strength (TS, dB) is essential for accurate assessment of fish abundance using acoustic methods. In order to investigate acoustic scattering characteristic of purpleback flying squid Sthenoteuthis oualaniensis, 25 squid specimens were collected by jig in the open sea in the northern South China Sea in September 2017 near geographical position 18°42.9′N 113°05.5′E. The TS of 25 specimens were measured respectively one by one using Simrad EY60 split-beam scientific echosounder with 120 kHz and self-made tethering-controling device. In this paper, we primarily explored the impact of different parameters on the single target detection for Sthenoteuthis oualaniensis, and the parameters included pluse length determination level (PLDL, dB), min normalized pluse length (min NPL), max normalized pluse length (max NPL) and maximum standard deviation of minor-axis angles (MIA). Then we analyzed comprehensively the stochastic nature of single TS which was highly variable, and concluded the mathematical regression relation between TS of S. oualaniensis and mantle length (ML, cm). The results showed: (1) As the PLDL increased, the number of single target of squid detected increased firstly and then decreased, and the number was the largest when PLDL was 6 dB, while the average TS of all single targets increased monotonously. With increase of min NPL, the number of single squid target decreased; in the range of min NPL<0.7, the average TS of all single targets presented increasing obviously. When the max NPL was less than 1.2, the number of single squid target increased as the max NPL increased, but the average TS decreased; when the max NPL fell in between 1.2 and 1.8, the number of single squid target presented increasing slowly, but the average TS remained relatively stable. As the MIA increased, the number of single squid target increased, but the average TS decreased; (2) In this study, the optimum parameters setting of single target detection were as follows: PLDL=6.00 dB, Min NPL=0.7 dB, Max NPL=1.8, MIA=0.8°; (3) The maximum and minimum value of the average single TS of live Sthenoteuthis oualaniensis specimens were respectively -48.6 dB and -63.63 dB, and the corresponding mantle length of Sthenoteuthis oualaniensis were respectively 25.2 cm and 12.4 cm. The mathematical regression relation between TS of Sthenoteuthis oualaniensis and mantle length (ML) were concluded as follows: TS=34.22 Lg ML–98.23 (N=16, R2=0.603). This TS measurement was the first attempt to investigate the investigate acoustic scattering characteristic and TS of live Sthenoteuthis oualaniensis using tethering controlling method at sea by field work. The results of this paper not only accumulated important information and experience for further investigating the acoustic scattering characteristics and improving the acoustic estimation precision of Sthenoteuthis oualaniensis, also provide the reference for measuring TS of other squid or fish by tethering method at sea.
Length distribution data provide insight into the dynamics of fish populations. However, it is hard to determine the sample size required to describe size structure. In order to compare the relation between the precision of frequency distributions and sample size for several commercial fish species in the Wentai fishing ground, a resampling approach was used to calculate the mean square difference of length distributions based on actual sampling size and various simulated sampling sizes. The results showed that: ①Factors such as biology difference and seasonal variation would affect the relation of the precision of frequency distributions and sample size. ②The accuracy for estimating the precision of length frequency distributions would be impacted by the numbers of length intervals in iteration calculation. ③The precision of length frequency distributions could be considered as a theoretical basis to optimize sample size. For the reason of lacking domestic researches on sampling design and optimization, the results of this study could provide certain technical reference.
The paper studied the occurrence time and physiological characteristics of slow growth seahorse. Comparisons of the growth, the ratio of RNA/DNA, digestive enzymes and related immune enzymes activities in normal growth seahorses[(8.57±0.61) cm, (1.51±0.38) g] and slow growth seahorse [(6.68±0.35) cm, (0.81±0.14) g]Hippocampus erectuswere studied in a cultural experiment for 110 d. The results showed that the average daily gain, specific growth rate, condition factor and viscera index in the normal growth seahorses were significantly higher than those of the slow growth seahorse, respectively. The normal growth seahorses grew faster than that of the slow growth seahorses after the body length was5.026 cm. The amylase, protease and lipase activities in normal growth seahorses were as the same tendency as those of the slow growth seahorses under different reaction temperatures (5 °C, 15 °C, 25 °C, 30 °C, 35 °C, 45 °C and 55 °C) and pH (2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 and 9.0). However, the digestive enzymes activities of the former were higher than those of the latter, except amylase activity at 35-55 °C and protease activity at 5–25 °C. The activities of ACP、AKP、T-AOC and SOD in normal growth seahorses were 12.83%, 48.21%, 44.71%and 65.75% more than those of the slow growth seahorses, respectively. The MDA of the normal growth seahorse was only 61.09% of that in the slow growth seahorse, and the ratio of RNA/DNA in the normal growth seahorse was higher 23.75% than that of the slow growth seahorse. The growth, digestion and immunity of he normal growth seahorses were obviously better than those of the slow growing hippocampus when their body length were more 5.026 cm.
With the aim to explore the molecular mechanism of vitellogenin (Vtg) in Scatophagus argus, we cloned the full-length cDNA sequence of three types of vtg by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) procedures. The length of the vtgAa cDNA is 5360 bp (GenBank No. KY676847), and it encodes a protein consist of 1696 amino acids. The length of the vtgAb cDNA is 5346 bp (KY654346), and it encodes a protein consist of 1699 amino acids. The length of the vtgC cDNA is 4244 bp (KY676848), and it encodes a protein consist of 1275 amino acids. Sequence analysis showed that three vitellogenin homologs of Scatophagus argus have highest homology with Morone americana (83%, 85% and 85%). VtgAa and VtgAb contain all the three major portions, but VtgC lacks phosvitin (PV). Quantitative real-time PCR (qPCR) assay were employed to determine the mRNA expression of vtgAb in the liver after 17 α-ethynylestradiol (EE2) injection in vivo and hepatocytes after exposure EE2 in vitro. Results of qPCR showed that the hepatic expression of vtgAb was higher than vtgAa and vtgC. 48 h after injection, mRNA expression of vtgAb was extremely increased and obviously decreased after 72 h. The expression of vtgAb mRNA was elevated after EE2 exposure to hepatic cells. Based on our results, expressions of vtgAb could be induced by EE2.