This study aimed to investigate the effects of different concentrations of fructooligosaccharide (FOS) instead of glucose (GLU) as the carbon source in the biofloc system. GLU was used as the carbon source in the control group, and 2.5
Fish diseases caused by parasites are considered one of the major causes of mortality in aquaculture, which can harm fish of various life stages from juvenile to adult fish. The study of fish diseases in the People's Republic of China started from the identification of a flagellated parasite Cryptobia branchiaslis Nie, 1955, which led to severe disease and death of grass carp fingerlings. During the past seventy years (1953–2023), China has made tremendous achievements in fish parasitology and developed a complete scientific system. In this paper, seventy years of research progress and achievements of freshwater fish parasitology in China are reviewed from four aspects, including pathogen biology, ecology, pharmacology, and immunology. Prospects for future development trends and cutting-edge hotspots are also discussed herein. This article provides readers majoring in fish parasitology and other related fields with comprehensive materials to fully understand the history, current status, and future development trends of fish parasitology in China.
The Yangtze River is the mother river of China. To promote the aquatic ecosystem protection of the great river, the Project of Yangtze Fisheries Resources and Environment Investigation (2017–2021) supported by the Ministry of Agriculture and Rural Affairs, P. R. China carried out by 24 institutes and universities that located in the Yangtze River basin surveys the status of (1) fish species composition and spatial distribution, (2) current fish abundance, (3) endangered fishes, (4) Yangtze finless porpoise, (5) aquatic eco-environments, (6) water-level fluctuation areas, (7) capture fisheries and recreational fisheries of the Yangtze River mainstream and 10 of its main tributaries, including Yalong River, Heng River, Min River (including Dadu River), Chishui River, Tuo River, Jialing River, Wu River, Han River, Dongting Lake and Poyang Lake. The results showed that there were 443 fish species (belonging to 163 genus, 37 families, and 18 orders) before 2017, but only 323 fish species (including 15 new recorded exotic species) were recorded in the project of 2017–2021. Among them, Cyprinus carpio, Carassius auratus, Hypophthalmichthys molitrix, Pelteobagrus fulvidraco, Coilia brachygnathus, Silurus asotus, Saurogobio dabryi, Ctenopharyngodon idellus, Pelteobagrus nitidus, Hemiculter leucisculus, Siniperca chuatsi, Coreius heterodon, Culter alburnus, Parabramis pekinensis, and Aristichthys nobilis were the dominant species across the whole Yangtze River system. It is estimated that there were 886 million individuals weighing 124.8 million kg, merely equivalent to 27.3% of the resources in 1950s, 30.9% of the resources in 1960s, or 58.7% of the resources in 1980s. In the new list of protected fishes that recorded in the Yangtze River system, only 15 of 29 were collected in this project of 2017–2021. Psephurus gladius has been affirmed to be Extinct by International Union for Conservation of Nature (IUCN). The wild individuals of Tenualosa reevesii and Luciobrama macrocephalus have disappeared for many years and maybe have been extinct already. Acipenser dabryanus has been affirmed to be Extinct in the Wild by IUCN. The natural propagations of A. sinensis, Myxocyprinus asiaticus and Trachidermus fasciatus have been interrupted for many years. The populations of Yangtze finless porpoise in the Yangtze River mainstream, Dongting Lake and Poyang Lake have steadily rising sizes and expanding distributions in 2017–2021. Parts of them migrate from one region to another with the seasons, which would result in the fluctuation of Yangtze finless porpoise population within some regions. The conventional indicators of water quality in the Yangtze River system were good and conformed to the water quality criteria of fishery in 2017–2021. In the last 40 years, the maximum surface water area in the Yangtze River basin extended to approximately 63,360 km2, the minimum surface water area covered approximately 26,396 km2, and the seasonal water-level fluctuation areas occupied approximately 36,964 km2. Compared with 1984–2000 period, the 2001–2020 period witnessed an overall decreasing trend in the frequency of surface water occurrence within about 25,869 km2 of aquatic areas. From 1984 to 2000 period to 2001–2020 period, permanent surface water has decreased by nearly 8,750 km2. In 2017, the fishermen were mainly 40–60 years old and their educational levels were mainly lower than junior high school. In 2017, most anglers were older than 40 and used hand rod and/or sea rod. Their average catch of each time was mainly less than 1 kg. Results suggested that the fishing ban in key waters of the Yangtze River basin is not only an ecological project of aquatic ecosystem conservation, but also a livelihood project for the fisherman to embrace industrial transformation and improve their living conditions. After the implementation of the fishing ban, the fisheries resources would gradually recover, and the Yangtze finless porpoise population size would also see a steady increase. However, the endangered species would remain threatened for a long time. The degraded waterbodies and water-level fluctuation areas would be the key restrictive factors for future aquatic ecosystem recovery in the Yangtze River basin. Since this survey was carried out before the fishing ban, the current results could provide a baseline for future evaluation of the effect of the Yangtze River fishing ban.
In order to understand the effect of brackish water and fresh water culture modes on the nutrient accu-mulation of Coilia nasus cultured in pond,the muscle nutritional composition and quality of Coilia nasus ecologic-ally cultured in brackish water(salinity 10-15)and freshwater(0.4-1.0)model were investigated and analyzed by biochemical analysis methods.The results show that the muscle crude fat content(7.27%)of C.nasus cultured in brackish water mode was significantly higher than that of freshwater mode(4.30%),while the muscle moisture(72.54%)and crude ash content(1.32%)of brackish water mode were significantly lower than that of freshwater mode(76.85%and 2.06%,respectively),No significant difference in the crude protein content of muscle was found between two cultural modes.Except that no significant difference in tryptophan and cystine was found between the two cultural modes,the contents of other 16 amino acids of brackish water mode were significantly lower than those of fresh water mode;the total amino acid(TAA),total essential amino acid(EAA),total half-essential amino acid(HEAA),total non-essential amino acid(NEAA),and total delicious amino acid(DAA)con-tents of brackish water mode were significantly lower than those of fresh water mode,and there was no significant difference in the EAA/TAA and EAA/NEAA specific values of C.nasus muscle between two cultural modes,while the DAA/TAA specific value(40.32)of brackish water mode were significantly lower than that of fresh water mode(40.68).The essential amino acid index(EAAI)(58.59)of brackish water mode was lower than that of fresh water model(72.04),while the specific value of branched amino acids to aromatic amino acids(F value)(2.44)of brackish water mode was higher than that of fresh water mode(2.35).In the 28 kinds of fatty acids detec-ted,there was no significant difference in the contents of 11 kinds of fatty acid between two cultural modes.In major fatty acids,C16:0,C18:0,C18:1n9c,C22:5n3(DPA)and C22:6n3(DHA)contents of brackish water group were significantly higher than that of fresh water group,while the C18:2n6c and C18:3n3 contents of brackish water mode were significantly lower than those of fresh water mode.SFA,MUFA and EPA+DHA contents of brackish water mode were significantly higher than those of fresh water mode;∑n3PUFA/∑n6PUFA(3.93)of brackish water mode was significantly higher than that of fresh water model(2.10),this is consistent with the fact that n3PUFA/n6PUFAs of migratory fish muscle is higher in seawater and lower in freshwater.Therefore,the muscle protein of C.nasus cultured in fresh water is more nutritious and delicious,while brackish water culture is beneficial to the accumulation of fat and the retention of the MUFA(especially C18:1n9c)in C.nasus.The osmotic pressure of brackish water may be near the isotonic point of C.nasus,and this is more conducive to the accumulation of nutrients and the growth of C.nasus.It is suggested that brackish water should be used in the commercial fish culture stage of C.nasus and fresh water should be used in the intensive culture stage of C.nasus before the sales.
To explore the feeding effect of fermented formula feed in red swamp crayfish(Procambarus clarkii),unfermented and fermented feeds were fed to juvenile P.clarkii[initial body weight(4.91±0.18)g]in an indoor circulating water system for eight weeks.The effects of fermented feed on growth,muscle quality,digestion,anti-oxidant capacity,and intestinal flora structure of P.clarkii were analyzed.The results showed that,① the dissolu-tion rate of fermented feed was significantly lower than that of unfermented feed.② The fermented diet signific-antly increased weight gain rate,and specific growth rate.Furthermore,it decreased feed conversion ratio,but had no significant effect on survival rate,hepatosomatic index(HSI),flesh content,and body composition.③ The fer-mented diet significantly improved muscle hardness,elasticity,chewiness and stickiness of P.clarkii,and decreased adhesion.④ The fermented diet significantly increased the activities of trypsin and lipase in hepatopan-creas and intestinal tract,the activities of superoxide dismutase,acid phosphatase,and alkaline phosphatase in serum and hepatopancreas,and the total antioxidant capacity of the hepatopancreas.⑤ The fermented feed signi-ficantly increased the length and width of intestinal villi.⑥The fermented feed improved the intestinal microbial structure of P.clarkii,significantly increased the relative abundance of Firmicutes and Actinobacteria,and increased the diversity of intestinal flora.Overall,the fermented feed effectively improved the growth perform-ance,muscle quality,digestion,and antioxidant capacity by improving the intestinal tract tissue structure and chan-ging the structure of intestinal microorganisms of P.clarkii.
To enhance the influence of fishery scientific journal,measures to enhance the influence of aquatic sci-ence and technology journals,we analyzed multiple aspects including the basic situation,submission and review process,editorial and publishing methods,editorial capabilities,and influence of the journals through literature analysis,field research,and questionnaire surveys.The results showed that only about half of the aquatic science and technology journals are included in important databases,and their influence indicators are lower than those of other agricultural science and technology journals.80.0%of the annual manuscripts received are less than 500;journals with a manuscript acceptance rate of less than 50.0%account for 52.0%;there are few high-level papers,and only 16.0%of the survey respondents are satisfied with the quality of the source of the manuscripts;the pub-lishing cycle is mainly bimonthly,accounting for 80.0%;over 90.0%of journals have an editorial system;57.1%of the survey respondents believe that the editorial board plays little or no role in improving the quality of the journal.By analyzing the research data,the paper proposes that the current publishing cycle of aquatic science and technology journals is long;the technical means of dissemination and publication are diversified;lack of high-quality manuscripts;The problems of not fully utilizing the resource advantages of the editorial board and affect-ing the level of publishing and restricting future development are addressed.Measures such as shaping the influ-ence of the journal through its academic orientation,establishing and improving the professional publishing model,guiding the establishment of a clustered development of journals,and guiding the formulation of a reasonable eval-uation system are taken to enhance the influence of aquatic science and technology journals.
Gymnocypris przewalskii is an important indigenous economic fish in Qinghai Lake,which plays a key role in the whole Qinghai Lake ecosystem and shows a strong saline-alkali tolerance and adaptability compared with other fishes.In order to explore the important functional genes of G.przewalskii during the process of saline-alkali tolerance,Illumina Hiseq technology was used to define the transcriptome of gill and kidney tissues of G.przewalskii in two areas(Qinghai Lake and the Quanji River).All kinds of clean data reached more than 6.74 Gb,and the percentage of q30 base was more than 94.38%.After quality control and assembly,a total of 541 429 uni-genes were obtained,the average length of N50 was 612 bp.The sequences acquired were blasted against NR,Swiss-Prot,pfam,COG,GO and KEGG databases,finally,107 568 unigenes could be annotated.Differential expression analysis showed that a total of 832 genes were co-expressed in the gills and kidneys in two regions.Gene ontology analysis indicated that differentially expressed genes(DEGs)annotated to binding,cellular process,metabolic process,and single-organism process accounted for a large proportion.Based on KEGG pathway ana-lysis,the pathways related to immunity,metabolism and penetration were enriched.According to the GO annota-tion of DEGs and the enrichment analysis of KEGG signaling pathway,we initially screened 35,34,and 25 genes related to osmotic,immunity,and metabolism of G.przewalskii,respectively.The osmotic related genes included calcium/calmodulin-dependent protein kinase,sodium/potassium transporting ATPase,and mitogen-activated pro-tein kinase,solute carrier family,etc,immune related genes mainly included interleukin,complement,integrin,granzyme B,etc;nitric oxide synthase,1,25-dihydroxyvitamin D(3)24-hydroxylase,cytochrome P450 and elonga-tion factor were related to metabolism of G.przewalskii.Sixteen differentially DEGs were randomly selected for quantitative real-time PCR(qRT-PCR),and the results were consistent with the RNA-seq.The result of this study enriches the basic data of G.przewalskii's omics research,and also provides a reference for further study of G.przewalskii in saline-alkali tolerance.
As an important serine/threonine kinase in the IKK family,TANK Binding Kinase 1(TBK1)plays a critical role in innate immune response by activating NF-κB and type I IFN signaling pathways in mammals.Although several studies have reported that fish TBK1 was involved in the regulation of type I IFN production,information on TBK1's close association with antimicrobial immune responses in the regulation of NF-κB and MAPK signaling pathways is still limited in teleost fish.In order to elucidate the regulation of fish TBK1 in NF-κB,I IFN,and MAPK immune response signaling pathways,the full-length cDNA of a TBK1 homologue,AjTBK1,was cloned by SMART RACE from Japanese eel,and its characteristics of expression in response to vari-ous PAMPs and Aeromonas hydrophila infection were investigated both in vivo and in vitro by quantitative real-time polymerase chain reaction(qRT-PCR).In addition,the subcellular localization of AjTBK1 GFP fusion pro-tein and the induction of AjTBK1 overexpression in the activation of NF-κB,AP1 and type I IFN performed by Dual-Glo luciferase assay system were also detected.Amino acid sequence analysis indicated that AjTBK1 encodes a polypeptide of 731 amino acids,which has the conserved N-terminal kinase domain(KD),a ubiquitin-like domain(ULD),a scaffold dimerization domain(SDD),and a C-terminal domain(CTD).The predicted three-dimensional structure of AjTBK1 is similar to that of human TBK1,and AjTBK1 is clustered with other fish famil-ies in the phylogenetic tree.Quantitative real-time PCR(qRT-PCR)analysis revealed that AjTBK1 is broadly expressed in a wide range of tissues,with high expression in liver and intestine.In vivo,the expression of AjTBK1 in the liver of Japanese eel was significantly increased by 1.8-fold at 6h,1.8-fold at 6 h,and 1.9-fold at 48 h after injection with LPS,viral mimic poly I:C and A.hydrophila infection,respectively.The AjTBK1 expression in kid-ney was found to increase at 12 h and 24 h with 1.9-and 1.6-fold after A.hydrophila infection,but decreased fol-lowing the stimulation of LPS and poly I:C.In vitro,the AjTBK1 transcripts of Japanese eel liver cells were signi-ficantly enhanced to its peak by the treatment of LPS,poly I:C,PGN,or the 106 CFU/mL A.hydrophila,being up to the 15.3-,5.8-,9.3-and 4.7-fold,respectively.Subcellular localization studies showed that AjTBK1 was evenly distributed in the cytoplasm of HEK293 cells in natural state.AjTBK1 was found to aggregate into spots in the cytoplasm upon the stimulation of LPS or poly I:C in HEK293 cells.Additionally,luciferase assays demonstrated that the AjTBK1 overexpression significantly enhanced the activation of NF-κB,AP1,and IFNβ-responsive pro-moters in HEK293 cells,and robustly up-regulated the activation of NF-κB,AP1,and IFNβ-responsive promoter,which were 1.8-,1.2-,and 1.92-fold induced at 24 h,12 h,and 24 h after cotransfection,respectively.These res-ults collectively suggest that AjTBK1 may function as important positive regulation in innate immunity of host against antibacterial and antiviral infection likely via the activation of NF-κB,AP1,and type I IFN signaling path-ways.
An eight-week feeding trial was carried out to evaluate the influence of vitamin E(VE)on the growth performance,antioxidation and immunity of hybrid grouper juveniles(Epinephelus fuscoguttatus ♀×E.lanceol-atus ♂).Six isoenergetic(340 kcal/100 g dry matter),isoproteinic(51.5%of dry matter)and isolipidic(9%of the dry matter)diets were formulated to contain graded levels of VE(4.1,26.3,40.7,57.1,116.8,209.6 mg/kg,dry matter basis).Triplicate groups of twelve fish[initial average weight of(14.22±0.01)g]were stocked into floating cages and offered their prescribed diet twice daily(8:00 and 16:30)to apparent satiation.After the growth experi-ment,the remained experimental fish from each group were used for a 72 h copper challenge.Results showed that fish fed 57.1 mg/kg VE exhibited higher weight gain percentage(WG)than fish fed 4.1 mg/kg VE.Whereas,condi-tion factor(CF),hepatosomatic index(HSI)intraperitoneal fat(IPF)values remained non-significant among all dietary groups.Whole-body and muscular compositions(moisture,protein and lipid)did not show significant dif-ferences among all dietary groups.Fish fed 209.6 mg/kg VE had higher hepatic VE concentration than fish fed 4.1 mg/kg VE.The total-antioxidant capacity(T-AOC)of liver,serum lysozyme(LZM)and immunoglobulin(IgM)concentrations were increased with the increasing VE levels,reaching a peak value at the 57.1 mg/kg level,and thereafter,it started to decrease as dietary VE level further increased.After the challenge,the survival rate of the experimental fish fed with 40.7,57.1 or 116.8 mg/kg VE diet was higher than that of the experimental fish fed with 4.1 mg/kg VE.The relative expression of nuclear factor E2-related factor 2(Nrf2)in head kidney of fish fed 4.1 mg/kg VE was lower than that of fish fed 40.7,57.1 or 116.8 mg/kg VE.Generally,the analysis of a quadratic broken line model based on WG and T-AOC indicated that the optimal dietary VE requirement of hybrid grouper juvenile was found to be 62.92 mg/kg and 86.25 mg/kg dry matter,respectively.
The present study was conducted to investigate the effects of dietary phosphorus levels on the nutri-tional metabolism and intestinal microbiome of the GIFT tilapia(GIFT Oreochromis niloticus).Three isonitrogen-ous and isoenergetic diets with total phosphorus(P)content of 0.26%(low P treatment),0.81%(moderate P treat-ment)and 1.51%(high P treatment)were prepared by using calcium dihydrogen phosphate as phosphorus source.Each diet was assigned to one treatment with four replicates and 30 fish per replicate.The fish with initial weight(8.42±0.09 g)were fed with the test diets for 8 weeks in an indoor recirculating aquaculture system(RAS).The results showed as follows:weight gain rate(WGR)and specific growth rate(SGR)of tilapia in moderate P treat-ment were significantly higher than those in low and high P treatments(P＜0.05),and feed conversion ratio(FCR)of tilapia in moderate P treatment was the lowest.The hepatosomatic ratio,viscerosomatic ratio and condition factor showed a gradual decrease with the increase of dietary phosphorus level.Dietary phosphorus level had a sig-nificant effect(P＜0.05)on the apparent digestibility of dry matter,crude protein,crude lipid and phosphorus in GIFT O.niloticus and they showed a trend of increasing and then decreasing with increasing dietary phosphorus level.KEGG annotation and enrichment analysis of differential metabolites showed that the main metabolic path-ways of down-regulated differential metabolites were cyanuric acid metabolism,biosynthesis of gluconate ester,alanine,aspartic acid and glutamate metabolism,and most of the upregulated differential metabolites were mainly enriched in the metabolic pathway of fatty acid synthesis in the fish in low P treatment compared with those in moderate P treatment;most down-regulated differential metabolites were mainly enriched in the following meta-bolic pathways:arginine and proline metabolism,phenylpropionic acid biosynthesis and most up-regulated differ-ential metabolites were mainly enriched in the metabolic pathways of amino sugars and nucleotide sugars in the fish in high P treatment compared with those in moderate P treatment.Ace,Chao1 and Shannon indices showed that the abundance and diversity of GIFT O.niloticus intestinal flora tended to increase with increasing levels of dietary phosphorus.Firmicutes,Actinobacteria,Proteobacteria and Bacteroidota were the dominant phyla in the intestinal flora of GIFT O.niloticus.The abundance of beneficial genera such as Romboutsia and Cetobacterium was the highest in the moderate P treatment while the abundance of Mycobacterium and Bacteroides showed a decreasing trend with increasing phosphorus content in the feed.In conclusion,moderate phosphorus in diet could improve the apparent digestibility of feed for GIFT O.niloticus,and phosphorus deficiency or excess in diet would inhibit amino acid metabolism.Phosphorus deficiency would accelerate the process of fatty acid synthesis.Appro-priate phosphorus in diets could improve the abundance and diversity of bacterial flora,which may be beneficial to intestinal health.
Dietary fat is an essential nutrient for fish growth.The appropriate sources and levels of fat in diets can not only meet the normal energy metabolism and physiological needs of culture fish,but also regulate its growth,immune,and reproductive performance.At present,a large number of studies on the utilization of fat sources in diets indicate that the demand for different fat sources in fish is essentially the demand for different types of fatty acids.Fatty acids are diverse and widely distributed in nature,and the absorption and utilization of dietary fatty acids by fish often vary depending on the length of the carbon chain.Previous studies have shown that the effects of fatty acids with different carbon chain lengths on fish are mostly concentrated on growth and development,gut microbiota,and lipid metabolism.However,there is little research on the effects of muscle fiber development and meat quality.Therefore,it is necessary to explore the mechanism of action of different fatty acid lengths on muscle fiber development.Therefore,108 healthy Megalobrama amblycephala with an initial average weight of(77.89±0.81)g were selected and randomly divided into 4 groups with 3 replicates each,and were fed with basal diet(control group)and butyric acid(BA),octanoic acid(OA)and palmitic acid(PA)instead of 1.5%soybean oil for 8 weeks.The results showed that the addition of fatty acids with different carbon-chain lengths had no signific-ant effect on growth,nevertheless,it could significantly improve the adhesiveness of muscle,the number of muscle fibers,the proportion of smaller muscle fibers(＜20 μm)and sarcomere length compared to the control group.In terms of gene expression,OA significantly increased the mRNA expression of the myogenic factor myf5.BA can up-regulate the mRNA expression of ampkα2 and sirt1 significantly,while down-regulating the myo-suppressor gene mstnb.Camk,the key gene of Ca2+-dependent signaling pathway,was also significantly elevated with the increase of the carbon-chain lengths of fatty acids in feed.This study showed that the dietary fatty acids with dif-ferent carbon-chain lengths can effectively achieve the enhancement of muscle fibers development and meat qual-ity of M.amblycephala through AMPK and Ca2+-dependent signaling pathways.This experiment provides basic data and theoretical basis for nutrient regulation of fish meat quality,and also a new pattern for nutritional enhancement of fish meat quality.
In order to compare the differences of larva growth and development among different families of Heliocidaris crassispinas,9 full-sibling families of H.crassispinas were constructed.The important indicators of larval growth and development,including fertilization rate,hatching rate,larva survival rate,metamorphosis rate and initial feeding rate,were compared in the 9 families.The results showed that the fertilization rate of every fam-ily was over 95%,without no significant difference(P＞0.05),but there are significant differences in other indicat-ors in 9 families(P＜0.05).The highest hatching rate,early larval survival rate,late larval survival rate,meta-morphosis rate and nitial feeding rate are family No.3(58%),family No.1(83%),family No.4(90%),family No.2(75%)and family No.9(100%),respectively,and the lowest are family No.6(0%),family No.3(42%),family No.2(76%),family No.9(6%)and family No.5(24.5%),respectively.The growth rate of family No.3 is 146%,which is the fastest in all families.While,the slowest one is No.5 families(76%).At the end of the experiment,the gonad development of family No.3 was obvious;the other families were not,yet.The Proteobacteria proportion of family No.3 is high,but Bacteroidetes proportion is low.The proportion of the two phyla of family No.5 is oppos-ite to that of family No.3.The results show that there are differences in production traits among different families of H.crassispinas,which has the potential for breeding and improving,and this study accumulate relevant data for the cultivation of H.crassispinas.
Stachyose is a functional oligosaccharide,which is utilized by bifidobacterium and lactobacillus in the intestines,and plays an important role in the digestive physiology and antioxidant properties of the body.Juvenile sea cucumbers Apostichopus japonicus has high nutritional value and is an important breeding species in the Yel-low Sea and Bohai Sea areas of China.This study investigated the effects of dietary stachyose on growth,digest-ive physiology and glycometabolism of juvenile sea cucumber A.japonicus.Six experimental diets were formu-lated to contain the graded levels of stachyose[0(D1,control group),0.04%(D2),0.11%(D3),0.15%(D4),0.21%(D5)and 0.27%(D6)dry diets].Each diet was randomly assigned to triplicate tanks of sea cucumber juven-iles with initial body weight(11.46±0.03)g for 67 days.The results showed that there were no differences in sur-vival rate(SR)and ratio of intestine weight to body wall weight(IBR)among all groups.Both weight gain rate(WGR)and the specific growth rate(SGR)increased with increasing stachyose content until reaching peak levels at 0.15%dietary stachyose,but decreased thereafter.The WGR and SGR of D2,D3,D4and D5 groups were signi-ficantly higher than D1 group.The WGR reached maximum value of 90.88%in the D3 group.There were no sig-nificant effects on moisture,crude protein,crude fat and ash of body wall of Apostichopus japonicus.The activit-ies of intestinal protease,lipase and superoxide dismutase were increased when dietary stachyose content increased from 0 to 0.15%and then decreased.The protease of D3 and D4 groups were significantly higher than other groups,meanwhile,the lipase of D3 group was significantly higher than other groups.The superoxide dismutase activity of D3,D4 and D5 groups were significantly higher than the control group.The content of malondialde-hyde was first decreased and then increased,and reached the lowest value in D3 group.There was no significant difference among the activities of amylase,alkaline phosphatase and acid phosphatase.The height of intestinal folds in D3 and D4 groups was significantly greater than that in the control group,and inflammatory cell infiltra-tion appeared in D6 group.There were no significant differences in the ratio of intestine weight to body wall weight and the thickness of muscularis among all group.With the increase of stachyose content,the activities of glucokinase and phosphoenolpyruvate carboxykinase increased,while the activities of fructosophosphate phos-phokinase and pyruvate kinase increased first and then decreased.The glucokinase activitie of D3,D4,D5 and D6 groups were significantly higher than the control group.The fructosophosphate phosphokinase activitie of D3,D4 and D5 groups were significantly higher than the other groups,and reached maximum value in the D4 group..The pyruvate kinase activitie of D3 groups were significantly higher than the other groups.The phosphoenolpyruvate carboxykinase activitie of D2,D3,D4 and D5 groups were significantly higher than the control group and signific-antly lower than D6 group.The results showed that dietary stachyose increased the glucose metabolism efficiency,improved the digestive physiology and antioxidant capacity of the body,and promoted the growth of the sea cucumber juvenile.With the weight gain rate as an evaluation indicator,quadratic regression analysis showed that the optimum dietary stachyose of sea cucumber juvenile was 0.129%diet.As a functional oligosaccharide,stachy-ose plays an important role in the digestion,metabolism and antioxidation of A.japonicus,and has deep research significance in the application of compound feed of A.japonicus.
In order to explore the molecular characteristics and expression characteristics of the rare minnow MHCⅡβ gene,the 810 bp cDNA sequence of the rare minnow Gobiocypris rarus MHC Ⅱβ was obtained by PCR amp-lification technology,including an open reading frame(ORF)of 759 bp,encoding 252 amino acids(aa).Bioin-formatics analysis showed that there were four conserved cysteine residues and a GXXGXXXGXXXXXXG struc-ture in the amino acid sequence of MHC IIβ,and the consistency with other relative fish was 51.78%-80.56%.The encoded protein molecules included a signal peptide,a MHC IIβ(β-1)domain,a IGc1(β-2)domain and a trans-membrane helical region.Quantitative Real-time PCR(qRT-PCR)results showed that the expression of MHC Ⅱβ gene was the highest in spleen,and higher in head kidney,gill and skin.After artificial infection with pathogenic bacteria,Yersinia ruckeri,the expression of head kidney was significantly up-regulated at 6 h,and liver was signi-ficantly up-regulated at 12 h,skin was significantly up-regulated at 24 h and 48 h,gill was significantly up-regu-lated at 6 to 24 h,and spleen was significantly down-regulated at 6 h,and approached the expression level of the control group at 96 h.The results show that MHC IIβ plays an important role in immune response,which provides reference for further revealing the regulatory mechanism of MHC family immune defense.
In order to explore the physiological acclimation of Gracilariopsis lemaneiformis to hypo-osmotic stress,in this study,the morphogenesis,photosynthetic physiological responses and ultrastructure changes of algal fragments from the main branches after being cultivated at combinations of four different low salinities(S 19.500,S 13.000,S 6.500 and S 0.000)and for five different periods(1,3,6,12 and 20 h)and then cultured at normal salinity for 28 days were analysed.The results showed that less than 12 h hypo-osmotic stress treatment could pro-mote the regeneration of buds in algal fragments of G.lemaneiformis.After 3 hours of hypo-osmotic stress with freshwater,increased fresh weight and number of regenerated buds obviously emerged in these fragments during normal salinity of culture.The relative growth rate(RGR)of algal fragments treated with freshwater for 3 hours was 0.91%/d,which was 61.27%higher than that of the control group.Furthermore,1 h or 3 h hypo-osmotic stress with freshwater had no significant negative effects on the photosynthetic physiological responses of algal frag-ments,manifesting their photosynthetic activity was stimulated after restoration to seawater at normal salinity.It suggested that the cell metabolic activity of algal fragments might be enhanced after hypo-osmotic stress with freshwater.Ultrastructural observations showed that abundant floridean starch grains and plastoglobuli,sporadic lipid droplets emerged in the epidermal cell after 3 hours of hypo-osmotic stress with freshwater which would provide metabolic energy and membrane components for the algal fragments upon budding regeneration.On the contrary,long-term hypo-osmotic stress with freshwater caused irreversible structural damages to the organelles such as chloroplasts and thylakoids.These results indicated that the 3-hour treatment of hypo-osmotic stress with freshwater for algal fragments from main branches would stimulate their budding regeneration.This study would provide technical reference for rapid asexual propagations of G.lemaneiformis seedlings.
In order to understand the influence of the side plate structure on the flow field effect of the octagonal prism artificial reef,this paper is based on the computational fluid dynamics method(CFD),using large eddy sim-ulation(LES)to analyze the octagonal prism type of four different side plate structures.The changes of the flow field around the artificial reef are numerically simulated.And the flow field effect indicators are analyzed with the volume of upwelling,the volume of wake vortex and upward transport flux.At the same time,the numerical model was verified by the water tank experiment.The results show that the maximum root-mean-square error between the experimental flow velocity of the flume and the numerical simulation flow velocity of the two sizes does not exceed 0.065.At 0° vertical upstream,the upwelling volume of type A,type C and type D reef is 35.6%,244.1%and 80.1%higher than that of type B reef,and the volume of wake vortex is 193.5%,115.8%and 88.8%higher than that of type B reef,respectively.The upward transport flux of type C and type D is greater than that of type A,and the maximum upward transportation flux of type C is 1.29 times that of type D.At different upstream angles,the correlation between the projected area of upstream surface and the volume of upwelling of types C and D is obvious,and that between the projected area of upstream surface and the volume of wake vortex of types C and D was small.The research results indicate that:the numerical simulation used in this paper is accurate and reliable.The increase in the number of side plates has a significant effect on improving the flow field effect of the octa-gonal prism artificial reef,especially the upwelling effect.When the lower side plate is fixed,the inclined side plate of the upper layer is helpful to enhance the upwelling effect of the reef,and the vertical side plate of the upper layer is helpful to enhance the wake vortex effect of the reef,and different side plate combinations will cause dif-ferent flow field effects.The research results can provide a reference for the optimal design of reef cell and the set-ting of relevant retarding parameters in large-scale marine numerical models.
Sea cucumber(Apostichopus japonicus)is one of the most important economic species of mariculture in north China,but the frequent outbreaks of various diseases such as skin ulceration syndrome hindered the sustain-able development of A.japonicus aquaculture.As an important part of disease prevention and control,probiotics will hopefully replace antibiotics and be widely used in aquaculture industry.This experiment was conducted to investigate the effects of Lactobacillus plantarum LP HMX-3 on growth performance,digestive enzyme activity,immune ability and intestinal flora of A.japonicus.A total of 270 A.japonicus with an average initial body weight about(4.22±0.05)g were randomly divided into 3 groups,three replicates for each group,30 A.japonicus for each repetition.The basal diet was used as control group(C group).Two experimental diets were obtained by adding 105 CFU/g(LL group)and 107 CFU/g(LM group)LP HMX-3 to the basal diet.The feeding experiment lasted for 8 weeks.The experimental results show that ①The final body weight,weight gain rate and specific growth rate of juvenile sea cucumber A.japonicus were significantly increased by adding LP HMX-3,and the LL group had better growth index.②Compared with control group,the intestinal amylase activity in LL group and the intestinal lipase activity in LM group were significantly enhanced,while there was no significant difference in intestinal trypsin activity among all groups,but the value of probiotics groups was higher,indicating that LP HMX-3 may improve the digestion and absorption of nutrients in A.japonicus.③Compared with control group,the activities of alkaline phosphatase and catalase were significantly increased in the group of LL and LM,and the acid phosphatase activity was significantly increased in the group of LM.There was no significant difference in super-oxide dismutase activity among all groups.Besides,the mRNA expression levels of Aj-p105 and Aj-catalase in LL and LM groups were significantly increased compared with that in control group,and the mRNA expression level of Aj-C3 in LM group was also significantly higher than that in control group.These results demonstrated that diet-ary with L.plantarum LP HMX-3 supplemented could enhance the immune capacity of A.japonicus.④All alpha indices suggested that LP HMX-3 significantly increased intestinal microbial richness and evenness,but the level of addition had little effect.The Beta diversity analysis indicated that the bacteria communities in probiotic supple-mented groups were quite similar,while different from control group.⑤At the level of phylum,the relative abund-ance of Proteobacteria in control group was significantly higher than any other groups,while that of Firmicutes in LL group increased significantly compared with control group.The relative abundance of Bacteroidota,Cyanobac-teria and Campilobacterota was significantly increased in the group of LL and LM,compared with those in control group.At the genus level,the relative abundance of Lactobacillus,Bifidobacterium,Streptococcus and Clostridium in LL and LM groups was higher than that in C group,indicating that LP HMX-3 significantly increased the abundance of potential probiotics.The results of the study suggested that adding L.plantarum LP HMX-3 to the diet could effectively promote the growth of A.japonicus,improve its digestion and immunity capacity to a cer-tain extent,and actively regulate the intestinal microflora of A.japonicus.In summary,the results of this study confirmed the probiotic effect of L.plantarum LP HMX-3 in A.japonicus,and provided technical support and sci-entific evidence for its application in aquaculture.
To further study the relationship between fish glucose metabolism and irisin,the irisin antibody and its application reliability need to be prepared and tested urgently.The Rosetta-irisin expression vector was construc-ted,and the mice were immunized after protein purification,dialysis,and ultrafiltration.The corresponding poly-clonal antibodies were obtained and their specificity and antibody titers were detected.The common carp irisin detection method was established to detect the changes of irisinA and irisinB in carp serum after glucose tolerance and RNAi experiments.The immunofluorescence method was used to detect the expression of irisin in carp brain,heart,hepatopancreas,and intestine,and the changes of irisin content in these tissues after glucose tolerance.Detection of the irisin content after carp myocytes differentiation was conducted.Compared with the BL21-irisin expression vector,the expression of carp irisinA/B protein by the Rosetta-irisin expression vector increased by 2.3/1.6 times at 4 h of IPTG induction;irisinA and irisinB antibody titers were 9.0×104 and 2.7×105,respectively.And there was no cross-reaction between irisinA and irisinB polyclonal antibodies,the irisinA and irisinB can be measured respectively.IrisinA and irisinB contents showed different changes after OGTT.After RNAi,irisin was significantly decreased.Immunofluorescence results showed that irisin was the most abundant in the brain,fol-lowed by hepatopancreas,and relatively less in the heart and intestine.After OGTT,the fluorescence intensity of irisinA and irisinB in the brain,liver,heart,and gut increased significantly.The results of qPCR and immunofluor-escence showed that the FNDC5 mRNA expression and irisin decreased significantly after carp myocyte differenti-ation.In this experiment,high affinity and specific irisinA and irisinB antibodies were prepared,and their applica-tion reliability was tested.The acquisition of this antibody laid the foundation for the systematic study of carp gluc-ose metabolism.At the same time,the irisin detection methods could be widely used in the quantitative study of irisin protein levels in other fish.
The illumination distribution in water is an important subject for efficient application research of fish-ing lamp.The traditional numerical calculation method could not accurately calculate the illumination distribution of the underwater fish gathering lamp in the offshore water.A new computing model of underwater illumination of fishing lamp was developed based on Monte Carlo method by using spectrum and luminous intensity of lamps and the inherent optical properties of seawater.Firstly,the vertical marine section was set as the target surface and divided it to some grids;secondly,photons with specific wavelength and direction were generated by random num-ber method,and then the attenuation coefficient of each photon was calculated by using chlorophyll concentration data,optical characteristics of pure seawater and its relationship with absorption and scattering coefficients;finally,all photons were emitted,and their transmission paths were tracked.The photons were recorded only if they fell into the target surface and the illuminance value of each grid was calculated according to the recorded position of photons.The calculation method was verified with flume test through collecting water samples.The Ads—area of closed region which enclosed by 0.1 lx contour line in marine section which ds m away from underwater fish-ing lamp and the Ids—maximum illuminance value in marine section were used to characterize the spatial dis-tribution of light field in water.In this paper,the effect of chlorophyll concentrations,scattering type in the marine water and the scattering asymmetry parameters on the illumination distribution of LED fishing lamp and MH fishing lamp were analyzed through numerical simulation.The results showed:(1)with the chloro-phyll concentration increases from 1 mg/m3 to 5 mg/m3,the A5m of LED lamp decreased from 1 073.90 m2 to 292.87 m2,which means A5m has reduced by 72.73%;the A5m of MH lamp decreased from 1 094.51 m2 to 304.57 m2,which means A5m has reduced by 72.17%;the I5m of MH decreased from 972.76 lx to 454.42 lx,which means the I5m has reduced by 53.29%;the I5m of LED decreased from 956.48 lx to 318.60 lx,which means the I5m has reduced by 66.69%.(2)when scattering type of the ocean water is Mie scattering and Rayleigh scattering,the I5m of MH is 956.48 lx and 318.60 lx,respectively;the I5m of LED is 1 057.96 lx and 992.42 lx,respectively.(3)with the scattering asymmetry parameters increases from 0.80 to 0.99,the A5m of MH lamp decreased from 1 094.89 m2 to 1 336.40 m2,A5m increased 22.05%;the A5m of LED lamp decreased from 1 076.52 m2 to 1 325.21 m2,A5m increased 23.10%;the I5m of MH increased from 962.52 lx to 1 122.48 lx,I5m increased 16.62%;the I5m of LED increased from 980.74 lx to 1 123.22 lx,I5m increased 14.53%.It was found chlorophyll concentrations had a significant effect on illumination distribution of fishing lamp,while the scattering type and the scattering asymmetry paramet-ers on the illumination distribution had no significant effects.The numerical simulation method proposed in this paper can accurately calculate the illumination distribution of fishing lamps in offshore waters,which would provide scientific basis for fishery supervision and reasonable application of fishing lamps.
