Abstract:The Penaeidae comprises 26 genera and approximately 200 species ，as most of Penaeidae shrimps in the same genus are morphologically similar ,just exhibited subtle morphological differences,which make identification of Penaeidae shrimps a difficult task based on taxonomic keys alone.In order to define the practicability of DNA barcoding in identification of Penaeidae shrimps, in this study,we used COI gene to examine 32 Kinds of Penaeidaes’Nucleotide composition、interspecific genetic distance and intraspeccific genetic distance,and build Neighbor-joining tree of 32 kinds of Penaeidae based on mtDNA COI gene. As a result,The COI sequences of 32 kinds of Penaeidae present base preference. On average, the content of A+T (61.50%) was significantly higher than that of G+C (38.50%). As calculated by Kimera-2-parameter model, the mean distance within-species was 0.003 ,the mean distance pairwise-species (0.468) is 156 times bigger than the mean distance within-species.The phylogeny showed that 30 kinds of Penaeidae from 32 kinds of Penaeidae can converge a monophyly with high support values.we can see the good use of mitochondrial COI-based DNA barcoding in Penaeidaes’ identification,we can use it as a necessary complement and a test of morphological taxonomic system.

Abstract:The natural resource of grass carp (Ctenopharyngodon idellus) in Yangtze River has significantly decreased in the past decades. In recent years, large-scale releases of brood grass carp are carried out for ecological restoration in Yangtze River. In order to assess the genetic effect of released brood fishes on wild population in the middle reach of Yangtze River, thirteen polymorphism microsatellite markers were selected to genotype the genetic differentiation among released and wild populations. Fifteen populations were sampled, including ten released and five wild populations. The results showed that polymorphic information content and gene diversity of the microsatellite loci was 0.8622 (0.657~0.950) and 0.8555 (0.675~0.936), respectively. The number of effective alleles of the 15 populations was ranged from 7.4503 to 10.1536, and allelic richness from 11.483 to 15.204, which indicated that genetic diversity of grass carp populations was moderately high. The total and pairwise genetic differentiation indexes (FST) were low to 5%, loci implying that there was no significant genetic differentiation among populations. The 15 grass carp populations were divided into 4 groups based on Bayesian clustering analysis and principal component analysis. According to above grouping and geographic?distribution of the 15 grass carp populations, we have conducted AMOVA analysis, as a result, most of the genetic variation of grass crap populations was from inter-individuals, the level of genetic?differentiation among groups was low(FCT < 5%; FSC < 5%). In summary, there was hardly genetic effect of releasing nature grass carp on wild populations in the Yangtze River under current model.

Abstract:Mannose receptor (MR), a member of the C type lectin receptor superfamily, is thought to be involved in the non-specific immune responses in animals. To illustrate the MR molecular structure of Carassius auratus var. Qihe (CaMR) and the role it played in anti-infection immunity, homology cloning and RACE techniques were used in the present study to obtain the complete cDNA sequence, and the real-time fluorescent quantitative PCR (qPCR) technique was used to measure the effect of Aeromonas hydrophila (A. hydrophila) infection on its gene expression. The full-length cDNA of CaMR contains 4473 bp, including 81bp at 5’UTR and 90 bp at 3’UTR. The open reading frame encodes a putative protein of 1433 aa with a signal peptide of 20 aa. The predicted amino acid sequences showed that CaMR contained a cysteine-rich domain (CRD), a single fibronectin typeⅡ domain (FNⅡD), eight C-type lectin-like domains (CTLDs), a transmembrane domain and a short C-terminal cytoplasmic domain, sharing highly conserved structures with MRs from the other species. Amino acid sequence homology and phylogenic tree showed the close relationship between CaMR and other cyprinid fishes. The MR mRNA could be detected in all the examined tissues with highest level in headkidney. The temporal expression patterns of MR in the headkidney, spleen, heart, and muscle post of infection with A. hydrophila were first rise and then fell, while in the intestine was decreased continually. The current research provides a basis for further revealing the function of CaMR in immune reaction and for its application in disease prevention and cure of Carassius auratus var. Qihe.

Abstract:Several species of molluscan bivalves have a peculiar mode of mtDNA transmission, known as doubly uniparental inheritance (DUI). In these species, two mitochondrial genomes, M-type mtDNA and F-type genomes, coexist in stable state. In this study, the cDNA sequence of M and F-type COII gene of H.cumingii was cloned by RACE, QRT-PCR was used to study the expression of M and F -type COII genes in H.cumingii at different stages. We found that (i) The full-length cDNA sequence of the M-type is 1244 bp; and F-type COII is 808 bp, the C-terminus extension to the M-type COII protein has four transmembrane regions confirming that the extension is functional (ii) M-type COII gene and F-type COII gene were all expressed in gonad tissues from embryos to 5-month-age old H.cumingii, and the expression level of F-type COII gene in the same period was significantly higher than that of M-type COII gene. (iii) In semi-age old H.cumingii, F-type mtDNA was expressed mainly in somatic tissues and little in gonads, while M type expressed mainly in gonads and little in somatic tissues; (iv) In one-age old H.cumingii, F and M type both expressed in female somatic tissues and gonads, while in males F type expressed in all tissues and M type only expressed in gonads; (v) In two-age old H.cumingii, F type was

Abstract:Class B scavenger receptors are a subclass of scavenger receptors family that recognize a large repertoire of ligands, and they have been shown to have a wide range of functions in lipids metabolism and immune defence. To better understand thefunctions of class B scavenger receptors inPortunustrituberculatus (Pt-SRB), the extracellular loop of Pt-SRB was sequenced and subcloned into the expression vector, and the expressed recombinant rPt-SRB protein was obtained in present study. Then the rPt-SRB was purified by nickel-nitrilotriacetic acid chromatography, and the polyclonal antibody against rPt-SRB was obtained from an immunized rat using a conventional method. Results of SDS-PAGE showed that the recombinant protein had a molecular mass of 49.2kDa and was predominantly expressed in the insoluble fraction. Moreover, western-blot analysis revealed that antiserum could specifically react with the rPt-SRB. Furthermore, immunofluorescent staining technique was used to determine and tissue distribution the cellular localization of Pt-SRB in this study. The results showed that the Pt-SRBwere expressedinthe tissues including intestine, hepatopancreas, gills, heart and muscle, but the Pt-SRB located in differentStissueSstructures. The results displayed that the green fluorescent signals were mainly located in the connective tissue of digestive tract and gland, epithelial cells of the gill and hepatopancreatictuble. In the crab hemocytes, the green fluorescent signalswere located in the membrane and cytoplasm but not in the nucleus which suggested that thePt-SRB was localized both in membrane and cytoplasm in the crab hemocytes. Our findings will help us to better understand potential functions of the Pt-SRB.

Abstract:A field survey in an artificial reef zone of Laoshan Bay was conducted to assess the demersal nekton and macroalgae in the area, and five dominant macroalgae (Hterosiphonia japonica, Ulva pertusa, Grateloupia turuturu, Corallina pilulifera and Corallina pilulifera) and two dominant fish species (Sebastes schlegelii and Hexagrammos otakii) and artificial reef model were studied to examine the attraction of artificial reef model and the five macroalgae to juvenile S. schlegelii and H. otakii in an experimental trough. The results showed that without artificial reef model and macroalgae in trough, S. schlegelii and H. otakii preferred to stayed in the edge area of the trough, and the distribution rate was 75.71% and 73.63% respectively. After the artificial reef model and macroalgae were deployed in the trough, these two kinds of fish would swim into artificial reef holes and macroalgae cluster quickly after a short escape response; their response time to G. turuturu was the shortest (12.75–21.00 s) and the longest was to artificial reef (66.50–151.25 s); the aggregation time of S. schlegelii was shoutest to G. turuturu (151.50±8.14 s) and that of H. otakii was shortest to H. japonica (56.00±2.53 s); the aggregation time of H. otakii in artificial reef was 216.25±5.59 s, much less than that of S. schlegelii (1343.50±5.38 s); the dwell time of two kinds of fish in artificial reef is much longer than the time in macroalgae cluster, and the time of H. otakii (211.85±7.96 s) is longer than S. schlegelii (199.75±16.82 s). Artificial reef and macroalgae cluster were attractive to them, increasing distribution ratio in the experimental areas from 0.91%–8.78% to 4.21%–31.42%, and the highest aggregation rates were observed in higher density of G. turuturu for S. schlegelii (30.42%±1.14%) and H. japonica for H. otakii (31.42%±1.74%), respectively, but the aggregation by the lower–density C. pilulifera was unapparent.

Abstract:In Pyropia haitanensis, meiosis occurs during the first two divisions of germinating conchospores, and then the latter formed a tetrad with diffierent genotype, finally the tetrad developed into a genotype chimeric blade. The heterozygous conchocelies was formed in the interspecific hybridization between Pyropia haitanensis and Pyropia dentata, which could produce conchospores after maturation, but the conchospores had serious cell breakdown at the early development stage of germination. Through the tracking observation of single conchospore germling, we found that cell breakdown occurred not only in the direct products of meiosis (dyad, triad and tetrad), but also in the mitosis when the number of germling cell was more than 4. In culture, most of the conchospores could form dyad after the first meiotic division, and then form triad or tetrad through the second meiotic division. When cultured for 4 days, 78.6% of the conchospores had developed into germlings containing 2-4 cells, and the rest were undivided conchospores; The percentage of germlings containing 2-4 cells that did not have dead cells was 99.7%, and 0.3% of individuals had dead cells. With the prolongation of culture time, most of the dyads developed into the triads and tetrads, while large-scale cells breakdown appeared in the triad and tetrad. After culture for 14 days, the percentages of triad and tetrad were 38.6% and 37.2%, respectively, in which 99.5% and 99.2% contained dead cells, respectively. In addition, 8.9% of the germlings could develop into individuals with more than 4 cells, but cell death also appeared in the subsequent mitosis. When cultured for 35 days, most of the cells of germlings had all died, still, about 1% of the germlings survived, but they did not develop from the complete tetrads, just developed from 1-2 surviving tetrad cells. After 45 days of culture, the surviving individuals could be divided into parental and recombinational type based on their morphology and color. The results confirmed that the hybrid breakdown occured in the early development stage of conchospores in interspecific hybridization of Pyropia, which could not only be used to assist in the more accurate identification of species, but also we could select new strains with recombination advantage from the surviving offspring.

Abstract:In recent years, red tilapia has been gaining popularity due to its very fast growth, the absence of black peritoneum, salinity tolerance and adaptability to any culture system. However, the pigmentation differentiation in genetic breeding and skin color variation during the overwintering period are the main problems limiting the development of commercial red tilapia culture. The pigmentation differentiation is not reversible and skin color variation during overwintering period is reversible with the environmental temperature increasing. Coloration patterns including whole pink, pink with scattered black spots and pink with scattered red spots have been found in our breeding population. In order to further understand the genetic molecular mechanism of pigmentation differentiation and variation so as to solve the skin color variation during overwintering period, this research compared the effects of different temperatures (16、20、25 and 30℃) on apparent color, tyrosinase (Tyr) activity and skin pigment cells of Malaysian red tilapia during overwintering period. After fifty days experiment, we found the body color of most fish in T16 group changed to pewter from pink at the beginning. Most of the abdominal skin color in T20 group fish also varied to pewter. But the fish body color in T25 group had only slight change and the body color of T30 group was still whole pink. The Tyr activity of fish back skin, abdominal skin and serum increased with increasing of temperature, and was highest in 25℃ group fish. However, the Tyr activity decreased in 30℃ group fish. The blood Tyr mRNA expression increased with increasing of temperature (P < 0.05), and the muscle Tyr mRNA expression in 25℃and 30℃ group fish were higher than that in 16℃and 20℃ group (P < 0.05). The melanocytes of fish back skin decreased in number with increasing of temperature by slice microstructure observation. The results suggest that the color variation during overwintering period of red tilapia may be related to the changes of skin melanocytes and Tyr activity. The further study of the regulatory mechanism would help to understand the genetic mechanism of fish body color and improve the body color features.

Abstract:The fatty acids profiles in the muscles, liver and abdominal adipose of five economic fish species on the markets of Shanghai in winter and summer were examined. The five fish species studied included carnivorous marine fish (Larimichthys crocea), omnivorous marine fish (Pampus argenteus), carnivorous freshwater fish (Anguilla japonica), omnivorous freshwater fish (Oreochromis mossambicus), and herbivorous freshwater fish (Ctenopharyngodon idella). The results indicated that fatty acid profile was different among these five fish species, and it was related with the living environment and feeding habit. Saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) tended to accumulated in abdominal adipose and liver, where fat content was high. However, polyunsaturated fatty acids (PUFAs), n-3 PUFAs and n-6 PUFAs were not correlated with tissue fat content. The SFAs, MUFAs, PUFAs, EPA and DHA content, as well as n-3/n-6 ratio were higher in carnivorous fish (A. japonica, L. crocea, P. argenteus) than in omnivorous fish (O. mossambicus) and herbivorous fish (C. idella). The n-3 PUFAs，EPA and DHA content in the muscle of marine fish (L. crocea and P. argenteus) were higher than that of freshwater fish (O. mossambicus and C. idella). In winter, the n-3 PUFAs content in abdominal muscle of C. idella and tail muscle of O. mossambicus were higher than that in summer, as well as that in the liver of A. japonica and P. argenteus. In summary, fatty acids profiles were correlated with the species, feeding habit, living environment, type of tissues and the season. The fillets of L. crocea, P. argenteus and A. japonica have high nutritional value because of its high n-3 PUFAs content. In general, fish in winter contained higher n-3 PUFAs than summer fish, thus the nutritional value of winter fish is higher than summer fish.

Abstract:In order to investigate the effects of L-tryptophan and melatonin for the serum glucose level and antioxidant capacity in the hepatopancreas of Chinese mitten crab (Eriocheir sinensis). The female crab with the average body weight of (16.58±2.20)g were randomly allocated into 8 groups (the processing experiments of L-tryptophan and melatonin had 4 groups respectively). Each experimental period was 30 d. (1)The feeding experiment of L-tryptophan: crabs were fed with diet which added 4 levels of L- tryptophan, and the L-tryptophan account for the diet were 0.36% (basal diet namely control group), 0.47%, 0.73% and 1.05% (named diet 1, 2, 3 and 4, respectively). The serum glucose level and T-AOC and the capacity of SOD in the hepatopancreas were determined. (2)The injection experiment of melatonin: on the 1st and 15th day, crabs were injected with saline(control group namely C)and different doses of melatonin which were 10-6 mol/crab (μM), 10-9 mol/crab (nM) and 10-12 mol/crab (pM). Then the haemolymph and hepatopancreas were collected separately for the determination of the serum glucose level and T-AOC and the capacity of SOD in the hepatopancreas on the 1st and 15th day. In addition, we analyzed the serum glucose level on the 30th day. The results showed that different levels of L-tryptophan had no significant effect on serum glucose level, its value was approximately 4.62±0.20mmol/L. The diet which contained 0.73% L-tryptophan could significantly increase the capacity of SOD (82.86±1.07)U/mL. Injection of melatonin into crabs resulted in hyperglycemia in a dose-dependent manner on the 1st day. Among them, the serum glucose level of μM reached up to (7.56±0.36)mmol/L, which was significantly higher than other three groups. Moreover, the injection of MT played an important role in promoting the T-AOC and the capacity of SOD, but only occurred on the 1st day. Comparing with C, pM and nM, the the T-AOC and the capacity of SOD of μM was higher than them significantly. In summary, 0.73% L-tryptophan can improve the capacity of antioxidant of crabs, but the effects on the serum glucose level are not obvious. The injection of 10-6mol/crab melatonin can improve the serum glucose level and antioxidant capacity of Chinese mitten crab in short time (1 d).

Abstract:(Objective ) This experiment was conducted to investigate the influence of dietary oxidized fish oil (OF) and the intervention of Arginine (Arg) on the intestinal health of juvenile yellow catfish (Pelteobagrus fulvidraco). (Method) A total of 600 healthy yellow catfish with an initial body weight of (4.41 ± 0.05) g were randomly divided into 6 groups with 4 replicates of 25 fish. During 56 d feeding trial, the fish were fed respectively six diets containing 2.5% fresh fish oil (FF), 1.5% FF + 1.0% OF (OF1), 0.5% FF + 2.0% OF (OF2), 2.5% FF + 0.48% Arg (FFA), 1.5% FF + 1.0% OF + 0.48% Arg (OFA1) , 0.5% FF + 12.% OF +0.48% Arg (OFA2). (Results) The results showed that the ACP, AKP activities and IL-6 content in intestine of yellow catfish were significantly higher in OF2 group (P<0.05). While addition of arginine to the oxidized fish oil diets, the AKP activity and IL-6 content in intestine of yellow catfish were significantly lower in OFA2 group (P<0.05). The SOD activity in intestine of yellow catfish showed a downward trend and the GSH-PX and CAT activities showed a reversed trend, but there was no significant differences among FF, OF1 and OF2 groups (P＞0.05). The SOD activity was significantly higher in OFA2 group (P<0.05). The MDA content in intestine of yellow catfish were significantly higher in OF2 group (P<0.05). Dietary oxidized fish oil and arginine had a significant interaction on the GSH-PX activity in intestine of yellow catfish (P<0.05). The CAT activity in intestine was significantly decreased by the arginine (P<0.05). The DAO activity in intestine of yellow catfish showed a downward trend and the iNOS showed a raised trend , but there was no significant difference among FF, OF1 and OF2 groups (P＞0.05). The DAO activity was significantly increased and iNOS significantly decreased in OFA2 group (P<0.05). The arginine had a significant impact on the DAO and iNOS activities in intestine of yellow catfish (P<0.05). The height of folds, the thickness of muscles and the number of goblet cells in foregut was significantly increased in OF1 group (P<0.05). In comparison with OF2 group, the height of folds was significantly increased in the OFA2 group (P<0.05). (Conclusion) The results suggest that dietary oxidized fish oil reduce the intestinal immune and total antioxidant capacity, and damage the structure in foregut of juvenile yellow catfish, but arginine supplementation can alleviate the inhibition induced by oxidized fish oil for intestinal immune, antioxidant capacity and tissue structure.

Abstract:Castor oil polyethylene glycol monoester glucoside(CPMG) is a kind of biodegradable and artificial material. Formalin-inactivated A.hydrophila bacteria with or without CPMG, CPMG + anisodamine mixture were administered on days 1 and 7 to gibel carps through immersion. Spleens were sampled on days 2, 4, 7, 11, 14 and 21 post-second vaccination, and the expression quantities of IgM, IL-1β, C3, C-lectin and lysozyme mRNAs in spleen were detected through the real-time fluorescence quantitative PCR (RT-PCR). Formalin-inactivated A. hydrophila vaccine with CPMG + anisodamine mixture were immersion administered just once, then, specific antibodies were detected and the fish were challenged intraperitoneally with lethal A. hydrophila at different times post-vaccination.SThe results of vaccination twice showed that fish immunized with inactivated A.hydrophila vaccine and CPMG exhibited enhanced expression of genes that are involved in both innate and adaptive immune responses (IgM, IL-1β, C3, C-lectin and lysozyme) compared to no adjuvant control or saline control. The relative percent survival (RPS) was found to be 70.6% on day 30 post-vaccination, while immunization with the antigen alone followed by an experimental challenge gave an RPS of 56.0%, moreover, the CPMG + anisodamine coupled vaccine showed an RPS of 88.2%.The results of vaccination just once showed that the CPMG + anisodamine coupled vaccine could augment the production of specific serum antibodies, which reached the highest level at 6 weeks post-vaccination. The resulting RPS calculated was 54.6%, 44.0% and 12.5% on days 30, 60, 120 post-vaccination, respectively. These results indicate that Formalin-inactivated A.hydrophila vaccine with CPMG immersion administered to gibel carps can significantly promote the gene expression of IgM, IL-1β, C3, C-lectin and lysozyme in spleen and enhance specific immune responses against A.hydrophila infection.

Abstract:To define the potential pathogens causing a sick F2 Chinese sturgeon (Acipenser sinensis) in a hatchery of Chinese sturgeon, a bacterial strain EM was isolated from the liver; spleen and ascites of moribund F2 Chinese sturgeon by traditional method of pathogen isolation. The strain EM was identified as Elizabethkingia meningoseptica by means of the 16S rDNA sequence, constructing phylogenetic tree and Biolog Microbial Identification System. The pathogenicity of the strain EM was confirmed by the infection experiment in healthy F2 Dabry’s sturgeon (Acipenser dabryanus). Meanwhile, histopathological analysis was performed in the sick F2 Chinese sturgeon,and the antibiotic susceptibility of the strain EM was carried out to guide the clinically choosing medicine. The results showed that themosiderin deposition, ballooning degeneration and hemolysis severely in liver, spleen and kidney of the sick F2 Chinese sturgeon. The strain EM was cofirmed to be pathogenic to healthy Dabry’s sturgeon by infection experiment, the same bacterium could be recovered from these infected Dabry’s sturgeon.The susceptibility test to antibiotics demonstrated that the strain EM from sick Chinese sturgeon was susceptible to minocycline, clindamycin, clarithromycin,amd midecamycin; medium susceptible to cefotaxime and cefoxitin, but resistant to other 29 kinds of antibiotics, which implied EM strain was resistant to multiple antibiotics.In short, the study firstly shows that Elizabethkingia meningoseptica could be infected Chinese sturgeon, which is also known as a pathogen to Dabry’s sturgeon. Preliminary study on biological characteristics, antibiotic susceptibility of Elizabethkingia meningoseptica, pathological features of diesased F2 Chinese sturgeon, will provide theory basis for disease control and prevention on conservation of Chinese sturgeon.

Abstract:ABSTRACT: In May 2016, a severe infectious disease occurred among the farmed Procambarus clarkii in Qianjiang, Hubei Province. Histological examination, virus isolation, Nested-PCR. artificial infection experiment and phylogenetic analysis were performed to explore its causes and the epidemic law. Principal symptoms included darkening of the body, reduction in vigour, antifeedant. Histopathologically, hepatopancreas, intestines, muscle, gill showed varying degrees of degeneration, necrosis and inflammatory cellinvasion. Pathologic changes were the same as the White spot syndrome virus (WSSV) infected arthropod. PCR detection results also showed that tissues of dying Procambarus clarkii were positive to WSSV, the positive rates of PCR was 55.55%（15/27）, while those were negative to Monodon baculovirus disease (MBV) and Infectious hypodermal and hematopoietic necrosis (IHHNV). Procambarus clarkii that dead in oral infection was positive for the presence of WSSV by Nested-PCR.The sequenced amplification products shared 100% identity with White spot syndrome virus isolate EG3, complete genome ( GenBank access number: KR083866.1) . Phylogeneticanalysis showed that the isolate was belonging to WSSV. Experimental infection of Procambarus clarkia, were conducted by feeding WSSV infected Procambarus clarkia. The results showed that a cumulative mortality of 100％was observed in the infected Procambarus clarkia, while no death in control group. By the detection of above, WSSV was determined the pathogen of the Procambarus clarkii disease.

Abstract:In May 2015, an unknown disease caused severe economic losses in a Common carp (Cyprinus carpio) culture pond in Sichuan Province. The mortality rate was 80%. Necropsy, bacteriologic test, histological examination, pathogenicity tests, virus isolation, PCＲ assay and phylogenetic analysis were performed to explore its causes. Principal symptoms included sunken eyes, hemorrhage at the base of the pectoral and pelvic fins, severe gill necrosis and swollen kidney. Bacteriologic test was negative. Histopathologically, the most important changes were observed in the gills and kidneys. The respiratory of gill lamellae was swelling and/ or dropping and congestion of the blood vessels in the gill filaments. The base of branchial epithelium also exhibit hyperplasia, hypertrophy and cellular layer increased. The obvious disorder in structure, swelling, and disintegration and necrosis were found in epithelial cells of renal tubulus. Positive results were obtained from all detected samples according to a standard PCR diagnosis of Koi herpesvirus (KHV/ CyHV-3) Sphi gene proposed by Office International des Epizooties (OIE) by using gills and kidney tissue DNA isolated from diseased Common carp. After filtration treatment，the kidney and liver homogenate was injected intraperitoneally into 20 healthy common carp，and the injected carp showed similar clinical symptoms as the fish that was naturally infected．Common Carp died acutely in the trial group with a cumulative mortality rate 90%．Tissue suspension was inoculated to the Common Carp Brain (CCB) monolayer cells and a typical cytopathic effect (CPE) was observed in CCB cells after three blind passages. Icosahedral viral particles were observed in cells under the electron microscope. The virus particles were spherical in shape measuring 180-200nm in diameter. Based on neighbor-joining analyses of the TK gene sequences，phylogenetic tree was constructed and the result showed that the isolate belongs to Asian 1 genotype. This is the first report of KHV infection in cultured common carp associated with high mortality in Southwestern China．The result present in this study is important for virus evolution，classification，viral diagnosis and disease control．

Abstract:Insulin is a member of a family of peptides and plays important roles in the regulation of nutrition metabolism in fish. To decipher the mechanism of insulin regulating nutrient metabolism, the present paper reviewed the progress involved in the structure and expression of three members (insulin, insulin receptor and insulin receptor substrate) of insulin signaling pathways, and the regulation of insulin in carbohydrate, lipid and protein metabolism. At present, although enormous progress has been made in the insulin signaling pathway, many basic questions remain and further investigations are needed: (1) studies involved in the functions of different isoforms of insulin, insulin receptor and insulin receptor substrate; (2) molecular mechanism of insulin regulating nutrient metabolism; (3) investigation into insulin signaling pathway and regulatory mechanism.