The environmental analysis and site selection of mussel and large yellow croaker aquaculture areas based on high resolution remote sensing

Mussel aquaculture and large yellow croaker aquaculture areas and their environmental characteristics in Zhoushan were analyzed using satellite data and in-situ surveys.A new two-step remote sensing method was proposed and applied to determine the basic environmental characteristics of the best mussel and large yellow croaker aquaculture areas.This methodology includes the first step of extraction of the location distribution and the second step of the extraction of internal environmental factors.The fishery ranching index(FRI1,FRI2)was established to extract the mussel and the large yellow croaker aquaculture area in Zhoushan,using Gaofen-1(GF-1)and Gaofen-6(GF-6)satellite data with a special resolution of 2 m.In the second step,the environmental factors such as sea surface temperature(SST),chlorophyll a(Chl-a)concentration,current and tide,suspended sediment concentration(SSC)in mussel aquaculture area and large yellow croaker aquaculture area were extracted and analyzed in detail.The results show the following three points.(1)For the extraction of the mussel aquaculture area,FRI1 and FRI2 are complementary,and the combination of FRI1 and FRI2 is suitable to extract the mussel aquaculture area.As for the large yellow croaker aquaculture area extraction,FRI2 is suitable.(2)Mussel aquaculture and the large yellow croaker aquaculture area in Zhoushan are mainly located on the side near the islands that are away from the eastern open waters.The water environment factor template suitable for mussel and large yellow croaker aquaculture was determined.(3)This two-step remote sensing method can be used for the preliminary screening of potential site selection for the mussels and large yellow croaker aquaculture area in the future.the fishery ranching index(FRI1,FRI2)in this paper can be applied to extract the mussel and large yellow croaker aquaculture areas in coastal waters around the world.

Spatial-temporal dynamics of bacterioplankton communities in the breeding area of large yellow croaker Larimichthys crocea in Sansha Bay,China

As an important spawning ground for large yellow croaker Larimichthys crocea,Sansha Bay,South China Sea has been a research hotspot.However,studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited.To address the issue,we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three distinct areas,i.e.,Breeding Area(BA),Yantian Harbor(YH),and Bay Margin(BM)of Sansha Bay.Results show that the structure of the bacterioplankton community in Sansha Bay had a significant seasonal succession.Moreover,the representative zero-radius Operation Taxon Units in different seasons were significantly different among the three selected sea areas.Specifically,during the breeding season,bacterioplankton communities in BA were characterized by compound-degrading bacteria,such as Rhodococcus and Owenweeksia,while in YH and BM,animal parasites or symbionts such as Vibrio and Arcobacter were dominant.Furthermore,the redundancy analysis and Spearman correlation analysis further explained that water temperature,dissolved oxygen,and ammonia nitrogen were the main environmental factors responsible for the difference.In addition,the bioindicator functions screened by Functional Annotation of Prokaryotic Taxa and random forest machine learning mainly relied on compound degradation,nitrite oxidation,and photoheterotrophy.The compound-degradationcorresponded bacterioplankton genera such as Rhodococcus had relatively higher abundance in BM,while Nitrospina corresponding to nitrite oxidation tended to be abundant in YH and BA.Based on the spatial and temporal variation in the composition and function of bacterioplankton,our findings provide a basis for understanding the theory of bacterioplankton community structure in the inner-bay habitat of the large yellow croaker in Sansha Bay.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Comparative study on the organoleptic quality of wild and farmed large yellow croaker Larimichthys crocea

To fill the blank in systematic study on the organoleptic quality of large yellow croaker Larimichthys crocea,we analyzed the organoleptic quality of the fish meat of wild,trash-fish-fed,and compound-feed-fed large yellow croaker.Six fish(weight:500 g)per group were sampled in the same period,and 89 indices of fish organoleptic quality were measured and analyzed.Results reveal significant differences in the body condition factor,skin/muscle color,flesh texture,odor,and taste aspects between wild and farmed fish.Compared with the wild fish,farmed fish showed fatter body shape,whiter skin or muscle color,tender muscle,higher level of fishy odor or volatile intensity,but lower delicious taste.In addition,compared with trash-fish feeding,compound-feed feeding could improve the body shape,skin color,flesh texture,and fish taste of large yellow croaker,but it also increased the fishy odor.In principle component analysis and cluster analysis,the present study preliminarily established the systematic evaluation with multiple indices to the quality of large yellow croaker.It shall be helpful for the evaluation or improvement of the quality of farmed large yellow croaker.

Molecular characterization of an IL-1β gene from the large yellow croaker（Larimichthys crocea） and its effect on fish defense against Vibrio alginolyticus infection

Interleukin 1β（IL-1β）, the first interleukin to be characterized, plays a key role in regulating the immune response. In this study, we determined the c DNA and genomic DNA sequences of the IL-1β gene from the large yellow croaker, Larimichthys crocea. Phylogenetic analysis indicated that the IL-1β（Lc IL-1β） gene was most closely related to that of European seabass（Dicentrarchus labrax）, sharing 67.8% amino acid identity. In healthy large yellow croaker, Lc IL-1β transcription was detected in all tested tissues, with the highest level found in the head kidney. Upon Vibrio alginolyticus infection, Lc IL-1β transcription in all tested tissues was significantly upregulated. Intraperitoneal injection of recombinant Lc IL-1β（r Lc IL-1β） improved the survival rate and reduced the tissue bacterial load after V. alginolyticus infection. In addition, r Lc IL-1β induced monocytes/macrophages（MO/MΦ） chemotaxis and increased phagocytosis and bactericidal activity in vitro. These results suggest that Lc IL-1β plays an important role in the large yellow croaker immune response against V. alginolyticus.

Cloning and mRNA expression of macrophage migration inhibitory factor (MIF) gene of large yellow croaker (P seudosciaena crocea)

Mammalian macrophage migration inhibitory factor （MIF） plays an important role as an indispensable mediator in the pathogenesis of inflammatory disease like septicemia, but little is known about the role of MIF homologue in fish septicemia. The authors have cloned the MIF homologue in large yellow croaker Pseudosciaena crocea （LycMIF） using RACE approach. The full-length cDNA of LycMIF was 634 bases and contained an ORF of 345 bases encoding a protein of 115 amino acid residues. As demonstrated by RT-PCR and QRT-PCR assay, MIF mRNAs were constitutively expressed in 11 selected tissues and were abundant in brain and liver. Moreover, the LycMIF transcripts in the liver and head kidney were responsive to bacteria infection and could be significantly up-regulated. Our results provide the first direct evidence that fish MIF was implicated in pathogenesis of fish vibrosis and play an important role in response to bacteria infection.

Replacement of Dietary Fish Oil with Vegetable Oils Improves the Growth and Flesh Quality of Large Yellow Croaker(Larmichthys crocea)

We investigated the effect of the replacement of dietary fish oil with vegetable oils on the growth and flesh quality of large yellow croaker(Larmichthys crocea). The basal diet(FO) was formulated to contain 66.5% fish meal and 6.4% menhaden fish oil; whereas the other 3 experimental diets were formulated by replacing the fish oil with 50% soybean oil(SO50), 100% soybean oil(SO100) and 100% palm oil(PO100), respectively. The 4 diets were randomly assigned to 4 floating sea cages(3.0 m × 3.0 m × 3.0 m), and each was stocked with 250 fish individuals with an initial average weight of 245.29 g ± 7.45 g. The fish were fed to apparent satiation twice a day at 5:00 and 17:00, respectively, for 12 weeks. Experimental analysis showed that the specific growth rate of fish fed SO50 or PO100 were significantly higher than that of fish fed FO or SO100(P<0.05), and crude lipid contents of ventral muscle and viscera were significantly lower in fish fed FO than in those fed the other 3 diets(P<0.05). No significant differences in condition factor, viscerosomatic index, hepatosomatic index, gutted yield and colorimetric values of fish among the dietary treatments were observed(P>0.05). Compared to FO diet, SO50, SO100 and PO100 diets led to substantial decreases in the liquid loss and water loss from fresh fillets(1 d, 4℃)(P<0.05). Similarly, thiobarbituric acid reactive substance(TBARS) values of fillets under different storage conditions(1 d, 4℃; 7 d, 4℃; 4 weeks,-20℃; 8 weeks,-20℃) decreased significantly after partial or complete replacement of fish oil with vegetable oils. These findings indicated that the growth performance and selected flesh quality properties(liquid holding capacity and TBARS value) of large yellow croaker were substantially improved by replacing dietary fish oil with vegetable oils.

Diagnosis of iridovirus in large yellow croaker by PCR

A rapid and sensitive PCR-based method for the detection of the large yellow croaker iridovirus (LYCIV) is described, which involves the amplification of a 295 bp fragment of the LYCIV ATPase gene from DNA isolated from naturally infected fish spleen. Sequencing of LYCIV ATPase gene fragment showed it shared 100% nucleotide sequence homology with the corresponding region of the ATPase gene of red sea bream iridovirus (RSIV) and sea bass iridovirus (SBIV), suggesting that LYCIV was homologous with RSIV and SBIV at least in part of the gemone. The specificity and sensitivity of the PCR procedure were tested on the iridovirus-infected fishes, the expected fragment was detected from spleen DNA samples of infected fishes, whereas no fragments were amplified from healthy fish spleen DNA, white spot syndrome baculoviruses (WSBV) DNA and pseudorabies virus (PRV) DNA. Detection limit of this method was 10(-7) ng positive plasmid DNA containing target sequence, equal to about 100 virions. In the infected experiment, first positive detection (1/4) appeared at Day 3 post-infection, all fish (4/4) tested positive at Day 7, however obvious symptoms were observed at Day 8, so LYCIV infection could be detected prior to the appearance of obvious symptoms. These results indicate that this PCR method could be used for early, rapid and specific detection of LYCIV infection.

A Comparison Study on Flesh Quality of Large Yellow Croaker (Larimichthys croceus) Cultured with Three Different Modes

To compare the flesh quality of large yellow croaker cultured with three different modes, enclosure culture(EC), cage culture with feeding trash fish(CCF) and cage culture with feeding formula diet(CCD), thirty six fish individuals of EC(484.6 ± 79.8 g), CCF(432.7 ± 87.9 g) and CCD(416.9 ± 49.5 g) were sampled to measure body color, flesh water holding capacity, flesh proximate composition, amino acids and fatty acids composition, and collagen and inosinic acid contents. The analysis showed that there was no significant difference in the yellowness of skin and the contents of crude protein and inosinic acid between CCD and EC(P > 0.05), and the two modes showed higher values than CCF(P < 0.05). Most of the amino acids(AA) in flesh were higher in EC than in CCF(P < 0.05), but CCD showed no difference in AA composition from the other two modes(P > 0.05). EC and CCD had higher contents of collagen, free AA and lower drip loss than CC(P < 0.05). In polyunsaturated fatty acids, EC showed significantly higher levels of C20:5 n-3 and C22:6 n-3 than CCF and CCD(P < 0.05), but CCD had significantly higher C18:2 n-6 than CCF and EC(P < 0.05). In conclusion, the flesh quality of CCD fish is similar to EC fish, and these two modes have better flesh quality than CCF.

Establishment of a Spleen Cell Line from Large Yellow Croaker Pseudosciaena crocea and its Primitive Application in Foreign Gene Transfection

A large yellow croaker,Pseudosciaena crocea,spleen(LYCS)cell line was established and the feasibility of using it for foreign gene transfection was evaluaed in this study.Primary culture of LYCS cells was initiated from spleen tissue pieces,which were cultured at 25℃ in Dulbecco's modiced Eagle medium/F12 medium(DMEM/F12,1:1)(pH7.2),supplemented with 20% fetal bovine serum,carboxymethyl chitosan,chondroitin sulfate,basic fibroblast growth factor(bFGF)and insulin-like growth factor-I(IGF-I).The cultured LYCS cells,in fibroblast shape,proliferated to 100% confluency 20 days later.Chromosome analyses indicated that the LYCS cells exhibited chromosomal aneuploidy with a modal chromosome number of 48 which displayed the normal diploid karyotype of P.crocea(6m+6sm+36t,NF=60).A LYCS cell line,with a population doubling time of 48.7 h at passage 60,has been established and subcultured to passage 70.Transgenic feasibility test demonstrated that positive green fluorescence protein(GFP)expression was observed in LYCS cells after pcDNA3.1-GFP plasmid transfection.In conclusion,a continuous foreign gene trans-fection feasible LYCS cell line has been established successfully.The cell line might serve as a valuable tool for studies of transgenic breeding and has potential applications for different kinds of cytotechnological studies.

Effect of Dietary Olaquindox on the Growth of Large Yellow Croaker(Pseudosciaena crocea R.) and the Distribution of Its Residues in Fish Tissues

Olaquindox(OLA), one of quinoxaline-N, N-dioxides, has been put under ban. However it was used as a medicinal feed additive early; it promotes the growth of livestock and prevents them from dysentery and bacterial enteritis. In this study, we evaluated the effect of dietary OLA on the growth of large yellow croaker(Pseudosciaena crocea R.) and the histological distribution of OLA and its metabolite 3-methyl-quinoxaline-2-carboxylic acid(MQCA) in fish tissues. Four diets containing 0(control), 42.5, 89.5 and 277.2 mg kg-1 OLA, respectively, were formulated and tested, 3 cages(1.0 m × 1.0 m × 1.5 m) each diet and 100 juveniles(9.75 ± 0.35 g) each cage. The fish were fed to satiation twice a day at 05:00 am and 17:00 pm for 8 weeks. The survival rate of fish fed the diet containing 42.5 and 89.5 mg kg-1 OLA was significantly higher than that of fish fed the diet containing 0 and 277.2 mg kg-1 OLA(P < 0.05), while the weight gain rate of fish fed the diet containing 42.5 and 89.5 mg kg-1 OLA was significantly higher than that of fish fed the diet without OLA(control)(P<0.05), but similar to that of fish fed the diet with 277.2 mg kg-1 OLA. Fish fed the diet with 277.2 mg kg-1 OLA had the highest content of OLA and MQCA in liver(3.44 and 0.39 mg kg-1, respectively), skin(0.46 and 0.09 mg kg-1, respectively) and muscle(0.24 and 0.06 mg kg-1, respectively). In average, fish fed the diet containing OLA had the highest content of OLA and MQCA in liver which was followed by skin and muscle(P < 0.05), whereas OLA and MQCA were not detectable in control. Our findings demonstrated that OLA and MQCA accumulated in large yellow croaker when it was fed with the diet containing OLA, thus imposing a potential safety risk to human health.

Intragenic and intergenic sequences regulating the expression of the 5'-to-5' linked adult α-and β-globin genes from large yellow croaker Pseudosciaena crocea

One adult α-globin gene and one β-globin gene have been cloned from the large yellow croaker Pseudosciaena crocea. Linkage analysis indicated that the α- and β-globin genes were oriented head-to-head relative to each other. To identify the regulatory elements present in the intergenic and intragenic regions of the globin complex, the intergenic region alone or together with the β-globin gene first intron was cloned into the luciferase-reporter vector pGL3-Basic respectively, and the chimeric constructs were tran- siently transfected into Vero cells and primary fish erythrocytes. The intergenic region cannot support the high-level expression of luciferase. However, the promoter activity of the intergenic region was strongly stimulated by the positive regulatory elements （PRE） located in the β-globin gene intron 1. Thus, it is proposed that the intergenic promoters and intragenic PRE were necessary for the effective expression of the linked α- and β-globin genes.

Thermal tolerance evaluation and related microsatellite marker screening and identification in the large yellow croaker Larimichthys crocea

Thermal tolerance to high temperature was evaluated in the large yellow croaker Larimichthys crocea. The survival thermal maximum for L. crocea was 33.0℃, the 50% critical thermal maximum （50% CTMax） was 35.5℃, and the critical thermal maximum （CTMax） was 36.0℃. Three microsatellite markers （LYC0148, LYC0200 and LYC0435）, associated with thermal tolerance were screened and identified using a Bulked Segregation Analysis （BSA） method. These markers have six amplified fragments in which four are related to thermal tolerance. These fragments were cloned and sequenced, and the results showed the core motif were all ＂AC＂ repeats. For LYC0148 and LYC0200, the lengths of fragments are 18l bp and 197 bp, respectively. For LYC0435, which has two fragments, the fragment lengths are 112 bp and 100 bp. The results provide useful molecular markers for thermal-tolerance breeding of large yellow croaker in the near future.

Temperature Tolerance of Large Yellow Croaker,Pseudosciaena Crocea(Richardson)Associated with Summer Season

L ethal temperature tolerance was determined for about 8 cm, age 0 Pseudosciaena crocea using both slow heating and rapid transfer protocol. The acclimatization temperature was 28 ℃ with summer season, lethal temperature ( LT50 value ) of slow heating protocol ( CTMax ) was 35.0 ℃, and the upper and lower incipient lethal temperatures of rapid transfer protocol were 34.2 ℃ and 17.5 ℃ respectively.

Effects of fish protein hydrolysate on growth performance and humoral immune response in large yellow croaker (Pseudosciaena crocea R.)

We investigated the effects of fish protein hydrolysate (FPH) on growth performance and humoral immune response of the large yellow croaker (Pseudosciaena crocea R.). One thousand and two hundred large yellow croakers [initial average weight: (162.75±23.85) g] were divided into four groups and reared in floating sea cages (3 m×3 m×3 m). The animals were fed with 4 diets: basal diet only (control) or diets supplemented with 5%, 10% and 15% (w/w) FPH. The results show that dietary FPH levels significantly influenced the growth and immunity of the large yellow croaker. Compared with the control group, total weight gain (TWG) in all treatment groups, relative weight gain (RWG) and specific growth rate (SGR) in fish fed with diets supplemented with 10% and 15% FPH were significantly increased (P<0.05). Similar results were observed in immune parameters [lysozyme activity, serum complements, immunoglobulin M (IgM)]. Lysozyme activity, complement C4 and IgM were also significantly increased (P<0.05) in fish fed with diets supplemented with 10% and 15% FPH, while complement C3 level was significantly increased (P<0.05) in all treatment groups. In general, with the supplementation of FPH, particularly at dose of 10%, the growth performance and immunity of the large yellow croaker can be improved effectively.

Influence of dietary conjugated linoleic acid on growth, fatty acid composition and hepatic lipogenesis in large yellow croaker (Pseudosciaena crocea R.)

We examined the effects of conjugated linoleic acid (CLA) on growth, fatty acid composition and enzyme activity of fatty acid oxidation in the liver of large yellow croaker. We divided 1600 fish (average initial weight 150 g) into 4 groups and reared them in 8 cages. Four dietary treatments were formulated to contain 0%, 1%, 2% and 4% (w/w) CLA, respectively. The fish were fed for 10 weeks ad libitum twice daily. We found that the dietary CLA had no effect on growth, biometric parameters and whole body proximate (P>0.05), but showed some significant effects on the fatty acid composition in both muscle and the liver. The activities of lipogenic enzymes were slightly depressed in fish fed with increasing levels of CLA when compared with control (P>0.05). Dietary CLA supplementation had no effects on liver lipid content, but significantly increased the contents of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (P<0.05) and decreased monounsaturated fatty acid (MUFA) content in both muscle and the liver. Dietary CLA inclusion resulted in significant increases of the biologically active cis-9, trans-11 and trans-10, cis-12 isomers in both tissues (P<0.05). The total accumulation of CLA was higher in the liver (3.83%, w/w) than in muscle (3.77%, w/w) when fed with 4% (w/w) CLA. This study demonstrates that large yellow croakers are capable of absorbing and depositing CLA and long-chain n-3 PUFA in the liver and muscle, showing that this species fed with CLA could be an important human food source for these healthful fatty acids.

Artificial induction of mito-gynogenetic diploids in large yellow croaker(Pseudosciaena crocea) by hydrostatic pressure

The present study investigated conditions for inducing mito-gynogenetic(endomitosis) diploids by hydrostatic pressure in the large yellow croaker Pseudosciaena crocea.In haploid control groups,the development of eggs was activated with ultraviolet radiated semen.All fry presented typical haploid syndrome in the haploid control groups,and were verified as haploids using cytometry.After hydrostatic pressure treatment,morphologically normal fry reappeared at different frequencies according to the intensity and time of pressure shock.Fry with normal appearance in the pressure treated groups were verified as gynogenetic double haploids(GDHs),containing only one allele from the female parent at all four diagnostic microsatellite loci.For a fixed duration of 3 min,the optimal intensity of blocking the first mitosis was determined to be 40 Mpa,which was similar to that of blocking the second meiosis.There was a "window" of starting time,from 36.1 min to 38.1 min post-insemination at 25.0±1.0°C,within which the production of GDHs was not significantly different.Maximum production of morphologically normal fries,9.36%±2.97% of developed eggs,was found when the eggs were shocked with hydrostatic pressure at 40 Mpa for 3 min,starting from 38.1 min post insemination at 25.0±1.0°C.

MicroRNAs identification and bioinformatics analysis in large yellow croaker Larimichthys crocea using an integrated comparative and ab initio approach

MicroRNAs(miRNAs) are a group of small, endogenous, single-stranded non-coding RNAs that post-transcriptionally regulate gene expression levels. Previous studies have revealed that miRNAs play key roles in multiple biological processes, such as growth and development in both animals and plants. Computational identification is an efficient method for miRNA prediction in organisms with a reference genome before high-throughput miRNA sequencing experiments. In this study, we employed an integrated strategy combining the homology-based and ab initio approaches to predict miRNAs from the genome and transcriptome of large yellow croaker, one of the most commercially important marine fish in China and East Asia. A total of 418 miRNA molecules, including 287 miRNAs by the homology-based method and 131 miRNAs by the ab initio approach, were identified for large yellow croaker. Additionally, 16 053 target genes were predicted and annotated for Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) databases. Meanwhile, we analysed single nucleotide polymorphisms(SNPs) around large yellow croaker miRNA and found that the miRNA seed regions were significantly less prone to mutations, indicating that the miRNA sequences were under strict natural selection based on their essential regulation functions in living cells. Twenty-two SNPs were identified in large yellow croaker miRNA seed regions, which dramatically influenced the miRNA-gene regulation networks. This is the first reported miRNA detection from both the genome and transcriptome using the integrated strategy for large yellow croaker species, and the miRNA and SNP analyses in this work provide important resources and a reference for subsequent miRNA functional investigations in large yellow croaker.

Expression Profile of Immune-Associated Genes in the Kidney of Cultured Large Yellow Croaker Larimichthys crocea in the East China Sea Area

To explore the effect of environment conditions on immune activity of fish, eight immune-associated genes responsible for innate immunity were selected from the Gen Bank, i.e. Pgrn-a, Ifit2, P-hepcidin, Lect2, β2m, Irf1, Il25 and Hsp96, and the m RNA expressions of them in the kidney of cultured large yellow croaker Larimichthys crocea in different sea areas in the East China Sea were examined with q PCR techniques. In the contrasts of immune-associated gene expression between areas and populations, significant differences were found, expression levels of these immune-associated genes were lower in the clear water area than in the poor water quantity area, and lower in May than in October. MY was more sensitive to environmental factors than DQ, which was coincident with the water quality in the culturing areas. Differential analyses of the expression levels of these immune-associated genes showed that significant up-regulation could be triggered by poor environmental factors. The expression patterns indicated that the expression levels of these genes were sensitive to ecological changes, thereby the immune-associated genes, especially Pgrn-a, Ifit2, β2m, Il25 and Hsp96, might serve as immediate and sensitive indicators of population immunologic vigor and ecosystem health. But the expression of immunity-associated genes at the level of gene transcription is highly influenced by multiple factors, and the exact causes or influencing factors of the up-regulation or down-regulation of these genes still need further thorough investigation.

微颗粒饲料中添加扇贝肽对大黄鱼稚鱼生长性能、消化酶活性和抗氧化力的影响

为了评估在人工微颗粒饲料中添加扇贝肽(Scallop peptide)对大黄鱼(Larimichthys crocea)稚鱼的生长性能、摄食相关基因表达、消化酶活性、抗氧化力和炎症基因表达的影响。本实验以初始体质量(8.16±0.84)mg的大黄鱼稚鱼为研究对象,在饲料中分别添加0%、0.05%、0.1%和0.2%的扇贝肽,共配制4种等氮(粗蛋白54.15%)等脂(粗脂肪16.52%)的人工微颗粒饲料,进行为期30 d的摄食生长实验。研究表明,饲喂0.1%扇贝肽饲料稚鱼的FBL(终末体长)、FBW(终末体质量)和SGR(特定生长率)显著高于对照组(P<0.05)。在摄食相关基因表达方面,与对照组的相比,人工微颗粒饲料中添加0.1%扇贝肽可显著提高大黄鱼稚鱼的npy(神经肽Y)和ghrelin(饥饿素)的mRNA表达量,相应地,当稚鱼被饲喂含有0.1%扇贝肽的饲料时,稚鱼的trh(促甲状腺激素释放激素)和leptin(瘦素)的mRNA表达量显著降低(P<0.05)。在消化酶活性方面,饲喂0.1%扇贝肽饲料稚鱼的胰腺段和肠段的胰蛋白酶活性显著高于对照组,同时饲喂0.05%扇贝肽饲料的稚鱼胰腺段的胰蛋白活性也显著高于对照组(P<0.05)。在肠道发育方面,与对照组相比,在人工微颗粒饲料中添加0.1%扇贝肽可以显著提高稚鱼肠道刷状缘的LAP(亮氨酸氨基肽酶)和AKP(碱性磷酸酶活性)活性(P<0.05)。在抗氧化力方面,与对照组相比,人工微颗粒饲料中添加0.1%扇贝肽可显著提高稚鱼内脏团SOD(超氧化物歧化酶)活性,且降低稚鱼内脏团丙二醛(MDA)的含量(P<0.05)。饲喂0.1%扇贝肽饲料稚鱼的内脏团总一氧化氮合酶(T-NOS)活性和诱导型一氧化氮合酶(iNOS)活性显著高于对照组(P<0.05)。在炎症基因表达方面,与对照组相比,添加0.1%和0.2%扇贝肽饲料可显著降低稚鱼的il-1β(白介素-1β)、il-6(白介素-6)和il-8(白介素-8)的mRNA表达量(P<0.05)。综上所述,在人工微颗粒饲料中添加0.1%扇贝肽可以增强促食因子的mRNA表达量、抑制厌食因子的mRNA表达量、增强消化酶活性、提高抗氧化力及缓解炎症反应,最终提高大黄鱼稚鱼的生长性能。