| Takifugu rubripes belongs to the class of teleosts,pufferfishes,puffer family,and genus Oriental puffer.It is an important marine economic aquaculture fish and a widely used aquaculture model organism.Because of its delicious meat,rich nutrition and high protein content,it is deeply loved by the majority of people.With more and more people in China accepting edible pufferfish and increasing demand abroad,many farmers choose to increase the breeding density in order to increase production,but too high breeding density will bring about slow growth of fish,It has a series of negative effects such as metabolic dysfunction and decreased immune function.Therefore,it is very important to study the effect of breeding density on the growth of Takifugu rubripes and to screen out a reasonable breeding density range.In this experiment,the juvenile Takifugu rubripes(initial body weight(9.27±0.15)g)in the factory recirculating aquaculture mode was used as the research object,and 3 breeding density groups were set up,respectively 4.64 kg/m~3(SD1 group),6.95 kg/m~3(SD2 group)and9.27 kg/m~3(SD3 group),each density group was set with 3 replicates,and the experimental period was 8 weeks.Samples were collected on the 14th,28th,42nd and 56th days of the experiment.By comparing and analyzing the growth traits,body index,liver function,antioxidant capacity,digestive capacity,and transcriptome of brain and liver of juvenile Takifugu rubripes between different density groups,the following results were obtained:1.The growth characters and survival rate of Takifugu rubripes are obviously affected by the breeding density.At the beginning of the experiment,the body weight,weight gain rate,specific growth rate,and body length growth rate of SD1 group were significantly higher than SD2 group and SD3 group(P<0.05).Significantly(P<0.05),the body weight and survival rate of SD3 group at the end of the experiment were significantly lower than SD1 and SD2 groups(P<0.05).Breeding density had no significant effect on the body index of Takifugu rubripes.At the end of the experiment,there was no significant difference in fatness,liver body index and visceral body index among the breeding density groups(P>0.05).2.Breeding density had a significant effect on ALP and AST in the liver of Takifugu rubripes,but had no significant effect on ALT.At the end of the experiment,the ALP of SD3group was significantly higher than that of SD1 group(P<0.05),the AST of SD1 group was significantly lower than that of SD2 group and SD3 group(P<0.05),and the ALT of the three density groups had no significant difference(P>0.05).This indicated that high breeding density would cause certain damage to the liver of Takifugu rubripes.3.The effect of breeding density on the antioxidant capacity and digestibility of Takifugu rubripes mainly occurred in the later period of the breeding experiment.The activity of superoxide dismutase(SOD)in SD3 group has been significantly lower than that in SD1 group and SD2 group since 28 days(P<0.05).The activity of catalase(CAT)in SD1 group was significantly higher than that in SD2 group and SD3 group at 42 d(P<0.05),and at 56 d,it decreased significantly with the increase of breeding density(P<0.05).The activity of glutathione peroxidase(GSH-PX)in SD3 group was significantly lower than that in SD1 group and SD2 group at 56 days(P<0.05).The content of malondialdehyde(MDA)in SD2 group and SD3 group was significantly higher than that in SD1 group at 56 days(P<0.05).There was no significant difference in total antioxidant capacity(T-AOC)throughout the experimental period(P>0.05).The results showed that the stress caused by high breeding density would inhibit the antioxidant capacity of Takifugu rubripes to a certain extent.In addition,the intestinal lipase activity of SD3 group was significantly lower than that of SD2 group and SD1 group at 56 days(P<0.05),while the intestinal amylase activity had no significant difference during the experimental period(P>0.05),indicating a high breeding density The induced stress also weakened the digestion ability of Takifugu rubripes to a certain extent.4.Breeding density had a significant effect on gene expression in the brain of Takifugu rubripes.In this study,a comparative analysis of the transcriptome was carried out on the brain tissue of Takifugu rubripes with different breeding densities,and a large number of differentially expressed genes were obtained.Then,the GO and KEGG enrichment analysis of the differentially expressed genes was carried out.Among them,GO items with higher enrichment include neurotransmitter biosynthesis,acetate metabolism,sequence-specific DNA binding,epidermal morphogenesis,neuropituitary hormone activity,calcium ion import,etc.KEGG with higher enrichment Pathways include neuroactive ligand-receptor interaction,MAPK signaling pathway,glycolysis/gluconeogenesis,adrenergic signaling,calcium signaling pathway,etc.The enrichment of differentially expressed genes to these GO entries and KEGG pathway indicated that the breeding density had certain effects on the nerve conduction,growth and development,and physiological metabolism of Takifugu rubripes.In addition,some genes that were greatly affected by breeding density and related to growth or neurotransmission were also screened.The more representative genes were LRRC17,ZIC1,ZIC2,ZIC5,PENK,SLC6A4,TPH2 and SHANK3.These genes are either related to the growth and development of Takifugu rubripes,or regulate the mental behavior of Takifugu rubripes,and directly or indirectly affect the growth and feeding state of Takifugu rubripes.5.Breeding density also had a significant effect on gene expression in the liver of Takifugu rubripes.In this study,a comparative analysis of the transcriptome was carried out on the liver tissues of Takifugu rubripes at different breeding densities,and a large number of differentially expressed genes were obtained,and then the differentially expressed genes were subjected to GO and KEGG enrichment analysis.Among them,the highly enriched GO items are serine aminopeptidase activity,CTP synthase activity,B cell receptor complex,scavenger receptor activity,lymphocyte activation,etc.These items are closely related to biological amino acid metabolism,energy metabolism,cellular immunity,etc.The highly enriched KEGG pathways include MAPK signaling pathway,lysine degradation,PPAR signaling pathway,Fox O signaling pathway,glycerophospholipid metabolism,etc.Response,lipid metabolism,and oxidative stress are closely related.In addition,some genes that are greatly affected by breeding density and are related to growth or immunity,such as SLC27A4,ZBTB16,CD79A,CD79B,SYK and CXCR4,etc.These genes directly or indirectly affect the growth development and health of Takifugu rubripes.To sum up,the breeding density has a significant effect on the growth traits,liver function,antioxidant capacity,digestive capacity,immune capacity,and life behavior of juvenile Takifugu rubripes.The longer the time and the higher the density,the greater the impact on the growth and development,antioxidant capacity,immune capacity and stress of the juvenile fish,namely SD3group>SD2 group>SD1 group.Considering comprehensively,the juvenile Takifugu rubripes showed better growth performance and living conditions under the breeding density test conditions of SD1 and SD2 groups.Therefore,it is suggested that the breeding density of juvenile Takifugu rubripes should be controlled in the factory recirculating aquaculture mode.It is appropriate within the range of 4.64～6.95 kg/m~3. |
PDF Full Text Request