| To investigate the reasons for the differentiation of individuals in the same growth group of cultured Nibea albiflora,this study used 8000 artificially cultured 3-month-old Nibea albiflora(body weight range:26.6 g-1.9 g)as experimental materials,and the top 5%individuals with the highest body weight(fast-growing group FG,body weight range:26.6 g-17.8 g)and 50%individuals with the middle body weight(ordinary group CG,body weight range:12.2g-7.0 g)as the research objects,In August 2021,a study was carried out on the differences in phenotype,respiration and excretion,hypoxia tolerance physiology and liver transcriptome between fast-growing and common populations.The results of the study showed that:(1)The analysis of biological phenotypic traits showed that FG>CG(P<0.05)was observed in all 33 biological phenotypic traits involved,indicating good differentiation between the two in terms of biological phenotypic traits;Through path analysis,the key core variable that affects BW(body weight)in the FG population is X3(body height).Through partial regression analysis,the optimal equation between the morphological traits of FG and BW is Y(FG)=0.452X6+0.079X1-0.3101;In the CG population,the key core variable affecting BW is X1(full length).Through partial regression analysis,the optimal equation between the morphological traits of CG and BW is Y(CG)=0.203X1+0.163X3+0.373X6-16.742.(2)From the aspect of shape to mass ratio indicators,only C12(net body mass/body mass),C13(visceral mass/body mass),Ci6(stomach mass/body mass),C17(gill mass/body mass),C19(net volume/volume),and C20(net body mass/net volume)showed significant differences(P<0.05)in the 20 evaluation indicators of shape to mass in the experimental subgroup;After principal component analysis,a total of 5 principal components with feature roots greater than 1 were obtained,with a cumulative contribution rate of 82.557%.Among them,PC1 can be classified as a motor and sensory factor related to food intake,PC2 can be classified as a food conversion factor.Based on the principle that the error is greater when the principal component is lower,PC3,PC4,and PC5 are all classified as energy utilization factors.The gradual introduction and removal method is used to screen out C15(liver and pancreas mass/body mass)and C16(stomach mass/body mass),C17(gill mass/body mass)and C19(net body mass/net volume)are the key variables to distinguish FG and CG.The Fisher classification function equations established can clearly distinguish the two discrimination results show that the discrimination accuracy of FG P1 and P2 are 86.6%and 96.3%respectively;The discrimination accuracy of CG,P1 and P2,were 96.7%and 87.9%,respectively,with a comprehensive discrimination accuracy of 91.97%.(3)In terms of diurnal ammonia excretion and oxygen consumption rhythms,the diurnal oxygen consumption rates were "diurnal>nocturnal"(P<0.05)and "diurnal ≈nocturnal"(P>0.05),respectively,and the diurnal ammonia excretion rates were "diurnal≈ nocturnal"(P>0.05)and "diurnal>nocturnal"(P<0.05),respectively."(P>0.05)and"diurnal>nocturnal"(P<0.05),and the diurnal ammonia excretion rates of both species were FG<CG(P<0.05),indicating that the diurnal ammonia excretion and diurnal oxygen consumption rhythms of both species were significantly different;at the point of asphyxiation,both species showed FG<CG(P<0.05)with 24:00 hour as the starting point of the experiment.At the point of asphyxiation,FG<CG(P<0.05)and oxygen content in water at the point of asphyxiation at 12:00 a.m.were not significantly different(P<0.05),indicating that FG had a stronger ability to tolerate hypoxia than CG in the early morning hours.(4)Let the time of death of the first fish in hypoxia be S,T2=0.9*S,T1=0.9*S/2,T3=2h of reoxygenation,T4=4h of reoxygenation and Ts=6h of reoxygenation.From the perspective of liver hypoxia tolerance physiology,the ACP,POD and CAT activity of FG during "hypoxia-reoxygenation" were significantly reduced at T1(P<0.05),while AKP activity showed an "increase-decrease" trend at T0,T1 and T3(P<0.05),SOD activity decreased significantly at T1(P<0.05)and increased significantly at T3(P<0.05);AKP,ACP,POD,CAT and SOD activity of CG increased significantly at T1(P<0.05)and decreased significantly at T2(P<0.05),and remained stable during the subsequent "reoxygenation"process.(P>0.05)and remained stable throughout the subsequent "reoxygenation" process.(5)Using |log2FC|>=1 and FDR<=0.01 as criteria,genes with log2FC>=1 were defined as up-regulated genes and genes with log2FC<=-1 were defined as down-regulated genes.A total of 31,377 transcripts with length greater than 1000 were screened in liver samples from the two experimental subgroups,with CG as the control group,there were 2264 FG up-regulated genes and The GO and KEGG enrichment analysis of differentially expressed genes showed that the differentially expressed genes were mainly enriched in GO for biological processes such as metabolic processes,organism mucosa,intercellular groups and catalytic activity,while in KEGG they were mainly enriched in pathways such as sugar digestion and absorption,bile secretion and antigen production. |
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