Analysis Indirect Genetic Effects Of Behavior And Growth Traits Of Fenneropenaeus Chinensis Under Competitive Environment

Chinese shrimp(Fenneropenaeus chinensis)is one of the representative aquaculture species in China.Since the outbreak of white spot syndrome virus disease in 1993,the output has dropped sharply,and the current output is about 56,000 tons.F.chinensis has the habit of attacking and cannibalism in breeding conditions.Studies have shown that under the restrictive feeding mode,the F.chinensis population has a strong competitive interaction,which has a heritable effect on the growth and survival of individuals.In order to further study the heritable effect of social interaction behavior of F.chinensis in a competitive environment.This study(1)Set different farming density gradients and analyze the behavior of shrimp under different densities.(2)Use the high-density breeding model to increase the intensity of competition and interaction between individuals within the group,and analyze the direct genetic effect(DGE)and indirect genetic effect(IGE)parameters of growth and survival traits.(3)Combining data of body weight and survival traits of a total of 300 test groups from 3 generations,combined with high-throughput SNP information and pedigree information evaluate whether the parameters of DGE and IGE of F.chinensis harvested weight can be more accurately estimated based on the data of a large-scale test group.Finally,establish a competitive environment to stimulate the expression of competition-related genes of F.chinensis and analyze the expression of competition-related genes calcineurin B in different families and individual nerve tissues.The research results will be a precise improvement of shrimp for reference.1. The effect of density on social interaction behavior of F.chinensisIn order to explore the effect of different densities on the behavior of F.chinensis.In this paper,three density gradients of 28 shrimp/m~2(DL),85 shrimp/m~2(DM),and142 shrimp/m~2(DH)are set.The differences between the four behavioral indexes such as the moving speed,moving distance,frequency of body contact and activity(proportion of activity time in total observation time)of F.chinensis under different densities were analyzed.In this paper,three density gradients of 28 tails/m2(DL),85tails/m2(DM),and 142 tails/m2(DH)are set up to analyze the change of behavior index of the moving speed,moving distance,body contact frequency and activity of F.chinensis under different densities.The results showed that the behavioral indicators observed in the experiment were positively correlated with the observed density,and the average moving distance and the average body contact frequency between the groups reached extremely significant difference(P<0.01);the activity did not reach a significant difference with increasing density.Moving speed except that the DL and DM groups did not reach a significant difference,there was a significant difference between DH and the other two groups(P<0.05).When the density increases from DL to DM,the frequency of body contact(54 times/shrimp.hour to 444 times/shrimp.hour)increases significantly,which in turn affects the rise of other behavior indicators.There is a strong social interaction between individuals due to lack of space.2. Analysis of indirect genetic effects on adult body weight of F.chinensis under high density modeTo investigate the heritable effects of social interactions in high-density breeding populations of F.chinensis,a total 4800 shrimps from 100 families of the G13generation were physically labeled,grouped and mixed.The group rearing mode(GRM)was that,each family was separated into 3 groups(16 individuals each)and assigned to3 cages randomly,and each cage containing 3 random families,which mean family could combined with 6 other families.The initial breeding density was about 98individuals per square meter.The growth test lasted 80 days,and genetic parameters of body weight and survival traits were evaluated using a two-trait animal model including IGE.Results showed that the proportion of the total genetic variance of harvested body weight to the phenotypic variance was 0.224±0.145 based on the two-trait animal model.The IGE variance of the harvested weight contributed 196%of the total genetic variance.Since the DGE-IGE covariance is negative(-0.036±0.012),the enlarged covariance contributes-228%to the total genetic variance,which also offset the contribution of IGE variance to the total variance completely.The significant negative correlation between DGE of harvested body weight and the IGE(-0.709±0.179)indicated a strong competitive interaction in experimental population under the high-density breeding mode,which also greatly reduced the available total genetic variation.The estimated heritability after the conversion of survival traits was 0.254,and IGE variance could not be divided.3. Analysis of indirect genetic effects of harvest weight in F.chinensis under multi-generation competitive environmentTo investigate whether a larger-scale test groups combined with high-throughput typing SNP data can improve the accuracy of genetic parameter estimates related to DGE and IGE.An experiment population of 9131 individuals from 300 test groups in3 generations(G10-G12)was employed taking advantage of single-trait and two-trait animal models.We also employed the traditional best linear unbiased prediction(the pedigree-Based Best Linear Unbiased Prediction,p BLUP)and single-step genomic(single step genomic BLUP,ss GBLUP)methods in the following study.21,612 SNPs were strictly filtered from all 614 parents of G10-G12 generations taking advantage of high-throughput sequencing.The results show that the ratio of IGE variance to standard error is 3.90?4.61,and the ratio of IGE-DGE covariance to standard error is 4.33?4.88.The accuracy of variance component estimates is better than most of other existing reports,which means that expanding numbers of test groups can effectively improve the accuracy of IGE-related genetic parameter estimates.The ratio of the total genetic variance of the harvested weight to the phenotypic variance by 4 different models is0.27-0.33.The prediction accuracy of ss GBLUP for DGE is improved by 10.81%compared with p BLUP,and the prediction deviation of ss GBLUP for DGE is smaller(1-0.67<1-0.59),which is also closer to the true value.In addition,the estimation results of the variance components of DGE and IGE indicate that individuals with strong competitiveness also have better survival performance,and the strong competitive interaction within the group under the competitive environment reduces the available total genetic variation.4. An analysis of genetic variation for calcineurin B gene expression in F. chinensis To investigate the expression characteristics of the calcineurin B gene(Fc CN-B)of F.chinensis at the level of individuals and families in a competitive environment.32 full-sib families were randomly selected from the G13 F.chinensis breeding core group constructed in 2018.A total of 640 shrimps with 20 shrimps from each family were randomly assigned to 20 cages with shrimp from 31 other families and then reared for2-3 days.Before sampling,the starved 2 days emptied their intestines,then put a small amount of feed on the cages to create a competitive environment,and then quickly took the ganglia of each shrimp and Real-time PCR method was used to detect the expression of Fc CN-B gene.The boxplot analysis of Fc CN-B gene expression showed that the expression level at the individual level is positive skew distribution,the mean(8.25)is less than the median(6.95),and existence of maximal individuals.The range is 43.48,the maximum value is 44.48 times the minimum value,and the coefficient of variation of expression between individuals is 67.52%.The coefficient of variation of Fc CN-B expression among families is relatively small(19.31%),and the maximum value is only2.20 times the minimum value.One-way analysis of variance showed that the expression level of Fc CN-B gene was significantly different at the family level(P<0.05),and this gene may be involved in regulating the competitive behavior of F.chinensis.The results of this study provide reference data for the analysis of the molecular mechanism of the competitive behavior of F.chinensis.