Abstract：Largemouth bass (Micropterus salmoides) is a very important commercial farming fish with the annual production of more than 340 000 t in China. But it is a carnivorous teleost, and a large amount of forage fish and fish meal were used as food for largemouth bass every year. The residual forage fish and fish meal not only increase the culture costs, but also pollute waterbodies and farmlands seriously. In order to reduce culture costs and protect the natural environment, the selective breeding of the largemouth bass strain suitable for formulated feeds was carried out. It is a way to improve the effective conversion capability of largemouth bass for formulated feeds. In the previous study, the lipid levels of the formulated feeds have significant effects on the expression levels of 2 lipoprotein lipase genes (LPL type1 and LPL type2) in livers of largemouth bass. The report suggests the 1 genes potentially related to the adaptability of largemouth to formulated feed. In the current study, the primers of LPL genes were designed according to the known cDNA and the PCR amplifications were performed with largemouth bass genome DNAs as templates. After amplifying and sequencing, the genomic sequences of LPL type1 gene with the length of 6 170 bp were identified including 10 exons and 9 introns, and LPL type2 gene with the length of 4 419 bp were identified including 5 exons and 4 introns. By use of direct sequencing, eleven SNPs were detected in LPL type1 gene, and 6 SNPs were detected in LPL type2 gene. A total of 192 individuals from the cultured adult fish population fed on iced fresh fish and a total of 142 individuals from the cultured juvenile fish population fed on formulated feed were genotyped according to the SNP sites. The results showed that the 11 SNPs in LPL type1 were closely linked, and were named as T+156A. As well as the 6 SNPs in LPL type2 were closely linked, and named as C-224T. But the SNP sites were not closed linked between the 2 genes. The genotype frequency and gene frequency of the SNPs were similar between the 2 populations. And the calculations showed that the 2 populations were in Hardy-Weinberg equilibrium for the 2 SNPs. The general linear model was applied to analyze the relationship between SNPs and the full/empty traits, as well as the growth traits of largemouth bass. The results showed that there were no significant association between the LPL SNP sites and the growth traits of the adult fish fed on iced fish (P＞0.05). But in the juvenile fish population fed on formulated feed, the T+156A SNP was significantly related to the full or empty of the stomach and intestine. And the fish with AA genotype of T+156A SNP have significantly higher growth trait values in body weight and body length than those with TT genotype (P＜0.05). The results hinted that AA genotype in T+156A SNP has significant association with the adaptability of largemouth bass to the artificial diets. LPL type1 gene can be used as a candidate gene for the largemouth bass fed on formulated feeds, with high survival rate and fast growth rate. The current study not only provides the reliable research data to promote the breeding work of new strain of largemouth bass adaptable to formulated feed, but also provides the experiences and references for the bait domestication work of other carnivorous fish.
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