Association of clonal diversity and population growth in the small-type rotifer Brachionus koreanus during hatchery mass production

Abstract In this study, we identify clones of S-type rotifers Brachionus koreanus based on haplotypes of mitochondrial gene cytochrome c oxidase subunit I (mtCOI) and microsatellite DNA genotypes. We then study how clonal diversity affects the population growth of rotifers in a mass culture at a hatchery using a lot of B. koreanus rotifers for analysis. Microsatellite DNA markers were also developed to identify clones of B. koreanus . Clones of B. koreanus were identified based on haplotypes of mtCOI, microsatellite genotypes, as well as a combination of these haplotypes and genotypes. Three haplotypes of mtCOI, three clones based on microsatellites, and six clones based on a combination of mtCOI haplotypes and microsatellite genotypes were identified. The population growth rate of mass-cultured rotifers was monitored for a month, and the correlation between population growth rate and these clonal diversities was analyzed. Observed was a significant positive correlation between the population growth rate and haplotype diversity ( r  = 0.695, P  = 0.004), however no correlations were found between the population growth rate and clonal diversity based on either microsatellite genotypes ( r  = 0.320, P  = 0.245) or a combination of mtCOI haplotype and microsatellite genotypes ( r  = 0.435, P  = 0.105). Some clones shared mtCOI haplotypes and microsatellite genotypes suggesting sexual reproduction occurred in the hatchery stock of B. koreanus . Statement of relevance This study showed the correlation between population growth rate and clonal diversities based on mtCOI haplotypes and microsatellite DNA genotypes in Brachionus koreanus . There was a significant correlation between the population growth rate and haplotype diversity and suggested genetic factor is one of the possible causes affecting population growth rate. Our results will be useful in mass-production and maintenance of Brachionus koreanus at hatcheries.