The Development Of Microsatellite Markers Of Brachionus Plicatilis

Brachionus plicatilis, a euryhaline species of the Rotifera, is widely distributedin both freshwater and marine environments. The high caloric value, small size andrelative ease of mass culture have all served to make B. plicatilis the only artificialbreeding species in the field of large-scale mariculture as a kind of important nurserybait. The life history of B. plicatili is comprised of two alternation of generations,parthenogenesis and sexual reproduction, which make them an ideal model forbiological studies. During parthenogenesis, females produce diploid amictic eggsthrough mitosis to clone themselves; while in sexual reproduction stage, femalesgenerate haploid mictic eggs by meiosis, which develop into males if not fertilizedand into resting eggs if fertilized. Those resting eggs have thick outer shells, acharacteristic that renders them both the resistance to harsh environments and theability to hatch under favorable conditions in order to start a new round ofparthenogenesis.The unique alternate life cycle of B. plicatilis，which affected bymany internal and external factors so as to produce sexually reproduction, hasthe important significance for reproduction and diversity of population.The earlier studies on B. plicatilis mostly focused on the classification andbreeding cultivation of B. plicatilis. In recent years, experts at home and abroad havealready begun the molecular biology and genetic researches on B. plicatili. However,due to limited the polymorphic genetic markers, the reaseearchers only made somepreliminary progress. It is a long way that to realize widespread application of SSR inthe molecular studies of B. plicatilis as the same as that in other organisms.In this study, a microsatellite enriching library of B. plicatilis was constructedwith FIASCO method with biotinylated (CCA)8probe. In total,56microsatelliteswere obtained and used to determine the genetic diversity of a cultured B. plicatilispopulation from Shandong Peninsula. Eight microsatellites were found to bepolymorphic. The number of alleles per locus ranged from2to4. The observed and expected heterozygositied ranged from0.1471to0.6364and from0.3139to0.6559,respectively. The genetic deviation index and polymorphism information contentranged from-0.3624to0.05353and0.2615to0.5841, respectively. No polymorphiclocus deviated from Hardy–Weinberg equilibrium and two loci were in linkagedisequilibrium. All the results indicated that the genetic diversity of the population ofB. plicatilis was not very abundant. In addition, the PAGE genotying results showedthat the population of B. plicatilis was species complex which obviously consist of atleast two sibling species. Although there were differences among the amplifications ofsibling species of B. plicatilis, those polymorphic microsatellite markers can still beused for the genetics analysis of the sibling species. Furthermore, it is requisite todistinguish of B. plicatilis because the sibling species are extremely similar and it isreliable to distinguish with molecular biology method based on morphologicalclassification.It is necessary for the development of microsatellite markers of B. plicatiliseither as initial feeds or model organism, and the microsatellites developed in thisstudy will facilitate the genetic diversity and population structure analysis ofB. plicatilis.