Population Genetics&MicroRNA Analysis Of Rimicaris Exoculata From Mid-Atlantic Ridge And Antiviral Compounds Screening From Marsupenaeus Japonicas

Rimicaris exoculata is a specialist adapted and specific to Mid-Atlantic Ocean Ridge (MAR). As the discovery of big population of this species in SMAR01station in the South Mid-Atlantic Ocean Ridge (SMAR), R.exoculata has been comfirmed to form several huge aggregations along the9000km-segment of MAR. This population connection of R.exoculata has been one of the most fascinating topic in hydrothermal vents ecology.Previous studies focused on R.exoculata populations along the northern part of MAR (NMAR). Very few samples were collected from the SMAR, and the huge and extensive Romanche Fracture zone in the equatorial belt was considered to be migration barrier for those vent benthos. In this study, the partial cytochrome oxidase I gene in the mitochondrial genome (mtCOI) and11microsatellite loci were used to analyze the genetics diversity of the newly discovered SMAR01population, and its connection to the norther ones. The main results were as follows:(1) Partial mtCOI sequences from34individuals and genotype of11microsatellite loci from32individuals were obtained. Among them,12haplotypes for mtCOI and130alleles (for microsatellite) were identified.(2) SMAR01population exhibited relative high haplotype diversity (0.754) and low nucleotide diversity (0.0024). The12haplotype formed a star-like topological structure, with the dominate type located in the center. Demorgraphic history inferred from the mismatch distribution was in agreement with the sudden-expansion model. For the11microsatellite loci, four loci exhibited significant deviation from the Hardy-Weinberg equilibrium, as the observed heterogeneity was much lower than the expected ones.(3) Compared with the northern populations, SMAR01population held much higher percentage of private haplotype. And the pairwise Fst value between SMAR01and other northern populations were higher than those between northern populations or as a whole, showing some degree of differentiation between south and north. Although gene flow between SMAR01population and norther ones ranged from8.17-27.03, it looked like that this degree of connection was not able to homogenize all populations on both sides of the equator.(4) FCA analysis comfirmed that there was light but significant differentiation between SMAR01and norther populations. A similar phenomenon was observed in one previous study, in which the statistic power was not large enough owing to the small smaple size. (5) Mismatch distribution from all populations agreed with the sudden-expansion model, and the Tajima’s D value for all of them were significant negative. However, when Tajima’s D tests were done in every potential group of different populations, the value and the statistic power of groups with SMAR01tended to be much smaller than others. This indicated that the connection between the north and south populations might decline after the recent expansion.Dense aggregation formation of R.exoculata in the hydrothermal vents fields along the MAR suggests their successful adaptation to the extreme environment. As widespread involvement in different cellular processes, microRNA is considered to be potential molecular marker of biological adaptation and evolution. So knowledge about microRNAs in R.exoculata will promote our understanding of vents species adaptation and evolution. For this purpose, we utilized high-throughtput sequencing method to deep mining microRNA in R.exoculata. The results were(1) We identified135microRNAs of high-and median-expression,101of which were known microRNAs shared between R.exoculata and other animals (based on miRBase V20.0), and the rest were potential specific microRNA in R.exoculata. The101known microRNAs were divided into three groups: group Ⅰ, containing27microRNAs, were found in almost every phylum in animal kindom; group Ⅱ, containing10microRNAs, were found only in protostomes; group Ⅲ, containing15microRNAs, were exclusively found in a variety of arthropods. Three out of the101microRNAs were previously found to be lost or unidentified in crustacean species.(2) We also analyzed the arm usage and iso-miRs in R.exoculata.To reveal the roles of bioactive compounds produced in crustacean under virus infection, we chose shrimp Marsupenaeus japonicas to screen for the potential small molecules. GC-MS was used to identify molecules that were differently expressed between the control group and the group injected with WSSV. Several compounds were obtained. The results showed that picolinic acid at high concentration (200mM,50μl) presented an antiviral activity. The mechanism of this process was not very clear. Our study indicate that shrimp was able to produce some molecules to facilitate the antiviral processes of host.