Nematode Diversity of Qingdao Coast Inferred from the 18S Ribosomal RNA Gene Sequence Analysis

The 18S ribosomal DNA gene （18S rDNA） sequences （approxtmately 1300 bp in length） were amplified from the DNA extracted from the free-living marine nematodes collected from the inter-tidal sediment of Qingdao coast in bulk with nematode specific primers. The PCR products were cloned, re-amplified, digested with Rsa I and Hin61 restriction endonucleases and separated in agarose gel. Among 17 restriction fragment length types, types 1, 2 and 6 covered 61.2%, 14.4% and 9.3% of the clones analyzed, respectively, while the remaining 14 only covered 21 clones, which accounted for 15.1% of the total. Twenty-four representative clones were sequenced and phylogenetically analyzed by referring to those currently available in RDP and GenBank databases. Although it was hard to assign these sequences to known species or genera due to the lack of the 18S rDNA sequence data of known marine free-living nematodes, the obtained sequences were assigned to the nematodes of Adenophorea. Among them, twelve sequences were close to Pontonema vulgate and Adoncholaimus sp., four to Daptonema procerus and two （identical） to Enoplus brews. Our results showed that free-living marine nematode diversities could be determined by PCR retrieving and analysis of the 18S rDNA sequences and an 18S rDNA sequence could be assigned to a species or a genus only if the 18S rDNA sequences of the free-living marine nematodes were accumulated to some extent.

Molecular Identification of a Species in Genus Nannochloropsis

Nannochloropsis is a genus of marine eukaryotic unicellular algae,which belongs to class Eustigmatophyceae.The spe-cies of Nannochloropsis which are fine rotifer feed and rich in eicosapentaenoic acid(EPA)are economically important.Species in this genus are usually 2-5μm in size and are morphologically similar,which makes their identification difficult.We obtained a monoclone of Nannochloropsis with plating method in this study.DNA was extracted and the quality was determined by restriction enzyme digestion and spectrophotometer analysis.The DNA extracted was used to amplify the sequences of 18S ribosomal RNA gene,ITS region of ribosomal RNA transcription unit and rbcL gene.The phylogenetic analysis was carried out by constructing the neighbor-joining trees with Tamura-Nei distances.The phylogenetic analysis showed that the monoclone is N.oceanica.