Phylogenetic Relationships Of Myriapoda And The Mitochondrial Genome Of Scolopendra Multilan Meirong Gong

Four monophyletic groups have traditionally been united as Myriapoda, namely Chilopoda, Pauropoda, Diplopoda and Symphyla. The relationships of myriapods are central to most questions in higher-level arthropod phylogeny. This research reviewed the relationships of the myriapods to other arthropoda, based on morphological and molecular sequence data and the studies of developmental biology. The review was followed the major controversies in the higher-level phylogeny of myriapods.The complete 18S rRNA sequences of four groups of Myriapoda plus Hexapoda (Protura, Diplura, Insecta) and Crustacea were used for phylogenetic study. Limulus polyphemus (Chelicerata) was included as an outgroup. The sequence data were used to infere phylogeny by maximum-parismony and maximum-likelihood methods. The results revealed that: 1. The Myriapoda are polyphyletic. 2. The Chilopoda appears to be sister to a clade containing the Insecta and Crustacea, but with low bootstrap support. Therefore, the position of the insect-crustacean is not resolved.. 3. The Diplopoda, Pauropoda, Symphyla and Hexapoda (Protura, Diplura) clustered to a clade. The cluster of Symphyla plus Diplura is significantly supported. Whereas the classification status of Pauropoda remains uncertain. 3. The Chilopoda and Diplopoda are monophyletic group respectively.Although there are some limitations, the mitochondrial DNA as a modelsystem is being used as a powerful tool in phylogeny analysis. It is the only molecular marker that can be used in the phylogenetic studies at genomic level. At least 35 arthropoda mitochondrial genomes were sequenced so far. Scolopendra multilan is a common species belonging to Scolopendromorpha, Chilopoda. The sequence of Scolopendra multilan mtDNA determined is 11700 bp in length, about 70% of the complete sequence. The sequenced portion contains 2 rRNA genes, 1 A+T-rich region, 8 protein-coding genes and 18 tRNA genes. The gene content of Scolopendra multilan is similar to that of the other arthropoda, and gene rearrangements are observed as in other myriapods. The start reading framae and stop codons, base composition in protein-coding genes and the codon usage of amino acids in Scolopendra multilane were compared with the three other myriapods. Meanwhile, base composition in rRNA genes, the secondary structrues of tRNA and the potential stem-loop structure in the noncoding region were also analysesed in the present study.