Complete mitochondrial genome sequences of two parasitic/commensal nemerteans, Gononemertes parasita and Nemertopsis tetraclitophila (Nemertea: Hoplonemertea)

Particle and Fibre Toxicology

Shi-Chun Sun³  Malin Strand²  Per Sundberg¹  Wei Shi⁴  Hai-Xia Chen¹  Dong-Li Xu³  Wen-Yan Sun³ 

[1] Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, SE-405 30 Gothenburg, Sweden;Swedish Species Information Centre, Swedish University of Agricultural Sciences, Box 7007, SE 75007 Uppsala, Sweden;Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China;Key Laboratory of Marine Bio-resource Sustainable Utilization (LMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China

关键词: Phylogeny;    Mitochondrial genome;    Parasitic/Commensal;    Nemertopsis tetraclitophila;    Gononemertes parasita;    Nemertea;   

Others  :  804226
DOI  :  10.1186/1756-3305-7-273

 received in 2014-04-20, accepted in 2014-06-14,  发布年份 2014

【 摘 要 】

Background

Most nemerteans (phylum Nemertea) are free-living, but about 50 species are known to be firmly associated with other marine invertebrates. For example, Gononemertes parasita is associated with ascidians, and Nemertopsis tetraclitophila with barnacles. There are 12 complete or near-complete mitochondrial genome (mitogenome) sequences of nemerteans available in GenBank, but no mitogenomes of none free-living nemerteans have been determined so far. In the present paper complete mitogenomes of the above two parasitic/commensal nemerteans are reported.

Methods

The complete mitochondrial genomes (mitogenome) of G. parasita and N. tetraclitophila were amplified by conventional and long PCR. Phylogenetic analyses of maximum likelihood (ML) and Bayesian inference (BI) were performed with both concatenated nucleotide and amino acid sequences.

Results

Complete mitogenomes of G. parasita and N. tetraclitophila are 14742 bp and 14597 bp in size, respectively, which are within the range of published Hoplonemertea mitogenomes. Their gene orders are identical to that of published Hoplonemertea mitogenomes, but different from those of Palaeo- and Heteronemertea species. All the coding genes, as well as major non-coding regions (mNCRs), are AT rich, which is especially pronounced at the third codon position. The AT/GC skew pattern of the coding strand is the same among nemertean mitogenomes, but is variable in the mNCRs. Some slight differences are found between mitogenomes of the present species and other hoplonemerteans: in G. parasita the mNCR is biased toward T and C (contrary to other hoplonemerteans) and the rrnS gene has a unique 58-bp insertion at the 5′ end; in N. tetraclitophila the nad3 gene starts with the ATT codon (ATG in other hoplonemerteans). Phylogenetic analyses of the nucleotide and amino acid datasets show early divergent positions of G. parasita and N. tetraclitophila within the analyzed Distromatonemertea species, and provide strong support for the close relationship between Hoplonemertea and Heteronemertea.

Conclusion

Gene order is highly conserved within the order Monostilifera, particularly within the Distromatonemertea, and the special lifestyle of G. parasita and N. tetraclitophila does not bring significant variations to the overall structures of their mitogenomes in comparison with free-living hoplonemerteans.

【 授权许可】

   
2014 Sun et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

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