Bryozoans are aquatic colonial filter-feeders playing an important role in the marine and freshwater benthic communities. This phylum still keeps a disputed position on the phylogenetic tree of Metazoa being under-investigated at both morphological and molecular levels. Bryozoa include predominantly marine Gymnolaemata and Stenolaemata and exclusively freshwater Phylactolaemata, among which the latter is a sister to two other groups. Here we report the results of sequencing and detailed comparative analysis of mitochondrial genome of the phylactolemate bryozoan Cristatella mucedo. This species proved to have the largest mitogenome among all studied up-to-date bryozoan species, 21 003 bp in length. It contains a number of non-coding regions of which three are of significant length (> 1 500 bp) in addition to a conservative for metazoans composition of protein-coding, rRNA and tRNA genes (with except trnY). Moreover, the trnS1/trnG/nad3 cassette is apparently duplicated in this species that is the unique feature of C. mucedo. Comparative analysis of gene order of C. mucedo and another phylactolaemate bryozoan Pectinatella magnifica confirmed their closeness to each other, and revealed their stronger similarity to phoronid and some other lophotrochozoan species than to marine bryozoans, indicating the ancestral nature of their gene arrangement. We suggest that the ancestral gene order independently underwent robust changes in different bryozoan clades showing mosaic distribution of conservative gene blocks among them regardless phylogenetic position. Altogether, our results support the early divergence of Phylactolaemata from the rest of Bryozoa and intense multiple rearrangement of mitogenome in marine bryozoans.
Предметные области Scopus
- Биохимия, генетика и молекулярная биология (все)