title: The complete mitochondrial genome of Solemya velum (Mollusca: Bivalvia) and its relationships with conchifera.
abstract: BACKGROUND
  Bivalve mitochondrial genomes exhibit a wide array of uncommon features, like extensive gene rearrangements, large sizes, and unusual ways of inheritance. Species pertaining to the order Solemyida (subclass Opponobranchia) show many peculiar evolutionary adaptations, f.i. extensive symbiosis with chemoautotrophic bacteria. Despite Opponobranchia are central in bivalve phylogeny, being considered the sister group of all Autobranchia, a complete mitochondrial genome has not been sequenced yet.
  
  
  RESULTS
  In this paper, we characterized the complete mitochondrial genome of the Atlantic awning clam Solemya velum: A-T content, gene arrangement and other features are more similar to putative ancestral mollusks than to other bivalves. Two supranumerary open reading frames are present in a large, otherwise unassigned, region, while the origin of replication could be located in a region upstream to the cox3 gene.
  
  
  CONCLUSIONS
  We show that S. velum mitogenome retains most of the ancestral conchiferan features, which is unusual among bivalve mollusks, and we discuss main peculiarities of this first example of an organellar genome coming from the subclass Opponobranchia. Mitochondrial genomes of Solemya (for bivalves) and Haliotis (for gastropods) seem to retain the original condition of mollusks, as most probably exemplified by Katharina.
authors.affiliation: Department of Biological Geological and Environmental Sciences, University of Bologna, Via Selmi, 3, Bologna 40126, Italy. federico.plazzi@unibo.it
authors.forename: Federico
authors.initials: F
authors.lastname: Plazzi
authors.forename: Anisa
authors.initials: A
authors.lastname: Ribani
authors.forename: Marco
authors.initials: M
authors.lastname: Passamonti
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D023061:Gene Order / Q000235:genetics; D054629:Genome, Mitochondrial / Q000235:genetics*; D023281:Genomics; D008974:Mollusca / Q000235:genetics*; D010802:Phylogeny
chemical_list: D004272:DNA, Mitochondrial