Complete female mitochondrial genome of Anodonta anatina (Mollusca: Unionidae): confirmation of a novel protein-coding gene (F ORF).

Freshwater mussels are among animals having two different, gender-specific mitochondrial genomes. We sequenced complete female mitochondrial genomes from five individuals of Anodonta anatina, a bivalve species common in palearctic ecozone. The length of the genome was variable: 15,637-15,653 bp. This variation was almost entirely confined to the non-coding parts, which constituted approximately 5% of the genome. Nucleotide diversity was moderate, at 0.3%. Nucleotide composition was typically biased towards AT (66.0%). All genes normally seen in animal mtDNA were identified, as well as the ORF characteristic for unionid mitochondrial genomes, bringing the total number of genes present to 38. If this additional ORF does encode a protein, it must evolve under a very relaxed selection since all substitutions within this gene were non-synonymous. The gene order and structure of the genome were identical to those of all female mitochondrial genomes described in unionid bivalves except the Gonideini.