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The controversy surrounding the origin of antitropical distribution of Mytilus mussels and the taxonomic status of southern hemisphere populations remain unsolved, despite the efforts. One of the limiting factors remains the lack of the complete sequences of the representative mitochondrial genomes which would allow their proper comparison with the relatively well-represented northern hemisphere congeneric mussels. To fill this gap we sequenced the representative maternal (F) genome of a native Chilean mussel. The genome is 16,748bp long and structurally identical to the northern hemisphere M. edulis and M. galloprovincialis F genomes. However, the genetic distance from them (≈5%) is twice as high as the maximum distance between them (<2.5%). Thus, the notion that the name M. chilensis should be used for native Chilean Mytilus mussels, with the same rank as M. galloprovincialis and M. edulis is supported. [ABSTRACT FROM AUTHOR]

Doubly uniparental inheritance (DUI) results in the existence of two gender-specific, divergent mtDNA lineages within a single species. Under DUI, the female genome (F) is transmitted from mothers to the whole offspring, and the male genome (M) is transmitted exclusively from fathers to sons. This system was first described in a marine musselsMytilus edulisinhabiting European coastal waters, over a decade ago. Despite that, the complete sequence of the M genome from the EuropeanM. edulismussels remained unknown. Here we announce it for the first time. The announcement is based on the two haplotypes isolated from heteroplasmic males of EuropeanM. edulissampled at two moderately distant locations: southern North Sea and western Baltic. The two M genomes are quite similar both in length (16,631 and 16,632 bp) and in sequence (98.3%). Furthermore, both newly sequenced genomes are closely related to the genomes described from BalticM. trossulus. [ABSTRACT FROM PUBLISHER]

Several bivalve species, including marine musselsMytilusare atypical in having two gender-specific and highly divergent mtDNA genomes. This peculiar genetic system allows not only the recombination to occur but also facilitates its detection. Previous reports associated the existence of mosaic recombinant haplotypes with the switch of their transmission route. Here we report nearly complete sequence of a mitochondrial genome isolated from a homoplasmic female individual of MediterraneanMytilus galloprovincialis. The genome has clear phylogenetic affinity with and organization identical to theM. galloprovincialisfemale haplotypes, in the coding part. However, the genome is very large, approximately 20,600 bp long, exclusively due to a long and complex control region. It contains an array of repeats, some of which are degenerated. A large part of the control region is derived from the paternal genome. This finding shows that not all haplotypes with recombinant control regions must be paternally inherited inMytilus. [ABSTRACT FROM AUTHOR]

The complete mitogenome ofAnodonta cygneais 15,613 bp long. This compact, circular molecule contains the set of 37 genes, typical for invertebrate mitogenomes, in the same order and orientation as in maternally inherited genomes of other bivalves from the same subfamily. There are only two unassigned regions longer than 200 bp (266 bp and 274 bp) and no indication of any supranumerary open reading frames. [ABSTRACT FROM PUBLISHER]

Anodonta anatinais a freshwater mussel of the family Unionidae. These mussels have a unique mitochondria inheritance system named doubly uniparental inheritance (DUI). Under DUI males have two, potentially very divergent mitochondrial genomes: F-type inherited from mother and M-type inherited from father. F-type is present in soma whereas M-type is present in gonadal tissues and sperm. Here we report two M-type sequences of complete mitochondrial genomes fromAnodonta anatina. They are 16,906 bp long and their sequences are similar (0.1% divergence). The genome organization is identical to the other Unionidean M-type genomes published to date. There are 38 genes, including the recently described M-type specific M ORF. The presence of tRNA-like repeat in one of the noncoding regions, suggests that the control region is located in this area. Nucleotide composition is quite extreme, with AT content (66.2%) higher than in any other of the six published Unionidean M genomes. [ABSTRACT FROM PUBLISHER]