Molecular genetic differentiation of native populations of Mediterranean blue mussels, Mytilus galloprovincialis Lamarck, 1819, and the relationship with environmental variables

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Evidence for a Fourteenth mtDNA-Encoded Protein in the Female-Transmitted mtDNA of Marine Mussels (Bivalvia: Mytilidae)

BACKGROUND: A novel feature for animal mitochondrial genomes has been recently established: i.e., the presence of additional, lineage-specific, mtDNA-encoded proteins with functional significance. This feature has been observed in freshwater mussels with doubly uniparental inheritance of mtDNA (DUI). The latter unique system of mtDNA transmission, which also exists in some marine mussels and marine clams, is characterized by one mt genome inherited from the female parent (F mtDNA) and one mt genome inherited from the male parent (M mtDNA). In freshwater mussels, the novel mtDNA-encoded proteins have been shown to be mt genome-specific (i.e., one novel protein for F genomes and one novel protein for M genomes). It has been hypothesized that these novel, F- and M-specific, mtDNA-encoded proteins (and/or other F- and/or M-specific mtDNA sequences) could be responsible for the different modes of mtDNA transmission in bivalves but this remains to be demonstrated. METHODOLOGY/PRINCIPAL FINDINGS: We investigated all complete (or nearly complete) female- and male-transmitted marine mussel mtDNAs previously sequenced for the presence of ORFs that could have functional importance in these bivalves. Our results confirm the presence of a novel F genome-specific mt ORF, of significant length (>100aa) and located in the control region, that most likely has functional significance in marine mussels. The identification of this ORF in five Mytilus species suggests that it has been maintained in the mytilid lineage (subfamily Mytilinae) for ∼13 million years. Furthermore, this ORF likely has a homologue in the F mt genome of Musculista senhousia, a DUI-containing mytilid species in the subfamily Crenellinae. We present evidence supporting the functionality of this F-specific ORF at the transcriptional, amino acid and nucleotide levels. CONCLUSIONS/SIGNIFICANCE: Our results offer support for the hypothesis that "novel F genome-specific mitochondrial genes" are involved in key biological functions in bivalve species with DUI

The role of plasticity-related functional reorganization in the explanation of central dyslexias

The genetic constitution of mussels (<i>Mytilus</i> spp.) was studied by means of three nuclear (Me 15/16, EF-bis, ITS) and one mtDNA (ND2-COIII) marker on a large European scale. In addition to a sharp cline between Atlantic and Mediterranean <i>M. galloprovincialis</i>, we observed a clear genetic distinction between the Black Sea and Mediterranean populations and a higher incidence of <i>M. trossulus</i> than reported so far in northern European populations. The frequency of <i>M. galloprovincialis</i> nuclear alleles was high along the Iberian Peninsula and decreased abruptly along the French coasts with a high frequency of <i>M. edulis</i> alleles in the Bay of Biscay, The Netherlands, Germany, Iceland, Barents and White Seas, and with little evidence of introgression between the two taxa. <i>M. trossulus</i> alleles were observed in the Baltic Sea and Danish Straits as expected. In addition, occurrence of <i>M. trossulus</i> alleles in cold waters of Iceland, Barents Sea and White Sea is reported for the first time

The re-appearance of the Mytilus spp. complex in Svalbard, Arctic, during the Holocene: The case for an arrival by anthropogenic flotsam

The blue mussel Mytilus spp. complex has re-appeared in the high Arctic in Svalbard after a thousand years, with the first recent indication of its appearance in 2002 at the mouth of Isfjorden on the west coast. We examine its genetic affinity to selected North Atlantic populations and the modes of spread that may be responsible for its recent re-colonisation. We record here its distribution on Svalbard archipelago along the north-western coastline and within Isfjorden collected over a seven years period. We record for the first time the intertidal occurrence that includes a presence close to a glacier front. Genetic composition of mussels Mytilus spp. from different Svalbard locations reveal similarities mainly with populations of M. edulis, M. trossulus and their hybrid from Western Europe, Faroe Island, Scotland and Norway. The re-introduction to Svalbard most probably involved shipping and natural or anthropogenic flotsam. It seems that a new transport vector - large plastic debris - plays a significant role in this process