An unusual type of mitochodrial DNA inheritance in the blue mussel Mytilus <B>An unusual type of mitochodrial DNA inheritance in the blue mussel Mytilus</B><P> <B>Eleftherios Zouros(1,2), Amy Oberhauser Ball(1), Carlos Saavedra (1,3) and Kenneth R. Freeman(4)</B><I><P> 1. Department of Biology and Marine Gene Probe Laboratory, Dalhousie University, Halifax, NS Canada, B3JH4J1<BR> 2. Department of Biology, University of Crete and Institute of Marine Biology of Crete, Iraklion, Crete, Greece<BR> 3. Present address: Departamento de Biologia Fundamental, Universidad de Santiago de Compostela, Satiago de Compostela (La Coruna), Spain<BR> 4. Halifax Fisheries Research Laboratory, Department of Fisheries and Oceans, P.O. Box 550, Halifax, NS Canada, B3J 2S7</I><P> Communicated by Bruce Wallace, April 21, 1994<B><P> Abstract</B><P> In animals, mitochondrial DNA (mtDNA) inheritance is predominantly maternal. In a few cases incidental transmission of paternal mtDNA was observed and estimated to account for only 10(-4) - 10(-3) of an individuals mtDNA content. In contrast, biparental inheritance is common in mussels of the genus <I>Mytilus</I>. Here we present direct evidence that sex and mtDNA inheritance are coupled in <I>Mytilus</I> . Females inherit mtDNA only from their mother, but they transmit it to both daughters and sons. Males inherit mtDNA from both parents, but they transmit to sons only the mtDNA they inherited from their father. In pair matings, this mtDNA inheritance pattern is associated with a strong sex-ratio bias. These findings establish a newly discovered type of cytoplasmic DNA transmission. We also present evidence that the phenomenon breaks down in interspecific hybrids.<I></I><P> Proc. Natl. Acad. Sci. USA<BR> Vol. 91, pp. - 7463-7467, August 1994. Genetics<P>