Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus  <B>Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus</B><P>Eleftherios Zouros(1/2), Kenneth R. Freeman(3), Amy Oberhauser Ball(1) & Grant H. Pogson(1/4)</B><P> (1)<I>Department of Biology and Marine Gene Probe Laboratory, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada </I><BR> (2)<I>Department of Biology, University of Crete and Institute of Marine Biology of Crete, Iraklion, Crete, Greece </I><BR> (3)<I>Halifax Fisheries Research Laboratory, Department of Fisheries and</I> <I>Oceans, PO Box 550, Halifax, Nova Scotia B3J 2S7, Canada </I><BR> (4)<I>Present address: Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK</I><P> INHERITANCE of mitochondrial DNA in animals was thought to be strictly maternal. Recently, evidence for incidental paternal mtDNA leakage was obtained in hybrid crosses of <I>Drosophila</I> and mice. In mice, the frequency of paternal mtDNA contributions was estimated at 10-4, compared with maternal contributions. The common occurrence in the marine mussel <I>Mytilus </I>of heteroplasmic individuals with two or more types of highly diverged mtDNA molecules was interpreted as strong evidence for biparental mtDNA inheritance by some, but not by others. We report here results from pair-matings involving two species of mussels, <I>Mytilus</I> <I>edulis </I>and<I> Mytilus trossulus. </I>Extensive contribution of paternal mtDNA, amounting to several orders of magnitude higher than that inferred for <I>Drosophila </I>or mice, was observed in both intra and interspecific crosses.<P> Nature. Vol 359. 1 October 1992<P>