The quest for Doubly Uniparental Inheritance in heterodont bivalves and its invention in Meretrix lamarckii (Veneridae: Meretricinae).

Doubly Uniparental Inheritance (DUI) is possibly the most striking exception to the well-known maternal inheritance of mitochondria. It poses several stimulating questions concerning among others the function of these organelles, sex determination, embryonic development, and evolutionary consequences. At present, DUI has been found in few species of bivalve molluscs, but more research is necessary to obtain a clearer picture of its distribution within the group, a picture that is mandatory to make any reasonable inference about its origin and evolutionary meaning. The debate about a single evolutionary origin of DUI versus multiple origins is still open. In this manuscript, we investigated seven species of heterodont bivalves and provide evidence for the presence of DUI in the venerid Meretrix lamarckii.