64.6 Friday, Jan. 6 Paternal mitochondrial inheritance is widespread in dioecious bivalves and may have multiple origins KAPPNER, Isabella; American Museum of Natural History, New York firstname.lastname@example.org
Unusual mtDNA inheritance is seen in some bivalve taxa, with male germlines inheriting paternal mitochondria genetically distinct from those in somatic cells and female germlines. The full extent of this divergence from a strictly maternal mitochondrial inheritance in Bivalves, one of the largest classes of marine animals, is still unknown. Absence of the trait has rarely been recorded. The phenomenon, Doubly Uniparental Inheritance (DUI), is widespread in Bivalvia: We report sex-associated sequence divergence in nine additional clam species, now extending detection across eight bivalve families. Also, we refute DUI in six species. We spawned sperm for pure germline samples, otherwise dissected testis, a mosaic of germ and somatic cells, requiring cloning. COI and 16S were routinely sequenced and, in several cases, entire mitogenomes were determined. Several ideas for the function and mechanisms of DUI have been proposed. Most bivalves lack sex chromosomes yet are dioecious. Thus, DUI is appealing for controlling sex determination and reproductive mode. We used our expanded dataset to show a highly significant correlation between DUI occurrence and patterns of reproduction. Reliable paternal transmission occurs only in dioecious bivalves (but not in all), and does not occur in hermaphroditic species. Phylogenetic character mapping of the ancestral state and diverse genetic properties suggest DUI arose at least twice with several losses. We discuss the implications for DUI function and whether the development of bivalves, including germline transmission of endosymbionts, predisposes them to this unusual evolutionary pattern.