Mitochondrial Genome Inheritance in Bivalve Mollusks

Bivalve mollusks display one of the most intriguing exceptions to strict maternal inheritance of mitochondria in the animal kingdom. In many bivalves, a system known as doubly uniparental inheritance (DUI) gives rise to two distinct mitochondrial lineages: the F-type genome transmitted via eggs and the M-type genome passed through sperm. This arrangement leads to sex-associated heteroplasmy in males and homoplasmy in females. Mitochondrial genomes in these taxa show remarkable plasticity, including gene order rearrangements, duplications, deletions, and lineage-specific open reading frames. These features not only underpin mechanisms of paternal transmission but also contribute to non-respiratory functions such as sncRNA-mediated gene regulation and potential roles in sex determination. Comparative studies of F- and M-type mitogenomes have revealed rapid sequence divergence, lineage-specific gene losses or gains, and evidence of purifying selection acting on essential protein-coding genes. Phylogenomic analyses based on mitogenomes are reshaping our understanding of bivalve systematics, resolving deep relationships among major clades and illuminating the evolutionary origins of DUI. Beyond fundamental evolutionary insights, knowledge of mitochondrial inheritance in bivalves has practical implications for aquaculture, conservation genetics and the study of mitonuclear interactions across Metazoa.

Research from Nature Portfolio

Recent work on Donax clams has uncovered the complete absence of all seven core subunits of respiratory complex I in male-transmitted mitogenomes. Comparative assembly of three Donax M-type genomes revealed unique long open reading frames with no homology to known genes, suggesting novel adaptations to paternal transmission and raising questions about bioenergetic compensation mechanisms. In a foundational study of southern-hemisphere blue mussels, mitogenome sequences from multiple Mytilus species confirmed conserved gene order and the presence of the atp8 gene—absent in many other bivalves—while phylogenetic analyses supported the monophyly of Pteriomorphia and clarified species limits within the Mytilus edulis complex. These studies demonstrate how mitogenomic architecture and sequence variation inform both the evolutionary history of DUI and the systematics of globally important bivalve taxa.

Mitochondrial Genome Inheritance in Bivalve Mollusks publication trend

The graph below shows the total number of articles in mitochondrial genome inheritance in bivalve mollusks across all publications each year (not limited to Nature Index journals).

Technical terms

Doubly uniparental inheritance (DUI): A system in which two mitochondrial lineages (F-type and M-type) are transmitted separately through eggs and sperm.

Heteroplasmy: The presence of more than one mitochondrial genome type within a single individual.

F-type mitogenome: The female-transmitted mitochondrial genome lineage in DUI species.

M-type mitogenome: The male-transmitted mitochondrial genome lineage in DUI species.

Short non-coding RNA (sncRNA): Small mitochondrial transcripts that can regulate nuclear gene expression.

Purifying selection: Evolutionary process that removes deleterious mutations from a population, preserving essential gene function.

References

1. Mitonuclear Sex Determination? Empirical Evidence from Bivalves. Molecular Biology and Evolution (2023).
2. Structure, Evolution, and Mitochondrial Genome Analysis of Mussel Species (Bivalvia, Mytilidae). International Journal of Molecular Sciences (2024).
3. The absence of canonical respiratory complex I subunits in male-type mitogenomes of three Donax species. Scientific Reports (2024).
4. Mitogenomics of southern hemisphere blue mussels (Bivalvia: Pteriomorphia): Insights into the evolutionary characteristics of the Mytilus edulis complex. Scientific Reports (2016).
5. Comparative mitogenomic analysis and phylogeny of Veneridae with doubly uniparental inheritance. Open Biology (2024).