Putative sex-linked heteroplasmy in the tellinid bivalve Limecola balthica (Linnaeus, 1758)

Doubly uniparental inheritance (DUI) is a remarkable exception to the maternal inheritance of mitochondria in metazoans. Found in bivalves, DUI is characterized by females transmitting u0027femaleu0027 (F) mitochondria that persist in oocytes and in somatic tissues of both sexes, whereas males pass on u0027maleu0027 (M) mitochondria that persist in the male germ line (reviewed by Zouros, 2013). The evolution and maintenance of this feature remains unclear, especially as its prevalence among bivalve species is still unknown. DUI can be detected by looking for distinct mitochondrial DNA sequences (or mitotypes) in the sperm and somatic tissues of males. Although it has been found in about 40 species (Degletagne et al., 2015), authors have pointed out the difficulties of detecting DUI, as the genetic distance between the F and M mitotypes can be very high, reaching 50% amino-acid divergence in some unionoids (Doucet-Beaupre et al., 2010). Testing for the presence of DUI is therefore of prime interest for understanding how this feature spread within the Bivalvia and how many times it evolved. We set out to test for the presence of DUI in Limecola balthica (Linnaeus, 1758) (previously known as Macoma balthica; Huber, 2015).