Animal mitochondrial genomes typically encode 37 genes: 13 proteins， 22 tRNAs and two rRNAs. However， many species represent exceptions to that rule. Bivalvia along with Nematoda and Platyhelminthes are often suspected to fully or partially lack the ATP synthase subunit 8 () gene. This raises the question as to whether they are really lacking this gene or is this maybe an annotation problem? Among bivalves， has been inferred to lack an ATP8 gene since the characterization of its mitochondrial genome in 1992 Even though recent bioinformatic analyses suggested that is present in spp.， due to high divergence in predicted amino acid sequences， the existence of a functional gene in this group remains c... More