Densoviruses in oyster Crassostrea ariakensis.

Densoviruses have short ssDNA genomes and mainly infect arthropods. To characterize viral nucleic acid in shellfish, oysters (Crassostrea ariakensis) were analyzed using viral metagenomics. Two large de novo assembled contigs, CaaDV1 and CaaDV2, consisting of nearly complete densovirus genomes (5860 nucleotides (nt) and 4034 nt) with two major ambisense protein coding regions were identified. Several potential non-structural proteins and capsid proteins were encoded by these genomes, but these were divergent from the existing densoviral species. The NS1 protein of the two CaaDVs shared 43.3%~61.5% amino acid identities with the sea star-associated densovirus and cherax quadricarinatus densovirus, with the four species clustering by phylogenetic analysis. This is the first report of densovirus detection in shellfish, increasing the potential host range of densoviruses and the genetic diversity of the genus Ambidensovirus.