Identification and Full Characterisation of Two Novel Crustacean Infecting Members of the Family Provides Support for Two Subfamilies.

Multiple enveloped viruses with rod-shaped nucleocapsids have been described, infecting the epithelial cell nuclei within the hepatopancreas tubules of crustaceans. These bacilliform viruses share the ultrastructural characteristics of nudiviruses, a specific clade of viruses infecting arthropods. Using histology, electron microscopy and high throughput sequencing, we characterise two further bacilliform viruses from aquatic hosts, the brown shrimp () and the European shore crab (). We assembled the full double stranded, circular DNA genome sequences of these viruses (~113 and 132 kbp, respectively). Comparative genomics and phylogenetic analyses confirm that both belong within the family but in separate clades representing nudiviruses found in freshwater and marine environments. We show that the three thymidine kinase () genes present in all sequenced nudivirus genomes, thus far, were absent in the Crangon crangon nudivirus, suggesting there are twenty-eight core genes shared by all nudiviruses. Furthermore, the phylogenetic data no longer support the subdivision of the family into four genera ( to as recently adopted by the International Committee on Taxonomy of Viruses (ICTV), but rather shows two main branches of the family that are further subdivided. Our data support a recent proposal to create two subfamilies within the family , each subdivided into several genera.