Our results provide another source of evidence that passive lateral gene transfers have occurred regularly during evolution from bacteria to viruses and eukaryotes, and between viruses and eukaryotes [49] [50] [51] [52] . Even if the pox-D5 NTPase genes in the GfIV genome, and the MCP and SfAV061-like genes in the CsIV genome, indicate that they have an ascovirus origin, they provide only limited evidence supporting an ascovirus origin of ichnoviruses. Indeed, their sequence conservation and biological characteristics suggest that there were repeated lateral transfers during evolution between ascoviruses and wasp genomes, including the proviral ichnovirus loci. This raises an important issue about the role of lateral transfers during co-evolution of the NCLDVs and non-NCLDVs, ichnovirus, wasp and parasitized host. Indeed, genetic materials of various origins have been exchanged and maintained during co-evolution. This therefore suggests that ichnoviruses might be chimeric entities partly resulting from sev- Symbiogenesis was first proposed as an evolutionary mechanism when it became widely recognized that mitochondria and plastids originated from free-living prokaryotes [7] . The genomes of the endosymbiotic cyanobacteria and proteobacteria, respectively, at the origin of chloroplasts and mirochondria have evolved by reduction of several orders of magnitude to the approximate size of plasmids. Concurrently, nuclear genomes have been the recipients of plastid genomes. This relocation of the genes encoding most proteins of the endosymbiotic bacteria to the host nucleus is the ultimate step of this evolutionary process, so-called endosymbiogenesis [7, 53] . Recent studies of plants have revealed a constant deluge of DNA from organelles to the nucleus since the origin of organelles [54] . This allows the host cell to have the genetic control on its organelles, in a relationship that is closer to enslavement or domestication than to a symbiosis or a mutualism in which the organelles would recover benefits from their contribution to the eukaryotic cell well-being. To date, this deluge of DNA is considered to correspond to passive lateral transfers that result from the interactions between the life cycle of the organelle and nuclear replication.