ABSTRACT
Polydnaviruses have a somewhat eomplex genome organization and an intriguing life cycle. The family name of these insect DNA viruses is derived from their characteristic segmented (or polydisperse), often supercoiled, double-stranded DNA genome. The virus replication cycles of three ichneumonid polydnaviruses, CsV, HeV, and DtV, appear to be similar and a common morphogenetic pathway can be envisaged for them. The viral DNA was sensitive to DNase digestion but insensitive to RNase digestion. The genomes of two ichneumonid polydnaviruses, CsV and HeV, have been examined in detail. The mechanism of viral DNA replication is unknown, and attempts to identify viral origins of DNA replication on viral circular DNAs have been futile (personal observations). The parasitic hymenoptera species appear to serve as an excellent reservoir not only for polydnaviruses but for several other unusual viruses or, better, "viruslike particles." In some cases these unusual parasitoid viruses may be partly responsible for some of the physiological changes observed in parasitized habitual host larvae.
