Fuselloviruses, also known as Sulfolobus Spindle-shaped viruses (SSVs), are "lemon"- or "spindle"-shaped double-stranded DNA viruses. Among them, SSV1, SSV2 and the satellite viruses pSSVx and pSSVi have been investigated at the structural, genetic, transcriptomic, proteomic and biochemical levels, thus becoming models for dissecting DNA replication/gene expression in Archaea. Important progress has been made including elucidation of temporal genome expression during virus infection and induction of replication, SSV1 lysogeny maintenance as well as differentially expression of pSSVx replicase. Future researches focusing on these model systems would yield insightful knowledge of life cycle and DNA replication of fuselloviruses.