The study investigates the properties of OLPVRI (Organic Lake Phycodnavirus Rhodopsin) and two other type 1 viral channelrhodopsins (VCRIs), which are found in the genomes of giant viruses infecting phytoplankton. The researchers demonstrate that VCRIs accumulate exclusively intracellularly and, upon illumination, induce calcium release from intracellular IP3-dependent stores. This light-induced calcium release is sufficient to control muscle contraction in tadpoles expressing VCRIs. The ability of VCRIs to photorelease calcium without altering plasma membrane electrical properties suggests they could be potential precursors for optogenetics tools, with applications in basic research and medicine. The study also reveals that OLPVRI localizes to the endoplasmic reticulum and triggers an increase in cytoplasmic calcium proportional to the light intensity, highlighting a unique function among rhodopsins. Further experiments show that OLPVRI-mediated photocurrents are mediated by changes in intracellular calcium and that the release of calcium from IP3-dependent stores is crucial for the observed effects. The findings suggest that VCRIs can hijack intracellular calcium dynamics to control cellular processes, potentially influencing host behavior and virus replication.The study investigates the properties of OLPVRI (Organic Lake Phycodnavirus Rhodopsin) and two other type 1 viral channelrhodopsins (VCRIs), which are found in the genomes of giant viruses infecting phytoplankton. The researchers demonstrate that VCRIs accumulate exclusively intracellularly and, upon illumination, induce calcium release from intracellular IP3-dependent stores. This light-induced calcium release is sufficient to control muscle contraction in tadpoles expressing VCRIs. The ability of VCRIs to photorelease calcium without altering plasma membrane electrical properties suggests they could be potential precursors for optogenetics tools, with applications in basic research and medicine. The study also reveals that OLPVRI localizes to the endoplasmic reticulum and triggers an increase in cytoplasmic calcium proportional to the light intensity, highlighting a unique function among rhodopsins. Further experiments show that OLPVRI-mediated photocurrents are mediated by changes in intracellular calcium and that the release of calcium from IP3-dependent stores is crucial for the observed effects. The findings suggest that VCRIs can hijack intracellular calcium dynamics to control cellular processes, potentially influencing host behavior and virus replication.