Research on the ecology of the carnivorous sponge-associated iridovirus (CaSpA-IV) reveals its presence in the Cnidaria

Carnivorous sponge–associated iridovirus (CaSpA-IV) is a recently described virus identified in two deep-sea cladorhizid sponge species from the Gulf of Maine and Baffin Bay. To assess its ecological distribution and potential transmission pathways, we molecularly screened for CaSpA-IV in 32 calanoid copepod samples collected across Newfoundland and Labrador coastal and shelf waters, along with 24 mucus swab and tissue samples collected from six individual deep-sea Paragorgia arborea coral colonies, and three seawater samples from the Gulf of Maine. Two P. arborea tissue specimens from different colonies were sequence-confirmed as CaSpA-IV-positive, making this the first detection of an iridovirus in this host. All copepod and seawater samples tested negative. However, calanoid copepods cannot be definitively ruled out as a transmission vector due to limited sampling. These findings demonstrate that CaSpA-IV may infect two invertebrate phyla in geographically distant benthic habitats. Future work should focus on whole-genome sequencing of diverse CaSpA-IVs and targeted sampling of other potential vectors/hosts to elucidate transmission routes and the ecological impact of this virus.