Salt cycles drive mixed clonal-aggregative multicellularity in a choanoflagellate
Researchers show Choanoeca flexa forms multicellular sheets clonally, via aggregation, or through a mix—clonal-aggregative multicellularity—driven by evaporation–refilling salinity cycles in Curaçao splash pools. Low salinity supports both cell division and aggregation to build sheets, while hypersalinity triggers dissociation into desiccation‑resistant cysts that can rehydrate into sheets. Aggregation is active, requires living cells, and exhibits kin recognition and species specificity; density and salinity shift the balance between clonal and aggregative modes. Genomic analyses identify candidate kin‑recognition loci. Together, the findings reveal a flexible, environmentally entrained route to multicellularity, expanding our understanding of choanoflagellate biology and potential premetazoan life histories.