Calliactis parasitica is a large sea anemone (family Hormathiidae) renowned for its commensal relationship with hermit crabs, particularly Dardanus species in the Mediterranean Sea and Atlantic Ocean. The anemone voluntarily relocates to hermit crab shells, gaining mobility and access to food scraps while the crab benefits from the anemone's nematocyst-based chemical defense. The species displays complex behavioral repertoires during shell transfers, making it a model for cnidarian nervous system function. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.