Metridium senile, the plumose anemone (family Metridiidae), is a common sea anemone in subtidal rocky habitats of the northern Atlantic and Pacific, with a cylindrical column and plumose, feathery oral disc adapting it for filter feeding on suspended particulate matter including phytoplankton and small detritus. The species reproduces by both asexual laceration and sexual reproduction, tolerating a wide range of temperatures and salinities. Metridium senile is a model for studying cnidarian aging, reproduction, and subtidal community ecology across both Atlantic and Pacific coasts. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.