Sea anemones are conspicuous and ecologically important members of marine communities. Despite their ubiquity, the biodiversity of sea anemones is generally under-described, in large part because they have relatively few macro anatomical features with which to be distinguished.
The sea anemone Metridium senile is one of the most common sea anemones in temperate northern waters, being reported from all coasts of both the Northern Atlantic and North Pacific Oceans. This species, known as the "Fluffy Anemone" for its dense and shaggy crown of tentacles, is an able colonizer of man-made structures and a key constituent of natural rocky communities from the intertidal zone to depths of about 100 meters. This unusually broad geographic, bathymetric, and ecological range raises questions about the cohesiveness of Metridium senile: no non-invasive species of anemone shows such breadth in range. We will use tissue samples from populations on the US Pacific and Atlantic coasts to determine whether Metridium senile is simply unusually successful colonizer or whether the name is applied to genetically distinct units.