First record of the plumose sea anemone, Metridium senile (Linnaeus, 1761), from the Falkland Islands.
Metridium senile is a circumboreally distributed sea anemone (Cnidaria: Anthozoa: Actiniaria) native to the northern hemisphere, and has been presumed as introduced to several locations in the southern hemisphere. Although the sea anemone fauna of the Falkland Islands is not well known, to date no historical records of Metridium senile exist. In 2019, we conducted biodiversity surveys to gather information about sea anemones present in the islands. During these 2019 surveys, we detected M. senile from three locations: Stanley (eastern Falklands), the Bird Island (south-west Falklands), and in the northern Jason Islands (north-west Falklands). The species was well established at each location, with evidence for asexual reproduction occurring in the western sites. We confirmed the identification by morphology and DNA analysis. Stanley populations are distinct in color variation from the southwestern and northwestern populations, which may indicate separate introduction waves or pathways and the potential for additional, undetected locations of M. senile.