Night Anemone

Phyllodiscus semoni

The night anemone, Phyllodiscus semoni, is a unique sea anemone found in the central Indo-West Pacific, including regions like Indonesia, the Philippines, and southern Japan. It is easily recognizable by its broad basal disc and the distinctive pseudo-tentacles on its column, which vary greatly in appearance among individuals. These pseudo-tentacles can mimic the look of corals, algae, or even dead coral rock, providing effective camouflage. The upper section of the column is smooth, and the oral disc features a ring of up to 160 long tentacles. This species inhabits shallow waters, typically not deeper than 40 meters, and is often found in coral reef environments. During the day, the night anemone retracts its tentacles and oral disc, spreading its pseudo-tentacles to maximize light exposure for its symbiotic photosynthetic dinoflagellates. At night, it extends its tentacles to feed on zooplankton and small invertebrates. The night anemone is venomous, capable of delivering a painful sting that can lead to severe dermatitis and, in rare cases, acute kidney damage. Divers should exercise caution when encountering this species. The conservation status of Phyllodiscus semoni has not been evaluated by the IUCN.