Stichodactyla mertensii, commonly known as Mertens' carpet sea anemone, is a species of sea anemones in the family Stichodactylidae. It is regarded as the largest sea anemone with a diameter of over 1 m (3.3 ft), the next largest being Heteractis magnifica, which has longer tentacles. This species has an oral disc that can be described as more ovoid than circular that contours to the surrounding substrate and is attached to the substrate by adhesive verrucae, which are wart-like projections. Its blunt or pointed tentacles are uniformly shaped, and are only about 1–2 centimetres (0.39–0.79 in) long. It contains obligate symbiotic zooxanthellae, and is a host to around half the species of anemonefish and one damselfish, Dascyllus trimaculatus.
Stichodactyla mertensii
A. clarkii in a 'normal' color
A. clarkii showing a melanistic variation
Sea anemones are a group of predatory marine invertebrates constituting the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.
Sea anemone
Actinodendron arboreum, the hell's-fire anemone
Striped colonial anemone
Brooding anemone (Epiactis prolifera) with developing young