Mertens' sea anemone

Scientific name : Stichodactyla mertensii

The largest sea anemone, with over 1 m diameter. Disc shaped, with sometimes folded edges. Short and regular tentacles, 1-2 cm long, more spaced and longer in the central area and missing around the mouth. Green or brown tentacles, light brown column with orange or pink stains. Adhaesive verrucae under the oral disc edge hold the disc in position.
Easy to confound with the 2 species belonging to the same genus, Stichodactyla haddoni and Stichodactyla gigantea. Apart from the less tightly packed tentacles, the easiest way to distinguish them is based on the environment: S. mertensii is always on rocky bottoms, S. gigantea and S. haddoni on the sand.

Associated organisms
This is a species with zooxanthellae. Obligate association with anemone fishes (in our area Amphiprion clarkii, Amphiprion sandaracinos, Amphiprion ocellaris), also associated occasionally with the three spot damsel Dascyllus trimaculatus and with the porcelain crab (Neopetrolisthes oshimai).