Heteractis magnifica has the basic morphology of most anemones, living its entire life in the polyp form (looking like a cylindrical column with tentacles). This species has a sticky foot on a pedal disc, and an oral disc which contains the mouth and surrounding tentacles. Heteractis magnifica is the second largest in size of all sea anemones. The oral disc reaches 1 m in diameter or can be as small as 1.25 cm. Typically H. magnifica is between 300 and 500 mm in diameter. The foot, which is used to anchor the animal to various hard surfaces, is also larger than most anemones. The oral disc of an anemone is a flat to slightly curved structure with a mouth in the center, used for both feeding and producing waste. The oral disc can be yellow, brown, or green and is often slightly elevated so that the mouth protrudes out.
Many tentacles surround the oral disc; these are located within 20 to 30 mm of the mouth. The lower part of the tentacles closest to the mouth is the same color as the oral disc (usually shades of brown), but the distal portion of each tentacle can vary in color. Tentacles can range in color from red, pink, purple, orange, and green, but are most commonly tannish. Tentacles are about 75 mm long, and some are branched. Heteractis magnifica has characteristic swollen or bulb-like tips on the finger shaped tentacles. Within these tips are cnidocytes, which contain many nematocysts, structures for delivering toxins use in capturing food and defense.
Adult and baby magnificent anemones are very similar in physical appearance. Magnificent anemones lack skeletons and can grow large when nutrient levels are high, but they can shrink when nutrients are scarce. Members of this species can also look like a ball if they contract their tentacles so that only a tuft of tentacles, if any, remain visible.
Range length: .014 to 1 m.
Average length: .4 m.
Other Physical Features: ectothermic ; heterothermic ; radial symmetry ; venomous
Sexual Dimorphism: sexes alike