Edwardsiella lineata

Edwardsiella lineata, the lined anemone, is a species of sea anemone in the family Edwardsiidae. It is native to the northwestern Atlantic Ocean where it occurs in the subtidal zone. E. lineata is a small, delicate-looking, white or brownish anemone with a length of up to 3.3 cm (1.3 in). It has forty tentacles and has acontia (threadlike defensive organs thrown out of the mouth or special pores when irritated). It lives in a slender mucous tube immersed in sediment. E. lineata is native to shallow temperate waters in the northwestern Atlantic Ocean, where it occurs between Cape Cod and Cape Hatteras. It is typically found in rock crevices and on and under rocks in the sublitoral zone at depths to 20 m (66 ft), but can also be infaunal, burrowing in soft sediment. It sometimes occurs in large numbers. E. lineata has a simple internal structure and is unusual among sea anemones in that it can divide by transverse fission. It can also reproduce sexually and the planula larva has recently evolved a partially parasitic lifestyle. The host is the pelagic ctenophore Mnemiopsis leidyi. On entering a host, the larva adopts a worm-like appearance and feeds on the contents of the host's gut. When sufficiently developed, or if the host dies, it exits the host and regains its planula larval form. If another host is available it can once again adopt the worm-like phase, but if no new host is available, it can settle on the seabed and undergo metamorphosis into a juvenile sea anemone polyp. The planula larvae are sometimes the cause of a form of irritating dermatitis in humans known as seabather's eruption. When the larvae get trapped under swimwear they defend themselves by firing their venomous nematocysts into the skin, causing a red blotchy rash that may blister. No treatment is required, and the symptoms subside after a week or two.