Sea slugs, snails, crabs, sea stars and some fish species, including mosshead sculpins, eels, flounders and butterflyfish, eat sea anemones. Predators with thick protective coverings, such as crustaceans, seem to be resistant to the anemones' toxin-producing nematocysts, which form anemones' main defense mechanism.
Some sea anemones crawl away when they are attacked by certain snails. Although the snail gets stung when it touches the sea anemone, the toxin from the anemone's nematocysts are ineffective and the snail continues to feed. The anemone pulls in its tentacles and inflates, eventually detaching itself and floating away.
Sea anemones are related to corals and jellyfish. Many sea anemones can move, despite appearing to be rooted in one place. They have a muscular foot at the bottom of their body and move by sliding along, floating away or flexing their muscles to swim. Sea anemones are also predators, eating small fish and micro-organisms. They use their nematocysts for predation as well as defense. Their tentacles also sting and paralyze prey. Certain organisms, such as clownfish and hermit crabs, can live within the poisonous tentacles of some sea anemones. These creatures form symbiotic relationships with sea anemones. One type of hermit crab carries a small anemone on its shell and transfers it to a new shell when it outgrows its old one.