The lion's mane jellyfish can grow up to 2 m width by its pileus ("bell") and its tentacles up to 30 m long. The largest Lions Mane Jelly recorded was 120 FT, but most jellyfish are far smaller, usually some 30 cm by pileus width and up to 50 cm by tentacle length. It eats mainly plankton and is itself eaten by sunfish, sea turtles and some seabirds. Like all jellyfish, it lives only for one year.