Moon Jelly (Aurelia aurita) — identification, habitat & look-alikes

The moon jelly is a see-through jellyfish of the northeastern Atlantic, recognized by the four horseshoe-shaped rings showing through its bell. It was long thought to live in oceans worldwide, but many look-alike moon jellies elsewhere turned out to be separate species. In the US it lives in the Northeast, where it was introduced.

Appearance

Appearance: Almost entirely clear, usually 10–16 in (25–40 cm) across, with four pinkish to purple horseshoe-shaped gonads showing through the top. A fringe of short, fine tentacles lines the bell.

Look-alikes

Southern moon jellyAurelia marginalis

Looks nearly identical; moon jellies generally can't be told apart without genetic testing. Location helps — this one lives from the mid-Atlantic coast south and in the Gulf of Mexico.

Why they get mixed upLong lumped under the same name.

Greater moon jellyfishAurelia labiata

Most have a bell edge with 16 scallops and grow a bit larger (up to about 18 in, or 45 cm), but neither trait is a sure sign. Location helps most — it's the moon jelly of the Pacific coast from northern California to Alaska.

Why they get mixed upThe moon jelly West Coast visitors usually see, with the same clear bell and four rings.

Asian moon jellyAurelia coerulea

Can't be told apart reliably in photos. It's the common moon jelly of Japan, Korea, and China, and also occurs off California.

Why they get mixed upFormerly treated as the same species.

Where it lives

Typical habitats: Coastal seas
Bays
Estuaries
Range: Native to the northeastern Atlantic, including the Baltic Sea. Established populations in the northeastern US and Argentina were introduced.
Preferred conditions: Handles the lower salinity of bays and estuaries well.

Behavior

Diet: Plankton, small crustaceans, mollusks, and fish eggs caught on its short tentacles.

Life cycle

Reproduction: Adults release eggs and sperm. Larvae settle on the bottom as tiny polyps, which, cued mostly by seasonal temperature changes, slice off baby jellies one after another.
Lifespan: Adult jellies typically live about 6 months to a year.

Cautions

Cautions: It does sting, but the venom is mild and most people feel little or nothing.

Name and classification

About the name: A 2021 revision found that jellies once all called Aurelia aurita belong to at least 28 species. Older articles and aquarium signs calling any moon jelly 'Aurelia aurita' may really be about another species.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed

More species to explore

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