Sea Walnut

Mnemiopsis leidyi

About This Animal

SIZE: Up to 5 inches long

RANGE: Native to western Atlantic, including the Gulf of Mexico, introduced elsewhere

HABITAT: Coastal waters and estuaries

DIET: Small planktonic crustaceans, fish eggs and larvae

ON EXHIBIT:  Jellies: Living Art exhibit at Ocean Journey

Sea walnuts are not true jellyfish, instead they belong to a group of animals know as comb jellies.  Comb jellies have no stinging cells, but instead use sticky mucous to catch their prey.  These animals get their name from rows of paddle-like hairs called combs.  Like tiny prisms, the combs refract visible light into a pulsing rainbow.

In the 1980’s comb jellies were accidentally introduced into the Black Sea – most likely via ship ballast water.   Without a natural predator, the comb jellies quickly took over their new home and devastated local anchovy fisheries.  Despite the introduction of a natural predator, Beroe jellyfish, that has helped control the invading comb jellies, the Black Sea fisheries have yet to recover.