Jellyfish

Jellyfish are gelatinous marine animals in the phylum Cnidaria, known for their bell-shaped bodies and stinging tentacles.

Jellyfish are gelatinous marine animals in the phylum Cnidaria, known for their bell-shaped bodies and stinging tentacles. They are not fish, but drifting ocean animals that feed mainly on small marine organisms such as plankton and crustaceans. Most species have short lifespans, though some can live longer in captivity or have unusual life cycles.

Biology

Jellyfish are marine cnidarians with a soft, gelatinous body and tentacles lined with stinging cells. The term usually refers to the medusa stage of these animals, which drifts or swims in the water column.

Feeding

Jellyfish are generally carnivorous and feed on zooplankton, small crustaceans, fish eggs and larvae, small fish, and sometimes other jellyfish. They capture prey with their tentacles and sting it before ingestion.

Life cycle and lifespan

Many jellyfish species have complex life cycles that can include both polyp and medusa stages. Adult jellyfish often live only a short time in the wild, commonly months rather than years, although some species can persist longer in captivity or under unusual biological conditions.

Stings and human safety

Jellyfish use nematocysts to immobilize prey and for defence, and some species can sting humans. Sting severity varies widely, and clothing such as wetsuits may reduce exposure but does not guarantee full protection.

Largest species

The lion’s mane jellyfish is widely cited as the largest jellyfish species by overall size, with very long tentacles. Other large jellyfish species also exist, but lion’s mane is the standard answer in general references.