Jellyfish

Jellyfish can survive in polluted waters where many fish and other marine animals cannot live!

Some jellyfish survive in extreme environments, like the Arctic jellyfish that lives in water temperatures as cold as 28°F (-2°C)!

Sea turtles, especially leatherback turtles, are important jellyfish predators, with a single turtle able to eat hundreds of jellyfish per day!

Jellyfish tentacles can still sting even when separated from the body or after the jellyfish has died and washed up on shore!

Some small fish hide among jellyfish tentacles for protection, developing immunity to the jellyfish’s stings!

When water conditions change or food becomes scarce, some jellyfish can shrink in size to use less energy until conditions improve!

Jellyfish are eaten by sea turtles, sunfish, some seabirds, and other jellyfish species!

Life Cycle

Jellyfish have a complex life cycle with four main stages: egg, planula larva, polyp, and medusa (adult jellyfish)!

Most jellyfish begin life as tiny eggs that develop into swimming planula larvae, which then attach to surfaces and grow into polyps!

A single jellyfish polyp can clone itself to form a colony of polyps, each capable of producing multiple jellyfish!

In a process called strobilation, polyps stack up a series of discs that break free one by one as baby jellyfish called ephyra!

It takes about 2–3 months for a baby jellyfish (ephyra) to grow into a fully-formed adult medusa!

Some jellyfish species reproduce sexually, with separate male and female individuals releasing eggs and sperm into the water!

In some jellyfish species, eggs develop while attached to the female’s oral arms, providing protection until they develop into swimming larvae!

Diet and Feeding

Jellyfish digest their food very quickly, sometimes in as little as 4–8 hours!

Some jellyfish species, like the Deep Sea Atolla jellyfish, use bioluminescence (glowing light) to attract prey in the dark ocean depths!

The Man O’ War jellyfish has specially adapted tentacles that can contract to pull captured prey up to its digestive polyps!

The Crown jellyfish captures prey by creating a current that pulls water and small animals into its bell, where they become trapped!

The upside-down jellyfish gets most of its energy from tiny algae living inside its tissues, which produce food through photosynthesis!

Box jellyfish are active hunters that can swim at speeds up to 4 miles per hour (6.4 km/h) to chase prey!

Fun and Unique Facts

Jellyfish blood is colorless, unlike the red blood of humans and many other animals!

Some species of jellyfish can clone themselves if cut in half, with each half growing into a complete jellyfish!

NASA has sent jellyfish to space to study how zero-gravity affects their development!

The Irukandji jellyfish is one of the most venomous creatures on Earth, but it’s so small (about the size of a grape) that it’s almost invisible in water!

Some Indigenous Australian cultures had special knowledge of jellyfish seasons and used this to plan safe swimming times!

The crystal jellyfish (Aequorea victoria) is completely transparent except when it glows blue-green at night!

Jellyfish can shrink when food is scarce and grow again when food becomes available.