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Marine invertebrates


Pacific sea nettlePacific sea nettle Jellyfish are marine invertebrates with bell-shaped bodies and stinging tentacles. Because jellyfish are not fish, scientists refer to them as scyphozoans, the "true jellyfish". They are more than 90% water and have no heart, bones or brain. Some swim by jet propulsion, but most are carried by the ocean tides and currents. Jellyfish belong to the cnidarian phylum of invertebrates, which also includes sea anemones, sea pens and coral polyps.

A school of box jellyfishA school of box jellyfish

Stinging tentacles

Jellyfish float with their tentacles hanging down in the water. Each tentacle is armed with stinging cells, used to paralyse or kill prey. Jellyfish feed on small fish and other marine creatures that become caught in their tentacles. The most venomous creature on Earth is the box jellyfish. Just a touch of its powerful stinging tentacles can kill a person in four minutes.

Lion's mane jellyfishLion's mane jellyfish

Lion's mane jellyfish

Some jellyfish, such as the box jellyfish, have a sting powerful enough to kill a human within a few minutes of contact.

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