Jellyfish

Jellyfish are amazing animals. They are invertebrates. That means they have no skeletal system. They have no blood and believe it or not they don’t have a brain. Even though all of this makes you think jellyfish are bound to become extinct, that is far from true. Jellyfish, or jellies, have been around since before dinosaurs. A jelly has a simple nervous system. It detects light, it is able to smell and it feels things when it brushes against something.

Jellyfish can’t really swim because they don’t have bones or bony structures. They mostly drift in the oceanic currents. They can pulse their bodies to help them along using muscles in their bells. They often suck water in and then blow it out to propel themselves forward. They can travel long distances between pulsing and the currents. This helps them avoid predators. Jellies are also predators. They feed on zooplankton, fish eggs, larva and even other jellyfish. Sometimes there is a bloom, or a large gathering of jellies. At places where there is a bloom, the hungry jellies eat all the eggs and baby fish in the area.

Parents & Teachers!

Scan this to download a lesson on Jellyfish, plus a bonus project: “build-a-jelly

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Jellyfish come in all different shapes and sizes. Most of them have a bell with tentacles hanging from it. The tentacles can be long and skinny or wide and look like seaweed. The largest jelly is the Lion’s Mane Jellyfish. It can grow to about the size of a Blue Whale. In comparison the Irukandji jellyfish is about the size of a pencil eraser. One jelly looks like a fried egg if you look down from the top, one, the Man-O-War looks like it has a sail. Many are see through and a lot of them are bioluminescent. Bioluminescent means they can create a chemical reaction that makes light. It makes them look like they are glowing brightly in the water.

Did you know some cultures eat jellyfish?

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Books!

Jellyfish (Amazing Animals) by Valerie Bodden

Jellyfish by Christina Leaf

Jellyfish by Victoria Blakemore

Would you ever try jellyfish salad?

Jellyfish are known for their very painful stings. They don’t mean to sting anyone but if you brush against one it may just hurt — a lot! A jelly stings you with its tentacles. Each tentacle has little organs called nematocysts. These are used to sting prey. The poison in the nematocysts help them digest their food quickly. The tiniest jelly, the Irukandji jellyfish has very toxic venom that is 100 times worse than that of a cobra. Two people have died. The box jellyfish has killed more people than that. Most stings are very painful but definitely not deadly.