Jellyfish are marine animals who have soft bodies with the shape of an umbrella or a bell. They inhabited every ocean from the surface to the deep sea. They belong to invertebrates so they are not actually a fish. There are around 200 species of jellyfish in the world. Most of the species have roam the ocean for about 500 million years, it was long before the dinosaur lived on earth.

    Jellyfish have a gelatinous body and some tentacles hanging on it. These tentacles are long, stinging and venomous. They use their tentacles to paralyze their prey or to strike back the enemy when they are threatened. They have a mouth and it is located in the center underside of their body. They use it to eat and to squirt water so their body will be pushed to the opposite direction. Most of their species have a transparent body which consist of 98 percent water. They will likely be dissapear if they are washed up on the beach as the water evaporates. They do not have brain or eyes. To be able to see or smell the environtment, they use some sensory nerves on their tentacles.

(Source : http://britishcourse.com/contoh-report-text-jellyfish.php)

"They use their tentacles to paralyze their prey or to strike back the enemy when they are threatened." What does it mean by the sentence?