There are very few animals that eat jellyfish since they are covered in stinging cells. If it were not for that defense, jellyfish would be very vulnerable floating in open water with all of their soft tissue exposed. There are a few animals that are immune to jellyfish venom and eat their gelatinous tissue. Many species of sea turtles feed almost exclusively on jellyfish. Ocean sunfish also eat jellyfish. There are also a variety of birds and fish that will dodge the venom-packed outer tentacles to take bites out of the relatively defenseless inner tissue. One of the biggest predators of jellyfish is other jellyfish. Although they will not eat other individuals of the same species, there is a jellyfish food chain and different species feed on each other. Lastly, jellyfish is considered a delicacy in some Asian cultures and there are fishermen who catch jellyfish so they can be dried and sold as food in restaurants. Jellyfish salad is a popular dish in China.
The Austalian sea wasp (Chrionex fleckeri), also known as the Box Jellyfish, is one of the most venomous animals on the planet, killing two swimmers per year on average. Its venom causes excrutiating pain and is toxic to nerve, muscle and heart tissue. If someone comes in contact with several tentacles from an Australian Sea Wasp, they can die within minutes.
The term “box jellyfish” actually refers to a sub-group of jellyfish comprising about 20 species from all over the world. They go by this name because of their cube-shaped bells, which are distinct from the round bells of other jellyfish. Most box jellyfish have very potent venom. They can easily kill and digest fish and shrimp half their size. They range in size from the Irukandji jellyfish at 2 cm to the Australian Sea Wasp with tentacles several feet in length. Even though they lack a central nervous system, box jellyfish can swim around obstacles using very simple light-sensing organs. They are also very powerful swimmers. Whereas most jellyfish drift along at the mercy of the ocean currents, the powerful swimming contractions of a box jellyfish propels it at over 4 miles per hour.
Swimmers are rightfully fearful of box jellyfish since their sting is so dangerous. In popular tourist destinations like Australia, some beaches are closed for weeks at a time when box jellyfish are present. Other beaches are enclosed by protective nets that keep swimmers safe from the jellyfish.
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