The largest jellyfish is the Arctic giant jellyfish, which is found in the northwest Atlantic Ocean. In 1870, a large Arctic jellyfish was washed into the Massachusetts Bay in the United States. Its umbrella body was 2.28 meters in diameter and its tentacles were 36.5 meters long. The smallest jellyfish is only 12 mm in length.
When ctenophores swim in the sea, they emit blue light, which is very beautiful. Biologists in Singapore are currently conducting an experiment to transplant the luminous gene from jellyfish into other fish.
A few years ago, the American "World Wildlife" magazine combined the opinions of scholars from various countries and listed the ten most poisonous animals in the world. Top of the list is the box jellyfish, a marine animal living in the ocean. Box jellyfish, also called sea wasps, are coelenterates that mainly live in the waters off the northeastern coast of Australia and often float in the shallow waters of the Queensland coast. Adult box jellyfish are as big as a football, mushroom-shaped, and nearly transparent.
On both sides of its body, there are two primitive eyes that can sense changes in light, and more than 60 strip-like tentacles are trailing behind it. These tentacles are what make people deadly, and they can extend up to 3 meters away. On each tentacle, there are densely arranged cysts, and each cyst has a hollow "poison needle" that is invisible to the naked eye and filled with venom. An adult box jellyfish has billions of venom sacs and stingers on its tentacles, enough to kill 20 people, which shows how toxic and murderous it is. There are also receptors on its tentacles that can identify proteins on fish, shrimp or human skin. When a box jellyfish finds its prey, it quickly floats over, wraps the prey tightly with its tentacles, and immediately sprays venom with its stingers. Once the venom is sprayed on a person's body, many bright red scars will immediately appear on the skin. The venom quickly invades the person's heart and will kill the person in just two or three minutes, leaving no time for rescue. Why are box jellyfish so toxic? It's not entirely clear yet, but researchers have found that its venom primarily damages the heart. A healthy person's heart has millions of muscle cells, all of which beat at the same rhythm.
The study also found that acetic acid can kill the tentacles of box jellyfish, so scientists suggest that tourists who go swimming and diving in Queensland should bring a bottle of vinegar with them to use if they encounter box jellyfish. However, scientists are analyzing the structure of box jellyfish venom in the hope of creating preventive and therapeutic drugs to avoid further deaths caused by box jellyfish.