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Monday, February 8, 2010

Common Jellyfish

The jellyfish is not only one of the most fascinating creatures in the marine kingdom, it is one of the oldest surviving species of the animal kingdom. Jellyfish have existed in our world for more than 650 million years, since even before the dinosaurs. There are more than 2000 discovered species of jellyfish, but new species are being discovered regularly as humans cover more and more unchartered territories within the ocean. Jellyfish inhabit all levels of the water, right from the surface to the very depths of the marine world. As we discover newer regions in the water world, we find newer species of jellyfish that inhabits that region.

Here are some of the most common jellyfish from around the world.

Moon Jellyfish (Aurelia aurita): The moon jellyfish is perhaps the most common jellyfish in the world. It inhabits tropical waters between the range of 70 degrees N and 40 degrees S. They can tolerate water temperatures in a wide range between -6 degrees C and 31 degrees C, and they can exist in waters whose salinity is extremely low, sometimes as low as 0.6% only.

The body of the moon jellyfish is translucent with patters of stripes or spots, and four horseshoe-like organs can be seen from within. These are the four gonads of the moon jellyfish and they provide the most distinctive characteristic of the moon jellyfish. The size of the moon jellyfish ranges from 6 to 20 inches. The tentacles of the moon jellyfish contain venomous nematocysts and can cause a mild prickling and burning sensation to humans.

Lion's Mane/Winter Jelly (Cyanea capillat): This is a very well known species of jellyfish, thanks to its frequent appearance in popular fiction. This jellyfish prefers the cold, frigid waters of the North Atlantic oceans and even there, they are abundant during the coldest winter months. Some of the largest known jellyfish are lion's mane jellyfish with a bell of about 7 feet and tentacles that can grow up to 150 feet. The size of the winter jellyfish decreases as it approaches warmer water. Its sting is moderately painful and can cause a burning or prickling sensation in humans.

Cannonball Jelly/ Cabbage Head Jellyfish (Stomolophus meleagris): This species of jellyfish is commonly found trapped in fishing nets across the world, clogging them and causing damage. This jellyfish is one of the species that do not have the characteristic tentacles that are common to many species of jellyfish. Instead the cannonball jellyfish has a thick finger like protrusions, which are its oral arms. The bell of the cannonball jellyfish is typically white in color and has a purple of brown band at the rim. Oral arms extend from under the edge of the bell and are useful in capturing food and transporting it to the mouth. The oral arms are connected to each other to form a strong feeding mechanism for the cannonball jellyfish.

The cannonball jellyfish grows to about 8 or 10 inches in diameter. The sting of the cannonball jellyfish is completely harmless to human beings.

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