The Mysterious and Intimidating Jellyfish
Few marine creatures are as mysterious and intimidating as jellyfish. Though easily recognized, these animals are often misunderstood and feared by beach goers, even though most jellyfish are harmless. Jellyfish belong to a large group of marine animals that include attaching organisms such as sea anemones, sea whips, corals and hydroids that grow attached to rocks or other hard surfaces. Both stationary and mobile members of this group have radial symmetry with body parts radiating from a central axis. This allows jellyfish to detect and respond to food or danger from any direction. Lacking a brain, jellyfish instead have an elementary nerve net capable of detecting light, odor and other stimuli and coordinating the animal’s responses. Most are somewhat transparent or glassy, with a bell shape. The bell may be less than an inch across or more than a foot across. The largest are the cyanea capillata specie or the lion’s mane jellyfish, it can reach 2.5 meters in diameter and its tentacles grow to more than 40 meters long. Regardless of their size or shape, most jellyfish are very fragile, consisting mostly of water. Jellyfish inhabit all the world’s oceans and can withstand a wide range of temperatures and salinities. Most live in shallow coastal waters, but a few inhabit depths of 12,000 feet.