The stinging structure consists of a hollow coiled thread with barbs along its length. Venom Apparatusįor defense and feeding jellyfish have specialized stinging cells which contain venom. Pickled or semi-dried mushroom jellyfish are consumed in large quantities in Asia, where they constitute a multimillion-dollar part of the seafood business. Some species, including the mushroom and cannonball jellyfish, are considered a delicacy by humans. In turn, many marine animals, including spadefish, sunfish, and sea turtles eat jellyfish. Larger jellyfish can capture and devour large crustaceans and other marine organisms. Carnivorous, they feed on a variety of small floating organisms as well as comb jellies and occasionally other jellyfish. Jellyfish form an important part of the marine food web. For horizontal movement from place to place however, jellyfish largely depend upon ocean currents, tides and wind. Some jellyfish, such as the sea wasp, descend to deeper waters during the bright sun of the midday and surface during early morning, late afternoon and evening. However, muscles that contract the bell, reducing the space under it, force water out through the opening with pulsating rhythm that creates vertical movement. LocomotionĪdult jellyfish drift in the water with limited control over horizontal movement. Jellyfish medusae normally live for a few months however, the polyp stage may survive for years. After several days they attach themselves to something firm on the sea floor gradually transforming into flower like polyps to start the life cycle over again. Embryos develop either inside the female or in brood pouches along the oral arms.Įventually, small swimming larvae leave the female and enter the water column. During reproduction the male releases sperm into the water and the swimming sperm are swept into the female. The reproductive organs (gonads) develop in the lining of the gut. The dominant and conspicuous medusa are either male or female. In a few weeks, they grow into an adult jellyfish, called a medusa. Each individual saucer develops into a tiny jellyfish which separates itself from the stack and becomes free swimming. When fully developed, polyps constrict in their bodies, eventually producing larvae which resemble a stack of saucers. Polyps can multiply by producing buds or cysts that separate from the first polyp and develop into new polyps. Using their tentacles, polyps feed on microscopic organisms in the water. They begin life as small polyps attached to solid surfaces such as rocks or shells. Jellyfish have alternate generations in which the animal passes through two different body forms. Most live in shallow coastal waters, but a few inhabit depths of 12,000 feet. Jellyfish inhabit all the world's oceans and can withstand a wide range of temperatures and salinities. Regardless of their size or shape, most jellyfish are very fragile, consisting mostly of water. The tentacles of some jellyfish grow to more than 100 feet long. A few species reach seven feet in diameter. The bell may be less than an inch across or more than a foot across. Most are somewhat transparent or glassy, with a bell shape. Jellyfish exist in many sizes, shapes and colors. Lacking a brain, jellyfish instead have a elementary nerve net capable of detecting light, odor and other stimuli and coordinating the animal’s responses. These arms transport food captured by the tentacles into the mouth. Jellyfish have a simple digestive cavity with four to eight oral arms near the mouth. In between is a layer of thick elastic jellylike substance called mesoglea or middle jelly. Jellyfish have an outer layer which covers the external body surface, and an inner layer which lines the gut. This allows jellyfish to detect and respond to food or danger from any direction. Jellyfish and their relatives such as the Portuguese man-of-war are mobile, either actively swimming or pushed by winds and currents.īoth stationary and mobile members of this group have radial symmetry with body parts radiating from a central axis. 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. This publication will help coastal residents and vacationers learn which jellyfish to avoid, and the ones you can safely ignore. Though easily recognized, these animals are often misunderstood and feared by beach goers, even though most jellyfish in South Carolina waters are harmless.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |