Coast watch (1979) (20472807158)

East Coast sea nettle
Title: Coast watch
Identifier: coastwatch00uncs_15 (find matches)
Year: 1979 (1970s)
Authors: UNC Sea Grant College Program
Subjects: Marine resources; Oceanography; Coastal zone management; Coastal ecology
Publisher: (Raleigh, N. C. : UNC Sea Grant College Program)
Contributing Library: State Library of North Carolina
Digitizing Sponsor: North Carolina Digital Heritage Center



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NATURALIST'S NOTEBOOK
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The East Coast sea nettle is commonly found in 80-degree coastal waters. Although an encounter with a stinging jellyfish is one that most swimmers are not likely to forget, many jellyfish are actually harmless. Still, sightings in North Carolina waters send swimmers scampering. Jellyfish come in many shapes and sizes, from tiny, thimble-shaped Caribbean species to the Arctic lion's mane, whose bell can reach eight feet in diameter, and tentacles can stretch to 200 feet. "Jellyfish have been on the Earth for over 650 million years," says Ken Bradley, education instructor at the N.C. Aquarium at Pine Knoll Shores. "So even though they're simple creatures in a lot of ways, they have been around longer than sharks — and even before dinosaurs." Though they float mostly with the current, jellyfish are able to swim. Using a primitive kind of a jet propulsion, they push water in and out of their umbrella, or bell- shaped body. Usually they stay within saline waters up to 40 feet deep, but some are found in freshwater lakes. There are also deep-sea jellyfish in oceans all over the world. Although jellyfish are composed mostly of water, a complex system of nerves allows them to smell and taste. Through touch receptors and light-sensing organs, they are able to react to the world around them. Jellyfish are held together simply by muscle fibers laced through their bodies and connected to their mouths. Special sacks located around the rim of their bodies help them to maintain balance. Long tentacles, trailing from beneath their bodies, have the same effect on prey as they do on innocent passers-by. "They catch their food pretty much by luck," says Bradley. Whatever brushes against their tentacles is a candidate for their next meal. When the tentacles touch a prey, the jellyfish first stuns it with stinging cells called cnidocytes. Each cnidocyte contains a tiny harpoon called a nematocyte. When touch or chemicals trigger the cnidocyte, the nematocyte not only shoots into the prey, but another toxin also is released to stun or kill the food. Then the oral arms, which cover the long tube where the mouth is located on its central surface, help the jellyfish to engulf its prey. "Since a lot of jellyfish eat tiny zooplankton and other baby sea creatures, their stings are not strong enough to break our skin," says Bradley. For the same reason, jellyfish prove to be tasty meals for turtles. "Any sea turtle — especially a loggerhead — loves jellyfish. They are able to eat them without worrying about the sting associated with it." THE ODD ONES AMONG US Joe Pawlik, professor of marine invertebrate zoology at the University of North Carolina at Wilmington, says that this year large numbers of the Portuguese man-of- war (Physalia physalis) were spotted along Wilmington area beaches. "It's unusual to find so many making it to shore here because we usually have offshore breezes," says Pawlik. "But if part of the Gulf Stream breaks off and spins toward the coast, the wind carries their float as a sail. "Although the Portuguese man-of-war and the jellyfish are both jelly-like and they both sting, they are in completely different classes at the taxonomic level. It's basically the difference between a colonial and a noncolonial organism," Pawlik says. The man-of-war is composed of a colony of animals with various organisms working together as one unit, whereas the jellyfish is only one organism. Though the man-of-war is more toxic, it is easier to spot — and avoid — since it floats above the surface. It is also visible by a vivid pinkish-blue body and tentacles that trail as far as 65 feet behind the umbrella. Beachgoers here can relax knowing that they won't encounter the Australian box jellyfish (Chironex flecked), or the sea wasp. The most venomous animal on earth, its sting is more toxic than a cobra's, and it can kill a human in minutes, says Pawlik. These jellyfish can see, move toward prey and feed on fish. However, a species of box jellyfish lives approximately 300 to 400 yards off the coast of Wrightsville Beach, according to Pawlik. He and colleagues brought up several of the jellyfish while trawling. "Despite the fact that they were in our trawls, and we had every opportunity to get very badly stung, no one did. These do not 24 AUTUMN 2002