Jellyfish - They're Not Just Grape

This topic submitted by Rebecca May ( at 11:13 PM on 6/5/02.

Some of the students captured and released a Magnificent Green Turtle in Snow Bay, San Salvador, Bahamas. See other beautiful phenomena from the Bahamas.

Tropical Field Courses -Western Program-Miami University

Jellyfish became the subject of my research topic partly because I wanted to research a type of animal. I figured researching an animal might help me with material in future classes, since my major is zoology. My initial interest in jellyfish stemmed from the fear people have towards them. I wanted to find out exactly how dangerous they were and see if they were feared with good reason. After skimming articles on jellyfish I was also intrigued by their simplicity. Although jellyfish can be feared creatures, when looking at the basic information about them, they are relatively simple in anatomy and the majority of them are not a major threat to humans.
There are various ways of classifying jellyfish. Jellyfish fall under the category of animals called invertebrates (Young Science 1991). Instead of a backbone, they are supported by mesogloea, which is a jelly-like substance that is found between their two layers of skin. Despite their name, jellyfish, also called medusa, are not classified as fish (World Book 1989). They belong to the phylum Coelenterates, and are separated into two classes: Scyphozoa, large jellyfish, and Hydrozoa, small jellyfish (World Book 1989). The difference between these two classes is that the Hydrozoa are not fully matured jellyfish. They are stationary and their mouth points upward instead of downward like free-swimming jellyfish (Nichols 1971). Some scientists classify jellyfish as plankton because they live near the surface of the water (Young Science 1991). They are the largest form of animal plankton, also known as Zooplankton (Young Science 1991). Common names are given to different types of jellyfish based on their physical features.
Most jellyfish have similar anatomies. The combination of mesogloea, and two skins make up the body of the jellyfish, also known as the bell (Young Science 1991). Mesogloea is not only helpful in support and buoyancy, but is also the reason for the common name of the animal (World Book 1989). Jellyfish have a mouth that consists of a short tube, with four oral arms, that World Book encyclopedia describes as “frilly projections,” around its edges, that hang down from the center of the bowl-shaped body (1989). Tentacles are attached to the edges of the body, and their length and number differ depending on the jellyfish (World Book 1989). Jellyfish can range from pea sized to ten feet in diameter (Stidworthy 1990). Despite the fact that 95% of their composition is water, they can be brightly colored in a variety of shades (Stidworthy 1990). Although predominately water with few major organs, jellyfish do possess sensory skills. Each of the eight notches around the radially semetric bell is actually a pigment spot which is sensitive to light (Stidworthy 1990). These spots are called rhopalia and they contain organs, called statocyts, which help the jellyfish keep its balance (Vancouver Aquarium 2000). Simple sense organs such as these will make sure the jellyfish has its bell pointed toward the water’s surface and help to keep its path of movement from straying too far to either side.
Jellyfish, like all animals, must find a way to produce. A jellyfish, only four inches in diameter, can produce 40,000 eggs daily (Earney 2000). Small jellyfish, called buds, are grown on polyps, hollow cylinders that attach themselves to a stationary surface (Young Science 1991). These polyps are grown from the eggs produced by the mother jellyfish (World Book 1989). The buds are arranged like a stack of saucers on the polyp, often looking like other sea plants rather than jellyfish, until they are released (Nichols 1971). Jellyfish that are released after reaching an acceptable size are known as medusae, and these medusae then mature into full-grown jellyfish (Nichols 1971).

Unfriendly features of jellyfish include their ability to sting. Thorny threads that come out of the sides of the tentacles, like little whips, sting animals that come into contact with the jellies (Young Science 1991). It may be a general tendency to assume that only the tentacles of the jellyfish are poisonous, however all surfaces of the jellyfish include cells with stinging capabilities, even those in the digestive cavity (Vancouver Aquarium 2000). Even dead jellyfish can sting with the poison left in their tentacles (Young Science 1991). While the common jellyfish cannot kill a human, a type of jellyfish called a sea wasp, found off the coasts of Australia and the Philippines, can kill a human in less than three minutes with its sting (World Book 1989). Young Science states that the tentacles help the jellyfish to feed by giving off a poison that paralyses small sea animals, and these tentacles then pull the animals into the mouth of the jellyfish (1991). The jellyfish gathers its prey while it moves. The jellyfish expands and contracts its body, so that it can move upward as it shoots water out beneath it (Gabb 1966). When the jellyfish stops this movement, it sinks toward the ocean floor, collecting small animals that touch its tentacles or oral arms on the way (World Book 1989). These animals are passed to the mouth and swallowed after they have been stung (Stidworthy 1990). Luckily, humans have ways of protecting themselves from jellyfish’s stings.
Because of the pain associated with the jellyfish sting, people have developed ways to avoid and treat these painful stingers. Some people can be seen slowly walking into the ocean, dragging their feet along the sand; a step that is known to some as the “jellyfish shuffle.” This moves the sand and warns jellyfish of ones presence in the water, apparently causing them to avoid the area. Tourists may be warned not to dive head first, or run in the water in order to avoid jellyfish stings (Earney 2000). If a person is stung by a jellyfish there are several steps to the treatment process. After one brings the victim to shore and calms the victim, one should check circulation and breathing (Earney 2000). Large fragments of jellyfish should be removed with tweezers or a gloved hand, and the wound should be washed with seawater or vinegar (Earney 2000). Vinegar prevents the sting from getting worse by inactivating any stinging cells left on the skin (Scott 1997). Fragments of jellyfish that are still stuck to the skin can be removed by applying shaving cream to the area and then scraping it off with a flat edge and rinsing it with more seawater (Earney 2000). A variety of agents have been used as attempts at healing the sting of a jellyfish. These include heat, ice, placebo sugar pills, meat tenderizer, manure, mustard, figs, and urine (Scott 1997). Contrary to the beliefs of some, laboratory tests did not show urine as being a helpful healing agent, rather, they instead gave evidence that both urine and alcohol can cause stinging cells that were previously inactivated to fire, causing the patient more pain instead of relief (Scott 1997). Stings should be treated with care and the victim should be monitored in case of side effects other than itching and burning, such as nausea, headaches, weakness, muscle spasms, chest pains, confusion, agitation, unconsciousness or respiratory failure (Earney 2000). Having the capability to sting creates a safety barrier for the jellyfish.
Despite its potential for harm, the sting of the jellyfish does not scare away all predators. Other animals that can be found feeding on jellyfish include the ocean sunfish, banner fish, arrow crab, and the leatherback sea turtle, as well as other jellyfish and humans (Earney 2000). Jellyfish can also be harmed from factors outside of the food chain. Environmental pollution, such as the pesticide DDT, and pollution from publicly owned treatment works (POTWs) also affect the lives of many water inhabiting creatures, jellyfish included (MU Student Research 2001). Tourism can also prove harmful to these ocean dwellers. According to Cornell student Andrea Earney, tourism can lead to erosion of soil, over fishing, and increased environmental waste, all of which can harm the habitats and populations of jellyfish (2000). Some solutions to these man-made problems include upgrading treatment plants, pre-treating industrial wastes and controlling the sources of the pollution (MU Student Research 2001). Programs assigned to these tasks, such as the Clean Water Act (CWA) and the Coastal Zone Management Act (CZMA) both controlled by the Environmental Protection Agency, could also make their participation mandatory instead of voluntary (MU Student Research 2001). Companies may also be more willing to increase their efforts to protect the beaches if they are more aware of the damage that is taking place.
It is becoming necessary to preserve the lives of jellyfish because they are helping to preserve the lives of humans. These animals are being used for medical research. Some jellyfish are providing the simple pleasure of relaxation to patients just by swimming in an observing tank (Vancouver Aquarium 2000). Other jellyfish are used by researchers for a bioluminescent chemical, which is used to help track the movement of chemicals throughout a human body (Earney 2000). Undoubtedly even more medical research involving jellyfish will evolve in the next few years.
Throughout my research it has become apparent to me that jellyfish play an important role in the ocean and on the land. By just searching for “jellyfish sushi,” I found such delicacies as “spicy jellyfish with cucumber,” and “jellyfish salad” on the menus of restaurants in Japan and China. I was surprised to learn that jellyfish extend to the food chain above land as well as that of the sea. Along with the important role jellyfish play in the ecosystem, and that which they are beginning to play in medical research, it is clear that it is important to preserve these creatures and their habitat as long as possible.

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