--Hal, from 2001, discusses the year 2000 problem. Outstanding Apple quicktime movie!
The stingray is a beautiful and mysterious creature that lives in a wide range of waters and environments. It is a wonderfully graceful fish that has an undeserved reputation of being aggressive and dangerous. Stingrays are bottom dwellers that feed on small animal that live on the ocean floor. They are gentle graceful animals that can be enjoyed by everyone.
The stingrayÕs body is very flat and oval shaped. It has eyes and gill slits on the top front part of its body but no identifiable head. They have large pectoral fins that many refer to as wings but they are in fact fins. They use these fins to ÒflyÓ through the water. The type of movement is very similar to a wave. It starts at the front where the fin is raised and then pushed down creating a wave that goes down the body. It does this over and over so the fins are constantly rippling and that provides its propulsion. StingraysÕ skeletons are made entirely of cartilage there is no bone in their bodies. This puts them in the Chondrichthyes class along with sharks who also have skeletons made of cartilage. That is interesting because their ancestors have very well developed bone structure. We do not know how long it takes them to grow or how long the actually will live. Their size ranges from nine inches when they are born to six feet across for a large female. Males are smaller than females and can be as small as only two feet across. The average is three to five feet. They have no actual teeth. They have many rows of flat teeth that they use to crush their prey more than cut and tear it apart. Stingrays have a long whip like tail almost twice as long as their bodies with very sharp barbs at the base. It is these barbs that put the sting in stingrays.
If a stingray is stepped on it will raise its tail and try to spear the person with its barbs. The barbs can puncture, tear, and cut the skin. They also inject very painful venom. The venom is protein based and not harmful although it can cause labored breathing. If stung put the affected area into very hot water. The water should be as hot as the patient can stand without causing a burn, around 110-115 degrees Fahrenheit for about 30-90 minutes. The protein in the venom is sensitive to heat and soaking the limb in hot water eases the pain almost immediately. After the protein has been deactivated by the heat one should clean the area to prevent infection and make sure there are no parts of the barb imbedded in the wound. This action by the stingray is only taken when stepped on or threatened and cornered. In fact it cannot sting while swimming. The tail and barbs are a defensive weapon only. It is never used to kill its food.
Stingrays feed on many small bottom dwelling creatures of the sea. Crabs, shellfish, marine worms, conch, shrimp, and occasionally small fish are all part of the stingrayÕs diet. StingraysÕ eyes are on the opposite side of their bodies as their mouth. So they canÕt really see what they are eating. They have very sensitive senses of smell and touch as well as electro-receptors that tell them what they are eating and where it is. They skim across the bottom using their senses and receptors looking for food. Once they have found it they settle on top of it and almost completely burry themselves in the sand, only the eyes and tail can be seen when they are feeding. It has been thought that when buried like this they are either waiting in ambush or sleeping but neither is the case.
Stingrays donÕt have much of a social system they move throughout their environment and spend most of their lives alone. They only get together to mate or in places such as Stingray City in Cayman Islands where they are fed regularly. Since they live solitary lives there isnÕt very much known about any social structure in the groups at places like Stingray City.
They live in many types of water in very cold water as far north as Delaware all the way down the coast of the United States to the Florida Keys and the Bahamas, and throughout the Caribbean to as far south as Brazil. Shallow water in sounds, bays, and sea grass fields are where they prefer to live. They live on the sandy bottom away form large reefs and walls because their mouth is underneath them it is hard to feed where there is no bottom. They prefer 82-90 degree Fahrenheit water temperature in shallow water, 8-40 feet deep. They will come into shore in water as shallow as a few inches and have been seen as deep as 180 feet. They are slightly nocturnal. Many more are seen eating during the night than during the day but they will move about and eat during the daytime.
Stingrays spent their lives alone except when mating. During mating the eggs are fertilized inside the female where the stay to develop. The females carry the fertilized egg inside her where they survive on the yolk sack and then on uterine milk until they are ready to hatch. This usually takes four to eleven months and litters range from two to ten pups. They are then released from her body to fend for themselves. When they are born the baby stingrays are about nine inches in diameter, very thin in proportion to an adult, and come out folded like a newspaper. The barbs on the tail are still soft and flexible when born so as not to hurt the mother.
They stingrayÕs main predators are large fish such as jewfish and sharks especially the hammerhead shark and of course humans. Hammerheads use their large wide head to hold the stingray down while taking bites out of its body. Although their barbed tail is a good deterrent to people walking in shallow water it doesnÕt work very well against its natural predators so it will either try to flee or try to burry itself with sand and hide. People also catch and eat stingrays. IÕve never had stingray but apparently it is quite tasty. They can be caught simply by jigging with some bait and a hook right off the bottom of sea grass beds or other shallow sandy areas. IÕm not sure how much meat is on them but they could be fun to catch.
Stingrays might not live with other stingrays but they are rarely alone. They have a bit of an entourage that follows them around. Since the stingray swims very close to the bottom of the ocean it stirs up the sand underneath it disturbing many small animals the smaller fish eat. Stingrays also visit cleaning stations where it has a symbiotic relationship with the bluehead wrasse and Spanish hogfish clean their bodies of parasites that harm the stingray. These animals all get along well because the stingray gets cleaned of parasites and other unwanted guests on its body and the bluehead wrasse and Spanish hogfish get a free meal.
Stingrays are quite abundant around the United States and are not endangered at all. It is true that some people like to eat them and their skin is used to make belts, boots, and other exotic clothing but there isnÕt enough of a demand to hurt its population. They have been helping economies of several islands throughout the Caribbean, Stingray City in the Cayman Islands being the most famous. Large groups of stingrays gather to be fed and over time become used to human contact. People flock to these places to pet and play with what used to be exotic creatures. Because of the way that they feed off the bottom they suck their food into their mouths before breaking it up so they canÕt bite people. In places where people feed them it is not uncommon for people to get ÒbittenÓ by the stingrays, but all this consists of is a sucking sensation very similar to a hicky. If one does decide to try and taste you do not pull away it will only suck harder and leave a mark very similar to a hicky.
I chose to do my discussion topic on stingrays because I have done a fair amount of scuba diving and snorkeling in my life and I have always seen stingrays. When I was younger I was very frightened of them. I thought that they would sting me and that would hurt and being young anything that hurt was bad so I would swim away from them. My parents tried to get me to overcome my fears at Sea World at a stingray-petting exhibit, but I wouldnÕt put my hand in the water. I eventually learned that they wouldnÕt hurt me if I didnÕt step on them and since I never saw them unless I was swimming and not walking I figured they wouldnÕt hurt me. Now I love them I always swim down and try to get very close to them and even pet them if they will let me. I have dove with people who are still scared of them and I try to help them not be afraid because they are everywhere and being afraid all the time isnÕt fun. I also like the way they swim. It really does look like they are flying through the water. I just think that they are beautiful creatures and I wanted to learn more about them.
1. The University of Michigan Museum of Zoology web page http://animaldiversity.ummz.umich.edu/accounts/dasyatis/d._americana$narrative.html
2. Ichthyology at the Florida Museum of Natural History web page http://www.flmnh.ufl.edu/fish/Gallery/Descript/SouthernStingray/SouthernStingray.html
3. Emedicine web page, http://www.emedicine.com/emerg/topic556.htm
4. Texas Parks and Wildlife web page http://www.tpwd.state.tx.us/expltx/eft/gulf/cspecies/stingray.htm
5. Texas Gulf Coast Fishing web page http://www.texasgulfcoastfishing.com/stingray.htm
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