Stingrays

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A whiptail stingray (Dasyatis americana) {1}

By: Diana Lohrer

Introduction


Stingrays are classified under the suborder called Myliobatoidei, which consist of eight families: Hexatrygonidae (sixgill stingray), Plesiobatidae (deep water stingray), Urolophidae (stingarees), Urotrygonidae (round rays), Dasyatidae (whiptail stingrays), Potamotrygonidae (river stingrays), Gymuridae (butterfly rays), and Myliobatidae(eagle rays). There are over 60 species of stingrays and many others that are closely related, including sharks. Stingrays are to be considered cartilaginous fishes, meaning they do not have bones and are supported by cartilage, which is a hard, flexible material found in humans ears and nose.

Fast Facts
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The world's largest freshwater giant stingray. It was found in Thailand on January 28, 2009, weighing an estimated 550 to 990 pounds and measured at 6.9 feet long {2}

Type: Fish

Diet: Carnivore
Average life span in the wild: 15 to 25 years
Size: Up to 6.5 ft (2 m)
Weight: Up to 790 lbs (350 kg)
Protection status: Threatened
Did you know? Ancient Greek dentists used the venom from the stingray's spine as an anesthetic.
Size relative to a 6-ft (2-m) man:
Illustration: Stingray compared with adult man {3}.
Illustration: Stingray compared with adult man {3}.










Characteristics


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The stingray's mouth, nostrils and two rows of gill slits are shown from underneath as their eyes appear on top. {4}

The Stingray's shape is wide, flat and round. Their mouth, nostrils and gill slits are underneath their body, while their eyes are on top. Scientists believe that they hunt by not using their eyes, but instead using special sensors called "ampullae of Lorenzin,"{5} they can sense the small electrical charges released by their prey. The stingrays have two long pectoral fins that attached to their body to form the "disc." Depending on the specie, the disc's shape may be circular, oval, wedge-shaped or triangular. The stingray also has a elongated tail that contains a venomous spine. Their tail can be used as a defense mechanism with very sharp edges and a point at the end. Stingrays are considered to be docile creatures, meaning they only use their sting in self-defense. When stingrays do feel as if they are in danger, they attack by facing the victim and flipping its long tail upward over its body to strike the opponent in front of it. The ray only has control over the tail, not the sting. The wound can cause pain, swelling, muscle cramps and infection from bacteria.

The blue-spotted stingray {6}
The blue-spotted stingray {6}
Not all, but some stingrays, for instance the blue-spotted stingray, have venom in their tail. This attribute can be very dangerous to humans by causing an excruciating wound that may also be deadly. However, stingrays do not forcefully attack humans. Most stingray-related injuries to humans take play with the ankles and lower legs due to someone unintentionally stepping on a buried stingray, frightening them. Stepping on a stingray in shallow water can be avoided by shuffling your feet along the bottom of the ocean floor as you enter or throwing rocks into the water to scare them away. Human stings are not life-threatening and are extremely rare unless the stinger strikes a vital area, which happened to be the case with the world-famous "Crocodile Hunter, " Steve Irwin, who died in 2006 from a shocking accident with a stingray. Irwin was swimming over a stingray, which must of frightened it, and caused the stingray to flip its tail forward and pierce him in the heart with its sting.




Behavior


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On the map, the area shaded in light yellow represents the locations where stingrays are found. {7}

Stingrays can be found in the Atlantic, Indian and Pacific Oceans. Most stingrays are marine, living in salt water, but they can also be found in freshwater. Stingrays prefer shallow, close to shore waters in warm parts around the world. People living in these areas have captured stingrays to use their tail spines for the tip of spears and daggers.

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A stingray camouflaged on the bottom of the ocean floor {8}

Stingrays use their color to camouflage along the bottom of the ocean floor. They hide in the mud and sand to either keep safe from predators, such as sharks, or wait for prey to swim by. Their source of food includes clams, oysters, shrimps, crabs and mussels. There are three ways that stingrays hunt their food: 1) Some are filter feeders that swim as they strain their small prey, such as microscopic plankton and small crustaceans, through their gills. An example of this feeder is the largest ray known, the manta ray. 2) Some stingrays are active hunters that find their prey on the ocean floor by capturing and crushing them with their flat, strong teeth. These bottom-dwelling animals include mollusks and crustaceans. 3) Other stingrays are known as electric rays, an example being the numbfish, that stun their prey with electricity.

Stingrays breath by using the organs located behind their eyes, called spiracles, which are very small holes. Rays bring in water through these holes and release it through their gill slits underneath their body. They tend to have two different ways of swimming. Some stingrays move their whole body in a wavy motion that drives them through the water, while others flap their fins, similar to bird wings, and "fly" through the water. Most rays swim in solitary. However some, for example the bat ray, forms schools of several hundred individuals.

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A stingray swimming by moving in a wavy motion. {9}
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A stingray swimming by flapping their fins {10}














Reproduction


Stingrays breed during the winter. The male stingray begins to court the female by following her closely and biting at her pectoral disc. Reproduction then occurs when the male goes on top of the female and places one of his claspers into the female's vent. The females hold the embryos in the womb without a placenta. Therefore, the embryos absorb the nutrients from a yolk sack and once this runs out, the mother provides milk from her uterus. The embryos develop inside their mother for 9 months. Female stingrays give birth to about five to ten young at a time, once a year. While the baby stingray is still inside the mother, it grows and develops so it looks like a little adult once the mother gives birth. From birth, the young stingrays may begin to hunt with their mother, but are capable to fend for themselves.

Food and Other Uses

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A grilled stingray in banana leaf. {11}

Stingrays can be caught by the use of fishing lines or spears. Stingrays are edible and are consumed by many fishing cultures around the world. Since the prehistoric period, their meat has been consumed by humans and still today, their meat is used as a source of protein in the underdeveloped countries. For the past centuries, stingrays have been hunted for their meat and are marketed for food in Europe and Asia. Their are stingray recipes used throughout the world. They may be
cooked by being grilled, battered or fried. The most treasured parts of the stingray includes the fin, the liver and the "cheek," or the area surrounding its eyes. The remaining parts of the ray are to be considered too rubbery to have value and cooking uses.

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A leathery made from the skin of a stingray {13}


A few stingrays species, called "scaly species" {12}, provide suitable leather that consists of tiny rock-hard pearls or scales. The stingray leather is known to be very strong, durable and resistant to fire, water, and tear. Their leather can be made into elegant products including handbags, purses, wallets, belts, boots and shoes.





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A snorkeler swimming with a southern stingray in the Cayman Islands {14}

Eco-tourism

A large eco-tourism industry has grown around southern stingrays. Tourists are beginning to find destinations where they can observe and feed the stingrays. Since stingrays are not usually visible to swimmers, divers and snorkelers find them in shallow, sandy and warm waters. In the Cayman Island and the Caribbean island of Antigua, there are locations called "Stingray City" where divers and snorkelers can swim and feed large southern stingrays. The rays are known to be very friendly.




Citation:

{1} "Stingrays." Seminole High School. Web. 27 Nov. 2011. <http://www.seminolestudents.com/jade/stingrays.html>.
{2} Trombetta, Guido. "World's Largest Giant Stingray." SeaWayBLOG. Web. 27 Nov. 2011. <http://seawayblog.blogspot.com/2009/03/worlds-largest-giant-stingray.html>.
{3},{7} "Stingrays, Stingray Pictures, Stingray Facts - National Geographic." Animals - Animal Pictures - Wild Animal Facts - Nat Geo Wild - National Geographic. Web. 11 Nov. 2011. <http://animals.nationalgeographic.com/animals/fish/stingray/>.
{4} "Top 10 Wildlife Hot Spots - Coastal Living." Coastal Living - The Best in Coastal Style, Travel, and Food. Web. 27 Nov. 2011. <http://www.coastalliving.com/travel/top-10/top-10-wildlife-hotspots-00400000000128/>.
{5} "Stingray Facts and Pictures -- National Geographic Kids." Kids' Games, Animals, Photos, Stories, and More -- National Geographic Kids. Web. 11 Nov. 2011. <http://kids.nationalgeographic.com/kids/animals/creaturefeature/stingray/>.
{6} "The Blue-Spotted Stingray (Taeniura Lymma), Red Sea, Egypt Photographic Print by Casey Mahaney at Art.com." Art.com - Posters, Art Prints, Framed Art, and Wall Art Collections. Web. 27 Nov. 2011. <http://www.art.com/products/p12898432-sa-i2053473/casey-mahaney-the-blue-spotted-stingray-taeniura-lymma-red-sea-egypt.htm>.
{8} "FLMNH Ichthyology Department: Atlantic Angelshark." Florida Museum of Natural History. Web. 29 Nov. 2011. <http://www.flmnh.ufl.edu/fish/gallery/descript/atlanticangel/atlanticangel.html>.
{9} "Stingray City! (July 1st, 2010)." Cayman Scuba and Snorkeling Journal. Web. 27 Nov. 2011. <http://caymanunderwater.blogspot.com/2010/07/stingray-city-july-1st-2010.html>.
{10} Mote Marine Laboratory. Web. 11 Nov. 2011. <http://www.mote.org/index.php?src=gendocs>.
{11} "Recipe ~ Grilled Stingray in Banana Leaf ~ by Sylvia Tan."Welcome. Web. 27 Nov. 2011. <http://enterarena.blogspot.com/2011/03/recipe-grilled-stingray-in-banana-leaf.html>.
{12} "Stingray - Life of Stingray Fish in the Wild." Exotic Leather Handbags, Purses, Wallets, Briefcases and Other Accessories... Web. 27 Nov. 2011. <http://www.tropicalleather.com/The-stingray-p-7.html>.
{13} "Genuine Stingray Leather Wallets. Stingray Skin Wallet." Genuine Exotic Leather Products Retail and Wholesale. Alligator, Crocodile, Stingray, Snake, Eel, Shark, Ostrich, Fish, Lizard, Peccary, Chicken, Hen Genuine Exotic Skins and Leather Goods. Web. 29 Nov. 2011. <http://www.thaishop4you.com/stingray_big_view/hkuk001_black.htm>.
{14} "Stingray City Snorkel Tour - Cayman Islands Tours, Trips and Excursions. Saving Guide to Cayman Islands Top Tours and Excursions." Cayman Islands | Complete Cayman Islands Vacation Planning and Savings Guide. Web. 27 Nov. 2011. <http://www.caymanactivityguide.com/tours/view.php?id=1>.

Information Sources:

1."How Do Stingrays Kill?: Saltwater Fish: Animal Planet." Pet Guides and Wild Animal Guides:Animal Planet. Web. 11 Nov. 2011. <http://animals.howstuffworks.com/fish/stingray.htm>.
2. "Stingrays, Stingray Pictures, Stingray Facts - National Geographic." Animals - Animal Pictures - Wild Animal Facts - Nat Geo Wild - National Geographic. Web. 11 Nov. 2011. <http://animals.nationalgeographic.com/animals/fish/stingray/>.
3. Mote Marine Laboratory. Web. 11 Nov. 2011. <http://www.mote.org/index.php?src=gendocs>.
4. "Stingrays." Seminole High School. Web. 27 Nov. 2011. <http://www.seminolestudents.com/jade/stingrays.html>.
5. "Stingray." Wikipedia, the Free Encyclopedia. Web. 27 Nov. 2011. <http://en.wikipedia.org/wiki/Stingray>.
6. "Sting Rays - Info and Games." Sheppard Software: Fun Free Online Learning Games and Activities for Kids. Web. 27 Nov. 2011. <http://www.sheppardsoftware.com/content/animals/animals/fish/shark_stingray.htm>.
7. "Southern Stingray Marine Life Profile - Dasyatis Americana - Profile of Southern Stingray - Atlantic Southern Stingray." Marine Life - Ocean Animals, Plants and Habitats. Web. 27 Nov. 2011. <http://marinelife.about.com/od/fish/p/southernstingray.htm>.