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General
Dasyatidae is a family of rays, cartilaginous marine fishes, related to skates and sharks.

Dasyatids are common in tropical coastal waters throughout the world, and there are fresh water species in Asia (Himantura sp.), Africa, and Florida (Dasyatis sabina). Most dasyatids are neither threatened nor endangered. The species of the genera Potamotrygon, Paratrygon, and Plesiotrygon are all endemic to the freshwaters of South America.

Dasyatids swim with a "flying" motion, propelled by motion of their large pectoral wings (commonly mistaken as "fins"). Their stinger is a razor-sharp, barbed, or serrated cartilaginous spine which grows from the ray's whip-like tail (like a fingernail), and can grow as long as 37 cm (about 14.6 inches). On the underside of the spine are two grooves containing venom-secreting glandular tissue. The entire spine is covered with a thin layer of skin called the integumentary sheath, in which venom is concentrated.[1] This gives them their common name of stingrays, but the name can also be used to refer to any poisonous ray.

Some adult rays may be no larger than a human palm, while other species, like the short-tail stingray, may have a body of six feet in diameter, and an overall length, including their tail, of fourteen feet.

Stingrays may also be called the whip-tailed rays though this usage is much less common.

Feeding
Stingrays are flat so as to hide on the depths of the sea. They ruffle up the sand and hide beneath it. Since their eyes are on top of their body and their mouths on the bottom, stingrays cannot see their prey. Instead, they use the sense of smell and electro-receptors, similar to those of the shark. They feed primarily on mollusks and crustaceans and occasionally on small fish. Their mouths contain powerful, shell-crushing teeth. Rays settle on the bottom while feeding, sometimes leaving only their eyes and tail visible.

Stinging Mechanism
Dasyatids generally do not attack aggressively or even actively defend themselves. When threatened, their primary reaction is to swim away. However, when they are attacked by predators or stepped on, the barbed stinger in their tail is whipped up. This attack is normally ineffective against their main predator, sharks.[2] Humans are usually stung in the foot region (depending on the size of the stingray); it is also possible, although less likely, to be stung by brushing against the stinger. The stinger often breaks off in the wound, which is non-fatal to the stingray, and will be regrown. Contact with the stinger causes local trauma (from the cut itself), pain and swelling from the venom, and possible later infection from bacteria on parts of the stinger left in the wound. Immediate injuries to humans include, but are not limited to: poisoning, punctures, severed arteries and possibly death. Fatal stings are extremely rare.

Treatment for stings includes application of near-scalding water, which helps ease pain by denaturing the complex venom protein, and antibiotics. Immediate injection of local anesthetic in and around the wound is very helpful, as is the use of adjunct opiates such as intramuscular pethidine. Local anesthetic brings almost instant relief for several hours. Other possible pain remedies include papain (papaya extract, contained in unseasoned powdered meat tenderizer), which may break down the protein of the toxins, although this may be more appropriate for jellyfish and similar stings. Folklore incorrectly holds that one should urinate on the stung area; in actuality, urine and vinegar are not effective treatments.[3] Pain normally lasts up to 48 hours, but is most severe in the first 30–60 minutes and may be accompanied by nausea, fatigue, headaches, fever and chills. All stingray injuries should be medically assessed; the wound needs to be thoroughly cleaned, and surgical exploration is often required to remove any barb fragments remaining in the wound. Following cleaning, a radiograph is helpful to confirm removal of all the fragments.[4] However, not all remnants are radio-opaque; ultrasound imaging is useful in difficult cases.