They are named after the barbed stinger on their tail, which is used exclusively in self-defense. Thestinger may reach a length of approximately 35 cm, and its underside has two grooves with venom glands. The stinger is covered with a thin layer of skin, the integumentary sheath, in which the venom is concentrated. Some species have several stingers, and a few, notably Urogymnus asperrimus, lack a sting entirely.
Other types of rays also referred to as stingrays are the river stingrays, the roundstingrays, the sixgill stingray, and the deepwater stingray. For clarity, the members of the family Dasyatidae are sometimes called whip-tail stingrays.
While most dasyatids are relatively widespread and not currently threatened, there are several species where the conservation status is more problematic, leading to them being listed as vulnerable or endangered by IUCN. The status of severalother species are poorly known, leading to them being listed as Data Deficient.
Stingrays generally do not attack aggressively or even actively defend themselves. When threatened, their primary reaction is to swim away. However, when attacked by predators or stepped on, the stinger in their tail is whipped up. This is normally ineffective against sharks, their main predator.
Depending on thesize of the stingray, humans are usually stung in the lower limb region. Stings usually occur when swimmers or divers accidentally step on a stingray, but a human is less likely to be stung by simply brushing against the stinger. Surfers and those who enter waters with large populations of stingrays have learned to slide their feet through the sand rather than taking steps, as the rays detect thisand swim away. Stamping hard on the bottom as one treads through murky water will also cause them to swim away. Humans who harass or appear to harass stingrays have been known to be stung elsewhere, sometimes leading to fatalities. The stinger usually breaks off in the wound. This is not fatal to the stingray as it will be regrown at a rate of about 1.25 to 2 centimetres (0.49 to 0.79 in) permonth. Contact with the stinger causes local trauma (from the cut itself), pain, swelling, and muscle cramps from the venom, and possible later infection from bacteria. Immediate injuries to humans include, but are not limited to: poisoning punctures, severed arteries, and sometimes death. Fatal stings are very rare, but can happen, famously including Steve Irwin.
Treatment for stings may includeapplication of hot, which can help ease pain by denaturing the complex venom protein, and antibiotics. Immediate injection of a local anesthetic in and around the wound, or a regional nerve blockade, can be helpful, as can the use of parenteral opiates such as intramuscular pethidine. Local anesthetic may bring almost instant relief for several hours. Vinegar and papain are ineffective. Painnormally 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 must be thoroughly cleaned, and surgical exploration is often required to remove any barb fragments remaining in the wound. Following cleaning, an ultrasound is helpful to confirm removal of...