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Revision as of 04:48, 4 September 2006 by 24.54.81.161 (talk) (→Steve Irwin)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff) For other uses, see Stingray (disambiguation).
| Stingrays | |
|---|---|
| |
| Bluespotted ribbontail ray, Taeniura lymma | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Order: | Rajiformes |
| Family: | Dasyatidae |
| Genera | |
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Dasyatis | |
Dasyatidae is a family of rays, cartilaginous marine fishes.
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). It is coated with a toxic venom. This gives them their common name of stingrays, but that name can also be used to refer to any poisonous ray.
Dasyatids 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 mechanically whipped up, usually into the offending foot; it is also possible, although less likely, to be stung "accidentally" by brushing against the stinger. Contact with the stinger causes local trauma (from the cut itself), pain and swelling from the venom, and possible infection from parts of the stinger left in the wound, as well as from seawater entering the wound. It is possible for ray stings to be fatal if they sever major arteries, are in the pelvic or chest region (such as the fatal wound suffered by Steve Irwin), or are improperly treated. Their stingers are normally ineffective against their main predator, sharks.
Treatment for stings includes hot water (as hot as the victim can stand), which helps ease pain and break down the venom, and antibiotics. Vinegar or urine may or may not be successful in easing pain; neither cleans the wound properly. Other possible pain remedies include papain (papaya extract, contained in unseasoned powdered meat tenderizer), which may break down the protein of the toxins, though this may be more appropriate for jellyfish and similar stings. 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.
Like other rays, dasyatids are viviparous (bearing live young in "litters" of 5–10). Since their eyes are on top of their head, and their mouths on the bottom, they cannot see their prey, and instead use their sense of smell and electro-receptors similar to those of the shark. They feed primarily on mollusks and crustaceans, as their mouths contain powerful, shell-crushing teeth, or occasionally on smaller fish; rays settle on the bottom while feeding, sometimes leaving only the eyes and tail visible.
References
- Froese, Rainer; Pauly, Daniel (eds.). "Family Dasyatidae". FishBase. August 2005 version.