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Stingray

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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

Dasyatis
Himantura
Pastinachus
Pteroplatytrygon
Taeniura
Urogymnus
See text for species.

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. This attack is normally ineffective against their main predator, sharks. Humans are usually stung in the 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. Fatal ray stings, such as that which killed Australian environmentalist Steve Irwin, are rare but can occur if stings are improperly treated, sever major arteries, or are in the pelvic region or chest.

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.

Underside of freshwater ray showing mouth

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.

As food

Rays may be caught on a fishing line using small crabs as bait, and are often caught accidentally; they may also be speared from above. They are edible; small rays may be cooked similarly to other fish, typically grilled or battered and fried. While not valuable themselves, stingrays can damage shellfishing grounds.

Stingray recipes abound throughout the world, with dried forms of the fins being most common. Generally, the most prized parts of the stingray are the fins, the "cheek" (the area surrounding the eyes,) and the liver. The rest of the ray is considered too rubbery to have any culinary uses.

Viewing

Stingrays are a large part of the Melbourne Aquarium
A stingray on the beach with unusually clear water in Eilat, Israel
Stingray City in Grand Cayman allows swimmers, snorkelers, and divers to swim and feed stingrays.

Dasyatids are not normally visible to swimmers, but divers and snorkelers may find them in shallow sandy waters, more so when the water is unseasonably warm.

The Baltimore Aquarium has a large tank where they may be viewed from above or below; many other aquariums exhibit rays.

In the Cayman Islands, there are a couple of dive sites called Stingray City, Grand Cayman where divers and snorkelers can swim with large southern stingrays (Dasyatis americana) and feed them by hand.

There is also a "Stingray City" in the sea surrounding the Caribbean island of Antigua. It consists of a large, shallow reserve where the rays live and snorkelling is possible, as the rays there are said to be very friendly.

The Georgia Aquarium allows petting of southern stingrays in their Georgia Explorer exhibit.

Also, the Mote Marine Aquarium in Sarasota, Florida allows you to pet a variety of rays in a controlled tank setting.

Small rays and other fishes can be petted in a "tactile tank" at Nausicäa, a large aquarium park in Boulogne-sur-Mer, on the English Channel coast in northern France. One ray has been known to be so friendly it tries to expose its entire ventral surface, ending up toppling over backward.

Stingrays are usually very docile creatures and very rarely attack humans.

Species

There are about seventy species in six genera:

External links

University of Pennsylvania Health System – Information on stingray poison.

References

  1. 'Crocodile hunter' Steve Irwin killed by a stingray The Guardian. September 4, 2006.
  2. Last, Manjaji-Matsumoto & Kailola (2006). "Himantura hortlei n. sp., a new species of whipray (Myliobatiformes: Dasyatidae) from Irian Jaya, Indonesia" (PDF). Zootaxa. 1239: 19–34.
  3. Last, Manjaji & Yearsley (2005). "Pastinachus solocirostris sp. nov., a new species of Stingray (Elasmobranchii: Myliobatiformes) from the Indo-Malay Archipelago" (PDF). Zootaxa. 1040: 1–16.
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