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Stingray

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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.

Like other rays, dasyatids are viviparous (bearing live young in "litters" of 5–10).


Feeding habits

Underside of freshwater ray showing mouth

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 molluscs and crustaceans or occasionally on small fish, and their mouths contain powerful, shell-crushing teeth. Rays settle on the bottom while feeding, sometimes leaving only the eyes and tail visible.

Aggression

File:Spine2ks2.jpg
A close up of a stingray's stinging barb

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 mechanically whipped up. This attack is normally ineffective against their main predator, sharks Cite error: The <ref> tag has too many names (see the help page)., are extremely rare (as of 1996, worldwide known deaths from stingray barb injuries numbered 17) , but can occur if a sting punctures the heart or chest, causing complications due to both the sting's location and the poison in the barbs.

Treatment for stings includes hot water (as hot as the victim can stand), which helps ease pain and break down the venom, and antibiotics. 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.

Stingrays are a large part of the Melbourne Aquarium

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. Whilst not independently valuable, the stingray's capacity to damage shellfishing grounds can lead to bounties placed on their removal.

Stingray recipes abound throughout the world, with dried forms of the wings being most common. Generally, the most prized parts of the stingray are the wings, 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 usually very docile creatures. The customary reaction of the stingray is to immediately flee the vicinity where a disturbance is located. Nevertheless, certain larger species located in waters where they are frisky due to possible attacks from feeding sharks should be approached with caution, as the stingray's defensive reflex and effort to flee may result in human contact with the stinger, resulting in serious injury or even, as has been noted above, fatality.

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.

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.

Most major aquariums feature stingrays, including the national Baltimore Aquarium. The Georgia Aquarium allows petting of southern stingrays in their Georgia Explorer exhibit. Similarly, visitors may use two fingers at a time to touch rays (with sting removed) and related guitarfish in outdoor exhibits at the Aquarium of the Pacific in Long Beach, California. Petting Stingrays is also permitted in a special tank at the Blue Planet Aquarium, Ellesmere Port, UK. Likewise, the Mote Marine Aquarium in Sarasota, Florida allows visitors to pet a variety of rays in a controlled tank setting. Coral World Marine Park in St. Thomas, USVI even allows supervised feeding of southern stingrays by visitors.

In 2006, the Tampa Bay Devil Rays added a 35 foot, 10000 gallon, touch tank in their stadium where fans get a chance to interact with dozens of rays.

Small rays and other fishes can be petted in a "tactile tank" at Nausicaä, 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 tried to expose its entire ventral surface, ending up toppling over backward.

A typically-placid stingray idling at the bottom of the sea, with unusually clear water, in Eilat, Israel

Species

There are about seventy species in six genera:

Stingray City in Grand Cayman allows swimmers, snorkelers, and divers to swim and feed stingrays.

References

  1. Information on Stingrays Surf Life Saving Queensland: Venomous & Poisonous Marine Animals - A medical and biological handbook 1996.
  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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