Stingray

June 2, 2011 by  


tufail

The stingrays are a group of rays, cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae (sixgill stingray), Plesiobatidae (deepwater stingray), Urolophidae (stingarees), Urotrygonidae (round rays), Dasyatidae (whiptail stingrays), Potamotrygonidae (river stingrays), Gymnuridae (butterfly rays), and Myliobatidae (eagle rays).

Most stingrays have one or more barbed stings (modified from dermal denticles) on the tail, which is used exclusively in self-defense. The stinger 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. A few members of the suborder, such as the manta rays and the porcupine ray, have lost their stings.

Stingrays are common in coastal tropical and subtropical marine waters throughout the world, and also includes species found in warmer temperate oceans such as Dasyatis thetidis, and those found in the deep ocean such as Plesiobatis daviesi. The river stingrays, and a number of whiptail stingrays (such as the Niger stingray), are restricted to fresh water. Most myliobatoids are demersal, but some, such as the pelagic stingray and the eagle rays, are pelagic.

Stingrays do not aggressively attack humans, though stings do normally occur if a ray is accidentally stepped on. To avoid stepping on a stingray in shallow water, the water should be waded through with a shuffle. Alternatively, before wading, stones can be thrown into the water to scare stingrays away. Contact with the stinger causes local trauma (from the cut itself), pain, swelling, muscle cramps from the venom, and later may result in infection from bacteria. The injury is very painful, but seldom life-threatening unless the stinger pierces a vital area. The barb usually breaks off in the wound, and surgery may be required to remove the fragments.

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