|Southern stingray, Dasyatis americana|
The stingrays are a large suborder of the rays. They are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families.
Most stingrays have one or more barbed stings on the tail, which is used only for self-defense. The sting may reach about 35 cm, and its underside has two grooves with venom glands. The sting is covered with a thin layer of skin, the sheath, in which the venom is held. A few members of the suborder, such as the manta rays and the porcupine ray, do not have stings.
Stingrays are common in coastal tropical and subtropical marine waters throughout the world. There are species in warm temperate oceans, and some found in the ocean. Some live in fresh water. Most stingrays live at or near the bottom of the water, but some are pelagic.
The flattened bodies of stingrays allow them to hide themselves. Stingrays agitate the sand and hide beneath it. Because their eyes are on top of their bodies and their mouths on the undersides, stingrays cannot see their prey. They use smell and electro-receptors similar to those of sharks.
Stingrays are ovoviviparous, bearing live young in 'litters' of five to thirteen. The female holds the embryos in the womb without a placenta. Instead, the embryos absorb nutrients from a yolk sac, and after the sac is depleted, the mother provides uterine 'milk'.
At the Sea Life London Aquarium 2 female stingrays have delivered 7 baby stingrays, although the mothers have not been near a male for 2 years. "Rays have been known to store sperm and not give birth until they decide the timing is right".
There are eight families in the stingray group. They are:
- Hexatrygonidae (sixgill stingray),
- Plesiobatidae (deep water stingray),
- Urolophidae (stingarees),
- Urotrygonidae (round rays),
- Dasyatidae (whiptail stingrays),
- Potamotrygonidae (river stingrays),
- Gymnuridae (butterfly rays), and
- Myliobatidae (eagle rays).
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