4.08.2013

Skates and Rays

Nicknamed the “pancake sharks,” skates and rays have a lot in common with their cartilaginous cousins; however, their outward appearances are quite different from those of sharks. The bodies of skates and rays, such as the blue-spotted stingray in Figure below, are broad and flattened instead of torpedo-shaped, as in sharks, and the gill slits of skates and rays are located under the body. Skates and rays feed on shallow, sandy reef flats where they can pin down their prey with their winglike fins. When not feeding, they often lie on the bottom to rest. For protection, many species possess one or more poisonous spines on the upper surface of their tails.

The bluespotted stingray hunts for
food on the reef floor


The southern stingray (Dasyatis americana) is usually inactive during the day but hunts most of the night by moving over the bottom of the reef. To uncover prey, it spews jets of water from its mouth into the sediment, or stirs up the sand and silt by vigorously flapping its pectoral fins. Once food is located, the ray lifts its body off the bottom with a pectoral disk and moves the prey into its mouth.

The male southern stingray is much smaller than the female, maturing at a disk width of about 1.5 feet (0.46 m). Females average about 3 feet (0.91 m) wide, but may grow to 6 feet (1.8 m). After mating, the embryos are carried in the mother and nourished first by yolk and then by special “uterine milk” that is produced in cells that line the stingray’s uterus. After about five months, three to five young are born. Venomous barbs on the tails of southern stingrays can be used for protection if the animals are disturbed; however, their venom pales in comparison to the venom of the bluespotted stingray (Taeniura lymma). This yellow fish is covered with bright blue dots to advertise its dangerous nature; the toxin is strong enough to injure, or even kill, humans.