IN SCHOOL

Stingrays: docile, yet dangerous

Photo: Wikimedia Commons  

Stingrays are fish, closely to the sharks. But they neither look like a fish nor as their closest cousin. They look like a round carpet swaying in the water, with a long tail trailing behind. Stingrays are docile and inactive for most part, but when disturbed, they may unleash the venom in their tail, in self-defence.

They are commonly found in the shallow coastal waters of temperate seas. They spend most of their time dormant and concealed under the sand in the sea floor, looking out for prey, while also camouflaging, to avoid predators. The predators may include sharks and larger rays.

Features

The flattened bodies are composed of cartilages (that forms your external ear too) and not bones. The pectoral fins are joined to their head and trunk. The eyes look as if popping out from the upper side, while the mouth, nostrils and gill slits are found on the underbelly. Most rays have strong jaws that help crush the shells of mollusc and crustaceans, which are their primary diet.

Stingrays have spines running down their tail which have toothed edges and sharp points. These barbed stingers are something similar to the dermal denticles of sharks. The stinger has two grooves with venom glands on the underside and the sting is concentrated under the skin. This venom as well as the spine can be fatal to humans. The tail may also be used to move in the water, but its main purpose is protection.

Senses

Stingrays do not use their eye sight to detect prey. Like their shark cousins, rays are equipped with electrical sensors called ampullae of Lorenzini, located around their mouth. This helps them sense the natural electrical charges of potential prey.

Edible rays

Some rays are edible and are eaten around the world.

Injury

Stingrays are not normally visible to swimmers, but snorkelers and divers who reach the shallow sandy waters can see them. They are also subjected to injury in ray attacks.

Stingrays, when felt threatened attack the person by stabbing with the tail. Usually, the injury is local and causes pain, swelling and muscle cramps from the venom. As such, the wound may not be dangerous unless the barb pierces a vital organ.

Swimming with rays

In the Cayman Islands, in the Caribbean Sea, a British Overseas Territory, divers and snorkelers are allowed to swim with stingrays. While in Belize, off the island of Ambergris Caye, in Central America, and in Tahitian island, French Polynesia, resorts offer guests the chance to feed the stingrays.



Factfile

Prey for stingrays includes clams, oysters, shrimps, crabs, and mussels.

Female stingrays give birth once a year. From birth, the young stingray is able to fend for itself.

A few members of the suborder, such as the manta and porcupine rays, do not have stingers.

Stingrays settle on the bottom while feeding, often leaving only their eyes and tails visible.