Sixgill stingray facts for kids
Quick facts for kids Sixgill stingray |
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Hexatrematobatis longirostris Chu & Meng, 1981 |
The sixgill stingray (Hexatrygon bickelli) is a special type of stingray. It is the only living member of its family, called Hexatrygonidae. Scientists first described this unique fish in 1980. It stands out from other rays because it has six pairs of gill slits. Most other rays only have five.
This ray has a soft, heavy body and can grow up to 1.7 meters (about 5.6 feet) long. It has a round disc shape and a long, pointy snout. This snout is filled with a jelly-like substance. The sixgill stingray is brownish on top and white underneath. It does not have rough skin like some other rays.
This ray lives on the ocean floor, usually deep down. You can find it on the upper parts of continental slopes and seamounts. These are underwater mountains. It lives at depths between 500 and 1120 meters (about 1,640 to 3,675 feet). The sixgill stingray has been seen in different places across the Indo-Pacific region. This includes areas from South Africa to Hawaii. It likely uses its long snout to search for food hidden in the sand or mud. Its mouth can stretch out a lot, helping it grab prey that is buried.
The sixgill stingray gives birth to live young, usually two to five pups at a time. The IUCN has listed this ray as "Least Concern." This means it is not currently in danger. This is because not many people fish in the deep waters where it lives.
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Discovering the Sixgill Stingray
The very first sixgill stingray found was a female. She was 64 centimeters (about 25 inches) wide. She was discovered on a beach near Port Elizabeth, South Africa. In 1980, two scientists, Phillip Heemstra and Margaret Smith, described her. They gave her a new species name and placed her in her own family.
The name Hexatrygon comes from Greek words. Hexa means "six," and trygon means "stingray." This name refers to its six pairs of gill slits. The species name bickelli honors Dave Bickell. He was a journalist who found the first ray.
After this discovery, scientists described four more types of sixgill stingrays. They based these new types on small body differences. However, later studies showed that these differences might just be due to age or individual variations. Things like snout shape and tooth count can change a lot. So, scientists now think there might only be one species of sixgill stingray. They are doing genetic tests to be sure.
Scientists also study how the sixgill stingray is related to other rays. They believe it is one of the oldest types of stingrays. An ancient relative, H. senegasi, lived about 49 to 37 million years ago.
What Does a Sixgill Stingray Look Like?
The sixgill stingray has a big, soft body. Its main body disc, made of pectoral fins, is round and a bit longer than it is wide. The snout is shaped like a triangle. In adult rays, the snout is very long, making up almost two-fifths of the disc length. This snout is filled with a clear, jelly-like substance. If a dead ray's snout dries out, it can shrink a lot.
Its tiny eyes are far apart. They are placed well in front of its larger spiracles. Spiracles are openings that help the ray breathe. Between its wide-set nostrils are two short, soft flaps. These flaps join in the middle to form a curtain of skin. The mouth is wide and almost straight.
Inside its mouth, it has many rows of small, blunt teeth. There can be anywhere from 44 to 102 rows. These teeth are arranged in a special pattern. Adults have more teeth than young rays. On the underside of its body, it has six pairs of small gill slits. Remember, most other rays only have five pairs. Some sharks, like the sixgill shark, also have six or more gill slits. One ray was even found with six gill slits on one side and seven on the other! Its pelvic fins are quite large and round.
The tail is fairly thick. It is about half to three-quarters as long as the body disc. It has one or two sharp, stinging spines on top, located far back from the body. The end of the tail has a long, leaf-shaped caudal fin (tail fin). This fin looks almost the same on the top and bottom. The ray's skin is delicate and completely smooth. It does not have rough dermal denticles, which are like tiny teeth on the skin.
The top of the ray's body is purplish to pinkish brown. The edges of its fins are a bit darker. Its skin can get easily scratched, leaving white spots. The underside of its body is white. The edges of its pectoral and pelvic fins are dark. The snout looks see-through, and the tail and tail fin are almost black. The biggest sixgill stingray ever found was a female, 1.7 meters (about 5.6 feet) long.
Where Sixgill Stingrays Live
The sixgill stingray has been found in many different places across the Indo-Pacific region. In the Indian Ocean, it has been seen near Port Elizabeth and Port Alfred in South Africa. It has also been found off southwestern India, some islands in Indonesia, and Western Australia.
In the Pacific Ocean, it lives from Japan to Taiwan and the Philippines. It has also been seen off Flinders Reef in Queensland, New Caledonia, and Hawaii. This ray is a bottom-dwelling species. This means it lives on the ocean floor. It usually lives on the upper parts of continental slopes and seamounts. These are deep areas, from 500 to 1120 meters (about 1,640 to 3,675 feet) deep.
Sometimes, it swims into shallower water. One ray was seen feeding at a depth of 30 meters (about 98 feet) off Japan. You can find it over sandy, muddy, or rocky ocean floors.
Biology and Life Cycle
The sixgill stingray's long snout can bend in many directions. This suggests that the ray uses it to search for food in the sand or mud on the ocean floor. The underside of its snout has special sensors called ampullae of Lorenzini. These sensors are arranged in rows. They can detect tiny electric fields made by other living things. This helps the ray find hidden prey.
Its mouth can stretch downward even further than its head length. This likely helps the ray pull out prey that is buried. The ray's jaws are not very strong. This means it probably does not eat animals with hard shells. There is a record of a sixgill stingray that had a bite wound. The bite was from a cookiecutter shark (Isistius brasiliensis).
The sixgill stingray has a viviparous way of reproduction. This means it gives birth to live young, instead of laying eggs. Scientists have recorded litters with two to five pups. When they are born, young rays are about 48 centimeters (about 19 inches) long. Both male and female rays become adults when they are about 1.1 meters (about 3.6 feet) long.
Sixgill Stingrays and People
Most of the time, not much fishing happens in the very deep waters where the sixgill stingray lives. Because of this, the IUCN has listed it as "Least Concern." This means it is not currently at high risk of becoming endangered.
However, around Taiwan, some sixgill stingrays are caught. They are sometimes caught by accident in bottom trawls. These are large nets dragged along the ocean floor. The number of rays caught seems to have gone down recently. This has led to some worries that too many might be caught in that area. But there is not enough clear data to confirm this.
Images for kids
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The cookiecutter shark is known to bite the sixgill stingray.
