Deepwater stingray facts for kids
Quick facts for kids Deepwater stingray |
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| Conservation status | |
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Plesiobatidae
K. Nishida, 1990 |
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Plesiobatis
K. Nishida, 1990
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P. daviesi
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| Plesiobatis daviesi (J. H. Wallace, 1967)
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Urolophus marmoratus Chu, Hu & Li, 1981 |
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The deepwater stingray (Plesiobatis daviesi), also called the giant stingaree, is a special type of stingray. It is the only member of its unique family, called Plesiobatidae. This ray lives in many parts of the Indo-Pacific ocean, usually on the upper parts of the continental slope. This means it lives where the land slopes down into the deep ocean. You can find it at depths of about 275 to 680 meters (900 to 2,200 feet).
This large stingray can grow up to 2.7 meters (9 feet) long and 1.5 meters (5 feet) wide. It has a flat, oval-shaped body, which is made up of its pectoral fins. Its snout is long, flexible, and wide. The deepwater stingray's tail is long and slender, with a distinct leaf-shaped caudal fin (tail fin) on the end. Its body is dark on top and white underneath. Its skin is covered with tiny, tooth-like scales called dermal denticles.
The deepwater stingray eats crustaceans (like crabs and lobsters), cephalopods (like squid and octopuses), and bony fishes. It can hunt both on the sea floor and higher up in the water. Female deepwater stingrays give birth to live young. The mother provides special "uterine milk" to feed her babies while they are growing inside her. If you catch one of these rays, you need to be careful because they have a long, venomous stinger. Even though deepwater fishing boats sometimes catch them, not enough are caught to threaten their population. Because of this, the International Union for Conservation of Nature (IUCN) says the deepwater stingray is of Least Concern, meaning it's not currently at risk of disappearing.
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Discovering the Deepwater Stingray
The deepwater stingray was first officially described by a scientist named John H. Wallace in 1967. He wrote about it in a report from the Oceanographic Research Institute in Durban. Wallace named the species daviesi to honor David H. Davies, who was the director of the institute.
The first specimens (examples) of this stingray were found in September 1996 near the Limpopo River in Mozambique. One was a grown-up male about 92 centimeters (36 inches) wide, and the other was a younger male about 33 centimeters (13 inches) wide. People also call this ray Davies' stingray or the giant stingray.
In 1990, another scientist named Kiyonori Nishida studied the deepwater stingray's body shape. He thought it was one of the most "primitive" or earliest types of stingrays. Because of this, he decided it needed its own special group, so he created a new genus called Plesiobatis and a new family called Plesiobatidae. The name Plesiobatis comes from ancient Greek words: plesio means "primitive," and batis means "ray."
Where Deepwater Stingrays Live
Deepwater stingrays are found in many different places across the Indo-Pacific region. They have been seen off the coasts of South Africa and Mozambique, near the Gulf of Mannar, around the Andaman Islands, in the South China Sea, and near the Ryukyu Islands in Japan. They also live along the southern and northwestern coasts of Australia, and near New Caledonia and Hawaii.
These stingrays are bottom-dwelling creatures. This means they live on or near the sea floor. They usually prefer the upper part of the continental slope, which is the gently sloping seabed that connects the shallow continental shelf to the deep ocean floor. They like areas with muddy or silty seabeds. While they usually live in deep water (275 to 680 meters), one was once found in much shallower water, only 44 meters (144 feet) deep, off Mozambique. They seem to be quite common in the tropical waters around Australia, but might be harder to find in other areas.
What the Deepwater Stingray Looks Like
The deepwater stingray has a soft, somewhat floppy body. Its large pectoral fins are joined together to form a disc shape, which is usually longer than it is wide. The front edges of this disc meet at a wide angle. Its snout is thin and very long, much longer than its small eyes. The eyes are located just in front of the spiracles, which are openings that allow the ray to breathe when it's resting on the seabed.
Its nostrils are large and round, and they are close to its mouth. There are wide grooves connecting the nostrils to the mouth. Between the nostrils, there's a flap of skin with a frilly edge. The mouth is wide and straight, and it has many rows of small, blunt teeth (32 to 60 rows in each jaw). As the ray gets older, it grows more teeth. Adult males have sharper, backward-pointing teeth in the middle of their mouths. Like other rays, it has five pairs of small gill slits underneath its body, which it uses to breathe.
The pelvic fins are small and have rounded outer corners. The tail is quite thick and is about as long as the body disc. It doesn't have any skin folds on the sides or any dorsal fins (fins on the back). There are one or two jagged stinging spines on top of the tail, located about halfway along its length. The slender caudal fin (tail fin) starts a little behind the stingers. It's shaped like a rounded leaf and is the same on the top and bottom.
The deepwater stingray's skin is covered with tiny, tooth-like scales called dermal denticles. These denticles are very dense over most of its body, but they are fewer or missing on the pelvic fins, near the edges of the disc, and around the mouth. The ray is purplish-brown to blackish on top. Some rays might also have darker blotches or spots. Its underside is white, with a thin dark border along the edges of its body disc. The tail is completely dark, and the caudal fin is black. This is a very large species. Off southern Africa, it can grow up to 2.7 meters (9 feet) long, 1.5 meters (5 feet) wide, and weigh up to 118 kilograms (260 pounds). However, off Australia, they are usually not known to be larger than 2.0 meters (6.6 feet) long.
What Deepwater Stingrays Eat and How They Live
The deepwater stingray's diet includes cephalopods (like squid), crustaceans (like prawns, crabs, and lobsters), and bony fishes (like eels). Its long, flexible snout is perfect for digging through the soft sediment on the seabed to find food. However, since its diet sometimes includes fish that live in the middle layers of the ocean (called mesopelagic species), it probably also hunts in the open water above the sea floor.
Scientists have observed that kitefin sharks (Dalatias licha) sometimes attack deepwater stingrays. These sharks are known for taking cookie-cutter-like bites out of larger animals.
Like other stingrays, the deepwater stingray gives birth to live young. The developing babies inside the mother are fed by a special substance called histotroph, which is often called "uterine milk." Because of its large size and deep-water lifestyle, this ray likely doesn't have many babies at once, and its pregnancy probably lasts a long time. Young rays are born at about 50 centimeters (20 inches) long. Males become ready to reproduce when they are about 1.3 to 1.7 meters (4.3 to 5.6 feet) long, and females mature when they are about 1.9 to 2.0 meters (6.2 to 6.6 feet) long. The size at which they mature can be different depending on where they live.
Deepwater Stingrays and Humans
When a deepwater stingray is caught, it can thrash its powerful tail very hard. Its long, venomous stinger can cause a serious injury to anyone handling it. These rays are sometimes caught by accident (this is called bycatch) in deep-water bottom trawls (large nets dragged along the seabed) and longlines (long fishing lines with many hooks). The meat of the deepwater stingray can be sold, but it's not considered very good quality.
The deep-water fishing industries in places like South Africa, Taiwan, Indonesia, and Australia are not very large. This means that only a small number of deepwater stingrays are caught. Because of this, the International Union for Conservation of Nature (IUCN) has listed this species as Least Concern. This means it is not currently in danger of extinction. However, if deep-water fishing grows in the future, the deepwater stingray could become more vulnerable. This is because it is probably rare and doesn't reproduce very quickly.
