Longtail butterfly ray facts for kids
Quick facts for kids Longtail butterfly ray |
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Pastinaca kunsa Cuvier, 1829 |
The longtail butterfly ray (Gymnura poecilura) is a type of butterfly ray. It belongs to the Gymnuridae family. This ray lives in the Indo-Pacific ocean. Its home ranges from the Red Sea to southern Japan and western Indonesia.
This ray can grow up to 92 cm (36 in) wide. Its body is shaped like a diamond. It is about twice as wide as it is long. The ray's color is brown to gray on top. It has many small, light spots. Behind its eyes are special openings called spiracles. These spiracles have smooth edges. You can tell this ray apart by its tail. The tail is about as long as its body. It has no fins. The tail has nine to twelve black and white bands that go back and forth.
The longtail butterfly ray lives on the ocean bottom. It likes sandy or muddy places. These are usually in coastal waters less than 30 m (98 ft) deep. It eats bony fishes, molluscs (like snails or clams), and crustaceans (like crabs or shrimp). This ray gives birth to live young. The baby rays first get food from a yolk. Later, they get special "uterine milk" from their mother. There is no special time of year for them to have babies. Females can have up to seven pups at a time. People catch the longtail butterfly ray for its meat. Both small local fishers and large commercial fishing boats catch them.
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What is a longtail butterfly ray?
The longtail butterfly ray was first described in 1804. An English zoologist named George Shaw gave it the name Raja poecilura. The name poecilura comes from Greek words. Poikilos means "of many colors" and oura means "tail". Later, this ray was moved into the Gymnura group.
Scientists are still studying if rays in French Polynesia are the same species. Studies show that the longtail butterfly ray is closely related to the zonetail butterfly ray (G. zonura). They live in many of the same places. Another name for this ray is the variegated butterfly ray.
Appearance and features
The longtail butterfly ray has a diamond-shaped body. This shape is common for its family. Its body is about twice as wide as it is long. The front edge of its body is gently wavy. The back edge is rounded. Its outer corners are slightly angled. The ray has a short, wide snout. It has a tiny tip that sticks out. Its eyes are medium-sized. Behind them are larger spiracles with smooth edges.
Its nostrils are close to its mouth. Between them is a short, wide flap of skin. The mouth is large and curved. It has more than 50 rows of small, pointed teeth in each jaw. The number of teeth grows as the ray gets older. There are five pairs of short gill slits on the underside of its body. Its pelvic fins are small and round.
The ray's tail is thin like a thread. It does not have dorsal or caudal fins. But it does have low ridges along its top and bottom. The tail is about as long as the distance from its snout to its vent. This helps tell it apart from other butterfly rays with shorter tails. Sometimes, there is a small stinging spine on the top of the tail near its base. Very rarely, there are two spines. The ray's skin is smooth and has no rough scales.
This ray is brown, greenish-brown, or gray on top. It has many small, pale spots. Sometimes it also has dark dots. The tail has nine to twelve black bands. These bands go back and forth with white bands. The white bands often have a small dark spot on top. The underside of the ray is white. It gets darker at the edges of its fins. The longtail butterfly ray can grow up to 92 cm (36 in) wide.
Where they live
The longtail butterfly ray is the most widespread ray in its family. It lives in the Indo-Pacific region. You can find it from the Red Sea and Somalia. It also lives across India and Sri Lanka, to China and southern Japan. It is found in the Philippines and the western islands of Indonesia. This includes Borneo, Sumatra, and Java. It has also been seen near French Polynesia. This ray is quite common in some areas.
This ray lives on the bottom of the ocean. It prefers coastal waters that are 10–30 m (33–98 ft) deep. It likes sandy or muddy ocean floors. It does not seem to move to different areas during different seasons.
Life cycle and behavior
The longtail butterfly ray eats bony fishes. It especially likes ponyfishes. It also eats molluscs and crustaceans. This ray does not usually gather in large groups.
Like other butterfly rays, this species gives birth to live young. The baby rays first get food from a yolk sac. Later, the mother makes a special "uterine milk" to feed them. Female rays have two working ovaries and uteruses. They can have babies all year long. But there is a peak time from April to October. We don't know how long the babies stay inside the mother. But it's possible that females can have more than one group of babies each year. A female can have at least seven pups at a time. The number of babies does not depend on the mother's size.
Newborn rays are 20–26 cm (7.9–10.2 in) wide. They look like tiny versions of the adults, but without a sting. Baby rays from the same mother might have different colors. Males become ready to have babies when they are about 45 cm (18 in) wide. Females are ready when they are about 41 cm (16 in) wide.
Human impact and conservation
People catch the longtail butterfly ray for its meat. It is also often caught by accident. This happens during both small-scale local fishing and large commercial fishing. This includes fishing in India, Thailand, and Indonesia. Fishers use nets that drag along the bottom. They also use nets that sit on the bottom. Sometimes they use other types of fishing gear.
We don't have exact numbers on how many rays are caught. But scientists think the longtail butterfly ray can be easily overfished. This is because it does not have many babies. There is a lot of fishing in most places where this ray lives. Because of this, the International Union for Conservation of Nature (IUCN) has listed this species as Vulnerable. This means it is at risk of becoming endangered.
