Giant Freshwater Stingray

Giant Freshwater Stingray

As National Geographic previously reported, freshwater stingrays are known to inhabit rivers in Southeast Asia and northern Australia, where they can reach enormous proportions, measuring up to 16.5 feet (5 meters) long and up to 1,320 pounds (600 kilograms). However, very little is known about these creatures, including how many are left, and if they ever enter saltwater.

Freshwater stingrays are hard to see, because they often bury themselves in river sediments. They hunt for clams and crabs by detecting their electric impulses. There are reports of the big animals overturning boats, though they rarely attack people.

Even so, stingrays can pack a powerful punch; they have a barb at the base of their tail that contains deadly poison and a stinger as long as 15 inches (38 centimeters).

Many scientists fear that freshwater stingrays are threatened by habitat loss and pollution.

Distribution and habitat

The giant freshwater stingray is known to inhabit several large rivers and associated estuaries in Indochina and Borneo. In Indochina, it occurs in the Mekong River to potentially as far upstream as Chiang Khong in Thailand, as well as in the Chao Phraya, Nan, Mae Klong, Bang Pakong, Prachin Buri and Tapi Rivers. In Borneo, this species is found in theMahakam River in Kalimantan and the Kinabatangan and Buket Rivers in Sabah; it is reportedly common in the Kinabatangan River but infrequently caught. Though it has been reported from Sarawak as well, surveys within the past 25 years have not found it there. Elsewhere in the region, recent river surveys in Java have not recorded its presence, despite the island being the locality of the species holotype. Historical records from Myanmar, the Ganges River in India, and the Bay of Bengal (the latter two as Trygon fluviatilis) have similarly not been corroborated by any recent accounts.

Disjunct populations of the giant freshwater stingray in separate river drainages are probably isolated from one another; though the species occurs in brackish environments, there is no evidence that it crosses marine waters. This is a bottom-dwelling species that favors a sandy or muddy habitat. Unexpectedly, it can sometimes be found near heavily populated urban areas.

Growth of stringray:

1. No one is sure how many giant stingrays are left, which habitats they prefer, or even if they ever venture into the ocean, where their more commonly known relatives dwell. These ancient fish, little changed over many millions of years, can reach 16.5 feet (5 meters) long and weigh up to 1,320 pounds (600 kilograms).
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   Reproduction:
   
   

   

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   When a male is courting a female, he will follow her closely, biting at her pectoral disc. He then places one of his two claspers into her valve.

   Stingrays are ovoviviparous, bearing live young in "litters" of 5 to 13. The female holds the embryos in the womb without a placenta. Instead, the embryos absorb nutrients from a yolk sac, and after the sac is depleted, the mother provides uterine "milk"

   At the Sea Life London Aquarium, two female stingrays have delivered seven baby stingrays, although the mothers have not been near a male for two years. "Rays have been known to store sperm and not give birth until they decide the timing is right".

3. Diet:
   
   

   

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   A stingray's diet includes small fish, snails, clams, and shrimp, and some other small sea creatures.
4. Behaviour:
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   The flattened bodies of stingrays allow them to effectively conceal themselves in their environment. Stingrays do this by agitating the sand and hiding beneath it. Because their eyes are on top of their bodies and their mouths on the undersides, stingrays cannot see their prey; instead, they use smell and electroreceptors (ampullae of Lorenzini) similar to those of sharks. Stingrays feed primarily on molluscs,crustaceans, and occasionally on small fish. Some stingrays' mouths contain two powerful, shell-crushing plates, while other species only have sucking mouthparts. Stingrays settle on the bottom while feeding, often leaving only their eyes and tail visible. Coral reefs are favorite feeding grounds and are usually shared with sharks during high tide.
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