Freshwater stingrays chew their food just like a goat

Date: September 16, 2016

Source: University of Toronto

 

A new University of Toronto study has found that some freshwater stingrays from the Amazon chew their food in a similar fashion as mammals.

Using a combination of high-speed video and CT scans Matthew Kolmann, a recently graduated PhD in the lab of U of T Scarborough's Nathan Lovejoy found that as the freshwater stingray Potamotrygon motoro eats it protrudes its jaws away from its skull, shearing from side to side in the process.

"It's pretty extraordinary when you think about it -- here's this bizarre-looking fish from the Amazon that evolved these behaviors separately from mammals, but chews its food just like a cow or a goat," he says.

Kolmann was first drawn to the question of how P. motoro and its close relative, Potamotrygon orbignyi, eat their prey after finding out both species feed on aquatic insects, unique for a family that also includes sharks, skates and other stingrays.

Stingrays have fins that encircle their head called a disk. They catch prey by lifting up the front part of their disk, which draws water and prey underneath, much like a suction cup. Once rays have trapped their prey, they grab it by rapidly protruding their jaws, shredding and tearing it apart.

"They don't actually use their mouth to catch their prey, which suggests that parts of the mouth can evolve away from that specific purpose and may be driving the novelty of this chewing behaviour," Kolmann says.


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Is this stingray the world’s largest freshwater fish?

March 15, 2015

Chuck Bednar for redOrbit.com – 

A massive 8-foot by 14-foot, 700 to 800-pound pregnant stingray caught in Thailand by nature conservationist and TV show host Jeff Corwin last week might be the largest freshwater fish of all time, according to various media reports.

The ray was caught and released in the Mae Klong River in Thailand’s Amphawa District, about one hour outside of Bangkok, National Geographic reported on Wednesday. Nantarika Chansue, a veterinarian and professor at Chulalongkorn University, assisted Corwin with the catch.

(Credit: Jeff Corwin/Twitter)

Chansue referred to the creature, officially known as Himantura polylepis, as “the big one,” but Zeb Hogan, a National Geographic fellow and professor of biology at the University of Nevada-Reno, explained that the team was unable to get an exact weight for fear of injuring the ray.

All they know is that it was really, really big

“It’s really hard to weigh these things without hurting them, because they are such big, awkward animals,” said Hogan, who had actually caught and tagged the same stingray back in 2009, when it was slightly smaller. “Certainly [this] was a huge fish, even compared to other giant freshwater stingrays, and definitely ranks among the largest freshwater fish in the world.”

Read more at

Photobombing stingray picture goes viral

The terrified trio were posing for a photo in the idyllic surroundings of the Cayman Islands when the slippery stingray crept up behind them.

They had reportedly enjoyed a day's snorkelling in Stingray City, a popular tourist destination where holidaymakers are encouraged to feed and touch the fish.

'Enjoy this unique experience of touching and feeding a stingray, together with snorkelling amongst magnificent coral reefs and colourful tropical fish,' explains Stingray City's official website. 

'Standing in only three feet of water you will be surrounded by more than two dozen friendly stingrays.'

When the role-reversing sea creature decided to reciprocate the friendly feelings it didn't receive quite the response he might have been expecting.

As two amused holidaymakers watch the events unfold, a look of terror can be seen on the three women's faces as the prankster poses calmly in the background.

The photograph, originally posted image sharing site Imgur, quickly went viral across various social-networking sites.

'Yes, this is the best photobomb ever,' said one Twitter user.

While another added: 'Is this the photobomb to end all photobombs?'

http://www.metro.co.uk/weird/913580-photobombing-stingray-picture-goes-viral#ixzz27x7Rm47Z

Female stingrays give birth to baby rays despite no contact with males

The baby stingrays arrived after two females were seen looking mysteriously bloated and later found to be pregnant.
The 15cm (6in) babies have now grown big enough to be moved to their new home in Sea Life London Aquarium’s SOS area – where they are proving a hit with visitors.

‘Rays have been known to store sperm and not give birth until they decide the timing is right but it’s not something I’ve seen before in my eight years here,’ said Paul Hale, head curator at the central London attraction.

‘The staff noticed two female stingrays looking bloated so gave them a health check and were surprised to discover they were both expecting, considering there have been no males in their display for so long. These pups will be very popular with our visitors this summer.’
Stingrays are named after their venomous, barbed tails, which are used in self-defence.
Australian naturalist Steve Irwin was killed by a stingray barb in 2006.


Read more: http://www.metro.co.uk/weird/871875-female-stingrays-give-birth-to-baby-rays-despite-no-contact-with-males#ixzz1V0Hoezb4

Rare stingray caught off Shetland

A specimen of the Violet or Pelagic stingray, Pteroplatytrygon violacea, has been caught by fishermen in the Shetland Isles.

The crew of the Guardian Angell hauled their nets near Whalfirth, at the north end of Yell Sound, Shetland when they noticed the ray still alive among the catch.

Realising that the fish was unusual, they took it to the nearby NAFC Marine Centre at Scalloway, Shetland where they confirmed that it was not the already rare locally common stingray, Dasyatis pastinaca but in fact the most northerly recorded catch of a Violet stingray.

The fish was a female, measuring 55cm from wing tip to wing tip, 47cm in body length and the total length including tail,(which was partly missing) was 112cm.

The Violet stingray gets its common name from its purplish colouration which is unusually on both the dorsal and ventral surfaces of the fish.

Possibly uniquely among stingrays, these fish swim in the middle of the water column rather than near or on the sea bed, feeding on jellyfish, squid, crustaceans and fish. They are more typically resident of tropical and sub-tropical waters and are distributed worldwide.

Bob Mehen
http://www.practicalfishkeeping.co.uk/content.php?sid=3280

Fossilised pig belongs to new species

9 October 2009

A fossilised pig discovered in a sand pit in Nakhon Ratchasima eight years ago has been found to belong to a new species.

And scientists have also named a new species of stingray in the past year.

The developments were revealed yesterday by the Nakhon Ratchasima-based Northeastern Research Institute for Petrified Wood and Mineral Resources, which supports research projects by scientists.

The institute said two new species had been confirmed this year.

The pig fossils were found in the Moon River basin in Nakhon Ratchasima by palaeontologist Rattanaphorn Hanta in 2001.

The discovery was published early this year in a palaeontology journal to confirm it was a new ancient pig species.

The pig, which lived in the late-Miocene period 6 million to 8 million years ago, was named Merycopotamus thachangensis after the Tha Chang village where the fossils were found.

"The pig fossils show the pig had a unique tooth shape pattern which is different from prehistoric pig species, but close to the pig species of present day," Ms Rattanaphorn said.

Judging from the shape of its skull, the pig lived in similar conditions to the hippopotamus. The pig, which is about 800cm tall with short legs, lived in swamps with adjacent grassland.

She found the fossils at a sand pit near the Moon River in Chalerm Phrakiat district, 20 metres below the surface.

Fossils of several other species, such as a mammoth and rhinos, were also uncovered.

Her team was waiting for confirmation of two new ancient elephant species also found as fossils at the site, Ms Rattanaphorn said.

Another species given a formal name by the institute this year is a stingray.

Chavalit Vidthayanon, the institute's deputy director, said a stingray of the genus Himantura, found in Songkhla lake in the southern provinces of Songkhla and Phatthalung, had been confirmed as a new species.

Known as pla kraben bua, the fish was well known among local people.

It has a sharply pointed snout and rounded wing. However, scientists do not know how many are left.

"I can't say exactly how many of them still exist.

"But local fishermen catch only 20 or so a year now, down from about five tonnes a year two decades ago, which suggests there are very few left," Mr Chavalit said.

He said the fish was at risk of extinction because of the poor condition of the Songkhla lake.

http://www.bangkokpost.com/news/local/25278/fossilised-pig-belongs-to-new-species

(Submitted by Terry Colvin)

Best Beware Thy Stingray

by Vera H-C Chan
February 25, 2009 12:13:42 PM

A record-breaking stingray capture, by the numbers:

• 1 rod and line
  
• 90 minutes for one British biologist (with help) to reel in the freshwater fish
  
• 13 men to drag said fish onto a boat
  
• 125 pounds—that's the difference between the stingray's weight at 771 pounds and the previous record rod-&-reel capture of a catfish

The Thailand capture of the massive female stingray was part of a program to tag such Maeklong River residents. The captive, part of a "vulnerable species" listed by the International Union for Conservation of Nature, measured a hefty 7 feet by 7 feet. That doesn't include the 10-foot-long poisonous tail.

Such creatures are dangerous, of course: Famed Australian TV personality Steve "Crocodile Hunter" Irwin died from a stingray barb at the Great Barrier Reef in 2006.

The numbers currently put one Ian Welch on the world record books. (Pictures of Welch posing with his female companion can be found here.) The stingray's resistance nearly dunked Welch into the river, and he was literally saved by the seat of his pants when a crewmate grabbed his trousers.

Another reason that this marine fish is so huge: She's pregnant. (Cue soap-opera gasp.) After she had been towed to the bank (too big to be onboard the boat), she was duly marked, had DNA samples removed, and returned to the river whence she unwillingly came. Welch gave her a farewell smooch, then spent the rest of the day with a cold beer and memories of her.

By the way, one number isn't known: the exact stingray population count, which has shrunk 20 percent in the past decade. With this lady's help, at least one more will be added to this number...and with a tale to tell.

British angler lands monster stingray in Thailand

Steven Morris guardian.co.uk
Tuesday 24 February 2009 13.35 GMT

Catch weighing up to 350kg could be the largest freshwater fish ever caught by rod and line

A British angler – with a dozen helpers – has landed what could be the biggest freshwater fish ever caught with a rod and line, it emerged today.

The giant freshwater stingray, weighing as much as 350kg (772lbs, or about 55 stone), was the size of a garden shed and so cumbersome that Ian Welch had to enlist the aid of 12 other people to get it out of the water.

Welch, a professional fisherman, biologist and columnist for the magazine Angler's Mail, was visiting Thailand to help with a stingray tagging programme when he landed the monster in the Maeklong river. The 45-year-old said he was nearly pulled over the side of the boat when the specimen took his bait.

He said: "It dragged me across the boat and would have pulled me in had my colleague not grabbed my trousers – it was like the whole earth had just moved. I knew it was going to a big one.

"It buried itself on the bottom and the main fight was trying to get it off the floor. I tried with every ounce of power but it just would not budge. After half an hour my arms began shaking and after an hour my legs went. Another 30 minutes went by and then I put a glove on and physically pulled the line with gritted teeth and somehow I found the reserves to shift the fish."

Once the stingray was off the bottom, Welch, who weighs a relatively modest 73kg, managed to lift it to the surface relatively easily.

"As soon as we saw it there was just silence because everyone was just in awe of this thing," he said. "That line from the film Jaws came to mind about needing a bigger boat because we had to get it to the shore to tag it."

The group managed to put a large net under the fish and towed it to the bank. Welch, from Aldershot, Hampshire, said: "It took 13 people to lift it into a large paddling pool we had set up in order to tag it and take DNA samples.

"I was absolutely exhausted afterwards and did very little for the rest of the day and just had a cold beer. As a life-long angler and a biologist it is great that my two passions have come together and culminated in something I could only have dreamed of."

The female stingray was about 2 metres (7ft) long and the same width, and its tail measured about 3 metres (10ft). From its measurements it was calculated that it weighed at least 265kg, and possibly up to 350kg.

Its venomous barb had to be wrapped in cloth while it was out of the water. Once it was tagged the fish was released back into the river. Welch said he swam out with the fish and kissed it goodbye.

Angler's Mail has billed Welch's specimen as probably the largest freshwater fish fully authenticated as caught by rod and line.

http://www.guardian.co.uk/world/2009/feb/24/stingray-catch-thailand-fishing