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How does this fish keep its 500 teeth nice and sharp? Scientists have the answer – CBC.ca

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The Pacific lingcod is constantly making new teeth.

The predatory fish have 500 pointy teeth in multiple rows, which they use to latch onto their prey and shred them into digestible bits. 

And in order to make sure their chompers are up to the task, they lose and replace about 20 teeth every day, according to a new study published in Proceedings of the Royal Society B.

“For you and I, that basically looks like losing a tooth every single morning,” co-author Karly Cohen, a doctoral candidate at the University of Washington, told As It Happens host Carol Off. 

“Like, we’d wake up and a tooth would be gone and then it would come back. It’s nuts.”

A summer of counting fish teeth 

The lingcod is a “ferocious looking fish” that can grow up to a metre in length, and weighs about 36 kilograms. It feeds on whatever creatures it can fit inside its mouth, and has jaws powerful enough to break through the shells of armoured crabs and other crustaceans. 

In order to eat its prey, it relies on its rows upon rows of razor sharp teeth.

“We can hold a piece of fruit and bring it to our face and chew down on it. But fish don’t have limbs — at least most of them don’t — in the way that we have limbs,” Cohen said.

“And so having this many teeth helps them not only chew through their food and bite through their food, but hold onto it.”

Researcher Karly Cohen looks at fish teeth under a microscope. (Submitted by Karly Cohen)

In order to study the toothy beast’s dental maintenance, the researchers kept 20 lingcod at the University of Washington’s Friday Harbor Laboratories to track how many teeth they lost and regrew on a daily basis.

They placed the fish in a seawater tank with red dye, which stained their teeth, then moved them back into their regular tank for 10 days.

After that, they moved the fish again to a tank with green dye, then euthanized them and examined their mouths to see how many teeth had both red and green colouring.  

“It’s a little horrifying when you look on in there and you just see the sea of small, pointy, clear cones,” Cohen said.

The team counted more than 10,000 teeth in total. Most of that work fell to Emily Carr, an undergraduate researcher at the University of South Florida and the lead author of the study.

“She really did the bulk of the sitting at the microscope and counting these teeny tiny teeth — which was an excellent way for her to spend her summer, in my opinion,” Cohen said.

Pacific lincod have multiple rows of ultra-sharp teeth, which it replenishes every day. (Submitted by Karly Cohen)

The researchers found the fish replaced the teeth from its back rows most often. Those are the ones that do most of the chewing, as opposed to the outer rows, which are designed for catching prey.

But the teeth aren’t coming out due to wear and tear, Cohen said.

“It’s not so much that they’re wearing away or breaking away. We tried to induced that in the lingcod by feeding them lots of hard prey, and it didn’t seem to change much,” she said.

“It seems like maybe somewhere in their own regulation of replacing teeth and their own maintenance, whatever that time cycle is that, they’ve adapted and evolved this pattern of replacement.”

The scientists suspect the fish lose and replace so many teeth so they’re always ready to chow down.

“I think it probably has to do with maintaining the ability to have sharp teeth and maintaining having a whole dental battery of really nice, sharp teeth that are ready to go and ready to eat,” Cohen said. 

The lingcod is not alone in the fish world when it comes to having lots and lots of teeth.

“It looks like fishes in general replace their teeth all the time throughout their life. The best case example of that is in sharks that are always replacing their teeth,” Cohen said.

“I mean, there are rivers in Florida where you can kind of bend down and scoop through the fresh water and you pull up fossils [of] shark teeth.”

But while shark teeth are well studied, the same can’t be said for most fish.

“This starts to give us a baseline understanding of just how quickly the replacement can happen in these bony fishes, and we can start to ask better questions about what drives the vastness or the speed of this replacement,” Cohen said.


Written by Sheena Goodyear. Interview produced by Ashley Fraser.

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A Surprisingly Large Number Of “Stars” You See In The Sky Are Actually Spacecraft – Wonderful Engineering

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Thousands of communication satellites are being designed and launched at a rapid pace. These satellites will have a negative impact on observational astronomy research and are likely to significantly disrupt recreational or traditional cultural stargazing.

If you look up in the sky, you might notice a sequence of bright star-like objects moving in a straight line. Those aren’t stars. They’re Starlink satellites, and they’ll soon be even more noticeable in the dark sky.

Samantha Lawler, assistant professor of astronomy at the University of Regina, recently wrote a piece in The Conversation warning that “one out of every 15 points” of light in the sky could someday be a satellite rather than a star. Moreover, she said he also thinks that satellite companies like Elon Musk’s SpaceX’s Starlink will immensely impact space research.

“This will be devastating to research astronomy and will completely change the night sky worldwide,” she wrote.

Lawler’s forthcoming study will be published in The Astronomical Journal, which will show evidence for the adverse stargazing effects of satellite megaconstellations like SpaceX’s.

Given that firms like SpaceX offer internet to locations around the world that might otherwise be without it, Lawler believes that regulatory agencies should limit the number of visible satellites in orbit.

“Our perspective of the stars will soon be changed forever,” she added if that doesn’t happen.

“We can’t accept the global loss of access to the night sky, which we’ve been able to see and connect with for as long as we’ve been human,” she wrote.

Our orbit is clogged with space debris. Starlink’s satellites have to avoid space junk as well. Will legislators intervene to put a stop to it? If prior responses to existential concerns like climate change are any indication, it will be considered later rather than sooner.

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Dinosaur tail found in Chile stuns scientists – Phys.Org

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Miniature models of the Stegouros elengassen, a species of dinosaur discovred in Patagonia in 2018, is seen on display December 1, 2021 in Santiago.

Chilean paleontologists on Wednesday presented their findings on a dinosaur discovered three years ago in Patagonia which they said had a highly unusual tail that has stumped researchers

The remains of the Stegouros elengassen were discovered during excavations in 2018 at Cerro Guido, a site known to harbor numerous fossils, by a team who believed they were dealing with an already known species of dinosaur until they examined its .

“That was the main surprise,” said Alexander Vargas, one of the paleontologists. “This structure is absolutely amazing.”

“The tail was covered with seven pairs of osteoderms … producing a weapon absolutely different from anything we know in any dinosaur,” added the researcher during a presentation of the discovery at the University of Chile.

The osteoderms—structures of bony plaques located in the dermal layers of the skin – were aligned on either side of the tail, making it resemble a large fern.

Paleontologists have discovered 80 percent of the dinosaur’s skeleton and estimate that the animal lived in the area 71 to 74.9 million years ago. It was about two meters (almost seven feet) long, weighed 150 kilograms (330 pounds) and was a herbivore.

According to the scientists, who published their research in the journal Nature, the animal could represent a hitherto unknown lineage of armored dinosaur never seen in the but already identified in the northern part of the continent.

The remains of a Stegouros elengassen, a new species of dinosaur discovered in Patagonia, is seen on display in Santiago Decembe
The remains of a Stegouros elengassen, a new species of dinosaur discovered in Patagonia, is seen on display in Santiago December 1, 20121.

“We don’t know why (the tail) evolved. We do know that within armored dinosaur groups there seems to be a tendency to independently develop different osteoderm-based defense mechanisms,” said Sergio Soto, another member of the team.

The Cerro Guido area, in the Las Chinas valley 3,000 km (1,800 miles) south of Santiago, stretches for 15 kilometers. Various rock outcrops contain numerous fossils.

The finds there allowed the scientists to surmise that present-day America and Antarctica were close to each other millions of years ago.

“There is strong evidence that there is a biogeographic link with other parts of the planet, in this case Antarctica and Australia, because we have two armored there closely related” to the Stegouros, said Soto.


Explore further

New dinosaur species from Chile had a unique slashing tail


More information:
Alexander Vargas, Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile, Nature (2021). DOI: 10.1038/s41586-021-04147-1. www.nature.com/articles/s41586-021-04147-1

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Dinosaur tail found in Chile stuns scientists (2021, December 4)
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Total solar eclipse brings darkness to Antarctic summer – CBC.ca

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Video released by NASA shows a total solar eclipse as seen from Western Antarctica on Saturday.

The Earth’s southernmost continent experiences continual daylight from mid-October until early April, but the eclipse brought a few minutes of total darkness.

NASA said the period of totality began at 2:44 a.m. ET. 

A solar eclipse occurs when the moon moves between the sun and Earth, casting a shadow on Earth, fully or partially blocking the sun’s light in some areas.

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For a total eclipse to take place the sun, moon, and Earth must be in a direct line. The only place that this total eclipse could be seen was Antarctica.

The eclipse was also expected to be visible partially from South Africa, Chile, New Zealand and Australia on Saturday.

North America gets its next glimpse of a full solar eclipse on April 8, 2024.

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