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Wednesday, December 01, 2021

This fish loses 20 teeth each day, then grows them all back

The researchers also found that, much like in humans, tooth replacement in lingcod is predetermined, which means teeth are replaced by teeth of the same type and teeth don’t grow bigger over time.

By: New York Times |
November 5, 2021 1:28:49 pm
teeth fishFluorescent microscopy images of each toothed element showing old teeth (at least partial red fluorescence) and newly replaced teeth (green fluorescence). Credit: University of Washington

Written by Annie Roth

If there is one place you don’t want to stick your finger, it’s the mouth of a Pacific lingcod. These fearsome fish, which can grow up to 5 feet in length and weigh 80 pounds, have around 500 needlelike teeth sticking out of jaws that are strong enough to crush crustaceans.

Having so many sharp chompers allows these ambush predators to subdue everything from slippery squid to heavily armored crabs. How lingcod maintain the sharpness of their terrifying teeth has long been a mystery. But a study, published in October in the Proceedings of the Royal Society B, claims that Pacific lingcod keep their teeth sharp and shiny by replacing about 3% of them every day. For a lingcod, that’s a whopping 20 teeth replaced daily. If you replaced your teeth at the same rate, you might lose and gain a new tooth every day — ouch!

Much of what scientists know about tooth replacement in fishes comes from sharks, which have multiple rows of teeth inside their jaws that are constantly being replenished, and other fish with unusual teeth. But shark teeth differ in significant ways from those found in the majority of fishes, which is why the lingcod findings could help scientists better understand the phenomenon of tooth replacement in fishes.

Around 20% of Pacific lingcod have fluorescent green or blue meat, and scientists aren’t sure why this happens. The fish are considered a smart seafood choice, and delicious when battered and fried. But otherwise, they are fairly average. Their teeth are similar to many other fishes’, which is one of the reasons “they serve as a really nice model for studying teeth in fish,” says Karly Cohen, a doctoral candidate at the University of Washington and a co-author of the new study.

In order to determine the frequency at which lingcod replace their teeth, Cohen and her colleagues kept 20 lingcod at the University of Washington’s Friday Harbor Laboratories and tracked how many teeth they lost and regrew over several days.

The fish were placed in a tank of seawater infused with a red dye that stained their teeth, then returned to their regular tank for 10 days. When the 10 days were up, the fish were placed in a tank containing a green dye, then euthanised and examined. The teeth that were present since the start of the experiment were both red and green, whereas the new teeth were only green.

After collecting and examining a total of 10,000 teeth, the scientists were able to determine how quickly lingcod lost and regrew their teeth and which teeth were replaced most often.

“It’s absolutely crazy how many teeth they replace,” said Emily Carr, an undergraduate researcher at the University of South Florida and the lead author of the study. Carr, who counted all 10,000 teeth by herself, noticed tooth replacement did not occur at the same frequency across the lingcods’ jaws.

Lingcod, like most fish, have two sets of jaws: oral jaws and pharyngeal jaws. Their oral jaws are used to capture and crush prey while their pharyngeal jaws, which are positioned in their throats, are used to chew their food and move it from their mouths to the stomach. Carr and colleagues found that teeth are replaced more frequently in the back of the mouth, where most of the chomping and crushing take place.

The way lingcod replace their teeth is likely crucial to their hunting strategy, says Kory Evans, a fish ecologist at Rice University in Houston. “The duller a lingcod’s teeth are, the harder it is going to be for it to hold on to its prey. So having the ability to shed teeth and replace them is pretty important.” In order to make it as a lingcod, Evans said, “you need sharp pointy teeth and all your teeth need to be on point.”

The researchers also found that, much like in humans, tooth replacement in lingcod is predetermined, which means teeth are replaced by teeth of the same type and teeth don’t grow bigger over time.

Cohen and her colleagues hope that their study will help scientists demystify the world of fish dentition and inspire others to study more fish species. Evans said he hopes some enterprising researchers will take a closer look in the mouth of the sheepshead fish.

“They have these weird, gross, humanlike teeth and I’ve got to know what’s going on there,” he said. “The people deserve to know.”

This article originally appeared in The New York Times.

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