If there’s one place you don’t want to put your finger on, it’s a Pacific lingcod’s mouth. These formidable fish, which can grow up to five feet in length and weigh 80 pounds, have around 500 needle-shaped teeth emerging from jaws strong enough to crush crustaceans.
Having so many sharp chompers allows these ambush predators to master everything from slippery squids to heavily armored crabs. How lingcod maintains the sharpness of its terrifying teeth has long been a mystery. But a study, published in October in the Proceedings of the Royal Society B, claims that the Pacific lingcod keeps its teeth sharp and shiny by replacing about three percent of them every day. For a lingcod, this represents up to 20 teeth replaced daily. If you replace your teeth at the same rate, you may lose and gain a new tooth every day – ouch!
Much of what scientists know about tooth replacement in fish comes from sharks, which have multiple rows of teeth inside their jaws that are constantly being renewed, and other fish with unusual teeth. But shark teeth differ significantly from those found in the majority of fish, which is why the ling cod results could help scientists better understand the phenomenon of tooth replacement in fish.
About 20 percent of Pacific lingcod have fluorescent green or blue meat, and scientists aren’t sure why this happens. Fish is considered a smart and delicious seafood choice when breaded and fried. But otherwise, they are quite average. Their teeth are similar to those of many other fish, which is one reason why “they make a very good model for studying fish teeth,” says Karly Cohen, a doctoral student at the University of Washington and co-author of the new study book.
In order to determine how often lingcod replaces its teeth, Cohen and her colleagues stored 20 lingcods at the University of Washington’s Friday Harbor Laboratories and tracked the number of lost and regrown teeth over several days. The fish were placed in a seawater tank impregnated with a red dye that stained their teeth, then returned to their usual tank for 10 days. Once the 10 days had elapsed, the fish were placed in a tank containing a green dye, then euthanized and examined. The teeth present since the start of the experiment were both red and green, while 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 regrown its teeth, and which teeth were replaced most often.
“The number of teeth they’re replacing is absolutely insane,” said Emily Carr, an undergraduate researcher at the University of South Florida and lead author of the study. Carr, who herself counted the 10,000 teeth, noticed that tooth replacement did not occur at the same frequency in the jaws of lingcods.
Lingcod, like most fish, has two pairs of jaws: the oral jaws and the pharyngeal jaws. Their mouth jaws are used to capture and crush prey while their pharyngeal jaws, which are positioned in their throat, are used to chew their food and move it from their mouth to the stomach. Ms. Carr and her colleagues have found that teeth are replaced more frequently at the back of the mouth, where most chewing and crushing occurs.
How the lingcod replaces its teeth is likely crucial to its hunting strategy, says Kory Evans, a fish ecologist at Rice University in Houston. “The duller a lingcod’s teeth, the harder it will be to hold onto its prey. So having the ability to lose teeth and replace them is quite important. In order to make it into a lingcod, Dr Evans said, “You need sharp, pointy teeth and all of your teeth need to be in focus.”
The researchers also found that, just like in humans, tooth replacement in lingcod is predetermined, meaning the teeth are replaced with teeth of the same type and the teeth do not grow larger over time.
Ms Cohen and her colleagues hope their study will help scientists demystify the world of fish teeth and inspire others to study more species of fish. Dr Evans said he hoped some enterprising researchers would take a closer look at the mouth of the sheep’s head fish.
“They have these weird, coarse, human teeth and I need to know what’s going on there,” he said. “People deserve to know. “