“Jaws” helped shape the global perception of great white sharks, but it shaped it all wrong. Photo: Unsplash
Teeth are just one factor that put some shark species at the top of the ocean food chain. They can be razor sharp, and number in the hundreds in one shark’s mouth alone. They fall out and grow back at rates that are absolutely fascinating. Unlike us, sharks have an endless supply of teeth. They lose them as frequently as every few days or weeks, and how fast they grow back is critical for species like bull sharks, for example, that can have as many as 300 teeth filling up a dozen rows.
But those chompers might be in trouble, says research published this week by a group of German scientists, suggesting ocean acidification threatens those all-important teeth. In short, it could impact tooth regrowth negatively and prevent them from growing back at a rate that keeps up with how fast they fall out.
“As shark tooth roots are not protected by soft tissue, unlike in mammals, they are naturally exposed to surrounding water. This exposure makes them especially susceptible to pH-induced degradation, notably in the osteodentine-rich regions,” the researchers explained in the new study.
To test the impact, the researchers kept 60 teeth from black tip reef sharks that had recently fallen out and placed them in artificial seawater tanks. One tank matched the ocean’s current average pH of 8.1, another had water with 7.3 pH, which is an acidification level projected for the year 2300. After eight weeks in those tanks, the teeth in the tank with increased acidification levels showed “increased root corrosion … and altered serration.”
“The damage we observed to enameloid and dentin layers underlines that even the typically more crystalline components of shark teeth are not immune to acidification,” the scientists wrote in conclusion. “Degradation of the crown structure could compromise the mechanical properties of teeth, especially in regions involved in prey capture and processing. Increased serration, while potentially beneficial for cutting efficiency, might lead to structural weakness and higher susceptibility to breakage.”
“It will be interesting to see in future studies if the damage to teeth seen in studies like this one results in a functional effect on a tooth’s ability to do its job … [and if] damaged teeth can still cut or puncture prey,” Lisa Whitenack, a professor at Pennsylvania’s Allegheny College told The Guardian.