By Anonymous -
Shark Teeth

By: Cecilia Vela

Humans are born with no teeth and in the first several years of life will grow about 20 teeth, our baby teeth. Losing them is exciting and a bit scary as they get wiggly until the eventually either fall out or get pulled out (1). Then we are left with a whole in our smile until our adult/permanent tooth grows up from our gums. Once we lose all of our baby teeth and have our molars come in we end up with about 32 teeth (1). These are known as our adult teeth and we keep those, hopefully, until the end of our days since no more will grow in. We also have different types of teeth, incisors for biting off pieces of food that we can then chew or grind with our flat back teeth/molars (1).
Nurse shark tooth         Sharks on the other hand can have up to 3,000 teeth at one time (2). Different species will vary in the number of teeth they have but all sharks are born with a complete set of teeth (3). While shark teeth have the same central pulp cavity and an enamel outer layer, they are essentially modified placoid scales (2). There are different shapes between different types of sharks depending on the prey they specialize on, but an individual shark’s teeth are all the same (2). This means that they do not have incisors and molars or individual teeth that specialize for different functions. Shark teeth all have the same purpose, they tear up food into bite sized pieces and swallow them down. Most shark have about 5 rows of teeth (2). Some sharks, however, have about 15 rows of teeth, and bull sharks, those crazy predators, have an astonishing 50 rows of teeth (3). The largest teeth are in the front and they get smaller the further back they go (2). The front, large ones often get damaged and or broken and fall out. When this happens the tooth in the next row just moves up and a new tooth develops in the back (2). These teeth can also simply break off into their prey (3). Their teeth rotate forward, growing new teeth as needed for the entirety of a shark’s life (2). Due to how many teeth they have, most sharks typically lose about 1 tooth per week (3). Some sharks, such as nurse sharks, just routinely loose those front teeth so that their teeth are always sharp and are replaced every 10-14 days, before they start to dull (2). It is common for sharks to lose, and grow, thousands of teeth in a lifetime (3).

A recent trip to the Oklahoma Aquarium was a great opportunity to get a first-hand encounter with this unique phenomenon.  We got to walk through a massive shark tank with sharks swimming all around and above us. This tank had both bull sharks and nurse sharks. While walking through this tank there were visible white…things on the floor, initially I just assumed it was debris, left over fish parts, and or just part of the tank. It was only after taking our private tour and walking above the tank that out tour guide informed us that those white things in the bottom were shark teeth. She informed us that sharks are nearly always losing teeth and replacing them with new ones. She stated that when they go in to clean the tank they just vacuum up all the teeth at the bottom and, since there are so many and then pass them out to children that come to the aquarium. We were lucky enough to get one to take home with us. 
            I was pretty amazed with this as I thought about losing and growing that many teeth and how fascinating that was. It makes sense for sharks since they rely on their teeth to be sharp enough to bit into and through slimy/slippery fish. It is simply one of those things I had never thought about or heard about. I knew sharks had lots of teeth but not that they grew so many and lost so many in their lifetime.  


Citations
(1) “Human Tooth.” Wikipedia, Wikimedia Foundation, 3 Apr. 2018, en.wikipedia.org/wiki/Human_tooth. https://en.wikipedia.org/wiki/Human_tooth 
(2) Shark Teeth - EnchantedLearning.com, www.enchantedlearning.com/subjects/sharks/anatomy/Teeth.shtml. 
(3) “Sink Your Teeth into This: 20 Facts about Shark Teeth.” Beach Chair Scientist, 25 Feb. 2015, http://beachchairscientist.com/2012/08/12/sink-your-teeth-into-this-20-facts-about-shark-teeth/



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