Grad Publication: Stephanie Crofts

     Below is some pretty awesome work co-authored by grad Stephanie Crofts in Scientific Reports. Make sure to congratulate Stephanie when you see her! Here's the paper.

        Megapiranha, an extinct fish related to piranhas and pacus, and lived during the Miocene epoch, about 10 million years ago.  Today, in the Amazon, red piranhas can get up to 50 cm (about 19.5 inches), and a single bite will take out a chunk of flesh about the size of a grape.  Megapiranha, on the other hand has been conservatively estimated to get up to 71 (28 inches) cm, and could bite off much larger pieces of meat.  Justin Grubich and the rest of the team that worked on this project wanted to know how hard a piranha the size of a dog could bite, and whether its bite was unusual relative to other animals of its size.

        In our recent paper, we worked with living piranhas and used measurements from the fossil fish to get a clearer understanding of bite performance.  Grubich and his team traveled to the Amazon in Brazil and very carefully measured bite force in live fish in the Amazon.  The data from these fishes were analyzed to determine whether a mathematical model could accurately predict their bite force.  When we found that the model worked we applied it to the anatomy of the extinct fish.  That said, a high bite force will only get you so far.  Piranhas also have amazingly sharp teeth to go along with their extremely strong bites. Working with digital models of piranhas, their nut eating cousins the pacus, and the Megapiranha we used finite element modeling to show that while the Megapiranha has sharp bladed teeth to cut like the piranha, their teeth are also robust enough, like the pacu, to spread out forces in the tooth and keep it from breaking when chomping on hard prey items.

Bite force quotients – considering both bite force and body size – compare the powerful bites of black piranha (S. rhombeus) and now-extinct Megapiranha (M. paranensis) with barracuda, blacktip shark (C. limbatus), bull shark (C. leucas), hammerhead shark (S. mokarran), the extinct 4-ton Dunkleosteus terrelli, great white shark (C caracharias) and the extinct whale-eating Carcharodon megalodon. Image from Grubich et al., Scientific Reports. Caption from the UW Today (linked).

For its body size, Megapiranha had the strongest bite force of any bony fish measured thus far, from 1240 - 4749 N; bite forces comparable to very large alligators coming form a fish that probably weighed less than 10 kilos (22 pounds).  This is especially terrifying when considering their teeth, combining the  slightly serrated blades of a piranha and durability of a pacu.   Mechanical tests showed that these teeth were able to crack through turtle shells, plates of catfish armor, and were even able to make a pretty good dent in cow bone!

UW Today Story


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Congrats Autumn 2018 Graduates!