PARIS – Outsized jaw muscles allow the black piranha to exert a bite force equivalent to 30 times its weight, a feat unmatched in the natural world, according to a finger-risking study published Thursday in the journal Scientific Reports.
Animals such as the great white shark, the hyena and the alligator can deliver more forceful bites, but their crunching power is much less impressive when viewed in relation to their overall size and weight, it said. Relative to their size, piranhas outperform even prehistoric monsters like Tyrannosaurus rex and the whale-chomping megalodon, a massive shark that preceded the great white.
For the research, scientists caught 15 black piranhas in Brazil’s Amazon River basin and risked their digits by teasing a customized force gauge between their serrated jaws. The fish, ranging from about 20 to 37 cm in length, “readily performed multiple defensive bites” on the gadget, wrote the team from the United States, Egypt and Brazil.
This was the first live measurement of bite force taken from the black piranha (Serrasalmus rhombeus), the largest of the notoriously carnivorous species.
Such undertakings are “rare, dangerous and difficult to perform,” wrote the research team. “While anecdotes of piranha-infested waters skeletonizing hapless victims are generally hyperbole, the effectiveness of their bite is not.” They pointed to “documented cases of S. rhombeus biting off and consuming human phalanges” — the bones in fingers and toes.
The measured bite force of the black piranha, at 320 newton (N) — roughly equal to the force of a weight of 32 kg — was nearly three times greater than that exerted by an American alligator of comparative size, said the study.
How does the tiny fish do it? It has jaw muscles of an “extraordinary” size and a highly modified jaw-closing lever. The muscle complex makes up more than 2 percent of the black piranha’s total body mass.
The team also used the data they gathered to estimate the bite force of the extinct Megapiranha paranensis to have been between 1,240 and 4,749 N. The fish from the Miocene period, which ended about 5 million years ago, were about 70 cm long and weighed about 10 kg, they said. “Our analysis predicts Megapiranha’s bite was equivalent to the anterior bite force of a great white shark weighing over 400 kilos,” said the report.
“If our fossil reconstructions and simulations are correct, then Megapiranha paranensis was indeed a ferocious bone-crushing megapredator of the Miocene epoch,” just like its modern-day relative, said the report.