Photo Credit: © Barry Fackler, FlickrWhat goes in must come out in some form, and with parrotfi

Photo Credit: © Barry Fackler, Flickr

What goes in must come out in some form, and with parrotfish, what comes out is sand.

Parrotfish chew on coral all day, eating not only the hard calcium carbonate skeleton but the soft-bodied organisms (called polyps) that cover the skeleton and the algae (called zooxanthellae) that live inside them. When parrotfish poop out the coral they eat, the soft tissues are absorbed and what remains comes out as sand-a lot of sand. In a year, one large parrotfish can produce 1,000 pounds (450 kg) of sand, the weight of a baby grand piano.

Photo Credit: Berkeley Lab

How do they get through all that sandy grit? It’s as though their teeth are made of steel.

No biomineral in the world is stiffer than the tips of parrotfish teeth. Parrotfish teeth are made of a material called fluorapatite which contains calcium, fluorine, phosphorous and oxygen, and is the second-hardest biomineral in the world. Fluorapatite scores a five on the Mohs’ hardness scale, making their teeth harder than copper, silver and gold. The teeth can also withstand a lot of pressure. One square inch of parrotfish teeth can tolerate 530 tons of pressure-equivalent to the weight of about 88 elephants.