When it comes to spotting prey, sharks and rays have a secret sense beyond sight and smell. Tiny goo-filled organs called Ampullae of Lorenzini detect the invisible electric fields produced by all living creatures.

DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe and meet extraordinary new friends. Explore big scientific mysteries by going incredibly small.

How do Sharks and Rays Sense Electric Fields?

Most animals don’t have the ability to detect electric fields. But sharks, rays, skates and sawfish — members of a group called Elasmobranchii — are masters of detecting electric signals. It’s one of their defining features. Elasmobranchs have specialized organs called Ampullae of Lorenzini. These tiny structures allow them to home in on weak bioelectric fields generated by nearby prey.

Elasmobranch’s electrosensory organs are named after a 17th century Italian physician, Stefano Lorenzini, who first identified them while dissecting an electric ray. Lorenzini noticed dozens of tiny pores around the animal’s mouth. Each of the pores led to jelly-filled canals that ended in pocket-like structures that he called ampullae, the Latin word for a type of round-bottomed flask.

Animals emit low frequency electric fields due to a process known as osmoregulation. This process allows the concentration of ions (charged atoms or molecules) to flow between the inside of our bodies and the outside. In order for our cells to stay intact, the flow of ions needs to be balanced.

But balanced doesn’t necessarily mean equal. The concentration of ions within a shrimp’s body is much lower than that of the sea water it swims in. Their voltage, or potential difference generated between the two concentrations across “leaky” surfaces, can then be detected by the ampullae.

More KQED SCIENCE:

Tumblr: kqedscience.tumblr.com
Twitter: www.twitter.com/kqedscience
KQED Science: ww2.kqed.org/science

— Read the article for this video on KQED Science:
ww2.kqed.org/science/2015/08/11/sharks-and-rays-sense-electricity-fish-cant-hide/
#deeplook