By Blaise Jones
Shark have a wide variety of amazing senses and none are more fascinating and alien than their electrosense. Through their ampullae of Lorenzini (also called the ampullae de Lornenzini) sharks are able to detect the minute electrical sensations that all living creatures generate.
The ampullae of Lorenzini are named after the Italian scientist Stefano Lorenzini, who, in 1678, was the first scientist to describe in detail the odd pits found on the heads and noses of sharks and stingrays. (Though it should be noted that another Italian scientist, Marcello Malpighi, first mentioned the ampullae in 1662.) However, neither scientist knew what exactly theses odd pits were for, speculating that they might be able to detect pressure or temperature changes.
It wasn’t until the 1960s that a pair of Dutch scientists discovered that these odd pits were actually a series of electro-receptive organs. Ironically enough, it was discovered in 2003 that these electroreceptors are so sensitive that they can in fact detect temperature changes, proving correct the scientific hunches of the Italian pioneers more than 300 years earlier.
Anatomy of an Ampullae
Each ampullae’s only external feature are the pits that line the faces and snouts of sharks and stingrays. These pits are slightly depressed and black in color, and the casual observer wouldn’t be faulted for thinking that the shark had gone a few days without shaving.
In actuality these pits are filled with an electro-receptive crystalline gel. Each pit is heavily insulated and can be anywhere from a few microns thick to as thick as a strand of spaghetti. The gel inside these pits is so sensitive that it can detect voltage as low as to 15 billionths of a volt per square centimeter. This is equivalent to being able to detect the electrical field of a flashlight battery from 10,000 miles away. Armed with that fine-tuned sensitivity, sharks can detect prey in pitch-black water from 3 feet away (1 m).
Once electricity is sensed, the gel triggers a synapse response in the shark’s brain based on the total information the external electrical current provides. The frequency and strength with which the synapse fires indicate the intensity of the electrical signal.
Some shark and stingray species have larger ampullae, which allows them greater sensitivity for electroreception. These sharks tend to live in very dark, murky water. Such species include the odd looking sawfish. These animals are practically blind and thus rely almost entirely on their electroreception to close in on their prey.
Other species have developed even further anatomical specializations to boost the efficiency of their ampullae. The hammerhead shark’s unique shape serves as a wide-reaching biological metal detector, allowing it to scan the bottom for stingrays hiding under the sand. The wide head of the hammerhead is covered in ampullae of Lorenzini, allowing individuals to “feel” their environment by constantly waving their head back and forth, scanning the water and floor near them for life.
The shocking looking goblin shark has an odd paddle sticking off the top of its head. This allows them to detect prey in front of them even in the darkest depths of the ocean. Once prey is detected, their jaw is able to shoot forward the entire length of their paddle, snatching up anything in front of them.
However, sharks and stingrays aren’t the only animals with ampullae. Australia’s platypus is the world’s only known mammal to also use ampullae on their bill to detect electricity when submerged. Already known to combine the features (and powers) of a duck and beaver, the platypus can also claim relationship to the shark and stingray thanks to their electroreceptors. As if the platypus couldn’t be more unusual, experts warn people to never pet a wild platypus and to keep dogs, cats and other pets away from them. On the back heel of a male platypus is a spur that contains enough poison to kill a dog. While the poison will not likely kill an adult human, it causes a great deal of pain (the spur is physically large) and the poison will cause swelling and extended pain in the area of the bite.
“Sharks: The Animal Answer Guide” by Gene Helfman and George H. Burgess
“The Encyclopedia of Sharks” by Steve Parker
#sharks #platypus #Lorenzini #electricity #TSF