Electric Eels Found To Leap Out Of Water To Shock Predators

Main image credit: Josh More/Flickr CC BY-NC-ND 2.0

ELECTRIC EELS HAVE BEEN FOUND TO SHOW SHOCKING LEAPING BEHAVIOR.

As if growing up to 2 meters and being able to produce an electric shock equivalent to that of a Taser isn’t impressive enough, researchers have confirmed a more unusual aspect about the electric eel. It seems that the animal, which isn’t actually an eel but a type of knife fish, isn’t content with just shocking its attackers underwater, but that under the right conditions they will leap out of the water to stun predators. 

More than 200 years ago, when the famous Prussian naturalist and geographer Alexander von Humboldt made the first scientific exploration to describe Latin America he faced many difficulties. But one of his most famous encounters occurred on March 19, 1800, when he described how locals caught electric eels by driving horses into the river, where the fish would then leap out of the water and stun the poor animals. This dramatic description quickly entered into legend, but in the centuries that followed no one had seen this unusual behavior repeated, leading most to think that von Humboldt exaggerated his electric experiences with the eels.

Yet it seems that there is far more truth to these accounts than anyone had previously given credit for. “The first time I read von Humboldt's tale, I thought it was completely bizarre,” explains Kenneth Catania, who has described this behavior for the first time in the Proceedings of the National Academy of Sciences. “Why would the eels attack the horses instead of swimming away?” 

The eel jumps up to place its chin on the "predator" before shocking it. Kenneth Catania/Vanderbilt University

He actually corroborated these original accounts in the first place by accident. Studying the eels at Vanderbilt University, he was attempting to catch them from their tank using a metal rimmed net (“In hindsight, probably wasn't the best design to use,” he notes). He found that every so often, the eels would leap from the water and press their chins against the net, while at the same time generating a series of high-voltage pulses.

By measuring the power of the shocks used during this electric behavior, Catania was able to determine that the eels used a different shocking pattern than they used to stun prey. He found that they only leap from the water to attack living animals that are partially submerged, and did so with more frequency when the water level in their tank was lowered. This, suggests Catania, implies that the behavior is used to protect themselves against land-based predators when the eels feel cornered or threatened, such as in the dry season when the water levels are much lower. This is also the time when some of the eels breed.

But why leap from the water, rather than just sidling up close? Well, it seems that the higher up the intruder they can get, the more powerful the shock they deliver. When shocking in the water, the electric current dissipates through the water, but by hitting the target with its chin and then shocking, the current travels through the target's body. “This allow the eels to deliver shocks with a maximum amount of power to partially-submerged land animals that invade their territory… [while] also allow[ing] them to electrify a much larger portion of the invader's body,” says Catania.

So after over two centuries of doubt and despite great interest in the animals, it seems that von Humboldt has finally been proven to be right, and that electric eels really do jump from the water to attack predators.

ORIGINAL: IFLS
By Josh Davis
06/06/2016, 20:00

Bio-Powered Chips Might One Day Fit Inside Cells

Illustration: Trevor Finney and Jared Roseman/Columbia Engineering

For the first time, researchers have developed a microchip that is powered by the same energy-rich molecules that fuel living cells, researchers say. This advance could one day lead to devices that are implanted within cells and harvest biological energy to operate.

The molecule adenosine triphosphate (.ATP) stores chemical energy and is used inside cells to ferry energy from where it is generated to where it is consumed. The new microchip relies on enzymes known as sodium-potassium ATPases. These molecules break down ATP to release energy the enzymes use to pump sodium and potassium ions across membranes, generating an electrical potential during the process.

“Ion pumps are electronics-like components in living systems,” says study senior author .Ken Shepard, an electrical engineer at Columbia University in New York. Shepard and his colleagues detailed .their findings in the 7 December edition of the journal Nature Communications.

The researchers embedded sodium-potassium ATPases taken from pig brains in artificial fatty membranes. There were more than 2 million of these molecules active per square millimeter of the membranes, about 5 percent of the density naturally occurring in mammalian nerve fibers.

In the presence of ATP, these ion pumps generated 78 millivolts. A “biocell” of two membranes provides enough of a voltage to operate a CMOS integrated circuit. The ion pumps have a chemical-to-electrical energy conversion efficiency of of 14.9 percent.

“These ion pumps generated an electrical field that we harnessed to power a solid-state system,” Shepard says.

Since ATP is only really found within cells and not in the bloodstream, Shepard cautions that this new system is not a way to power conventional implantable medical devices such as pacemakers.

“However, such a system might power an implant small enough to sit inside a cell,” Shepard says. “Solid-state materials are already used in nanoparticles for various therapeutic and imaging purposes in the body, but those are all just passive materials. Our idea is to make something that would have the ability to compute and act, to make decisions and then actuate in some way.”

Future research could also incorporate other membrane proteins into electronics, such as those responsible for taste and .smell, Shepard says. "There could be many ways to couple solid-state systems with the biological machinery of cells," he says.

ORIGINAL: .IEEE Spectrum

By Charles Q. Choi

Posted 9 Dec 2015

The Way Electric Eels Kill is Even Cooler Than We Realized

Electric eels are among the most badass predators on planet Earth. How many other creatures can deliver a shock powerful enough to paralyze a horse? But their superpowers are even more impressive than we realized. These eels don’t just use electricity to attack, they use it to see.

That’s the conclusion of a fascinating study published today in Nature Communications. In a series of laboratory experiments, neurobiologist Ken Catania and colleagues show how electric eels “electrolocate” their prey after paralyzing it, using energy fields to locate and swallow hapless victims almost instantly.

“The eel can use its electric attack simultaneously as a weapon and a sensory system,” Catania told National Geographic. “It’s sort of a science-fiction-like ability.”

Electric eels, which are actually a type of catfish, slink quietly about in the murky depths of the Amazon River, looking for ill-fated creatures on which to discharge their 600-volt weapon. We’ve known of the eel’s formidable hunting ability for decades, but the exact mechanics have proven difficult to study (you try capturing an 8 foot-long living taser and bringing it back to the lab—it ain’t easy).

Catania is more persistent than most. In a study published last year inScience, he showed that electric eels’ high voltage attacks can stimulate their prey’s motor neurons, causing involuntary muscle twitching. Using two or three small electric volleys, the eels will force prey to give away their location before charging up and delivering the paralyzing blow.

Electric eel honing in on an electrically conductive stimulus (red arrow), before initiating its suction-feeding strike. Image Credit: Catania et al. 2015

But how does the eel find its lunch once that prey is disabled? As Catania points out, electric eels will strike and engulf their victims lightning fast — usually within milliseconds.

Electricity figures in here, too, according to a series of laboratory experiments performed by Catania and his colleagues. National Geographic explains:

To understand what was happening, Catania brought electric eels into the lab and presented them with anesthetized fish that were insulated from the eel’s electroreceptors by plastic bags. With an electrode, Catania made the fish flinch, and the eel discharged its high-voltage attack. But then it didn’t seem to know what to do next—the eel lunged in the direction of movement in the water but didn’t attempt to suck the fish into its mouth.

Catania then put an electrically conductive carbon rod into the tank along with the fish. He made the fish flinch, and the eel attacked with a shock. Sometimes the eel started to move in the direction of the fish, but then it changed course to lunge at the rod wherever it had been placed in the tank. To the eel, the fish seemed to be in two places at once.

What these experiments are showing is that electric eels don’t just use voltage to immobilize prey: They follow electric fields, in order to track it. This places the eel in league with sharks, rays, and certain African fish as a predator that can electrolocate—an adaptation that’s similar to echolocation in bats and dolphins.

Me, I’m just grateful this particular hunting ability seems restricted to the water.

[Read the full scientific paper at Nature Communications h/t National Geographic]

ORIGINAL: Gizmodo

By Maddie Stone

10/20/15 3:26pm

Electric Eels Remotely Control the Movements of Their Prey

photo credit: Electric eel (Electrophorus electricus) / Kenneth Catania

Electric eels are badass. Not only can they produce an incapacitating 600-volt zap -- five times that of a U.S. wall socket -- they can also remotely control their prey through water. The predatory eels create a variety of electric discharges that range from lower-voltage ones sent out as environmental sensors to high-voltage strikes that allow them to hijack the nerves of their prey -- immobilizing the muscles and preventing escape. They can even send out short pulses that force the prey to give up their location. The findings were published in Science this week. 

To understand the mechanism of the eel’s shocking strike, Vanderbilt University’s Kenneth Catania conducted a series of experiments in large aquariums equipped with various detectors. When placed in tanks with delectable fish and worms, the scale-less Amazonian Electrophorus electricus releases pulses of electricity that appear to stun the prey and freeze them in place. Using a high-speed video system, he observed that an eel begins an attack with a high-frequency volley of high-voltage pulses up to 15 milliseconds before striking. In just three milliseconds, the fish are completely paralyzed. They regain mobility after a short period, and they could swim away if the eel doesn’t get to them first.

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“I have some friends in law enforcement, so I was familiar with how a Taser works,” Catania says in a news release. “And I was struck by the similarity between the eel’s volley and a Taser discharge. A Taser delivers 19 high-voltage pulses per second while the electric eel produces 400 pulses per second.” To the right is an eel in mid-attack on an immobilized fish.

The electric discharge induces an immobilizing whole-body muscle contraction by activating the motor neurons that control the prey fish’s muscles -- and not by controlling the muscles directly. Catania placed two fish behind a barrier: One was injected with saline solution, the other was injected with a paralytic agent that targets the nervous system. The muscles of the fish with the saline solution contracted involuntarily in response to the eel’s electrical discharges, but the fish given the paralytic drug showed no contractions. 

Furthermore, if the prey is nearby but hiding in rocks or plants, the eel can emit periodic, millisecond pulses of two or three discharges (doublets or triplets) that cause massive muscle twitches. Once the rapid contractions reveal the prey’s location, the eel throws down a full, tetanus-inducing volley. 

“Normally, you or I or any other animal can’t cause all of the muscles in our body to contract at the same time,” Catania says. “However, that is just what the eel can cause with this signal.”

These high-voltage discharges allow the eels to remotely control the prey’s neural pathways by mimicking the normal electrical pulses that the fish’s own neurons send to stimulate its muscle movement. Check out some great footage here: 

ORIGINAL: IFLScience

by Janet Fang

December 5, 2014