Hi all,

I am back with a second post for Biophysics Week: this one is long but super fun and has some really nice videos. So do check it out.

The electric eel, as the name might suggest, is a type of fish that can generate electricity to capture its prey. I knew only this basic fact about the electric eel until I started reading more about it recently. The more I read, the more fascinating I found its behavior. So here’s an attempt to narrate some of the underlying science that has been uncovered so far.

Electric Eels Generate Short Pulses to Paralyze Prey

A large portion of the recent research on electric eels has been done by Kenneth Catania, a professor at Vanderbilt University. In 2014, for instance, Catania’s study revealed the hunting mechanism of an electric eel in detail [1]. Turns out that the eel produces electric pulses at short intervals, enough to temporarily paralyze any small fish nearby, thus preventing their escape. Additionally, the electric zap causes an involuntary muscle twitch in its prey. Once the eel senses this movement, it launches a full high voltage attack to capture its prey.

The video below shows the mechanism of prey capture (electric charge release is shown in red).

Credits: Images, video and illustration: K. Catania/Vanderbilt University; Reported by Susan Milius; Produced and narrated by Ashley Yeager

The voltage generated by the eel in water may work on paralyzing small fish, but it is not enough to defend itself against large predators like crocodiles. As electric eels are often present in muddy waters close to the shore, a defense mechanism to escape from a large-predator attack is essential for its survival. In the next section, find out how.

The Electric Eel Uses Leap and Shock Strategy to Escape Predators

In 1800, naturalist Alexander von Humboldt noted that fishermen in South America followed an unusual method to catch eels. They used horses as a bait, and when the eels were exhausted from shocking the horses, the fishermen captured them safely.

Researchers realized there might be scientific basis behind this story. As eels need to increase the strength of their shock by minimizing the electricity lost in the surrounding water, they might have developed this defense mechanism. By jumping out of the water and touching the predator with its head, they can deliver a much stronger electric shock than that possible inside water.

In 2016, Catania confirmed this defensive leap-and-shock tactic of the eel experimentally [2]. He used an innovative approach to demonstrate this. He lowered an artificial conductive arm coated with LEDs into a tank from above. When the eel jumped out of the water and ‘electrocuted’ the artificial hand, the LEDs lit up, confirming the high voltage applied by the eel. He repeated the same with a fake crocodile head and saw the same. Here’s a video showing these experiments.

To top it all, last year, Catania went a step ahead and tested how much electricity passes through an actual prey himself [3]. He wore a conductive glove on top of a rubber glove on his hand and lowered it into the eel-tank. A connecting wire measured the current passing through his hand when the eel struck. In his report, Catania described the shock to be painful enough to jerk away his hand, comparing it to walking into an electric fence on a farm- not harmful enough to cause permanent damage but enough to deter one from touching it again. Check out the video of Catania being zapped himself (electric charge release shown in red)

While on one hand, some researchers are working on understanding the mechanism of this electric creature, others are trying to find applications based on this mechanism: biomimetics (if you need a reminder, I had written about how researchers are trying to mimic natural materials into technology last year). In one such interesting study inspired by the electric eel, researchers created an artificial battery made from stacks of gels that generates up to 110 V [4]. If you are interested in reading more about this biomimetic device, check out my story in Biotechniques News.

Hope you enjoyed these ‘shocking’ videos of the electric eel. Stay tuned for more exciting upcoming posts soon.

Original Publications

1. Catania, Kenneth. “The shocking predatory strike of the electric eel.” Science 346.6214 (2014): 1231-1234.
2. Catania, Kenneth C. “Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses.” Proceedings of the National Academy of Sciences 113.25 (2016): 6979-6984.
3. Catania, Kenneth C. “Power Transfer to a Human during an Electric Eel’s Shocking Leap.” Current Biology 27.18 (2017): 2887-2891.
4. Schroeder, Thomas BH, et al. “An electric-eel-inspired soft power source from stacked hydrogels.” Nature 552.7684 (2017): 214.