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 is a type of fish that can generate electricity (as the name might suggest) 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.
A large portion of the recent research on this topic has been done by Kenneth Catania, a professor at the Vanderbilt University. In 2014, for instance, Catania’s study revealed the hunting mechanism of an electric eel in detail . 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 it prey.
The video below shows the mechanism of prey capture (electric charge release is shown in red).
The voltage generated by the eel in water may work against 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. One way of increasing the strength of its shock is by minimizing the electricity lost in the surrounding water. The eel achieves this by jumping out of the water and touching the predator with its head, delivering a much stronger electric shock than possible inside water.
In fact, this ‘leaping out of water’ behavior of the eel was reported long back in 1800 by naturalist, Alexander von Humboldt, who saw 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. Since no follow up scientific reports regarding this behavior surfaced for about 200 years, scientists were skeptical of the story.
In 2016, Catania confirmed this defensive leap-and-shock tactic of the eel experimentally . 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 . 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 researchers like Catania are working on understanding the mechanism of this electric creature, few other researchers 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 . I wont write about that work here, as I am already covering the same for a news publication, but I will soon upload a link once I am done with the article for those of you who are interested.
Hope you enjoyed these ‘shocking’ videos of the electric eel. Stay tuned for more exciting upcoming posts soon.
- Catania, Kenneth. “The shocking predatory strike of the electric eel.” Science 346.6214 (2014): 1231-1234.
- 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.
- Catania, Kenneth C. “Power Transfer to a Human during an Electric Eel’s Shocking Leap.” Current Biology 27.18 (2017): 2887-2891.
- Schroeder, Thomas BH, et al. “An electric-eel-inspired soft power source from stacked hydrogels.” Nature 552.7684 (2017): 214.