It's shocking what animals can teach us about electricity

 

Black Ghost Knifefish Apteronotus albifrons, stolen from Wikimedia

A semi-serious look at bioelectricity, solar panels, and the fish that could maybe power your house, well, probably not.

Electricity has a reputation problem, and I promise you it’s not because I have been spreading around how much I dislike working on household electrical problems. On one hand, it powers your coffee maker, your phone, and whatever binge-worthy show you are pretending not to watch at 2 a.m (Taskmaster, of course). On the other hand, it can stop your heart. 

Is it good or bad? As with most things in biology, the answer is yes.

The animal kingdom has been quietly running electrical experiments for hundreds of millions of years, and the results are, frankly, embarrassing for us. While humans needed Benjamin Franklin, a kite, and a near-death experience to figure out the basics, fish had already sorted out passive detection, active field generation, and interspecies electro-eavesdropping before the dinosaurs showed up. Let us catch up.

Side note: Benjamin made his servant hold the kite string.

First, a brief defense of electricity

Every living thing generates electrical signals. Your muscles contract because of ion gradients across cell membranes. Your body uses lots of energy to maintain this sodium-potassium gradient between the inside and outside of your cells. Your heart beats in response to electrical impulses. Even tiny invertebrates under the sand of the seagrass bed broadcast a faint electrical signal. Electricity is not an invention; it is a fact of living things.

Most animals do not listen to electricity. Humans, dogs, pigeons, squirrels: All electroelectrically oblivious, going about their days completely unaware of the invisible electrical fields around them. A platypus, by contrast, closes its eyes, ears, and nose when it dives and navigates by the electric fields radiating off its prey. And sharks, of course, are famous for their electroreception, but more on this coming in a future blog.

The electrically gifted

Electric eels (not actually true eels) are the obvious headliners. Electrophorus electricus can generate over 800 volts, which is enough to stun a caiman and make a point. The electric organ is composed of stacked electrocytes, each functioning like a tiny battery cell, all firing in sequence to produce a single coordinated zap. The eel also uses lower-voltage pulses for navigation and electrolocation, essentially a biological fish-finder built right in. 

Side note: Props to Linnaeus for that name, love it. Although his original name was Gymnotus electricus, so props to Linnaeus and Theodore Gill (who moved it to the genus Electrophorus). See an image of this fish at the end.

The torpedo ray takes a saltwater approach. Because seawater conducts electricity much better than fresh water, the torpedo does not need the voltage the eel uses. It compensates with raw current, producing up to 50 amps at a peak power output approaching one kilowatt. That is roughly equivalent to a small space heater, delivered directly and personally to whatever annoyed it.

Side note, yes, another side note: Amps vs current: Current is the flow rate (like speed), amperes is the overall volume. The internet has a great analogy with a water pipe: Pressure on the water is current (volts), how much water is passing through the pipe is volume (amps), and the size of the pipe is resistance (ohms).

Weakly electric fish, by contrast, are the introverts of the group. Mormyrids in Africa and Gymnotiformes in South America independently evolved the ability to generate low-voltage fields, typically less than one volt, and use them to check out their surroundings. They can tell the difference between a conducting object and a non-conducting one just by sensing how the field distorts. They also use these fields to talk to each other, which is very romantic.

When two knifefish of similar frequency get too close, and their fields start to interfere, they each shift their discharge frequency away from the other to avoid jamming. Frequency is measured in Hertz (Hz), and that is the number of times per second the electric flow changes direction (in AC or alternating current). A marvelous jamming avoidance response, and it is the kind of polite electrical etiquette that humans abandoned sometime around the invention of the leaf blower.

Side note: I don’t hate leaf blowers…oh wait, yes I do. What a useless noise maker. 

The mammals got in on it, too, eventually

The platypus has about 40,000 electroreceptors packed into the skin of its rubbery bill, arranged in neat rows alongside mechanoreceptors that detect pressure and motion. When a shrimp flicks its tail, the electrical signal from that contraction arrives at the electroreceptors a fraction of a millisecond before the pressure wave hits the mechanoreceptors. The platypus triangulates from this timing difference to pinpoint exactly where its lunch is hiding. It hunts, in other words, by doing math; it is not aware that it is doing (that we know of, though I have heard a rumor that they use tiny chalkboards). Echidnas have a similar trick but with far fewer receptors, ranging from 400 in short-beaked species to around 2,000 in long-beaked ones, which is either a sign of laziness or efficiency.

The Guiana dolphin surprised researchers in 2011 by turning out to have electroreceptors too, built from repurposed vibrissal crypts, the little pits that held its whiskers as a juvenile. These former whisker holes, now empty and innervated, can detect electric fields as weak as 4.6 microvolts per centimeter, roughly comparable to a platypus. The dolphin uses this to find fish hiding in the sand, a hunting technique charmingly called crater feeding, which involves partially burying its face in the seafloor. Bottlenose dolphins appear to share this ability.

Guiana Dolphin, what a beautiful jumper. Stolen from Wikipedia.

Bees: Unexpected electricians of the pollinator world

Electroreception is mostly an aquatic thing, for good reason: Water conducts electricity, and air does not. Sensing electric fields in the open air is a bit like trying to smell something through a brick wall. Nonetheless, bees managed it.

Bumblebees are positively charged, from moving through the air, while flowers are negatively charged, from being connected to the ground. When a bee lands on a flower, the electrostatic attraction helps pollen jump onto the bee without any physical contact, which is either very efficient or a little rude, depending on the pollen.

More surprisingly, bees can detect the shape and strength of the electric field around a flower and use that information to decide whether the flower has been recently visited, since a prior visit briefly changes the flower's field. This gives bees a sort of real-time floral freshness indicator, a sixth sense for whether they are about to get a full nectar tank or be deeply disappointed. Bumblebees learn to use both electric field patterns and color together, suggesting their cognitive ability is substantially more sophisticated than a fuzzy body and a willingness to sting people who bother them.

Can we use any of this? The solar panel question

Here is where things get speculative in the best way. The question of whether electric animals could serve as energy sources has been asked, and the answer is, technically yes, practically no, but the biology is interesting.

Electric eels have been studied as a concept for biologically inspired power generation. A 2017 study demonstrated an eel-inspired soft-power system using hydrogel cells mimicking electrocytes, capable of generating some volts. It was not enough to power anything useful, but it showed the design worked. The fundamental limitation is that animals generate electricity by burning metabolic fuel, not by harvesting ambient energy. An eel shocking something is spending calories it ate earlier.

Solar cells, by contrast, genuinely harvest ambient energy (sunlight) and convert it directly into electricity without burning anything. They are, in this respect, more elegant than even the most impressive electric organ. A modern photovoltaic panel converts around 20 percent of incoming solar energy into electricity, and high-efficiency laboratory cells exceed 40 percent. Biological photosynthesis, for comparison, converts about 4 percent of solar energy into chemical energy.

The better biological comparison to a solar cell is not a fish, of course, but a leaf. Photosynthesis is a biological energy-harvesting system using ambient radiation, and it is genuinely ancient, elegant, and widespread. It is also inefficient enough that engineers stopped trying to copy it directly and instead just made silicon do the job.

However, real biological insights are being borrowed. Electroreceptor designs in fish have inspired robotic sensors. Platypus bill architecture has informed the development of soft, flexible electrode arrays for detecting small bioelectric signals in medicine. The jamming avoidance response in electric fish has been studied as a model for how distributed systems avoid signal interference, with applications in wireless communications. Biology, as usual, got there first.

Electricity is not good or bad, but a tool: The electric eel uses it to hunt. The bumblebee uses it to evaluate flowers. The platypus uses it to find crustaceans in the mud with its face. None of them is paying an electric bill, which is frankly the most enviable part.

Can solar cells save us? Possibly, yes, and that answer does not require any fish. But the animal kingdom's centuries of electrical innovation are worth studying, not because we are going to plug an eel into a power grid, but because evolution keeps finding solutions that engineers have not yet thought of. The torpedo ray solved a high-current delivery problem. The knifefish solved a signal interference problem. The bee solved a floral information problem. These are not trivial engineering challenges, and the solutions are sitting there in plain sight, just waiting to be reverse-engineered by someone willing to spend time watching a fish do something weird in a tank. Call it if you want it.

In the meantime, if you ever feel like the world is too mean, remember: somewhere in the rivers of South America, a small knifefish is politely adjusting its discharge frequency so it does not interfere with its neighbor's electrolocation, and it has been doing this, without complaint or confusion, for approximately 100 million years.

The electric eel, Electrophorus electricus. Something about this just says, " Don't touch". Stolen from Wikipedia

Sources and Further Readings:

Clarke D, Whitney H, Sutton G, & Robert D. 2013. Detection and learning of floral electric fields by bumblebees. Science 340(6128): 66-69. https://doi.org/10.1126/science.1230883

Crampton WGR. 2019. Electroreception, electrogenesis and electric signal evolution. Journal of Fish Biology 95(1):  92-134. https://doi.org/10.1111/jfb.13922

Czech-Damal NU, Liebschner A, Miersch L, Klauer G, Hanke FD, Marshall C, Dehnhardt G, & Hanke W. 2012. Electroreception in the Guiana dolphin (Sotalia guianensis). Proceedings of the Royal Society B: Biological Sciences 279(1729): 663-668. https://doi.org/10.1098/rspb.2011.1127

Hüttner T, von Fersen L, Miersch L, Czech NU, & Dehnhardt G. 2022. Behavioral and anatomical evidence for electroreception in the bottlenose dolphin (Tursiops truncatus). The Anatomical Record 305(3), 592-608. https://doi.org/10.1002/ar.24773

Hüttner T, von Fersen L, Miersch L, & Dehnhardt G. 2023. Passive electroreception in bottlenose dolphins (Tursiops truncatus): Implication for micro- and large-scale orientation. Journal of Experimental Biology 226(22), jeb245845. https://doi.org/10.1242/jeb.245845

Manger PR, & Pettigrew JD. 1996. Ultrastructure, number, distribution and innervation of electroreceptors and mechanoreceptors in the bill skin of the platypus, Ornithorhynchus anatinus. Brain, Behavior and Evolution 48(1), 27-54. https://doi.org/10.1159/000113185

Pettigrew JD. 1999. Electroreception in monotremes. Journal of Experimental Biology 202(10): 1447-1454. https://doi.org/10.1242/jeb.202.10.1447

Robert D, Clarke D, & Morley E. 2017. The bee, the flower, and the electric field: Electric ecology and aerial electroreception. Journal of Comparative Physiology A 203(9): 737-748. https://doi.org/10.1007/s00359-017-1176-6

Salazar VL, Krahe R, & Lewis JE. 2013. The energetics of electric organ discharge generation in gymnotiform weakly electric fish. Journal of Experimental Biology 216(13): 2459-2468. https://doi.org/10.1242/jeb.082735

Schroeder TBH, Guha A, Lamoureux A, VanRenterghem G, Sept D, Shtein M, Yang J, & Mayer M. 2017. An electric-eel-inspired soft power source from stacked hydrogels. Nature 552: 214-218. https://doi.org/10.1038/nature24670