The way these animals use electricity is mind-blowing

Around 350 species of fishes can produce electricity and humans have known that long before we knew what electricity was. The Romans and Greeks wrote about the torpedo ray’s “benumbing” power—a strange force that could kill small fish.

common torpedo (wikipedia)

The study of electric fish got entwined with the study of electricity. These animals have inspired the design of the first synthetic battery. The most powerful of the three electric eel species can incapacitate a horse.

electric eels (via AZanimals)

On the contrary, some fish electric fields are so benign that even humans can’t feel them. They are called weakly electric fish. They belong to two main groups—the elephantfishes of Africa, and the knifefishes of South America. Strong electric fields were understood to have evolved for offence or defense, but weak electric fields confused theorists. If it was not for killing, what was it for? It is now known that these electric fields are for sensing surroundings and communication. Electricity is to them what echoes are to bats, smells are to dogs, and light is to humans aka. very important.

Elephant nose fish (via tnaqua.org)

black ghost knifefish (science.org)

Hans Lissmann (1951) used electrodes to confirm that knifefish produce a continuous electric field from the organ in its tail.

Objects distort this field if they are either more or less electrically conductive than water. By sensing distortions, they can detect whatever produced them (another fish perhaps).This strange ability is known as active electrolocation. Electro-locating fish also sensitive to salinity. If Black ghost knifefish is released in a local river (no significant salt levels), it would probably struggle to detect any food, and die!

Electrolocation is different from other senses (touch, hearing etc) in sense that it requires active participation. Imagine if you had to “activate” your eyes in some sense to see. It is more like echolocation, where bats send sound haves and detect distortion in waves to detect objects.

ELECTROLOCATION is most similar to touch. (contradicting to above comparison, but what I mean is that it works like echolocation, but the application is like touch). Imagine it as “touch at a distance”, you could sense a surface by just being near it. It is omnidirectional. It can detect things that are even behind. This helps to avoid obstacles behind. It works at very short ranges as electric fields rapidly weaken the farther they are from their source.

The electric sense really is a modified form of touch, repurposed for sensing electric fields instead of flowing water.

Electric fields are great for communication too. They aren’t absorbed by obstacles. They don’t echo. They don’t even travel; instead, they instantly appear in space.

ELECTROCOMMUNICATION vs ELECTROLOCATION

Messages don’t carry far, but electrocommunication is less limited by range than active electrolocation. With electrolocation, fish have to produce their own field, which requires a lot of every and is limited. To double the range of electric sense, fishes would have to expend approximately eight times more energy while already having spent a quarter of its calories on generating its fields. But when “listening” to another fish’s electric signals, it doesn’t need to generate a field at all. It only needs more sensitive electroreceptors.

A fish might only be able to sense prey an inch around its body, but it can detect the signals of other electric fish from a few feet or more away.

Mammals with electric senses

One species of dolphin—the Guiana dolphin of South America have 8 to 14 electroreceptors. It is not completely known what they use it as it already has echolocation at its disposal.

wikipedia

Echidnas—egg-laying mammals from Australia sense small insects moving about within moist soil via electroreception.

Echidnas (brightly.eco)

Platypus has over 50,000 electroreceptors on its famous duck-like bill to find food.

Platypus (via britanica)

This ability is very ancient. We although do not have this ability, but our ancestors around 600 million years ago did certainly have it. This ability has been lost (that is why some fishes don’t have it) and then regained a few times (that explains why some mammals have it) in the evolutionary line.

The above extract is from the book AN IMMENSE WORLD (my favorite book). There is a whole chapter dedicated on animals that use electricity to sense the world. The above is just five percent at max. I have tried to pin down the most basic points and simplified it, but still a lot is left. I find it really interesting and will try to create several small blogs rather than making a big one. It would become boring that way. There are sharks with electroreception. There are positively charged bees and negatively charged flowers. I will also include why this ability evolved even though a lot of other sense organs were present in fishes. And much more..