Natures wonders: elephantnose fish electrolocation (Introduction)

by David Turell , Monday, November 06, 2023, 23:18 (381 days ago) @ David Turell

A new way to navigate in murky water:

https://www.scientificamerican.com/article/elephantnose-fish-sees-by-doing-an-electric-...

"Bats and dolphins are deservedly famous for their echolocation, but the elephantnose fish has a different superpower sense—electrolocation. And now new research suggests this bizarre-looking creature has to do an underwater jig to create the three-dimensional electric map it uses to “see” its surroundings.

"Eyesight alone wouldn’t get the elephantnose very far in the murky rivers of western and central Africa where the nocturnal fish makes its home. So a specialized organ in its tail emits a weak electric field that radiates outward from its body in pulses, and tiny receptors on its skin detect distortions to the field caused by objects or creatures nearby.

"These distortions create an “electric image”—a two-dimensional representation of the object being detected like a shadow cast on the fish’s skin. But researchers weren’t sure how the fish used that 2-D map to perceive a 3-D world.

"The answer, according to a new study published in Animal Behaviour, is that the elephantnose fish does a little aquatic dance. By wiggling around, it perceives objects from slightly different angles; stacked together, the various electric images it gets are enough for it to distinguish among 3-D objects.

“Fish are a lot more intelligent than people initially believe,” says the study’s first author Sarah Skeels, a postdoctoral researcher of animal cognition and behavior at the University of Oxford.

"Skeels has been thoroughly charmed by the elephantnose fish, and it’s easy to see why. It’s got a face like Gonzo the Muppet because of what is technically called its schnauzenorgan—a fleshy protrusion from its chin that’s functionally a cross between an elephant’s trunk and an antenna. The schnauzenorgan is chock-full of electroreceptors and can also be used to manipulate objects as the fish roots around in riverbed silt for its dinner.

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"After each fish went through several hundred training trials, it could pick the door that led to the sausage shape it associated with a treat in a matter of seconds, with an accuracy rate of 93 percent.

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[she limited their space] "With no room for their more flamboyant dance moves, the fish resorted to a lot of head bobbing and scanning with their schnauzenorgan. Their accuracy in locating the sausage-shaped object dipped to 71 percent, and they took longer to reach a decision—sometimes on the order of minutes. There was “a level of hesitancy you don’t see in the other trials,” Skeels says.

"Stefan Mucha, a postdoc studying weakly electric fish at the Humboldt University of Berlin, says Skeels’s paper was “very cleverly designed” and demonstrated the importance of movement to electrolocation—a small but meaningful piece in the complex puzzle of how the fish integrate electrical information into a usable map.

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"...computer engineers in Turkey have designed what they call the “electric fish optimization,” an algorithm based on the electrolocation and electrocommunication of weakly electric fish such as the elephantnose.

"It’s no wonder the elephantnose fish has the highest brain-to-body weight ratio of any vertebrate, the researchers say. “It’s just so complex, what they do, that we can’t really model it with our greatest computers,” Mucha says. “But it’s just a small fish!'”

Comment: great name for the nose organ! This has to be an irreducibly complex mechanism. It obviously cannot be made stepwise. The electric signal is not the problem but the varying signal produced. It is the brain's ability to interpret the bounce back signals as in radar and then the fish must learn to wiggle properly to produce the correct amplitude of signal.