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Josh Cassidy / KQED
Josh Cassidy / KQED

Watch Archerfish, the Champions of Spitting

Josh Cassidy / KQED
Josh Cassidy / KQED

In southeast Asia, archerfish spit streams of water at insects outside the water, knocking them in and making them convenient targets for gobbling. There are only seven known species of fish that use this hunting technique, and they've gotten quite good at it. Archerfish are able to calibrate the velocity of their spit to precisely hit their targets, using water as a weapon.

In this beautiful Deep Look video, we learn about the archerfish, its impressive spitting ability...and its puzzling ability to recognize human faces. Crank this up to 4K resolution and enjoy:

For more on the archerfish and the research discussed in the video, check out this KQED blog post. You might also enjoy our coverage of those archerfish face-recognition experiments.

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Animals
Goldfish Can Get Depressed, Too
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Don’t believe what Pixar is trying to sell you: Fish are not exactly brimming with personality. In aquariums, they tend to swim in circles, sucking up fragments of food and ducking around miniature treasure chests. To a layperson, fish don’t appear to possess concepts of happy, or sad, or anything in between—they just seem to exist.

This, researchers say, is not quite accurate. Speaking with The New York Times, Julian Pittman, a professor at the Department of Biological and Environmental Sciences at Troy University, says that fish not only suffer from depression, they can be easily diagnosed. Zebrafish dropped into a new tank who linger at the bottom are probably sad; those who enthusiastically explore the upper half are not.

In Pittman’s studies, fish depression can be induced by getting them “drunk” on ethanol, then cutting off the supply, resulting in withdrawal. These fish mope around the tank floor until they’re given antidepressants, at which point they begin happily swimming near the surface again.

It’s impossible to correlate fish depression with that of a human, but Pittman believes the symptoms in fish—losing interest in exploring and eating—makes them viable candidates for exploring neuroscience and perhaps drawing conclusions that will be beneficial in the land-dwelling population.

In the meantime, you can help ward off fish blues by keeping them busy—having obstacles to swim through and intriguing areas of a tank to explore. Just like humans, staying active and engaged can boost their mental health.

[h/t The New York Times]

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The Shocking Science of Electric Fish
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Like slippery Pokemon, electric eels can produce shocks strong enough to incapacitate large predators. But where do these electric fish get the power to generate such high-voltage attacks?

In a recent video, TED-Ed explains the volatile biology at play. Electric fish like electric eels (which are more closely related to catfish than actual eels) all contain at least one electric organ. This organ is packed with disc-shaped cells called electrocytes. These cells naturally release sodium and potassium ions which create a positive charge inside the cells and a negative charge outside them. But when electric fish send signals from their brains to these organs, it opens up the cells' ion channels, allowing the ions to re-enter. The result is an electrocyte with a positive interior and a negative exterior on one side and a negative interior and a positive exterior on the other—basically a biological battery. Once these cells are charged up, fish can use them to disrupt nearby electric signals, detect other fish, and even paralyze prey.

Fish aren’t the only animals that use electricity to their advantage. The oriental hornet, for example, makes electricity out of sunlight, while some spiders harvest charged particles by coating their webs in electrostatic glue.

[h/t TED-Ed]

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