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The Fish That Could Wear Braces

Image Credit: My iPad and I

Need some nightmare fuel? Have a look at the sheepshead fish (scientific name: Archosargus probatocephalus), a marine inhabitant that gets as much attention in dentistry as it does in ichthyology circles.

First identified in 1792 and found in states including Florida, Texas, and Louisiana, sheepsheads are a popular catch for two reasons: they’re delicious, and that giant, gaping maw full of actual teeth makes for quite the conversation piece. After all, it’s not every day you find a Lovecraftian monster flopping around on the floor of a boat.

“They eat a lot of hard-shelled invertebrates,” says Rob Robins, Ichthyology Collections Manager at the Florida Museum of Natural History. “The incisors at the front are used to pry loose food from a substrate, and the grinding teeth are used to bust them up.” According to Robins, the teeth found in the sheepshead aren’t materially different from human dentition. “Teeth are teeth,” he says. The fish has three rows of molars on top and two on the bottom and can deliver enough force to crush through a crab.

Aside from their pearly whites, sheepsheads—also known as “convict” fish for their black stripes—are conventionally built, typically growing 14 to 18 inches long and roaming the deep until they become food for larger predators. They’re sometimes confused with the Pacu, an Amazon fish with jagged teeth that snacks on the nuts falling from nearby trees. In a testament to the power of Internet fear-mongering, it was once erroneously reported the Pacu liked to attack human testicles.   

Sheepsheads have no such ambitions, though they are persistent. “They have something called an ascending process that allows them to essentially shoot their mouth out from their head and obtain their prey,” Robins says, which we infer to mean there’s no escape from this thing. Fortunately, they’re not known to bite humans—unless, he says, they’re provoked.

Provoked? “Well, if you painted your fingertip like a barnacle and put it in the fish’s face, it’s a possibility.”

So is never sleeping again. Listen closely for the sound of a captured sheepshead gnashing its teeth:

And have a look at some glamour shots:

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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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