Goldfish learned to drive tanks on wheels—and that’s not even the best part

What’s the weirdest thing you learned this week? Well, whatever it is, we promise you’ll have an even weirder answer if you listen to PopSci’s hit podcastThe Weirdest Thing I Learned This Week hits AppleSpotify, YouTube, and everywhere else you listen to podcasts every-other Wednesday morning. It’s your new favorite source for the strangest science-adjacent facts, figures, and Wikipedia spirals the editors of Popular Science can muster. If you like the stories in this post, we guarantee you’ll love the show.

FACT: The Drug Enforcement Administration had to get involved in the first successful cardiac xenotransplantation.

By Sandra Gutierrez G.

Because of tricky logistics, scarcity of viable organs, and various cultural apprehensions, doctors have been looking into xenotransplantation, where animal tissue is implanted into a human body. 

Researchers had been experimenting on baboons for years, and in 2021 a team at NYU successfully transplanted two genetically engineered porcine kidneys into human patients. But in January 20222, Muhammad Mohiuddin and a medical team at the University of Maryland School of Medicine upped the ante by successfully transplanting a pig’s heart for the first time. The patient, a  57-year-old David Bennet Senior, unfortunately died two months after the procedure, but the cause of death was unrelated to the porcine heart beating in his chest, which is why the operation was a true medical breakthrough. 

Before the surgery, the pig’s heart soaked in a particular concoction containing a mix of hormones and a very special ingredient—one gram per liter of dissolved cocaine. The solution was developed by Sweedish doctor Stig Steen, who gave it the cute name of “brain death cocktail.” In a 2016 paper, Steen showed that the liquid helped stabilize the pig’s heart for up to 24 hours after harvesting, which would theoretically increased the chances of a successful transplant. 

But the recipe behind the brew is proprietary, which means the team at the University of Maryland had to import it from Sweeden, creating a bureaucratic nightmare that forced the Drug Enforcement Administration to get involved.

It’s unclear exactly how this works and what’s the specific role of cocaine in this brew, but working with tissue that stays healthy for longer could be key not only for future xenotransplantations, but also to address organ shortages and making it possible to fly in organs from across state lines. 

FACT: Scientists once taught goldfish to drive.

By Rachel Feltman 

About a year ago, researchers in Israel published evidence that goldfish can learn to drive tanks. Fish tanks, that is. 

They started by crafting what they called FOVs—fish operated vehicles, of course—which basically amounted to aquariums secured to motorized wheels. The rig included a little camera hooked up to a Raspberry Pi computer, which pointed down into the water, tracked the movements of the fish inside, and translated them into wheel movements based on a simple algorithm. 

The researchers placed a pink board somewhere in the room, and the fish were given a food pellet the moment their tank-mobile successfully tapped the target. After a few days, the six goldfish—who it feels important to note were named after Pride and Prejudice characters—all learned how to steer their FOVs to the snack zone. They were able to navigate the vehicle from different starting points, and managed to ignore false targets and even recover and redirect when they bumped into walls. Apparently Mr. Darcy and Mr. Bingley were the best drivers. 

The point was to see whether goldfish have some innate sense of logic when it comes to navigating a space. The purpose of the FOV is just to make it possible for a fish to navigate a non-aquatic space. It doesn’t matter what the fish thinks is happening when it makes the tank move; what matters is that the fish is figuring out the best way to get to an arbitrary target, using extremely non-fish-native wayfinding points, because it knows there will be food there. 

They were even able to approach their targets from a variety of different angles, which suggests that they have some internal representation of the strange world around them. And they got faster over time. 

All of this helps support the idea that the way we navigate space, which we know has to do with parts of our hippocampus that are pretty similar in all vertebrates, has more to do with some innate inner mind mapping that goes on than it does species-specific ways of figuring out an environment. 

A study published in 2019 did genuinely teach rats to drive little cars. The point of that study really was to teach rats to drive, not just propel themselves around in a strange space. The idea was to show whether growing up in so-called enriched environments—cages with multiple levels to climb on and interesting stuff to play with—made rats better able to learn stuff and less likely to be stressed about the novelty. 

FACT: Rodent DNA revealed a black market seal trade.

By Sara Kiley Watson

150 years ago, sealers in New Zealand nearly brought fur seals, also known as Kekeno, to extinction. Nowadays, they are doing much better—the last recorded count shows in 2001 there were 200,000 of the fuzzy cuties bouncing around the rocky shores throughout mainland New Zealand, the Chatham Islands, and the sub-Antarctic islands, as well as parts of Australia. 

The hunting of Kekono began with the Maori people who lived in New Zealand and the Cook Islands pre-colonialism, but things got especially troubling with the arrival of Europeans. By the 1700s, seals were confined to the far south of New Zealand, and by the early 1800s the seal populations were already in dangerous decline and the legality of sealing became more of a legal gray area. 

But, a discovery that lays open some secrets about an illegal seal trade between Asia and New Zealand has only recently unfolded, with the help of tiny detectives—rodents that have stowed away on ships and created populations of two distinct species on the two islands of New Zealand. As it turns out, while one population can be traced back to trade with Europe, another population comes solely from Asia—a region where this seal trade was largely kept off the books. 

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