Why Do Scientists Keep Gluing Things to Animals?

Sam Westreich, PhD
Jan 16 · 7 min read

Stilts on ants, glasses on cuttlefish, transmitters on bees… is gluing attachments onto animals a requirement to be a scientist these days?

“What do you think — do they look good on me? Should I buy them?” Image source: University of Minnesota

In recent science news, researchers announced that they had attached 3D glasses onto a cuttlefish.

Now, you could just stop right there, and I’d still be on board. In fact, let’s not stop there! Put corrective lenses on cows! Zebras with drunk goggles! Lions with monocles — they’ll look so dignified!

There is a reason why these researchers put 3D glasses on cuttlefish. What’s odd, though, is that this isn’t the first time that scientists have decided to glue things to animals to see what happens. Not even close to the first time — I’ve read about other interesting experiments that all seemed to start with “we glued these things onto these animals, and then happened to observe…”

So today, let’s learn about three different experiments where scientists glued things onto animals, and t̶h̶e̶ ̶e̶x̶c̶u̶s̶e̶ ̶t̶h̶a̶t̶ ̶t̶h̶e̶y̶ ̶m̶a̶d̶e̶ ̶u̶p̶ the lessons that they learned.

3D Glasses on Cuttlefish!

This is an ACTUAL figure from the scientific paper, and is a great demonstration of why I, as a child, decided to pursue a career in science. Image source: Science Advances

Why? First, because a cuttlefish with retro 3D glasses looks cool as hell. But secondly, and perhaps more importantly, because the researchers wanted to know how the cuttlefish brain computes the distance to a target (like a tasty looking prawn).

When cuttlefish catch prey, they need to make sure they’re close enough to grab it with their tentacles, but not so close that they could scare the prey away. The researchers suspected that, like many terrestrial predators, these creatures used both eyes to figure out the distance to a target — a trait called stereopsis.

(Think about a cat, versus a cow. Cats have both eyes facing forward, so they can better figure out the distance to their prey. Cows have their eyes on the sides of their head, because grass doesn’t move — but they can get a wider (although blurrier) field of view for catching any approaching predators.)

Using the same technology that we use to enjoy 3D movies, the scientists projected images of little tasty shrimp on screens — some in front of the screen, some behind the screen. The retro-glasses-wearing cuttlefish fell for the illusion, showing that they use stereopsis to aid in hunting.

This ability is especially interesting because, unlike cuttlefish, squid and octopus don’t have this ability. Like a cow, squid and octopuses have their eyes on the sides of their head. Only cuttlefish have the ability to rotate their eyes so that they both point in the same direction, for hunting.

For an extra laugh, here’s how the researchers trained the cuttlefish to participate in this experiment:

…shrimp rewards were restricted to trials during which the cuttlefish responded to the on-screen target by extending its tentacles, i.e., it entered hunting mode[…]. Once this behavior became consistent, we affixed a Velcro patch… to the dorsal surface of the animal’s head. We achieved this by netting the animals out of the tank, patting the skin dry with a paper towel three times, and applying a superglue-covered Velcro patch directly to the skin and holding in place for 10 s. Immediately after returning the animals to the tank with care, we fed them with a large grass shrimp. Subsequently, we repeated training as detailed above[…]. Once… behavior was consistent, a custom-made pair of glasses… was placed onto the animal, attached via the Velcro patch, and training was repeated. A few hours after being fitted with glasses, some animals would reliably hunt, while other more cautious animals or those initially not interested in viewing the screen took up to 2 days to reliably interact with shrimp video stimuli.

I’m glad the animals were treated carefully and the glasses were merely held on with Velcro!

Stilts on Ants!

Ants, the little crawling hive insects that are the terror of picnics everywhere, seem to have the unerring ability to find food — and to communicate this to others, who then also find the food. Once a single ant discovers some tasty morsel, it isn’t long before dozens of her fellows are swarming over that food, chomping it into little bits to bring it back to their nest.

“Look at these little guys. You know what’s wrong with them? They’re too short. They can’t see over obstacles. They need… stilts!” Photo by Salmen Bejaoui.

But how do ants know how far away a bit of food may be? How do they measure distance? This question is especially significant in someplace like the Sahara Desert, where there are no real landmarks — just miles and miles of constantly shifting sand dunes.

To find out: stilts.

Researchers guessed that, in order to measure the distance from one location to another, the ants are capable of counting the number of steps that they take. To test this theory, they glued tiny little stilts to the legs of the ants, elongating their stride (with longer stilt-enhanced legs, the ants would go further with each step).

It turned out that the researchers were correct — when the ants left the nest on their normal legs, but received stilts before heading back, they overshot the nest, thanks to their newly lengthened legs. Even though they took the same number of steps, they ended up traveling further than intended.

After finding the nest, however, these stilts-equipped ants had no trouble going out for more food — their steps were longer, but they could still count their steps, and it was the same number of paces to the food and back to home.

It turns out ants can count!

Transmitters on Bees!

Bee, no transmitter attached. He can’t tell us where he’s going, so we need to monitor him, like people on house arrest. Photo by Kai Wenzel.

A normal radio tracker would, of course, be far too large to fit on a bee — so the scientists instead used radio frequency identification (RFID) chips. These chips are incredibly small and lightweight, because they don’t need to carry their own power source. Instead, they are activated by an external transmitter, reflecting a response to the signal sent out by the external transmitter.

(For examples of RFID chips, they’re used in tracking all sorts of things — they’re in DVD cases to prevent shoplifters from carrying them off (where the external transmitter is in those security scanners at the entrance of the store). They’re also used in many races to track individual runners and record their times (where the transmitter is at the end of the race, detecting the RFID chips that run across the finish line).)

Each bee had to receive a different RFID chip, which was carefully attached with a dab of glue. The bees were then infected with a low dose of a parasite, Nosema apis, and studied to see how it affected the insects.

The researchers discovered that the infected bees — despite looking like their normal cousins — carried less pollen, stopped working sooner, and died younger. It turns out that this parasite, previously thought to be fine in low doses, still causes damage to bee hives that get infected.

Understanding what these parasites do in bee colonies is incredibly important; many crops in the United States and around the world rely on bees to pollinate the plants to create fruit. If bees continue to decline, we will see shortages of many different fruits and vegetables.

Science is an interesting field, in part because the questions that many scientists ask have never been raised before. Because they’re novel questions, they often require novel solutions — there’s no set protocol in place for how to mess with the vision of a cuttlefish, or how to change the length of ant legs, or how to simultaneously track hundreds of bees at once.

I’ve had first-hand experience with these jury-rigged solutions; when I was in graduate school, working on my PhD, I needed to extract small amounts of frozen fecal samples, to sequence the DNA contained within. However, I needed to get a full core of the material, not just a scraping from the edge — and I had to do it without letting the sample warm up from its -80 degree state!

To find a solution, I headed over to the local hardware store, where, after some trial and error, I worked out that I could get a core sample using a hollow copper rod, a solid rod to act as a plunger, and a mallet to drive the rod into the frozen sample. Later, when I wrote up my scientific paper on this experiment, I had to describe this new method!

Whether it’s attaching 3D retro glasses to cuttlefish, stilts to ants, or RFID chips to bees, scientists often need to try new and unconventional methods to answer never-before-asked questions. The methods may seem silly — but the answers can have real-world impact.

Sam Westreich holds his PhD in genetics, focusing on methods for studying the gut-associated microbiome. He currently works at a bioinformatics-focused startup in Silicon Valley. Follow on Medium, or on Twitter at @swestreich.

Have a science-related question? Comment to suggest a topic for my next story. Or check out this related story:

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