By | August 17, 2023

Becoming invisible usually requires magic.

For some inch-sized squid, all it takes is a little genetic tweaking.

When these squid are genetically altered, “they’re really hard to spot,” even for their keepers, says Joshua Rosenthala senior scientist at the Marine Biological Laboratory in Woods Hole, Mass.

“We know we’re putting it in this aquarium, but they might be looking for half an hour before they can actually see it,” Rosenthal says. “They are so transparent.”

The transparent octopus offers scientists a new way to study the biology of a creature that is intact and moves freely.

“It changes the way you interpret what’s going on in this animal,” says Caroline Albertine, a colleague at the lab. “You can look through and see their three hearts beating, you can see their brain.”

The transparent squid is a genetically altered version of hummingbird bobtail squid, a species commonly found in the tropical waters from Indonesia to China and Japan. It is usually smaller than an inch and shaped like a dumpling. And like other octopuses, it has a relatively large and sophisticated brain.

The transparent version is made possible by a gene editing technique called CRISPRwhich became popular almost a decade ago.

Albertin and Rosenthal thought they could use CRISPR to create a special octopus for research. They focused on the hummingbird bobtail squid because it is small, a great breeder and thrives in lab aquariums, including one in the lab in Woods Hole.

“You can see him at the bottom,” Rosenthal says, “just sitting there, curled up in the sand.”

The squid is one that has not been genetically altered. So it is camouflaged to blend into the sand. It is possible because of organs in the skin called chromatophores. They contain pigments that can be manipulated to change the appearance of the octopus.

Albertin and Rosenthal wanted to use CRISPR to create a bobtail squid without any pigment, an albino. And they knew that in other squid, pigment depends on the presence of a gene called TDO.

“So we tried to knock out TDO,” says Albertin, “and nothing happened.”

It turned out that bobtail squid have a second gene that also affects pigment.

“When we targeted that gene, hear and surprise, we were able to get albinos,” says Albertin.

Since even intact octopuses have clear blood, thin skin and no bones, albinos are almost transparent unless the light hits them at just the right angle.

The team is described their success in July in the journal Current Biology.

Many labs would like to use the transparent squid. So in the lab at Woods Hole, a team of engineers spend long hours creating more of them.

Albertin lets me look over the shoulder of a technician looking under a microscope at an octopus embryo smaller than a BB pellet.

She uses forceps to gently remove the “jelly layers” surrounding the egg sac. Later, she will use a quartz needle to inject the embryo with genetic material that removes the pigment genes and creates a transparent octopus.

Early on, Albertin and Rosenthal realized that these animals would be of interest to brain researchers. So they got in touch Ivan Soltesz at Stanford and Christopher Niell at the University of Oregon.

“We said, ‘Hey, you guys, we have this incredible animal, want to look at its brain,'” Rosenthal says. “They jumped on it.”

Soltesz and Niell inserted a fluorescent dye into an area of ​​the brain that processes visual information. The color glows when it is near brain cells that are active.

Then the researchers projected images onto a screen in front of the octopus. And the brain areas involved in vision began to glow, something that would have been impossible to see in a pigmented octopus.

“The evidence that they were able to get from this made us all jump out of our skins,” says Albertin. — It was really exciting.

Because it suggests that her transparent octopus will help scientists understand not only octopuses, but all living things.

Copyright 2023 NPR. To see more, visit https://www.npr.org.

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