California scientists looking for new ways to explore the world’s oceans have created something that seems right out of a Hollywood movie — a cyborg jellyfish, half animal, half robot, that can swim nearly three times faster than a regular jellyfish — and which one day might be remotely steered to collect information from deep ocean waters.

Engineers at Stanford University and Caltech in Pasadena say the sci-fi jellyfish may rekindle memories of Arnold Schwarzenegger in Terminator, but could actually help expand our understand of the deep seas.

“We’re trying to take the best of what biology does naturally,” said John Dabiri, Centennial Professor of Aeronautics and Mechanical Engineering at Caltech. “And combine it with the best of what we can do as engineers and hopefully get the best of both worlds.”

Jellyfish are primitive invertebrates that have changed little in 500 million years. They don’t have brains, lungs or a central nervous system. And they weren’t harmed during the experiments, which took place in tanks on the Stanford campus, Dabiri said.

“These animals are 95% water,” he said. “It’s kind of like poking your finger in Jell-o.”

During the research, Dabiri and Stanford graduate student Nicole Xu created a prosthetic device about the size of a penny. It contained a microchip and tiny battery. Using a small wooden barb, they attached it to the underside of moon jellyfishes, a common jellyfish that is roughly 1 foot wide. They ran tiny wires from the device to electrodes on the jellyfishes’ muscle tissue.

Like a tiny cardiac pacemaker, the device sent out pulses of electricity. Jellyfish that typically swim about 4 feet per minute nearly tripled their speed because electric jolts made their bodies pulse faster. Yet they used just twice as much energy, measured by the amount of oxygen they consumed.

The animals release mucous when stressed. That didn’t happen during the experiments, Dabiri said, and they showed no harm when the gear was removed.

Compared to swimming robots, the bionic jellyfish were more than 1,000 times more efficient, said the researchers, who published their findings in the journal Science Advances on Jan. 29.

“This reveals that jellyfish possess an untapped ability for faster, more efficient swimming,” Xu said. “They just don’t usually have a reason to do so.”

So who needs a bionic jellyfish? Dabiri noted that operating a scientific research ship at sea for one day can cost $20,000 or more.

If scientists can refine the devices to steer the jellyfish and collect data, like water temperature, salinity, pH and other measures, they could more easily explore the oceans, he added, and learn about everything from pollution to climate change.

For decades, researchers have put tracking equipment onto large ocean animals. Stanford scientists have attached miniature video cameras and speedometers to giant Atlantic bluefin tuna to learn how the fish move through the water. They have put electronic sensors on great white sharks, sea turtles and other marine animals to track their movements and habits.

In November researchers from UC Santa Cruz and the Scripps Institution of Oceanography successfully stuck a heart monitor the size of a lunch box to the side of a 70-foot long blue whale with suction cups while it swam in Monterey Bay, and gave it an EKG for 8.5 hours until the device fell off.

But blending electronics with living tissue to change the way an animal moves is a new frontier. It creates what scientists call “biohybrid robots” and raises amazing possibilities as well as ethical questions.

In 2018, scientists at the University of Tokyo took muscle cells from rats, grown on a gel substance, and attached them to a robotic skeleton shaped like a finger. When stimulated with an electric current, the muscles contracted and expanded like a human finger.

The technology potentially could be used one day to replace missing or paralyzed fingers, arms or legs. More dramatic, microscopic biological robots could be injected into the human body in the future to kill cancer tumors or monitor heart disease.

When it comes to the jellyfish experiment, Kakani Katija, the principal engineer at MBARI — the Monterey Bay Aquarium Research Institute — agreed that researchers need more efficient, cheaper ways to explore the oceans. But unlike sensors that drop off and don’t change the way animals move, the more invasive work to make them swim faster could, in a jellyfish’s case, affect its feeding or reproduction, she said.

“It’s one thing to affix a sensor on an animal that is sized appropriately where it doesn’t affect their behavior,” said Katija, who was not part of the Stanford-Caltech research. “It’s another thing when it does. That’s the ethical tightrope the research will have to walk as it progresses beyond this early study.”

Hank Greely, a prominent medical and scientific ethics expert at Stanford, said it’s important that the jellyfish researchers took care to monitor whether the animals were harmed. Humans have used horses, cattle, pigs, dogs and other animals for thousands of years, he said, adding that this experiment raises new questions.

“There is something disconcerting about mechanically changing animals for our utility,” Greely said. “It’s less disconcerting when there are only a few of them, used for specific purposes. It’s more disconcerting if we release a self-reproducing set into the wild — not possible with these mechanical prostheses but eminently possible with genetic modifications. Is it wrong, is it right? I don’t know, but I am confident we will face these kinds of questions more and more often.”