They may not have a brain, but jellyfish do get stressed out when handled roughly, scientists find
By Lindsay Brownell
(BOSTON) — A clear plastic fish tank containing only saltwater sat on a table in the middle of a small, windowless room at the New England Aquarium. Surrounding the fish tank stood an unusual group of scientists: marine biologists stood shoulder-to-shoulder with roboticists, an evolutionary biologist, and a materials engineer, plus a photographer. They were soon joined by a member of the aquarium’s staff, who carried a white bucket in which a few golfball-sized jellyfish pulsed placidly. The staff member scooped up one of the jellyfish and gently placed it in the tank, and the scientists took their positions. For the next several hours, they chased the jellyfish around the tank using a homemade “jellystick” that looked like a short fishing rod with blue fettuccini pasta noodles attached to one end, which Nina Sinatra, Ph.D. (the materials engineer) had created just for that purpose.
The goal of this odd experiment was to see if the jellystick’s soft robotic “fingers” could capture live jellyfish and release them without harm. Each time they managed to corral a jelly, the scientists activated a hydraulic pump that caused the fingers to slowly curl inward toward the animal, gently trapping it against the jellystick’s flat plastic “palm.” Then, they simply reversed the pump to uncurl the fingers and the jellyfish swam free, seemingly no worse for the wear.
But the scientists were not satisfied with “seemingly.” The jellyfish might have looked physically fine, but how did they feel? Were they stressed out by their momentary pasta-noodle entrapment?
Calm, cool collecting
It may seem ludicrous to be concerned about the feelings of an animal that lacks eyes, ears, and even a true brain. But stress is not just an emotion: a complex cascade of molecular pathways is triggered in the body of an animal that is under stress, and those physiological changes also impact its behavior, just like humans who are under stress might respond by being irritable, mindlessly eating, or not eating at all.
Collecting an animal from its natural habitat, transporting it to a research facility, and poking and prodding it is a stressful experience that impacts an organism’s health and behavior, yet for centuries that was the primary way we studied the natural world. Only relatively recently have biologists made an effort to document their quarry on its own turf, partly driven by the observation that animals in captivity often have poorer health and shorter lifespans than those in the wild. Some animals are much easier to study in situ than others; jellyfish are some of the most difficult because they are aquatic, extremely delicate, and relatively little is known about them.
So, how do you tell if a jellyfish is stressed out?
The team created a new experiment in which they grabbed Aurelia aurita (moon jelly) jellyfish using three different methods: the jellystick’s ultra-gentle grippers, a rigid claw similar to those found on underwater remotely operated vehicles (ROVs), and the same claw while shaking the jellyfish for one minute. They then performed a transcriptomic analysis on the animals to see which of their genes’ expression patterns changed under the different gripping conditions..
The results were telling: compared to jellyfish that were not gripped at all, the soft robotic grippers caused 26 jellyfish genes to be expressed differently, while the claw resulted in 55 gene expression changes, and the claw plus shaking induced a whopping 121 changes. Of those changes, a handful stood out in particular: three proteins that are associated with the process of cell death (which can be triggered by stress) were significantly over-expressed in all of the claw-plus-shaking grabs and some of the claw-gripping grabs, but not in any of the ultra-soft gripper grabs or no-gripper conditions.
Based on these findings, jellyfish do indeed seem to get stressed out when they’re handled roughly. But not only that – the scientists were able to show that their soft robotic grippers could minimize the stress the jellyfish felt while they were temporarily captured.
“As a marine biologist who studies jellies often, I think that being able to interact with them in a way that is minimally disruptive to their everyday lives is one of the biggest advancements in this field in a long time,” said David Gruber, Ph.D., the senior author of a new paper in Current Biology that describes the team’s research. “Outfitting a research submarine with our ultra-gentle robotic grippers would allow scientists to temporarily capture jellies and other soft-bodied animals underwater, make some measurements, photograph them, non-invasively collect some of their DNA, and then let them go. Not only will we get more accurate data about their biology, we will know that we gathered that data without causing any harm to creatures that we love and respect.” Gruber is a Presidential Professor at Baruch College, CUNY. He is also an Explorer for National Geographic, a Research Associate in Invertebrate Zoology at the American Museum of Natural History, and a 2017-2018 Radcliffe Fellow at Harvard University.
“Genomics and soft robotics are cutting-edge sciences, and our project shows how exciting it can be when researchers in these fields collaborate. Ultimately, if we can work towards making critters like jellyfish more comfy during research, imagine what we can do for all the other animals we interact with as field biologists,” said co-first author Michael Tessler, Ph.D., a Postdoctoral Fellow at the American Museum of Natural History.
Some of those other animals, science has recently discovered, can be very, very old, making it even more imperative to handle them gently. “In 2009, the scientific community was shocked to learn that the black coral Leiopathes is 4,265 years old, and then 2017 that the glass sponge Monorhaphis chuni is 17,000-18,000 years old. Deep-sea researchers have an obligation to find new ways to obtain samples in a minimally invasive manner, and the jellystick represents a significant step in the right direction,” said co-first author Mercer Brugler, Ph.D., an Associate Professor of Biology at CUNY and Research Associate at the American Museum of Natural History.
Not just for jellies
The team’s ultra-soft grippers are not just a massive improvement in the tools used to conduct research on delicate underwater organisms; they are also a harbinger of a larger trend in the world of robotics. The word “robot” today probably conjures up an image of Tony Stark’s “Iron Man” suit or an autonomous vacuum toodling around an apartment floor (perhaps with kittens riding on top), but the robots of the near future will look vastly different. They will be integrated into clothing to help us move more efficiently, super-strong yet super-lightweight, and could even help shuttle drugs to their targets in our bodies. In short, they will essentially be extensions of ourselves.
“Robotics as a field has traditionally created robots that are optimized to perform a specific task over and over again, which has worked beautifully for applications like manufacturing products at a large scale. But now, as robots are moving out of automated factories and into daily human life, roboticists need to think about – and design around – the humans who will be interacting with their robots,” said Rob Wood, Ph.D., a Wyss Core Faculty member who is also the Charles River Professor of Engineering and Applied Sciences at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS), and a co-author of the soft robotic gripper research.
In addition to the ultra-soft gripper used to safely capture jellyfish, Wood’s lab has created tiny soft actuators that can bend and straighten, a wearable soft sensor that can measure the force and motions of the hand and fingers, and an entirely soft robot powered by chemical reactions, among others.
“The jellyfish study is a great proof-of-concept for this idea that robots can actually be better at certain tasks if they’re made softer and gentler. They could be used to harvest fruits from trees without bruising them, rehabilitate the muscles of stroke patients, and many other things that rigid-bodied robots are just too clunky and overpowered to accomplish today,” Wood added.
Wood, Gruber, and their collaborators, who call themselves the Squishy Finger/Soft Robotics for Delicate Deep-sea Marine Biological Interactions team, are continuing their deep dive into soft robotics, and are exploring their soft grippers’ ability to interact with other aquatic animals including mammals. They are also integrating several of their robotic devices for an upcoming research cruise with the Schmidt Ocean Institute.
“Serendipitous connections between people and disciplines that seem completely unrelated often result in groundbreaking discoveries and creations. We continue to be impressed by the collaborations between our Bioinspired Soft Robotics researchers and marine biologists, and we expect to see future paradigm shifts in both fields as a result,” said Donald Ingber, M.D., Ph.D., who is the Wyss Institute’s Founding Director as well as the Judah Folkman Professor of Vascular Biology at HMS and Boston Children’s Hospital, and Professor of Bioengineering at SEAS.
Additional authors of the Current Biology paper are John Burns from the American Museum of Natural History and the Bigelow Laboratory for Ocean Sciences, Nina Sinatra from the Wyss Institute and SEAS (who is now at Google), Daniel Vogt from the Wyss Institute and SEAS, Anand Varma from the National Geographic Society, and Madelyne Xiao from the American Museum of Natural History.
This research was supported by National Geographic Society (award no. PFA- RNG-2018-01); the CUNY Office of Research, the National Science Foundation (award no. DBI-1556164); the Helen Gurley Brown Revocable Trust, and Harvard’s Materials Research Science and Engineering Center (award no. DMR-1420570).