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Soft Underwater Gripper Tests Jellyfish Stress Response

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A soft robotic armature. A new ultra-soft gripper with silicone “fingers” inflated with water lets scientists grasp and release jellyfish without harm.
Anand Varma

Jellyfish and other soft-bodied marine animals present a unique challenge to researchers who study them: they are often too delicate for tools used to handle more robust marine species. To address that problem, researchers from the American Museum of Natural History and colleagues are piloting a softer approach to studying these animals in their natural habitats.

The team, which includes teams from Harvard’s Wyss Institute of Biologically Inspired Engineering, the John A. Paulson School of Engineering and Applied Sciences (SEAS), and Baruch College (CUNY), has developed a soft robotic “jellystick“ that gently grabs jellies during undersea research. The jellystick would allow researchers to take measurements, photograph, and non-invasively sample their DNA, without removing the animals from their natural environment, according to David Gruber, Museum research associate and senior author of the new research. “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 Gruber.  

In addition to creating the tool, the team has conducted a study to find out if the gentle gripper, which resembles a fishing rod with blue fingers that look like fettuccini pasta, is any less traumatic for its research subjects than more rigid grippers. Their findings, published this month in Current Biology, suggest that the jellystick is a better option.

Woman uses a soft robotic armature to grasp a jellyfish in a tank.
The researchers who designed the new tool conducted a study to determine if it caused jellyfish less stress during handling than more rigid grippers. 
Anand Varma

The team conducted a series of experiments to measure relative physiological stress levels in Aurelia aurita jellyfish, or moon jellies. They grasped and released the animals using three different methods: holding it with the jellystick’s ultra-gentle grippers, holding it with a rigid claw similar to those used on underwater remotely operated vehicles, and using the rigid claw while also shaking the animals. To determine the animals’ stress levels during the tests they measured changes in gene expression, since stress triggers molecular pathways in the body of an animal, and those physiological changes also impact its behavior. They found that the jellies were under far less physiological stress when they were held with the jellystick than during the other two methods.  

"Ultimately, if we can work towards making critters like jellyfish more comfy during research,” said co-first author Michael Tessler, a postdoctoral fellow at the Museum, “imagine what we can do for all the other animals we interact with as field biologists.”

The new tool may also help researchers study extremely old animals—such as the 4,265-year-old black coral Leiopathes discovered in 2009 or the 17,000–18,000-year-old glass sponge Monorhaphis chuni found in 2017—without harming them. “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 and Museum Research Associate Mercer Brugler.