Flexible-bodied sea creatures able to maneuver with speed and precision have a Franklin & Marshall College biologist researching their features for future applications including underwater vehicles.
Associate Professor of Biology Joe Thompson and his student researchers study a particular cephalopod, the cuttlefish, similar to squid but with a wider body or mantle, fins the length of the mantle, a large head, eight short arms and two tentacles.
"We're looking at the maneuverability in these animals and asking a series of questions. What aspects of the musculoskeletal system constrain movement? What does the network of muscle and connective tissue allow them to do? What does it prevent them from doing? And how does the musculoskeletal system drive movements of their appendages that are responsible for locomotion?" Thompson said.
Thompson said as both predator and prey, the cuttlefish is known as the master of disguise. "Cuttlefish spend a lot of time hiding around structures and some of them partially bury their bodies in sand," he said. "They wait until something comes by and then rush out and get it. Squid are not sit-and-wait predators. They are usually cruising around all the time. They see something and they race after it."
Thompson and two other researchers, a mechanical engineer and an engineer-trained biologist, are working under a $273,000, three-year collaborative grant from the National Science Foundation. While his colleagues address the question of the fin’s effect on the flow and movement of fluid around the cuttlefish, Thompson’s research focuses on how the cuttlefish’s musculoskeletal system works the fin.
"We're studying these guys because they have this interesting dual locomotive system," Thompson said. "They can use jets – squirt water out of internal body cavities that lets them rocket backward or forward – and they can use the fins and make very fine undulations to rotate their body, change their pitch, swim forward or backward. They use the jets for faster speeds and they use the fins for slower swimming and slower maneuvering. They use the jet to rocket off, but they use the fin to bank a curve, slow down one side of the body and spin around. The interplay between the two systems is pretty remarkable. It gives a lot of potential for maneuvering.”
Thompson and his students – juniors Danae Diaz, John Emmett and Garrett Largoza – began work on the NSF-funded project over the summer at the University of Maine's Darling Marine Center. There, they used electromyography – electrodes inserted into the fins – to record the muscles’ movements. Their work continues in F&M's labs. Thompson developed techniques for cephalopods by modifying techniques used to measure muscle activity and force production in other animals.
Diaz, a biological foundations of behavior major who is studying animal behavior, found the research opportunity, which involved different aspects of study each day, exciting and beneficial to her post-graduate studies.
“It was really valuable,” she said. “I want to become a professor and do research.”
Thompson said once they understand what the fin shape and size means for the cuttlefish’s locomotion – “Is this variation closely tied to the animal’s ability to catch prey and elude predators?” – they can build on the idea of an autonomous underwater vehicle that is propelled by a soft, fin-like actuator as opposed to a propeller.
"A propeller causes cavitation, which is noisy and loud," Thompson said. "It would be cool to have a vehicle that could insinuate itself into a natural setting and observe without scaring the organisms that are there."