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Snails and the M3
from Inside Electrical and Computer Engineering at the University of Michigan 2021
by Electrical & Computer Engineering at University of Michigan
SNAILS CARRYING THE WORLD’S SMALLEST COMPUTER HELP SOLVE MASS EXTINCTION SURVIVOR MYSTERY
More than 50 species of tree snail in the South Pacific Society Islands were wiped out following the introduction of an alien predatory snail in the 1970s, but the white-shelled Partula hyalina survived.
Now, thanks to a collaboration between biologists and engineers, scientists understand why: P. hyalina can tolerate more sunlight than its predator, so it was able to persist in sunlit forest edge habitats.
“We were able to get data that nobody had been able to obtain,” said David Blaauw, the Kensall D. Wise Collegiate Professor of EECS and co-developer of the Michigan Micro Mote (M3). “And that’s because we had a tiny computing system that was small enough to stick on a snail.” Most ecology and conservation studies involving data from sensors are done on vertebrate animals, which can carry larger and heavier devices than invertebrates. The current study not only offers insights into the conservation measures needed to ensure the survival of a species of snails, it points the way for future studies of very small animals through similar partnerships. “A lot of the coolest scientific work is done at the interface, where you have a classic problem and need to bring new approaches to find a solution,” said Diarmaid Ó Foighil, professor of Ecology and Evolutionary Biology (EEB) and Curator of the U-M Museum of Zoology.
How Society Island Snails Were Wiped Out
The giant African land snail was introduced to the Society Islands, including Tahiti, to cultivate as a food source, but it became a major pest. To control its population, agricultural scientists introduced the rosy wolf snail in 1974. But unfortunately, most of the 61 known species of native Society Islands tree snails were easy prey for the rosy wolf snail. P. hyalina is one of only five survivors in the wild. Called the “Darwin finches of the snail world” for their island-bound diversity, the loss of so many Partula species is a blow to biologists studying evolution. Ó Foighil and Bick hypothesized that P. hyalina’s distinctive white shell might give it an important advantage in forest edge habitats, by reflecting rather than absorbing light radiation levels that would be deadly to its darker-shelled predator. To test their idea, they needed to be able to track the light exposure levels P. hyalina and rosy wolf snails experienced in a typical day. Bick and Ó Foighil wanted to attach light sensors to the snails, but a system made using commercially available chips would have been too large for their purposes.
Matching the Technology to the Application
“In 2015, I was looking around to see who had the technology capable of tracking snails, and discovered that the people who can do this are also at Michigan. It was serendipitous,” said Cindy Bick, who received a Ph.D. in EEB from U-M. The system Bick found online was the M3, created to go where other sensing devices could not. Measuring just 2x5x2mm, including packaging, it could be used to track animals the size of the rosy wolf snail (with an adult shell 3-7cm) in their natural habitat. But could it be altered to sense light? It was time to move the M3 from the laboratory to the real world and adapt it for the special needs of their collaborators.
“It was important to understand what the biologists were thinking and what they needed,” said Inhee Lee (PHD ECE 2014), assistant professor of Electrical and Computer Engineering at the University of Pittsburgh. Lee adapted the M3 for the study.
A Partula hyalina snail resting on a wild red ginger leaf next to an M3 in a forest edge habitat in Tahiti. Photo: Prof. Inhee Lee
“The sensing computers are helping us understand how to protect endemic species on islands.” - Cindy Bick
Tahitian Experiments
After local testing enabled by local Michigan snails, 50 M3s made it to Tahiti. They were attached to the rosy wolf snails, and placed next to the P. hyalina snails, because of their status as a protected species. The data revealed a dramatic difference in how much sun reached the habitats of the surviving P. hyalina as opposed to the rosy wolf snail. During the noon hour, the P. hyalina habitat received on average 10 times more sunlight than the rosy wolf snails. Specifically, the average light intensity reached 7,674 to 9,072 lux for the P. hyalina habitat, but only 540 to 762 lux for the rosy wolf snail.
The researchers suspect that the rosy wolf doesn’t venture far enough into the forest edge to catch P. hyalina, even under cover of darkness, because they wouldn’t be able to escape to shade before the sun became too hot.
Model for Future Collaborations Between Biologists and Engineers
The success of this project broke new ground from the perspective of the engineers as well as the biologists. “It’s underappreciated how large a step it is to go from the lab into the field and get meaningful data,” said Blaauw. “It’s essential to achieve success in order to propel the technology forward, but it takes a great deal of trust among the collaborators.” “The M3 really opens up the window of what we can do with invertebrate behavioral ecology,” said Ó Foighil, “and we’re just at the foothills of those possibilities.”
