It's not quite like knitting sweaters for penguins, but a new conservation project relies on similar crowd-sourced crafting to save another kind of sea creature. MakerBot Industries, a 3-D printer company in New York, wants help designing and producing plastic shells to fight homelessness among hermit crabs.
Called Project Shellter, the campaign was created to address a "housing shortage," its organizers say. Hermit crabs are born without shells and don't make their own, so they scavenge for empty ones — not just once, but every time they have a growth spurt.
They're resourceful when shells are scarce, often settling for things like beer bottles or shotgun shells. But those rarely make good substitutes for a seashell, and many wild hermit crabs now face a life-threatening lack of housing, according to Katherine Bulinski, a geoscientist at Bellarmine University who serves as Project Shellter's research adviser. The problem is partly due to people collecting abandoned shells from beaches, although much of the marine life that makes those calcium carbonate shells is also increasingly threatened by ocean acidification.
Where ecologists might see a quandary, though, MakerBot saw an opportunity. The company sells a 3-D printer called the Thing-O-Matic, which carves plastic models from digital, user-created blueprints. For Project Shellter, it's working with designer Miles Lightwood to crowd-source a variety of designs, hoping at least some will suit the crabs. Bulinski has said she initially considered distributing biodegradable plastic shells in the wild, but Lightwood tells MNN the goal for now "is to keep natural shells in the wild by creating a printable, crab-approved alternative for domestic use." The final material for those shells is yet to be determined, he adds, but biodegradable polyactic acid is being considered as well as traditional plastic.
A hermit crab ignores one of Thing-O-Matic's initial designs. (Photo: MakerBot Industries)
While plastic shells are already sold commercially for pet hermit crabs, Project Shellter adds a twist by letting people worldwide design their own. Organizers hope this diversity of ideas will produce a style that hermit crabs like, and eventually lots of different ones. But they're still limited by nature's design standards.
The species of hermit crabs used in the project, Coenobita clypeatus, typically live in sea-snail shells, so that's what the initial design (pictured above) is based on. Lightwood and his MakerBot colleagues have set up "crabitats" in their Brooklyn offices, and for now they're still trying to get their in-house hermits to accept any of their designs. So far they've recorded two "crab encounters of the first kind," meaning two crabs have examined the shells as potential homes (see the video below). The next two steps, according to Bulinski's shell-assessment guidelines, are "switching" — in which a crab may try on a shell several times — and finally "adoption."
"A future phase of the project, pending a crab-approved design, may include using the interior volume of the crab-approved shell in other non-shell shapes," Lightwood says. Until then, he's working to ensure a free exchange of designs online. "The current shell designs are released into the public domain, and all contributed designs are encouraged to use the same licensing for maximum adoption and use," he says.
In a pinch, wild hermit crabs will take whatever they can get, says Rafael Lemaitre, a research zoologist at the Smithsonian Institution. "If it's a matter of life or death, they'll get into anything," he tells MNN. "There are all kinds of examples of hermit crabs getting into soda cans or whatever else they can find. If they don't get into something, someone will pick at their abdomen and eat them up." As this photo shows, a shell-less hermit crab is pretty vulnerable:
Photo: Arnstein Rønning/Wikimedia Commons
Still, Lamaitre adds, they'd prefer to be picky — a luxury more common among pet hermit crabs. "Some species may prefer shells that have been in the water. I think, given the choice, they would prefer shells that have been weathered out, or have a more natural type of appearance," he says. "These things tend to be overgrown with a variety of microorganisms, so they may prefer that, too."
The shell shortage isn't necessarily a problem for all hermit crabs, Lemaitre points out, since the pet trade "is almost exclusively centered on semi-terrestrial species of the genus Coenobita, of which there are 18 known species." But since those species spend much of their adult lives on land, he adds, they need to find most of their shells outside the water, which can put them in competition not only with other hermit crabs, but also seashell-collecting humans.
Ultimately, any threat to hermit crabs could also endanger their ecosystem, since the scavengers play several key ecological roles. "They're food for a variety of organisms, and they also tend to eat things that have died," Lemaitre says. "They're omnivores; they'll eat anything, so they kind of clean the environment." Their shells also "serve as a habitat for a variety of worms, protozoans and smaller crustaceans," he adds, so when a shell is occupied by a hermit crab, "everybody benefits."