This guest post is the second part of a two part interview with Project Shellter research advisor, Dr. Katherine V. Bulinski. Part one is available here.
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Miles Lightwood (ML): Another idea you shared was an alternate approach to addressing the shortage with printed shells. Please explain.
Dr. Katherine Bulinski (KB): One approach that was initially considered is that these printed shells could be distributed in the natural habitat if a hermit crab shortage had been identified. We discussed the use of biodegradable plastics for such an application so that the environmental impact should be less than if you used a non-biodegradable plastic. I think it is very important to be wary of manipulating a natural ecosystem by introducing man-made (or in this case, machine made) products as we may not recognize all of the possible effects of our actions.
Another more immediately practical approach would be to encourage people that have hermit crabs to use the printed shells instead of the natural shells available at pet stores. Part of the reason for the shell shortage in some parts of the world is over-collecting of shells in different regions. In the natural environment, empty snail shells would either be used by a hermit crab, be broken apart naturally to become carbonate sand, slowly dissolve into ocean water, become buried or become a surface for small organisms to grow on. When possible we should try to leave natural ecosystems as untouched by people as possible, so printing shells for commercial use so that natural shells can remain a part of the ecosystem would be a positive goal for this project.
ML: Is there any advice or insight on hermit crabs or their shells you can provide for Project Shellter contributors?
KB: Hermit crabs evolved over time to use the shells of certain species of gastropod as homes. Most snail shells curve to the right and hermit crabs evolved to have an abdomen that curves to the right to make effective use of the shape of the snail shell. In my paper I cite research that shows crabs select shells based upon several criteria:
- Opening (aperture) size - the opening must be the correct size for the crab to use its larger left claw as kind of protective barrier
- Opening (aperture) shape - some crabs prefer round openings, while others may prefer oval openings
- Shell length and width - the shell must be the correct size to allow the crab to fully retract when threatened
- Shell weight/thickness - the crab expends energy to haul around the shell and therefore it must not be too heavy. The shell must be sturdy enough to withstand being carried around and to withstand possible attacks from predators, so it must not be too light either.
- Shell damage - in the natural world, many of the shells that are used by hermit crabs are not pristine. Many have holes and chips along the aperture but are still used because shells are so limited in certain ecosystems. Hermit crabs prefer shells that are undamaged as crabs in damaged shells are more easily evicted by other hermit crabs and these crabs are also more vulnerable to predators.
When printing shells for this project it may be necessary to experiment with any or all of these properties to create a shell that a hermit crab will call home. Additionally, the interior surface of a natural shell is smooth, so the lines I see on 3D prints might need to be sanded or otherwise smoothed.
ML: Do you have any last thoughts to share with Project Shellter contributors?
KB: Hermit crabs play an important scavenging role in both marine and terrestrial ecosystems and I hope this project helps to conserve the snail shells that are found in their natural habitat. I wish all contributors success and am looking forward to watching the project unfold!
ML: One more thing: do you think a printed shell will have the sound of the ocean in it like a real one?
KB: (Laughs) I don’t know, but there’s only one way to find out!
Thank you Dr. Bulinski for acting as research advisor! I look forward to sharing the crowd-sourced science of Project Shellter with you.
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