"Due to global ocean pollution and human over-harvesting, ... hermit crabs are facing a severe housing shortage; there aren't enough shells discarded by marine gastropods to go around, and it doesn't look good for these little guys.
The drive to remain housed for this species is so strong that biologists routinely find them living in discarded glass jars, the tops of soy sauce containers and any other form of refuse in which they can hide.
Thankfully, artist Elizabeth Demaray recognized this problem, and did something about it. The Hand Up Project, attempting to meet the new needs of natural life forms is her solution to the global hermit crab housing shortage. With the aid of a paleontologist and a mechanical engineer, she designed these structures with the intention to make artificial shells that are better than what nature can provide.
The improved forms have a large internal space to weight ratio, which the animal seeks, and because they are non-biodegradable they will out live the life span of the species itself, thereby assuring many generations of hermit crabs ample hand-me-down housing." - Treehugger, thanks to Jasmin Chua.