Creature Feature: Limpets
For many years, spider silk has been the strongest biological material known to man—even stronger than man-made steel. Now, unexpectedly, a small tide pool dweller has emerged as the new biological beacon of strength: the limpet.
Limpets are small gastropods with cone-shaped shells that live among rocks on the shore and in tide pools. Most are only a few inches in size. As a member of the mollusk family, they are closely related to snails and similarly use a single foot under their shell to move.
Their shell protects them from predators such as sea stars, birds and crabs. By creating a mucus layer within the shell, a strong seal is formed between the rock and limpet allowing them to lock themselves tightly to rocks—preventing predators from picking them up. When attacked, limpets often try to catch a piece of their predator under the rim of their shell before clamping it down to the surface.
Being able to cement themselves to rocks also comes in handy when the tide goes out; limpets are able to use this skill to avoid air exposure and stay wet.
The limpet’s tongue, or radula, is bristled with tiny but very powerful teeth that are used to scrape algae from rocks for food. The teeth are less than a milimeter long, but a new study published recently in the Journal of the Royal Society, Interface, reveals that the fibers creating the teeth are made up of an iron-based material called goethite. The research showed them to be five times stronger than most spider silk, with a tensile strength comparable to a single string of spaghetti holding up 3,000
one-pound bags of sugar.
Limpets have been known to literally bulldoze any other species out of their way, whether they be barnacles, invaders or other limpets. They also generate a slime trail left behind on the rock so they can tell where they’ve already been. The slime also promotes growth of algae for future food. Some species of limpet have even been known to have a home ‘scar’—a portion of the rock indented by their teeth—that they return to at the end of feeding each day. Creating an indentation fitted to their shell shape likely creates a more efficient seal against the air at low tide.
The ultra-thin nature of the limpet’s teeth fibers is what allows for its strength, and some researchers believe that engineers could use this information in the future. According to Professor Asa Barber at the University of Portsmouth, “These teeth are made up of very small fibres, put together in a particular way—we should be thinking about making our own structures following the same design principles.” Perhaps limpets are on their way to being the next model in efficiency and strength engineering.