Frightening sharp teeth, eating everything in their way, the strongest known biological structure in the world (at least according to two websites), I’m here to tell you about the vicious…limpet. Yes, that sweet little mollusc—such as the Sydney species Cellana tramoserica—apparently has the world’s roughest tongue (well radula), covered with hundreds of teeth in order to scrape algae off rocks. (See the horror picture here…ahem, not to scale.)
Scanning electron microscope image of limpet teeth (University of Portsmouth: Asa Barber) from https://www.abc.net.au/science/articles/2015/02/18/4182365.htm
Limpets live in the intertidal zone, so they have evolved to withstand some harsh conditions. Their low, conical, disc-shaped shell (“patelliform”) is ideal with a lower surface area to withstand strong waves and they also produce a very strong super-glue-like mucus to help them stick to rock. They are also able to trap water underneath their shells, so they don’t dry out when the tide is low. I always thought they ate away a home scar to match their shell, but I read recently that in fact their shell grows to match the home scar (to make a better seal).
Limpets have one “foot” covered in a shell. I can’t for the life of me picture how the radula relates to the foot. Is there a mouth? I have no idea. They are predated on by starfish, birds, fish, seals and humans and apparently can live 10-20 years! Their “eyes” are simple cup shaped dips in their skin allowing them only to see dark, light and direction of light, however they are reliably able to return to their home scars after wandering. Even if scientists do all sorts of mean things like remove their trail they might be following or spin around the rock under them. Meaning it can’t be topographic memory or external cues. The most popular theory is they follow their own snot. Oh, ok, mucus trail. And when they have found their way home, they will orient their bodies in exactly the same position as before. Every time.
All in all, they are a pretty fascinating little creature. So, do yourself a favour and read this well-written piece about them:
https://medium.com/do-contribute/the-power-of-limpets-115b577cf4a6 and go here for a cute video of them at speed: https://www.youtube.com/watch?v=TXw2JEdOY30