Mollusc Week: True Limpets.

As this clip demonstrates, some things in nature are more filmable than others. Guess what? We have to cover at least one boring mollusc here because, hey, it's weird and most of us probably never heard of it outside of science class or a Monty Python clip.

These are star limpets (Patelloida sacchroides). Source here will tell you more.

Meet the true limpet, i.e. any member of the large family Patellogastropoda. As the lengthy name might imply, limpets are related to snails and slugs, and true limpets can only be found on rocky coasts near the sea. The other limpets can be marine or freshwater, and some have even adapted their mantles to breathe air or survive intense conditions around hydrothermal vents. The big difference seems to be who has gills and who has 'lungs,' but there are so many false limpets that there may be more subtleties in the classification than that.  One would think that the false limpets would be far more interesting than the true limpets, which are about as active as presented in the "documentary" and are therefore very rarely covered on television.

Limpets are marine slugs with very odd houses. The shell of a true limpet is like a flat cone, making it blend in very well with whatever rock the limpet sees fit to adhere to. Some stay stuck so long that they get algae growing on their shells. The last time we saw that was with the three-toed sloth; algae is great camouflage.

Not sure how "true" these are. Please correct me if they're fakes. Source.

Limpets make sloths look active. They don't move very much, lest they dry out in the sun. When they do move, it is to scrape off algae from the rocks. This, too, is done very slowly. MOst of them are also under 3 inches long, so not only are they slow, they're small. Yep, that's Grade A documentary material, there.

Here's the kicker: Once a limpet really clamps down, it is impossible to remove through force alone.  The limpet would rather die than leave its rock - seriously, limpets will break if you try to pull them off. It's as futile as trying to pry a hardcore WoW addict away from his computer. They can even adjust their strategy to the type of predator. On the plus side, next time you meet a particularly stubborn person, call him/her a "limpet;" the joke may well be lost on them, but you can laugh to yourself.

And yes, finally, limpets can be eaten. The largest true limpet, the Mexican Giant Limpet (Patella mexicana,), is actually under threat from overharvesting. If limpets are around, people The shells of limpets are also valuable to some collectors, so as long as you can get them off the rock, a limpet can become a gold mine. Consider that every time you need help getting motivated; limpets are awesome once they let go of the rock.