Along our Sussex beaches there are millions of shells of the Common Slipper Limpet - so named because the empty shell resembles a tiny slipper up to 50mm long.
After storms you can find groups of the living animals all stacked up. These stacks have the largest and oldest Slipper Limpets at the bottom and these are female. The smaller shells on top are males. However, if the females die, the largest male will turn into a female - they are a "sequential hermaphrodite". They can live at depths down to 70 metres.
They were first accidentally introduced from North America to Essex between about 1890 in association with oysters, and since then have become an invasive species that competes with native filter-feeding invertebrates for food and space and is considered a pest on commercial oyster and mussel beds. However, they are said to make good eating.
The Slipper Limpet’s scientific name is Crepidula fornicata means ‘a small arched boot’ – Crepidula from ‘small boot’ in Latin and fornicata comes from the Latin word fornix, meaning arch.