Slipper limpets are a frequent find on the beach at Studland in Dorset. They are unique in their lifestyle. They settle in groups, one on top of another and interbreed within the group, each individual changing sex at least once. That’s the peculiar habit from which their name is derived – Crepidula fornicata (Linnaeus). The largest individual at the bottom of the heap is always female. The smallest animal is male – with intersexes between the two. There can be as many as ten molluscs attached to each other in the clump.
The species originates in America from whence it was accidentally introduced to Great Britain in the 19th Century along with a consignment of imported American oysters.
The bluey-green colouring on some of the Slipper Limpet shells is due to microscpoic algae. The pinky-purple patches are an encrusting calcareous alga known as ‘Pink Paint’ (Lithamnion sp.). In the lower picture, there are some small calcareous tubes attached to one of the shells on the left – these were made by the marine worm Pomatoceros triqueter Linnaeus. Another shell is perforated by many small circular holes. These were made by an encrusting sponge, like Cliona celata Grant, which is now absent but in life dissolved the holes in the shell.
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