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.
COPYRIGHT JESSICA WINDER 2011
All Rights Reserved
Jessica's Nature Blog 
Thanks for your photos of and introduction to this bizarre [to us] creature.
Steve Schwartzman
http://portraitsofwildflowers.wordpress.com
LikeLike
These are bizarre, with their coiled stacks of up to 12 individuals – but I thought they might be a familiar sight to readers from the US where this species originates.
LikeLike
I grew up on Long Island, in New York, and often went to Atlantic Ocean beaches as a child, but I never saw anything that looked even vaguely like one of these limpets.
By the way, when I got to your words “That’s the peculiar habit from which their name is derived…” I at first thought you meant “Studland,” which is coincidental but appropriate.
LikeLike
That’s funny – the link between the behavioural habits of the Slipper Limpet and the place name! More so than you can have imagined. Studland beach has a naturist area where, on occasion, the human activities are reputed in some regards to mimic those of this humble mollusc.
LikeLike
It is only recently that I realised that this species was invasive. I remember these shells as being the most common of those found on the beaches of South East England as a child 40 years ago.
LikeLike
Yes, they seem such a familiar part of British beaches but they were brought over in the 1800’s. They might have come in with consignments of American oysters for relaying in British waters (an unsuccessful enterprise). Slipper limpets are considered a pest now as they compete for ground with other shellfish like mussels and oysters – they settle on top of beds of native species and suffocate them with the detritus they excrete. However, in isolated instances, like in the Solent in the late 1980’s, the banks of dead empty slipper limpet shells on the seabed provided settlement material or cultch for an unexpected batch of oyster spat that was washed out of the Beaulieu River from cultivated beds. This led to a temporary boom in the local oyster fishing industry. Without the Slipper Limpet shells, there would not have been so much suitable ground for the oyster spat.
LikeLike
Wow, that is interesting. I am a mature student studying Marine Biology at Blackpool College and have chosen this animal for my presentation on Invasive species. Nobody up here is familiar with the Slipper Limpet so I should be able to give a talk with a fresh edge hopefully.
LikeLike
I am pleased that the information is useful. Good luck with the presentation.
LikeLike
Thank you. I need to find some shells for visual props now
LikeLike
I went to the beach today thinking I could get some slipper limpet shells for you but there were none at Ringstead Bay. I’ll look again next time I visit the seashore.
LikeLike
WOW, thank you for the thought. My presentation isn’t until May so if you do see some before then it would be much appreciated if you could collect some for me. Of course I would pay the postage and package costs.
I enjoyed reading your blog today on Piddocks. This is an important species of the Fylde Coast, so it is of particular interest to me.
Thanks again,
Ian
LikeLike
I’ll see what I can do. I hope the storms have not washed them all away – the entire topography of many local beaches has changed recently – you may have seen something about Chesil Beach in the media, for example. Do you just want empty shells? How many shells do you need for the presentation?
LikeLike
Thank you!
Yes, empty shells. Two dozen would be good if you can find them please.
I have seen a few articles on Chesil Beach recently (one of my favourite places). I would imagine that many places along the South-western coast have altered significantly during this winter.
Thanks again,
Ian
LikeLike
OK. I will be on the lookout for them, and will let you know when I have collected them.
LikeLike