Slipper Limpet, Crepidula Fornicata

This post is inspired by a poem from Isabel Galleymore which I looked at in a poetry class and fell in love with.  It’s part of her collection Significant Other which I’d highly recommend.  Whilst the poem is enjoyable by itself, knowing more about the slipper limpet heightens the pleasure and appreciation of Galleymore’s skill.

Whilst slipper limpets are found in the UK, they are a non native species that arrived from America in the 19th century.  The first live slipper limpets were found in Liverpool Bay and are likely to have hitched a ride on the back of oysters.  During the 19th century, eating oysters became fashionable in London and native stocks rapidly became depleted.  To meet demand, oysters were imported from America, along with the now invasive stowaway.

Slipper Limpets live under rocks in the intertidal zone and feed by filtering plankton from the water.  They have thin, flattened shells which has a little shelf and when flipped upside down, apparently look like a slipper hence the name.  The first half of the scientific name actually means slipper in Latin and whilst we’re thinking about the name, it’s also important to note they aren’t actually a limpet… They are instead a type of sea snail.

They live in groups of up to 12 with one stacked upon another, largest at the bottom and getting smaller as you go up the tower (or Galleymore’s “high-rise orgy“).  The base slipper limpet attaches herself to things like rocks, scallops, crabs and mussels and thus the slipper limpets live a sedentary life.  And it is always either a female or an empty shell, with the rest of the stack being male.  It is advantageous for females to be bigger than males so they can carry more eggs.  And they can lay between 10,000 and 200,000 eggs so they need plenty of space!

The male has a penis that can be as long as his body, and it needs to be; it has to extend round and under the female’s shell in order to reach her genital opening.  It is because they need to be so close that they attach to one another – imagine being stuck with your ex literally on your back until you die…

Slipper limpets are born male and will later change sex, something known as sequential hermaphrodism.  Recent research has shown that the change occurs as a result of physical contact with another male.  However, it’s not instant and doesn’t happen as a result of every contact.  The change itself takes about 60 days – or about two moon cycles – to change sex and during this time the penis shrinks and disappears and the female organs develop.

The more you learn about the slipper limpet, the more appropriate you think the scientific name is.  But whilst it would be fun to imagine an animal named for it’s sexual habits, fornicate unfortunately comes from the Latin word for arch – fornix – and refers to their arched shape.

Peak breeding occurs during May and June and most females spawn twice a year, after neap tides.  Egg capsules are brooded under the foot of the female, attached to the inside of her shell or her foot.  The young hatch as larvae after 3 to 4 weeks and will stay in larval form for about 4 to 5 weeks.  After this they will leave home.  In their early life they are able to move, slowly crawling to find a suitable site to set up home, but generally after about two years they are stuck wherever they are.  Hopefully having chosen the perfect spot, given they live up to 10 years.  If they settle alone, they will turn female and become the base slipper limpet.  Alternatively, they will join an existing chain and wait their turn.

Scientists have been looking at the Slipper Limpet to see if it has any medical benefits for us and hemocyanin – the same chemical that makes the blood of horseshoe crabs and octopuses blue – has been found in their blood and is effective in treating breast and bladder cancer.  Their tough fleshy food may also have uses for human medicine.  Collagen from it can be used in regenerative medicine, such as advanced wound care and bone and nerve repair.  Whilst collagen is found in virtually every living organism, the collagen from the slipper limpets is stable in the same range as human collagen and thus provides an alternative source – at present collagen from cows and pigs is used.

Returning to the poem, I am in awe of Galleymore’s ability to make us stop and think twice about this seemingly dull, drab, slightly gnarled looking creature.  Without her poem, I wouldn’t know about the slipper limpet and I certainly wouldn’t have had so many conversations about it.

Links