Cool critter of the month: Slipper Limpet (Crepidula fornicata)

Phylum: Mollusca

Family: Calyptaeidae

Where do they live? These guys live in the intertidal zone, often attached to any hard substrate…. Literally any.  Although you can find them on the soft substrates as well as clinging onto rocks and pilings, you can find them quite happily living on other creatures such as crabs, oysters – and even other slipper limpets!  These guys can form chains of around 12 limpets long, with the largest ones sitting at the bottom, and the smallest at the top.  The slipper limpet is native to the east coast of America.  It’s pretty widespread too, with its most northerly point starting in Nova Scotia in Canada and most southerly in the Gulf of Mexico.

“But wait a minute” I hear Europeans, cry – “I’m sure I’ve seen these on our intertidal zones too”.  Well yes you have.  On the eastern side of the Atlantic these limpets are classed as invasive, most likely introduced accidentally when the Atlantic oyster (Crassostrea virginica) was brought over from America*.  It also seems to have been introduced into the Pacific too, with limpets being reported in British Columbia Canada, Washington State USA, and Japan.

Why are they awesome? Depending on your point of view of invasive species, slipper limpets may be loathed. But just because we consider them invasive doesn't mean that they aren't incredible.  Just take a look at some of these open access science describing some of their amazing features

They are everywhere Even ignoring the whole introduction thing that got them across the Atlantic/into the Pacific, these guys are much more mobile than you might think for a snail.  Just consider their native distribution – which is far from local.  The secret to their success lies in their larval stage and crucially their velar lobes which act like flat, disc-like wings.  By manipulating the surface area of their lobes they could alter their swimming speed, giving them more opportunity to reach their settlement grounds so they can begin metamorphose into the form we see below.  It is possible that this method of swimming is much more energy efficient than another common method of larval locomotion – beating cilia (really tiny hair-like structures) as fast as possible.  This open access paper is available here. Check it out for a video on a 19 day old limpet swimming (download in the ‘supporting information section’, and also the main 'feature' image attached to this post.

It may be small, but it can alter the seafloor Slipper limpets can settle in high densities on the seafloor – and indeed they have done in part of the Mont Saint Michelle bay in France.  This is not good news for the flatfish in the area.  Here the limpets are in such high abundance that they almost form shell mats which prevents the flatfish from settling on and burying in the seafloor.  There’s are double whammy here for the flatfish, because the bay is also a key nursery ground. This open access paper can be read here http://ow.ly/J5CBg.  You can also read a little more about the limpets’ expansion into the bay here http://ow.ly/J5CDq

I don’t wanna grow up yet Spending your larval stage in the plankton is pretty common in more sedentary marine critters.  Generally, the larvae will “know” when to settle and metamorphose into their adult forms when they encounter suitable substrate or receive a chemical cue emitted by adults which signals* the location of good habitat (it’s good because the adults are living there).  But the ocean is awfully big, and the ocean climate is constantly changing so sometimes Larvae don’t get these cues for quite some time.  Fortunately they have developed the ability to delay when they begin metamorphosis – and doing so doesn’t seem to cause them any problems.  This open access paper is available to read here http://ow.ly/J5CX6

* This open access paper can be accessed here http://ow.ly/J5CHV   There’s also an open access paper outlining its establishment in Ireland available here http://ow.ly/J5CJk.

Some technical info about the image:  It’s a confocal image (extended focus Z stack), stained with phalloidin (F-actin; purple), DAPI (cell nuclei, blue), anti-serotonin (yellow), and anti-acetylated tubulin (red). The shell (green) image was created from the DIC picture collected during the confocal scan. The C-shaped line of nuclei are cells at the edge of the velum; the acetylated tubulin (red) staining reveals the ciliated surface of the velum. The F-actin staining (purple) highlights the main larval retractor muscle. Serotonin (yellow) reveals the serotonergic neuron cell bodies and axons.