Most Unwanted: Slipper limpet
Crepidula fornicata
Habitat: Marine
Threat: Threatens native ecosystems and species
Status: Potential
This is a species of mollusc that was introduced to Europe in the 19th century. The slipper limpet has also been introduced to Ireland accidentally along with imported oyster spat but so far has failed to become established.
What is it
This species of mollusc inhabits the area around the low water mark and into the shallow subtidal. It is often found attached to shells of mussels and the native oyster. MarLin describes this species as possessing an oval shell, up to 5 cm in length, with a much reduced spire. The large aperture has a shelf, or septum, extending half its length. The shell is smooth with irregular growth lines and white, cream, yellow or pinkish in colour with streaks or blotches of red or brown. Slipper limpets are commonly found in curved chains of up to 12 animals. Large shells are found at the bottom of the chain, with the shells becoming progressively smaller towards the top.
Impact
In shallow bays where the slipper limpet has been introduced in France, it can completely smother the sediment creating beds with several thousand individuals per m2. Dense aggregations of slipper limpet trap suspended silt, faeces and pseudofaeces altering the benthic habitat. Where slipper limpet stacks are abundant, few other bivalves can live amongst them. The slipper limpet is a serious threat to oyster beds because of this.
It has also been observed that live maerl thalli, which are a protected species and form an important protected habitat, become covered in slipper limpets and the spaces between the thalli of the bed become clogged with silt; this kills the maerl thalli and dramatically alters associated communities. No management measures have proven effective for this species in this habitat.
Where is it from
Originally found on the east coast of the Americas between Canada and Mexico.
Where is it now
Now introduced to British-Columbia, Washington state, Japan and Europe, where it is found on the Atlantic coast between Denmark and Spain, in Sicily and the Adriatic Sea.
How can it get here
Contaminant of oyster spat.
Hull fouling
What you can do to prevent its arrival
Aquaculture managers and owners should avoid getting spat material from areas that are known to have slipper limpet present or nearby.
Report all sightings.
Additional reading
Habitas Invasive Alien Species in Northern Ireland
