Mytilopsis leucophaeta

 
A brackish water zebra mussel Mytilopsis leucophaeta was identified from Cardiff docks, in South Wales in late 1996 (Oliver, Mettam & Holmes in press). The full size range of individuals has been found, and it appears to be established in Wales
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This species was described from Belgium (under a different name) in 1835 and is present in other European countries, but it is not clear whether it has arrived in Britain from the continent or its native America. This find is of particular interest as a fresh water member of the zebra mussels (Dreissenoidea), Dreissena polymorpha, has caused considerable problems in the North American Great Lakes by smothering other species, habitats and commercial property.
 
In the Aquatic Nuisance Prevention and Control Act 1990, which was enforced to prohibit the release of freshwater ballast into the Great Lakes, it was estimated that the effects of the zebra mussel will have cost $5,000 million by the year 2000.