Zebra Mussel - Dreissena polymorpha

    Description

    Adults are up to 3 to 4 cm in length with a typical mussel shape. The shell is yellow with darker bands or zig-zags. It is highly variable, as suggested by its latin name, and some specimens lack the stripes and can be all white or all brown/black.

    Similar Species

    The only similar mollusc with a similar shape is Mytilopsis leucophaeta but this is a brackish warter species and not found in Leicestershire or Rutland.

    Identification difficulty
    Habitat

    Lakes, canals. reservoirs and slow rivers. It attaches itself to solid surfaces such as walls, stones and other mussels. It can colonise soft sediments if dead mussel shells provide sufficient substrate for it to attach to. Larvae are sensitive to UV light so it is not normally found below 1m in depth where it can form huge colonies.

    When to see it

    All year round

    Life History

    This is a non-native pest species that arrived in Britain in the 1820's. Since 1999 there has been a dramatic increase in its abundance and it can be a problem in water treatment or extraction facilities, such as at Rutland Water.

    UK Status

    Widespread in England, but less common elsewhere in Britain.

    VC55 Status

    Widespread but local in Leicestershire and Rutland.

    Leicestershire & Rutland Map

    UK Map